Humans and Neanderthals: Less different than polar and brown bears

https://phys.org/news/2020-06-humans-neanderthals-polar-brown.html

Humans and Neanderthals: less different than polar and brown bears
Credit: Kennis & Kennis Reconstructions

Ancient humans, Neanderthals and Denisovans were genetically closer than polar bears and brown bears, and so, like the bears, were able to easily produce healthy, fertile hybrids according to a study, led by the University of Oxford’s School of Archaeology.

The study, published 3 June in the journal Proceedings of the Royal Society B, shows that the genetic distance values between humans and our ancient relatives were smaller than the distance between pairs of species which are known to easily hybridize and have fertile young.

Professor Greger Larson, Director of the Palaeogenomics & Bio-Archaeology Research Network (PalaeoBARN) at Oxford and senior author of the study says, “Our desire to categorize the world into discrete boxes has led us to think of species as completely separate units. Biology does not care about these rigid definitions, and lots of species, even those that are far apart evolutionarily, swap genes all the time. Our predictive metric allows for a quick and easy determination of how likely it is for any two species to produce fertile  offspring. This comparative measure suggests that humans and Neanderthals and Denisovans were able to produce live fertile young with ease.”

The long history of matings between Neanderthals, humans, and Denisovans has only recently been demonstrated through the analysis of ancient genomes. The ability of mammalian species, including , to produce fertile hybrid offspring has been hard to predict, and the relative fertility of the hybrids remains an open question. Some geneticists have even said that Neanderthals and humans were at the “edge of biological compatibility.”

So the team developed a metric using genetic distances to predict the relative fertility of the first generation of hybrids between any two mammalian species. They did this by analyzing genetic sequence data from different species that had previously been shown to produce hybrid offspring. By correlating the genetic distance with the relative fertility of the hybrid offspring, it was possible to show that the greater the evolutionary distance between any two species, the less likely it is that the  between them would be fertile. In addition, the team used the distance values to determine a threshold of fertility.

When the distance values between humans, Neanderthals and Denisovans were calculated, they were even smaller than the values between several pairs of species which are known readily and easily to hybridize—including  and , and coyotes and wolves. This suggests we could have predicted the existence of Neanderthals and Denisovans in our genomes as soon as the first genetic sequences were generated.

This proxy can also be used to predict the likelihood that any two mammal species can give birth to live hybrids, a useful tool that can be used in decisions about whether to place animals together in zoos.

Richard Benjamin Allen, joint first author of the study says, “Many decisions in  have been made on the basis that related organisms that produce hybrids in captivity should be prevented from doing so. Such an approach has not considered the significant role that hybridisation has played in evolution in the wild, especially in populations under the threat of extinction. Our study can be used to inform future conservation efforts of related  where hybridization or surrogacy programs could be viable alternatives.”


You’re Not So Different From an Octopus: Rethinking Our Relationship to Animals

Remember back when we were all tubes?

Sy Montgomery does. That was a simpler time, eons before the octopus and Homo sapiens went their separate evolutionary ways, and certainly long before that highly intelligent cephalopod, which appeared some 300 million years ago, ended up boiled, stewed and fried. “Our lineage goes back a half-billion years ago when everyone was a tube,” says Montgomery, a naturalist and author of many books about animals. “That was when there were no eyes. Yet we have evolved almost identical eyes. I just love that.”

Montgomery’s enthusiasm and devotion to Earth’s creatures — and the similarities we share with them — has inspired her readers to get to know the eight-tentacled and big-brained wonders in The Soul of the Octopus, and taken us to the ends of the Earth and back to our own backyards in such award-winning books as Spell of the Tiger and Birdology.

A real-life Dr. Dolittle, Montgomery says she’s always related best to animals and — sometimes straining the patience of her bipedal family members — has long treated her home as a land-bound ark for orphaned animals. In scientifically precise but poetic prose, she writes that we share greater similarities than differences with the electric eel, the tarantula, the tree kangaroo and the snow leopard. Don’t forget, she says, that we hail from the same genetic pool, or more likely, gurgling swamp. By paying attention to the commonalities we have with our fellow animals — our singular capacity for what Montgomery argues is a broad range of emotions and zeal for life — humans can transcend the “we-shall-rule-the-Earth” anthropocentric focus, she says, and see that we are all in this together.

“We are on the cusp of either destroying this sweet, green Earth — or revolutionizing the way we understand the rest of animate creation,” Montgomery said. “It’s an important time to be writing about the connections we share with our fellow creatures. It’s a great time to be alive.”

Montgomery recently chatted with Leslie Crawford, author of animal-focused children’s books Gwen the Rescue Hen and Sprig the Rescue Pig, and compared notes on delving into the minds of animals.

Leslie Crawford: Do you understand animals more than people?

Sy Montgomery: As a child, I grew up on an Army base and I did not have a single human friend. It allowed me the freedom to get to know other species. I vividly remember my 20s like it was yesterday. As a young person, I was often worried about whether or not I was reading other people correctly. And yet these are organisms that use the same English language. It’s terrific to be in my 60s and know I can read animals. I have always read animals better than people.

What did you find surprising about humans as a child?

I was shocked to learn that people use their language to lie. Even little kids lie. Of course, animals will lie, too. A sea snake will say, I’m three or four sea snakes. Chimpanzees lie all the time. But the degree to which humans use language to lie shocked me. I’ve always dealt with animals in a very straightforward way. I wasn’t ever trying to conceal things from them. Humans often want incorrect information about you and project incorrect things on you.

So much has changed about our understanding of animals since you started writing about them. When did you first realize that animals are sentient beings?

I think most of us realize as children that animals are sentient beings. But then, somehow, for so many people, this truth gets overwritten — by schools teaching old theories, by agribusiness that wants us to treat animals like products, by the pharmaceutical and medical industries who want to test products on animals as if they were little more than petri dishes. But thankfully, scientific and evolutionary evidence for animal sentience has grown too obvious to ignore.

What have you learned about animals and consciousness?

You don’t want to project onto animals your wishes and desires. You have to respect your fellow animals. I don’t want to roll in vomit, but a hyena would enjoy that. I don’t want to kill everything I eat with my face, but that’s what I’d do if I’m a great white shark. If I were eating a carcass, I would not be as happy about it as a scavenger. We have different lives but what we share is astonishingly deep, evolutionarily speaking.

When did you know you were an animal person?

Animals have always been my best friends and the source of my deepest joy. Before I was 2, I toddled into the hippo pen at the Frankfurt Zoo, seeking their company, and totally unafraid. When I learned to speak, one of my first announcements to my parents was that I was really a horse. The pediatrician reassured my mother I would outgrow this phase. He was right, because next I announced I was really a dog.

My father loved animals. Growing up, my mother had a dog named Flip who she adored. But I seem to have had an even greater attachment to animals than they did. My friend, the author Brenda Peterson, says that I must have been adopted at the local animal shelter.

How many animals do you currently live with?

Right now, the only animal who lives with us is a border collie named Thurber. I travel a lot: Thailand, Ecuador, Germany, Spain. I can’t force my husband to have a house filled with animals. I had chickens but predators got almost all of them. Weasels got into the coop. They are so smart. Even though we buried wire beneath the floor, weasels need just a tiny opening to get through. You can never weasel-proof an old barn.

It sounds like you have some respect for weasels even though they killed your chickens?

They were there first. I learned my chickens were killed on Christmas morning when I brought a bowl of popcorn to them and saw this white creature with black eyes staring at me. You’d think I’d be angry. But the beauty and ferocity of this creature filled me with awe. At the same time that I mourned my beloved chickens, I admired the weasel.

You originally studied psychology. How do you go about thinking about what animals are thinking? Or is it a mistake for people to imagine animals are thinking in a way that we think?

I triple majored in college, and psychology was one of them. But thinking about animals wasn’t really part of the coursework. I think it’s perfectly reasonable to assume that nonhuman animals share our motivations and much of our thought processes. We want the same things: food, safety, interesting work and, in the case of social animals, love. But we can’t always apply human tastes to animals — otherwise fish would seek to escape from the water and hyenas wouldn’t roll in vomit.

When did you stop eating meat and dairy and why do you think some people make the decision and others don’t?

I read Animal Liberation, by Peter Singer, in my 20s. Even though I loved meat, I haven’t eaten it since. I can’t wait to try the Impossible Burger!

In writing Sprig, I learned so much about pigs, including how smart they are. What do you love most about pigs?

They are so sensitive and emotional. And they’re wise. They know what matters in life: warm sun, the touch of loving hands and great food.

Similarly, when I wrote Gwen, I found out how remarkable hens are with their own superpowers, including keen eyesight and a strong community that includes watching out for each other.

I agree with you. I love these aspects of their lives. I love how similar they are to us in so many ways, but I also love the otherness of these animals.

Speaking of “otherness,” in your book Soul of an Octopus, you came to know Athena, an octopus, as a friend. But can a person really know an octopus?

Until the day I met Athena in 2011, pretty much all of the creatures I got to know personally were vertebrates. We are so like fellow mammals, with whom we share 90 percent of our genetic material.

I didn’t know if I would be able to bring what I understand about other animals to an invertebrate, but I was delighted to see it was true of the octopus. It was clear the octopus was just as curious about me as I was about her.

There are some animals who aren’t interested in you. But when you have an octopus look you in the face and investigate you with her suckers with such an intensity, well, what that octopus taught me [about consciousness] blew me away. When Athena grabbed me, I correctly understood that she wasn’t being aggressive, just curious.

How do you convince people to consider an octopus as something other than something to eat?

I tell them about my octopus friends, Octavia and Kali and Karma — specific individuals to whom they could relate.

I have realized that preaching to people about seeing animals as worthy of the same compassion and dignity as is owed humans doesn’t work. But if preaching isn’t effective, what do you think works to change hearts and minds — and stomachs?

Teach by example. It’s the most powerful tool we have. Your love for pigs, told through your stories of Sprig and Gwen, is contagious because of your example. You show how much fun it is to let these animals enrich your life and make others want to be part of it. That’s much more appealing than a lecture.

Are there one or two calls to action you would ask of people who want to improve the world for animals?

I would suggest that individuals find the action that best suits them. For me, when I was young, working 14 hours a day and making relatively little money, I had no extra time for volunteer work, and my tithes to animal causes amounted to far too little. But I could change my diet, so I did. For another person, an overnight change to vegetarianism or veganism might be too tough, but perhaps they could volunteer at a shelter.

I personally hate politics, though I vote and donate. But other people might throw themselves joyously into working toward electing candidates that support conservation and animal welfare legislation. Happily, we can all work with our individual strengths to make the change animals deserve.

What about everything we learn daily about climate change and the growing risk of mass extinctions?

Sometimes you don’t want to read the headlines. It’s so depressing. During the civil rights movement, I was too young to have anything to do with that. But now we can choose to be part of what is definitely a movement, one that recognizes that nonhuman animals think and know and feel the way we do. We know this based on cognitive and behavioral science. That change has happened within my lifetime, which is fantastic.

The fact that we live during a challenging time gives us an opportunity to be courageous. I’m thrilled to be able to apply my courage to such a worthy endeavor and with such worthy partners.

This article was produced as part of a partnership between Stone Pier Press and Earth | Food | Life, a project of the Independent Media Institute.

Earth’s odd rotation may solve an ancient climate mystery

A geologic change might have plunged lush landscapes into arid zones, killing off an array of creatures—and it might happen again one day.

AT FIRST, IT seems like a case of extinction by climate change: More than 160 million years ago, during the Jurassic period, a fanciful menagerie crept, swam, and flew through the cool, damp forests of what is now northeastern China. Then, almost in a geologic instant, the air grew warmer and the land dried out. As the water disappeared, so too did the life. And yet, researchers have struggled to pin down a climate-related culprit behind this ecological collapse.

Now, a study published in the journal Geology suggests that it wasn’t the climate that changed, but the geographic location of the landscape. Paleomagnetic signatures in the area’s rocks indicate that sometime between 174 and 157 million years ago, the whole region shifted southward by a startling 25 degrees, plunging once lush landscapes into zones of desiccating heat.

The ancient rocky lurch was part of a phenomenon known as true polar wander, in which the topmost layers of the planet, likely all the way down to the liquid outer core, rotate significantly even as Earth continues its daily turn around its usual spin axis.

In the Jurassic, the surface and mantle made this twist around an imaginary line through the crook in Africa’s west coast known as the Bight of Benin. The change would have been massive: If a similar shift were to happen today, a flag planted in Dallas, Texas, would end up where Northern Manitoba, Canada, currently sits. On the other side of the world, the continent of Asia would soar southward.

JURASSIC CLIMATE SHIFT

More than 160 million years ago, northeastern China was home to a wide array of plants and animals known as the Yanliao Biota. A dramatic change in climate from temperate to arid conditions likely led to their demise. But what drove this shift has long been a mystery.

Earth’s monster jump

A new study of paleomagnetic data from northeastern China suggests that between

174 and 157 million years ago, the entire surface of Earth rotated a staggering 25 degrees, which would have moved the landscape inhabited by the Yanliao Biota from a cool, humid zone into a hot, dry band.

North

Pole

North

Pole

HUMID

East Asia, 174–157

million years ago

How did this happen?

This colossal change can be explained by true polar wander, which occurs when a mass imbalance causes the entire surface of Earth and its mantle to rotate around the core. While true polar wander has likely occurred throughout the planet’s history, this ancient event was particularly drastic.

STRUCTURE OF EARTH

TRUE POLAR WANDER

Excess mass is

redistributed

toward the

Equator.

spin

axis

crust

mantle

outer core

inner core

Earth’s layers

not to scale

Earth’s surface rotates with the mantle around the core.

Earth continues

to spin around

its axis.

KATIE ARMSTRONG, NG STAFF. SOURCES: ZHIYU YI, YONGQING LIU, AND JOSEPH G. MEERT, “A TRUE POLAR WANDER TRIGGER FOR THE GREAT JURASSIC EAST ASIAN ARIDIFICATION”, GEOLOGY, 2019; XU XING, ET AL, “AN UPDATED REVIEW OF THE MIDDLE-LATE JURASSIC YANLIAO BIOTA: CHRONOLOGY, TAPHONOMY, PALEONTOLOGY AND PALEOECOLOGY”, ACTA GEOLOGICA SINICA, 2016; C.R. SCOTESE, PALEOGEOGRAPHIC LAND EXTENT

“We’re experiencing true polar wander as we speak,” says Dennis Kent, a paleomagnetist at both Rutgers and Columbia University who wasn’t part of the new study team.

To be clear, these more recent forays are not the source of modern-day climate change, which is driven by humans’ relentless release of greenhouse gasses into the atmosphere. In addition, the magnitude of this Jurassic shift—and whether true polar wander is even a real phenomenon—remain under debate.

“It’s a reasonable area of discussion,” says Christopher Scotese, director of the PALEOMAP Project. “But it’s more controversial than people give it credit for.”

Studying Earth’s past and present geologic wanderings may not only help resolve the controversy, but also improve our understanding of the planet’s complex machinations.

“It’s so important that there’s still fundamental science being done,” says Lydian Boschman, a geologist at Eidgenössische Technische Hochschule (ETH) Zürich who was not a study team member. “If we don’t understand the foundations, then there’s nothing we can do on top of that.”

Twisty-turny past

While deep geologic gyrations can have drastic impacts on Earth’s surface, the planet’s magnetic field remains largely unchanged by such events, since it is generated by the churn of molten iron and nickel in our planet’s outer core, some 1,800 miles below the surface. Researchers can therefore turn to iron-rich minerals attuned to magnetic fields to untangle the planet’s past twists and turns. As sediments collect and solidify or lava cools to stone, these minerals align themselves with the global magnetic field like compass needles, recording a snapshot of a region’s location on our planet at a given period in the past.

But not all rocks are perfect stenographers. As sediments are turned to rock, compression can tweak the magnetic signature and impact their inferred planetary position. By removing this sedimentary confusion and looking only at volcanic rocks, Kent and the late Edward Irving, who worked at the Geological Survey of Canada, found the signatures of a monster jump during the Jurassic period. Their results, published in 2010, suggested that Earth’s surface shifted some 30 degrees between 160 and 145 million years ago.

Subsequent studies started to fill in the gaps in the record, and increasingly it seemed that the entire world was in on the Jurassic mega-shift, with evidence found in modern-day AfricaNorth AmericaSouth America, and the Middle East. But one place appeared to largely stay put: the Eastern Asian Blocks, a zone that includes most of Mongolia, China, North Korea, and South Korea.

“It hardly moved in terms of latitude during that entire period,” says study coauthor Joseph Meert, a paleomagnetist at the University of Florida. “That didn’t seem to really jive well with aridification.”

Part of the challenge was that studies documenting the region’s position with paleomagnetic analyses didn’t sample from a large enough swath of time, Meert explains. While volcanic rocks faithfully record magnetic north, this pole has a tendency to roam, so researchers must average their analyses with data covering several thousands of years to account for these wanderings. (Magnetic north just changed, and here’s how we’re trying to keep up.)

The region itself was also frequently excluded in discussions of global change because of its complex history, Kent adds. While the path of other landmasses can be traced back to the supercontinent Pangea, which broke up roughly 180 million years ago, East Asia’s route remains unclear.

“They were doing their own dance out there,” Kent says.

In the summer of 2015 and spring of 2018, the latest team set out in search of a more robust paleomagnetic record to untangle the geologic movements of East Asia, says lead study author Zhiyu Yi of the Chinese Academy of Geological Sciences in Beijing.

Rocks across China tell very different stories, as portrayed by their starkly different hues. The early to middle Jurassic deposits are dark and rich with coal, hinting at a humid ancient landscape chock full of plants. By contrast, the late Jurassic formations hosted rusty red deposits laid down in drier conditions. (Learn about the bizarre fossil finds that revealed Asia’s oldest known forest.)

The team sampled volcanic rocks interwoven into these contrasting formations at a total of 57 sites. In 2017, their analyses confirmed past work that showed the younger red rocks were laid down at low latitudes, where hot and dry conditions likely prevailed, Yi says. But the moment of truth came in the summer of the following year, when they analyzed the older samples and discovered that they formed at surprisingly high latitudes.

“At that moment, I knew what these data mean to us—we finally found the [true polar wander] signals,” Yi writes via email.

True polar wander may be behind the demise of northern China’s array of life known as the Yanliao Biota. This die-off set the stage for a new jumble of creatures to arise known as the Jehol Biota, which includes the fossil Jeholosaurus shown here.

PHOTOGRAPH BY O. LOUIS MAZZATENTA, NAT GEO IMAGE COLLECTION

Meert admits that he was a little skeptical of the massive shift at the start, but the new findings have him convinced: “We were saying, Yes, yes, this is it,” he says, recalling the time he sat down to dinner with Yi in Beijing to review the data. “The sense of motion and everything just seemed to fit neatly together. So we had a beer and toasted and said, Let’s do this.”

The results suggest that the Jurassic surface rotated by at least 6.7 inches each year, which led to the slow drying of the East Asian landscape that likely killed off many of the region’s ancient plants and animals known as the Yanliao Biota. Past studies hint that another smaller wander around 130 million years ago returned East Asia to temperate climes, setting the stage for the rise of a burst of life known as the Jehol Biota. These exceptionally preserved fossils have yielded many startling finds, including the discovery of the first known feathered dinosaur that was not directly related to birds. (Read about the dinosaurs that didn’t die.)

Spinning futures

“The beauty is that it is very simple,” says Giovanni Muttoni, a paleomagnetist at the University of Milan, Italy, who was not involved in this work but has extensively studied the big Jurassic wander. The motion and magnitude line up with past work, he notes, and they connect mysterious changes in climate with this planetary twist.

However, Scotese isn’t convinced that true polar wander occurred at all during the last 200 million years, arguing that the effects could be explained by the movement of tectonic plates. During the Jurassic period, he says, Asia and North America inched along as if they were on a seesaw that pivoted around Europe. While North America moved northwest, Asia shifted southeast.

“There’s a huge amount of noise in the paleomagnetic database, and often paleomagnetists do all sorts of contortions to try to minimize the noise or correct things that they think are errors,” he says. “I just disagree with that philosophy. I feel that’s biasing the database.”

Ancient whales walked on four legs and moved like giant otters — seriously

This illustration shows an artistic reconstruction of two individuals of Peregocetus, one standing along the rocky shore of nowadays Peru and the other preying upon sparid fish. The presence of a tail fluke remains hypothetical.

(CNN)The whales we know today look nothing like they did millions of years ago.

Instead, cetaceans, the group including today’s whales and dolphins, evolved 50 million years ago from small four-legged animals with hooves.
Rather than being one of the largest creatures on Earth, as they are now, they came from creatures that were the size of an average dog.
Paleontologists have discovered skeletons of these early creatures in India and Pakistan, but this new find, as discussed in Thursday’s edition of the journal Current Biology, was found in the Pisco Basin on the southern coast of Peru.
The 2011 find by Mario Urbina and his international team contained several surprises.
“As this is the first four-legged whale skeleton for South America and the whole Pacific Ocean, the discovery in itself was a major surprise,” study co-author Olivier Lambert wrote in an email. Lambert works at the Royal Belgian Institute of Natural Sciences. “We were also surprised with the geological age of the find (42.6 million years ago) and with the preservation state [of] so many bones from most parts of the skeleton, even including a patella (kneecap), some small ankle bones, and the last phalanges with marks of tiny hooves.”
This is the oldest known whale found in this part of the world, and it is the most complete skeleton anyone has ever found outside India and Pakistan. This particular creature would have been up to 4 meters long, or 11 feet, tail included.
The team that found it named it Peregocetus pacificus. It means “the traveling whale that reached the Pacific.”
Scientists had known that the whales’ body shape had changed over the years, making the creatures better adapted to life in the water; however, they didn’t know how the creature had moved from South Asia to South America. Early whale ancestors were not fully aerodynamic like whales are today.
“Four-legged whales, the ancestors of nowadays whales and dolphins, have been previously found in three main regions: the geologically oldest come from India/Pakistan, somewhat younger taxa [the plural of taxonomy] were described from North and West Africa, and even younger ones from the east side of North America,” Lambert said. “Based on the available evidence, and on the fact that the postcranial skeleton is poorly known in species from both Africa and North America, several questions remained debated: When did quadrupedal whales reach the New World? Which path did they take? And what [were their] locomotion abilities during that long travel?”
This 2011 discovery confirmed that the animals were probably good swimmers and good at getting around on land.
Unfortunately, scientists did not find the last part of the tail section of this creature, but the first vertebra connecting this section of the bones was similar to what modern-day beavers and otters have.
This figure shows the bones of Peregocetus, including the mandible with teeth, scapula, vertebrae, sternum elements, pelvis, and fore- and hind limbs.

The ancient whales also had long toes that were most likely webbed, meaning they moved a lot like today’s otters. That’s probably how they crossed the Atlantic Ocean, researchers said. Today, a giant otter-type creature would have to swim a long way to migrate, but at that time in the Earth’s history, the distance between Africa and South America was two times shorter and the currents were strong.
From South America, they probably migrated to North America, as well. They probably didn’t become fully marine animals until about 12 million years after this creature roamed the Earth, scientists think.
There are many intermediary stages of this “spectacular evolutionary history” that have been found over the years, “but we still miss elements, so we should keep searching in other parts of the world, especially in the Southern Hemisphere, for skeletons of these strange four-legged whales, to make the whole scenario better understood,” Lambert said.
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Scientists will continue to dig in this area in Peru. They hope to find bones that may be even older so that they can fill in more pieces of this puzzle about how the whale evolved over time.
“A skull would be great, as well as the tip of the tail,” Lambert said.

How Beauty Is Making Scientists Rethink Evolution

The extravagant splendor of the animal kingdom can’t be explained by natural selection alone — so how did it come to be?

A male Indian peafowl.CreditCreditKenji Aoki for The New York Times

By Ferris Jabr

Amale flame bowerbird is a creature of incandescent beauty. The hue of his plumage transitions seamlessly from molten red to sunshine yellow. But that radiance is not enough to attract a mate. When males of most bowerbird species are ready to begin courting, they set about building the structure for which they are named: an assemblage of twigs shaped into a spire, corridor or hut. They decorate their bowers with scores of colorful objects, like flowers, berries, snail shells or, if they are near an urban area, bottle caps and plastic cutlery. Some bowerbirds even arrange the items in their collection from smallest to largest, forming a walkway that makes themselves and their trinkets all the more striking to a female — an optical illusion known as forced perspective that humans did not perfect until the 15th century.

Yet even this remarkable exhibition is not sufficient to satisfy a female flame bowerbird. Should a female show initial interest, the male must react immediately. Staring at the female, his pupils swelling and shrinking like a heartbeat, he begins a dance best described as psychotically sultry. He bobs, flutters, puffs his chest. He crouches low and rises slowly, brandishing one wing in front of his head like a magician’s cape. Suddenly his whole body convulses like a windup alarm clock. If the female approves, she will copulate with him for two or three seconds. They will never meet again.

The bowerbird defies traditional assumptions about animal behavior. Here is a creature that spends hours meticulously curating a cabinet of wonder, grouping his treasures by color and likeness. Here is a creature that single-beakedly builds something far more sophisticated than many celebrated examples of animal toolmaking; the stripped twigs that chimpanzees use to fish termites from their mounds pale in comparison. The bowerbird’s bower, as at least one scientist has argued, is nothing less than art. When you consider every element of his courtship — the costumes, dance and sculpture — it evokes a concept beloved by the German composer Richard Wagner: Gesamtkunstwerk, a total work of art, one that blends many different forms and stimulates all the senses.

This extravagance is also an affront to the rules of natural selection. Adaptations are meant to be useful — that’s the whole point — and the most successful creatures should be the ones best adapted to their particular environments. So what is the evolutionary justification for the bowerbird’s ostentatious display? Not only do the bowerbird’s colorful feathers and elaborate constructions lack obvious value outside courtship, but they also hinder his survival and general well-being, draining precious calories and making him much more noticeable to predators.

A male plum-throated cotinga.CreditKenji Aoki for The New York Times
Image
A male plum-throated cotinga.CreditKenji Aoki for The New York Times

Numerous species have conspicuous, metabolically costly and physically burdensome sexual ornaments, as biologists call them. Think of the bright elastic throats of anole lizards, the Fabergé abdomens of peacock spiders and the curling, iridescent, ludicrously long feathers of birds-of-paradise. To reconcile such splendor with a utilitarian view of evolution, biologists have favored the idea that beauty in the animal kingdom is not mere decoration — it’s a code. According to this theory, ornaments evolved as indicators of a potential mate’s advantageous qualities: its overall health, intelligence and survival skills, plus the fact that it will pass down the genes underlying these traits to its children. A bowerbird with especially bright plumage might have a robust immune system, for example, while one that finds rare and distinctive trinkets might be a superb forager. Beauty, therefore, would not confound natural selection — it would be very much a part of it.

Charles Darwin himself disagreed with this theory. Although he co-discovered natural selection and devoted much of his life to demonstrating its importance, he never claimed that it could explain everything. Ornaments, Darwin proposed, evolved through a separate process he called sexual selection: Females choose the most appealing males “according to their standard of beauty” and, as a result, males evolve toward that standard, despite the costs. Darwin did not think it was necessary to link aesthetics and survival. Animals, he believed, could appreciate beauty for its own sake. Many of Darwin’s peers and successors ridiculed his proposal. To them, the idea that animals had such cognitive sophistication — and that the preferences of “capricious” females could shape entire species — was nonsense. Although never completely forgotten, Darwin’s theory of beauty was largely abandoned.

Now, nearly 150 years later, a new generation of biologists is reviving Darwin’s neglected brainchild. Beauty, they say, does not have to be a proxy for health or advantageous genes. Sometimes beauty is the glorious but meaningless flowering of arbitrary preference. Animals simply find certain features — a blush of red, a feathered flourish — to be appealing. And that innate sense of beauty itself can become an engine of evolution, pushing animals toward aesthetic extremes. In other cases, certain environmental or physiological constraints steer an animal toward an aesthetic preference that has nothing to do with survival whatsoever.

These biologists are not only rewriting the standard explanation for how beauty evolves; they are also changing the way we think about evolution itself. For decades, natural selection — the fact that creatures with the most advantageous traits have the best chance of surviving and multiplying — has been considered the unequivocal centerpiece of evolutionary theory. But these biologists believe that there are other forces at work, modes of evolution that are much more mischievous and discursive than natural selection. It’s not enough to consider how an animal’s habitat and lifestyle determine the size and keenness of its eyes or the number and complexity of its neural circuits; we must also question how an animal’s eyes and brain shape its perceptions of reality and how its unique way of experiencing the world can, over time, profoundly alter both its physical form and its behavior. There are really two environments governing the evolution of sentient creatures: an external one, which they inhabit, and an internal one, which they construct. To solve the enigma of beauty, to fully understand evolution, we must uncover the hidden links between those two worlds.

A male lesser bird-of-paradise.CreditKenji Aoki for The New York Times
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A male lesser bird-of-paradise.CreditKenji Aoki for The New York Times

Perhaps no living scientist is as enthusiastic — or doctrinaire — a champion of Darwinian sexual selection as Richard Prum, an evolutionary ornithologist at Yale University. In May 2017, he published a book, “The Evolution of Beauty,” that lucidly and passionately explains his personal theory of aesthetic evolution. It was nominated for the Pulitzer Prize for general nonfiction, but within the scientific community, Prum’s ideas have not been as warmly received. Again and again, he told me, he has asked other researchers for feedback and received either excuses of busyness or no reply at all. Some have been openly critical. In an academic review of Prum’s book, Gerald Borgia, one of the world’s foremost experts on bowerbirds, and the ethologist Gregory Ball described the historical sections as “revisionist” and said Prum failed to advance a credible case for his thesis. Once, over a lunch of burritos, Prum explained his theory to a visiting colleague, who pronounced it “nihilism.”

Last April, Prum and I drove 20 miles east of New Haven to Hammonasset Beach State Park, a 900-acre patchwork of shoreline, marsh, woodland and meadow on Long Island Sound, with the hope of finding a hooded warbler. Birders had recently seen the small but striking migratory species in the area. Before he even parked, Prum was calling out the names of birds he glimpsed or heard through the car window: osprey, purple martin, red-winged blackbird. I asked him how he was able to recognize birds so quickly and, sometimes, at such a great distance. He said it was just as effortless as recognizing a portrait of Abraham Lincoln. In Prum’s mind, every bird is famous.

Binoculars in hand, we walked along the park’s winding trails, slowly making our way toward a large stand of trees. Prum wore jeans, a quilted jacket and a beige hat. His thick eyebrows, round spectacles and sprays of white and gray hair give his face a vaguely owlish appearance. In the course of the day, we would see grazing mallards with emerald heads, tree swallows with iridescent turquoise capes and several sparrow species, each distinguished by a unique ornament: swoops of yellow around the eye, a delicate pink beak, a copper crown. On a wooded path, we encountered a lively bird flinging leaf litter into the air. Prum was immediately transfixed. This was a brown thrasher, he told me, describing its attributes with a mix of precision and fondness — “rufous brown, speckled on the breast, yellow eye, curved beak, long tail.” Then he reprimanded me for trying to take a picture instead of observing with my “binos.”

About two hours into our walk, Prum, who is a fast and fluid talker, interrupted himself midsentence: “Right there! Right there!” he said. “There’s the hooded! Right up against the tree!” Something gold flashed across the path. I raised my binoculars to my eyes and scanned the branches to our right. When I found him, I gasped. He was almost mythological in his beauty: moss-green wings, a luminescent yellow body and face and a perfectly tailored black hood that made his countenance even brighter by contrast. For several minutes we stood and watched the bird as it hopped about, occasionally fanning white tail feathers in our direction. Eventually he flew off. I told Prum how thrilling it was to see such a creature up close. “That’s it,” Prum said. “That moment is what bird-watching is about.”

As a child growing up in a small rural town in southern Vermont, Prum was, in his words, “amorphously nerdy” — keen on reading and memorizing stats from “The Guinness Book of World Records” but not obsessed with anything in particular. Then, in fourth grade, he got glasses. The world came into focus. He chanced upon a field guide to birds in a bookstore, which encouraged him to get outdoors. Soon he was birding in the ample fields and woods around his home. He wore the grooves off two records of bird calls. He befriended local naturalists, routinely going on outings with a group of mostly middle-aged women (conveniently, they had driver’s licenses). By the time Prum was in seventh grade, he was leading bird walks at the local state park.

In college, Prum wasted no time in availing himself of Harvard University’s substantial ornithological resources. The first week of his freshman year, he got a set of keys to the Museum of Comparative Zoology, home to the largest university-based ornithological collection in the world, which today has nearly 400,000 bird specimens. “I’ve been associated with a world-class collection of birds every moment of my adult life,” he says. “I joke with my students — and it’s really true — I have to have at least 100,000 dead birds across the hallway to function intellectually.” (He is now the head curator of vertebrate zoology at Yale’s Peabody Museum of Natural History.) He wrote a senior thesis on the phylogeny and biogeography of toucans and barbets, working on a desk beneath the skeleton of a moa, an extinct emu-like bird that stood 12 feet tall and weighed 500 pounds.

After graduating from Harvard in 1982, Prum traveled to Suriname to study manakins, a family of intensely colored birds that compete for mates with high-pitched songs and gymnastic dance routines. In 1984, he began graduate studies in biology at the University of Michigan, Ann Arbor, where he planned to reconstruct the evolutionary history of manakins through careful comparisons of anatomy and behavior. In the process, a colleague introduced him to some research papers on sexual selection, piquing his interest in the history of this fascinating yet seemingly neglected idea.

Yellow plumes from a male lesser bird-of-paradise.CreditKenji Aoki for The New York Times
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Yellow plumes from a male lesser bird-of-paradise.CreditKenji Aoki for The New York Times

Darwin was contemplating how animals perceived one another’s beauty as early as his 30s: “How does Hen determine which most beautiful cock, which best singer?” he scribbled in a note to himself sometime between 1838 and 1840. In “The Descent of Man,” published in 1871, he devoted hundreds of pages to sexual selection, which he thought could explain two of the animal kingdom’s most conspicuous and puzzling features: weaponry and adornment. Sometimes, males competing fiercely for females would enter a sort of evolutionary arms race, developing ever greater weapons — tusks, horns, antlers — as the best-endowed males of each successive generation reproduced at the expense of their weaker peers. In parallel, among species whose females choose the most attractive males based on their subjective tastes, males would evolve outlandish sexual ornaments. (It’s now well known that all sexes exert numerous different evolutionary pressures on one another and that in some species males choose ornamented females, but to this day, many of the best-studied examples are of female preference and male display.)

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Unlike natural selection, which preserved traits that were useful “in the struggle for life,” Darwin saw sexual selection as exclusively concerned with reproductive success, often resulting in features that jeopardized an animal’s well-being. The peacock’s many-eyed aureole, mesmerizing yet cumbersome, was a prime example and remains the mascot of sexual selection today. “A great number of male animals,” Darwin wrote, “as all our most gorgeous birds, some fishes, reptiles and mammals, and a host of magnificently colored butterflies have been rendered beautiful for beauty’s sake.”

Darwin’s peers embraced the idea of well-armed males dueling for sexual dominance, but many scorned the concept of animal aesthetics, in part because it was grounded in animal consciousness and female desire. In one critique, the English biologist St. George Mivart stressed “the fundamental difference which exists between the mental powers of man and brutes” and the inability of “vicious feminine caprice” to create enduring colors and patterns. The English naturalist Alfred Russel Wallace, who independently formed many of the same ideas about evolution as Darwin, was also deeply critical. Wallace was particularly tormented by Darwin’s suggestion of beauty without utility. “The only way in which we can account for the observed facts is by the supposition that color and ornament are strictly correlated with health, vigor and general fitness to survive,” Wallace wrote. In other words, ornamentation could be explained only as a heuristic that animals use to judge a potential mate’s fitness — a view that came to dominate.

In the early 1980s, while researching the history of sexual selection, Prum read a seminal 1915 paper and a 1930 book on the subject by the English biologist and statistician Ronald Fisher, who buttressed Darwin’s original idea with a more sophisticated understanding of heredity. At first, Fisher argued, females might evolve preferences for certain valueless traits, like bright plumage, that just happened to correspond with health and vigor. Their children would tend to inherit the genes underlying both their mother’s preference and their father’s trait. Over time, this genetic correlation would reach a tipping point, creating a runaway cycle that would greatly exaggerate both preference and trait, glorifying beauty at the expense of the male’s survival. In the early 1980s, the American evolutionary biologists Russell Lande and Mark Kirkpatrick gave Fisher’s theory a formal mathematical girding, demonstrating quantitatively that runaway sexual selection could happen in nature and that the ornaments involved could be completely arbitrary, conveying no useful information whatsoever.

Although Fisherian selection was certainly not ignored, it was ultimately overshadowed by a series of hypotheses that seemed to rescue beauty from purposelessness. First, the Israeli biologist Amotz Zahavi proposed a counterintuitive idea called the handicap principle, which put a new spin on Wallace’s utilitarian explanation for sexual ornaments. Extravagant ornaments, Zahavi argued, were not merely indicators of advantageous traits as Wallace had said — they were a kind of test. If an animal thrived despite the burden of an unwieldy or metabolically expensive ornament, then that animal had effectively demonstrated its vigor and proved itself worthy of a mate. Similarly, in 1982, the evolutionary biologists W.D. Hamilton and Marlene Zuk proposed that some ornaments, in particular bright plumage, signaled that a male was resilient against parasites and would grant his children the same protection. Many scientists began to think of sexual selection as a type of natural selection. Scores of researchers joined the hunt for measurable benefits of choosing an attractive mate: both direct benefits, like better parenting or more desirable territory, and indirect benefits, namely some evidence that more alluring males really did have “good genes” underlying various desirable qualities, like disease resistance or higher-than-average intelligence.

A male Guianan cock-of-the-rock.CreditKenji Aoki for The New York Times
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A male Guianan cock-of-the-rock.CreditKenji Aoki for The New York Times

After more than 30 years of searching, most biologists agree that although these benefits exist, their prevalence and importance is uncertain. A few compelling studies of frogs, fish and birds have shown that females who choose more attractive males typically have children with more robust immune systems and a greater chance of survival. On the whole, however, the evidence has not equaled the enthusiasm. A 2012 meta-analysis of 90 studies on 55 species found only “equivocal” support for the good-genes hypothesis.

Prum thinks the evidence for the heritable benefits of choosing a beautiful mate is scant because such benefits are themselves rare, whereas arbitrary beauty is “nearly ubiquitous.” Over the years, the more he contemplated runaway selection, the more convinced he became that it was a far more powerful and creative evolutionary force than natural selection, which he regards as overhyped and boring. “Animals are agents in their own evolution,” he told me during one conversation. “Birds are beautiful because they are beautiful to themselves.”

In the summer of 1985, around the same time that biologists were rekindling their interest in sexual selection, Prum and the nature documentarian Ann Johnson (who would later choose him as her husband) traveled to Ecuador to continue studying manakins. The first morning, while hiking through a cloud forest, Prum heard odd bell-like notes, which he took to be the murmurings of parrots. Later that day, on the same trail, he heard the strange sounds again and followed them into the forest. He was astonished to find that the source was a male club-winged manakin, a small cinnamon-bodied species with a red cap and black-and-white mottled wings. The manakin was jumping around in a showy manner that suggested he was courting females. Instead of singing with his throat, he repeatedly lifted his wings behind his back and vibrated his feathers furiously against one another, producing two electronic blips followed by a shrill buzzing ring — a sound Prum transcribes as “Bip-Bip-WANNGG!”

At the time, Prum had not fully developed his evolutionary theory of beauty, but he immediately suspected that the club-winged manakin was emblematic of nature’s capacity for pushing creatures to aesthetic extremes. The bird’s singular vibrato haunted him for years. In the early 2000s, when Prum had become a professor of biology at the University of Kansas, he and his graduate student Kimberly Bostwick revealed that the demands of courtship had drastically altered the bird’s anatomy, turning it into a living violin. Male club-winged manakins had feathers with contorted shafts that rubbed against each other 100 times a second — faster than a hummingbird beats its wings. Whereas a vast majority of birds have light, hollow bones in service of flight, Bostwick has recently shown via CT scans that male club-winged manakins have solid ulnas — wing bones — which they need to withstand the intense quivering. Female manakins have inherited related anomalies as well.

Although there are no published studies of the club-winged manakin’s aeronautics, Prum says it’s obvious from observation that the birds fly awkwardly — even the females. The self-perpetuating pressure to be beautiful, Prum argues, has impeded the survival of the entire species. Because the females do not court males, there can be no possible advantage to their warped bones and feathers. “Some of the evolutionary consequences of sexual desire and choice in nature are not adaptive,” Prum writes in his recent book. “Some outcomes are truly decadent.”

In the following decade, as Prum’s hearing declined, he withdrew from field research and birding, but he still managed to make a series of groundbreaking scientific discoveries: He helped confirm that feathers evolved in dinosaurs long before the emergence of birds, and he became one of the first scientists to deduce the colors of a dinosaur’s plumage by examining pigment molecules preserved in fossilized feathers. All the while, he never stopped thinking about sexual selection. Prum formally presented his theory of aesthetic evolution in a series of scientific papers published between 1997 and 2015, proposing that all sexual ornaments and preferences should be regarded as arbitrary until proven useful.

Despite his recent Pulitzer nomination, Prum still stings from the perceived scorn of his academic peers. But after speaking with numerous researchers in the field of sexual selection, I learned that all of Prum’s peers are well aware of his work and that many already accept some of the core tenets of his argument: namely that natural and sexual selection are distinct processes and that, in at least some cases, beauty reveals nothing about an individual’s health or vigor. At the same time, nearly every researcher I spoke to said that Prum inflates the importance of arbitrary preferences and Fisherian selection to the point of eclipsing all other possibilities. In conversation, Prum’s brilliance is obvious, but he has a tendency to be dogmatic, sometimes interrupting to dismiss an argument that does not agree with his own. Although he admits that certain forms of beauty may be linked to survival advantages, he does not seem particularly interested in engaging with the considerable research on this topic. When I asked him which studies he thought offered the strongest support of “good genes” and other benefits, he paused for a while before finally responding that it was not his job to review the literature.

A male painted bunting.CreditKenji Aoki for The New York Times
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A male painted bunting.CreditKenji Aoki for The New York Times

Like Darwin, Prum is so enchanted by the outcomes of aesthetic preferences that he mostly ignores their origins. Toward the end of our bird walk at Hammonasset Beach State Park, we got to talking about club-winged manakins. I asked him about their evolutionary history. Prum thinks that long ago, an earlier version of the bird’s courtship dance incidentally produced a feathery susurration. Over time, this sound became highly attractive to females, which pressured males to evolve adaptations that made their rustling feathers louder and more noticeable, culminating in a quick-winged strumming. But why, I asked Prum, would females be attracted to those particular sounds in the first place?

To Prum, it was a question without an answer — and thus a question not worth contemplating. “Not everything,” he said, “has this explicit causal explanation.”

Prum’s indifference to the ultimate source of aesthetic taste leaves a conspicuous gap in his grand theory. Even if we were to accept that most beauty blooms from arbitrary preferences, we would still need to explain why such preferences exist at all. It’s entirely conceivable that an animal might be inherently partial to, say, a warbling mating call or bright yellow feathers, and that these predilections would have nothing to do with advantageous genes. Yet such inclinations are inarguably the product of an animal’s neurobiology, which is itself the result of a long evolutionary history that has adapted the animal’s brain and sensory organs to specific environmental conditions. In the past two decades, a cohort of biologists have dedicated themselves to studying how an animal’s “sensory bias” — its ecological niche and its particular way of experiencing the world — sculpts its appearance, behavior and desires. Like Prum, they don’t think beauty has to be adaptive. But where Prum celebrates caprice, they seek causality.

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Molly Cummings, a professor of integrative biology at the University of Texas at Austin, is a leading researcher in the field of sensory ecology. When I visited her last spring, she drove us to one of her field laboratories: a grassy clearing populated with several large concrete basins. The surface of one basin was so packed with woolly algae and pink-flowered water lilies that we could hardly see the water. Cummings began pushing some of the vegetation out of the way, forming shady recesses that permitted our gaze at the right angle. “Let me see if I can find a big, beautiful boy,” she said.

A paper-clip-size fish swam toward us. I leaned in for a closer look. His silver body was decorated with a single black dot and a stripe of iridescent blue; his lengthy tail, shaped like a knight’s blade, was streaked with yellow. “Oh, yeah, there’s a guy courting,” Cummings said. “He’s coming up to that female, trying to impress her.” The fish, a male swordtail, seemed almost manic in his effort to be noticed. He darted back and forth in front of the female, shimmying as he went, his scales reflecting whatever light managed to breach the murk.

A little while later, we drove the few miles back to her campus laboratory, where shelves of fish tanks lined several rooms and Ernst Haeckel’s resplendent illustrations of jellyfish undulated across the walls. As we toured the facilities, Cummings told me about the arc of her career. While an undergraduate at Stanford University, she spent a summer scuba diving in the giant kelp forests at Hopkins Marine Station, adjacent to the world-renowned Monterey Bay Aquarium. After college, she moved to James Cook University in Townsville, Australia, where she studied marine ecology and discovered the work of the biologists John Lythgoe and John Endler, both of whom were interested in how the type of light in an animal’s environment shaped its visual system.

Cummings thought about the fish she had observed in California and Australia. She was astounded by the dynamic beauty of surfperch in the kelp forest: the way they communicate through the color and brightness of their skin, flashing blue, silver and orange to attract mates. Equally impressive was the diversity of their aquatic habitats. Some patches of water were sparkling and clear; others were cloudy with algal muck. In Australia, sunlight bathed the many vibrant species of reef fish almost constantly, but they lived against a kaleidoscopic backdrop of coral. How did fish evolve effective and reliable sexual ornaments if the lighting and scenery in their homes were so variable?

The tips of the outer tail feathers of a male king bird-of-paradise.CreditKenji Aoki for The New York Times
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The tips of the outer tail feathers of a male king bird-of-paradise.CreditKenji Aoki for The New York Times

After earning a postgraduate degree in Australia in 1993, Cummings began a Ph.D. at the University of California, Santa Barbara. For several years, she studied various species of surfperch, repeatedly diving in the kelp forests with a Plexiglas-protected spectrometer to quantify and characterize the light in different habitats. At night, she would use powerful diving lights to stun surfperch and take them back to the lab, evading the hungry seals that routinely trailed her in hopes of making a meal of the startled fish. After hundreds of dives and careful measurements, Cummings discovered that water itself had guided the evolution of piscine beauty. A female’s preference for a blaze of silver or blue was not arbitrary; it was a consequence of the particular wavelengths of light that traveled farthest through her underwater niche. Whichever males happened to have scales that best reflected these wavelengths were more likely to catch the eye of females.

In her studies, Cummings showed that surfperch living in dim or murky waters generally preferred shiny ornaments, while surfperch inhabiting zones of mercurial brightness favored bold colors. Later, Cummings found that Mexican swordtails occupying the upper layers of rivers, where the clear water strongly polarized incoming sunlight, had ornaments that were specialized to reflect polarized light — like a stripe of iridescent blue. These findings parallel similar studies suggesting that female guppies in Trinidad prefer males with orange patches because they first evolved a taste for nutritious orange tree fruits that occasionally fell into the water. “Some people think female preferences just somehow emerge,” Cummings says, “but what has been overlooked is that in many cases, it’s a result of environmental constraints. It’s not always random.”

What a creature finds attractive depends on more than the unique qualities of its environment, however; attraction is also defined by which of those qualities cross the threshold of awareness. Consider the difference between what we see when we look at a flower and what a bumblebee sees. Like us, insects have color vision. Unlike us, insects can also perceive ultraviolet light. Many plants have evolved flower parts that absorb or reflect ultraviolet light, forming patterns like rings, bull’s-eyes and starbursts. Most creatures are oblivious to these ornaments, but to the eyes of many pollinators, they are unmistakable beacons. There is an entire dimension of floral beauty invisible to us, not because we are not exposed to ultraviolet light, but because we do not have the proper biological hardware to perceive it.

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Michael Ryan, a professor of zoology whose lab and office are just a few floors below Cummings’, has spent more than 30 years investigating how the quirks of an animal’s anatomy determine its aesthetic preferences — a career he details in his recent book, “A Taste for the Beautiful.” Since 1978, Ryan has been traveling to Panama to study a mud-colored frog called the túngara. Like the club-winged manakin, the túngara has a unique form of beauty that is not visual but aural. At dusk, male túngara frogs gather at the edges of puddles and sing to seduce females. Their mating call has two elements: The main part, dubbed the whine, sounds precisely like a miniaturized laser gun; sometimes this is followed by one or more brief barks, known as chucks. A long and complex mating call is risky: It attracts frog-eating bats. Yet there is a high payoff. Ryan has shown that whines followed by chucks are up to five times as appealing to females as whines alone. But why?

According to the adaptive model of beauty, the chucks must convey something about the males’ fitness. As it happens, larger males, which produce the deepest and sexiest chucks, are also the most adept at mating, because they are closer in size to females. (Frog sex is a slippery affair, and a diminutive male is more likely to miss his target.) Moreover, the túngara frog has an inner organ tuned to 2,200 hertz, which is close to the dominant frequency of a chuck. Together, these facts seem to indicate that the túngara’s puddle-side serenade is an example of adaptive mate choice: Females evolved ears tuned to chucks because they indicate the biggest and most sexually skilled males.

Ryan’s research revealed a stranger story. When he examined the túngara frog’s family tree, he discovered that eight frog species closely related to the túngara also have inner ear organs sensitive to frequencies of about 2,200 hertz, yet none of them produce chucks in their mating call. Ryan thinks that eons ago, the ancestor of all these species probably evolved an inner ear tuned to roughly 2,200 hertz for some long-abandoned purpose. The túngara later revived this neglected auditory channel, probably by happenstance. Male frogs that happened to burp out a few extra notes after whining were automatically favored by females — not because they were more suitable mates, but simply because they were more noticeable.

Like the glistening scales on the surfperch and swordtails that Cummings studied, the túngara’s costly mating call did not evolve to convey any pragmatic information about health or fitness. But that doesn’t mean that these traits were arbitrary. They were the result of specific, discernible aspects of the animals’ environments, anatomy and evolutionary legacy. “I took a real beating when I suggested this idea in 1990,” Ryan says. “It was very widely criticized. But now sensory bias is considered an important part of the evolution of these preferences.”

During our walk at Hammonasset, while admiring seabirds from shore-side cliffs, I asked Prum about sensory bias. He said it could not possibly explain the staggering diversity and idiosyncrasy of sexual ornaments — the fact that every closely related sparrow species has a unique embellishment, for example. Prum sees sensory bias as just another way to maintain the predominant “adaptive paradigm” that refuses to acknowledge his theory of aesthetic evolution. Tellingly, Prum and Ryan do not discuss each other’s work in their recent books.

A male king bird-of-paradise.CreditKenji Aoki for The New York Times
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A male king bird-of-paradise.CreditKenji Aoki for The New York Times

While mulling over the similarities and discrepancies between Prum’s ideas and those of his peers, I kept returning to a passage in his book. In 2010, Prum and his colleagues revealed that a crow-size dinosaur called Anchiornis huxleyi was beautifully adorned: gray body plumage, an auburn mohawk and long white limb feathers with black spangles. Why dinosaurs originally evolved feathers has long perplexed scientists. At first, layers of fuzzy filaments, similar to a chick’s down, most likely helped dinosaurs repel water and regulate body temperature. But what explains the development of broad, flat feathers like those found on Anchiornis? Flight is the intuitive answer, but the first planar feathers were probably too primitive for flight or gliding, lacking the distinct asymmetry that makes birds’ feathers aerodynamic. In his book, Prum advocates for an alternative hypothesis that has been gaining support: Large feathers evolved to be beautiful.

The aesthetic possibilities of fuzzy down are limited. “The innovative planar feather vane, however, creates a well-defined, two-dimensional surface on which it is possible to create a whole new world of complex color patterns within every feather,” Prum writes. Only later did birds co-opt their big, glamorous plumes for flight, which is probably a key reason that some of them survived mass extinction 66 million years ago. Birds transformed what was once mere frippery into some of the most enviable adaptations on the planet, from the ocean-spanning breadth of an albatross to the torpedoed silhouette of a plunging falcon. Yet they never abandoned their sense of style, using feathers as a medium for peerless pageantry. A feather, then, cannot be labeled the sole product of either natural or sexual selection. A feather, with its reciprocal structure, embodies the confluence of two powerful and equally important evolutionary forces: utility and beauty.

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Most of the scientists I spoke with said that the old dichotomy between adaptive adornment and arbitrary beauty, between “good genes” and Fisherian selection, is being replaced with a modern conceptual synthesis that emphasizes multiplicity. “Beauty is something that arises from a host of different mechanisms,” says Gil Rosenthal, an evolutionary biologist at Texas A&M University and the author of the new scholarly tome “Mate Choice.” “It’s an incredibly multilayered process.”

The environment constrains a creature’s anatomy, which determines how it experiences the world, which generates adaptive and arbitrary preferences, which loop back to alter its biology, sometimes in maladaptive ways. Beauty reveals that evolution is neither an iterative chiseling of living organisms by a domineering landscape nor a frenzied collision of chance events. Rather, evolution is an intricate clockwork of physics, biology and perception in which every moving part influences another in both subtle and profound ways. Its gears are so innumerable and dynamic — so susceptible to serendipity and mishap — that even a single outcome of its ceaseless ticking can confound science for centuries.

On my last day in Austin, while walking through a park, I encountered a common grackle hunting for insects in the grass. His plumage appeared black as charcoal at first, but as he moved, it shimmered with all the colors of an oil slick. Every now and then, he stopped in place, inflated his chest and made a sound like a rusty swing set. Perhaps dissatisfied with the local fare, or uncomfortable with my presence, he flew off.

In his absence, my attention immediately shifted to something his presence had obscured — a golden columbine bush. From a distance, its flowers resembled medieval illustrations of comets, big and bold with long, trailing streamers. Up close, I was struck by the complexity of a single blossom: a large yellow star wreathed a cluster of five tubular petals, shaped like angel’s trumpets and pooled with nectar. A tuft of pollen-tipped filaments fizzed through the very center. Viewed from above, the flowers looked like huddles of tiny birds with their beaks pressed together and wings flared. The name “columbine” comes from the Latin for “dovelike.”

Why are flowers beautiful? Or, more precisely: Why are flowers beautiful to us? The more I thought about this question, the more it seemed to speak to the nature of beauty itself. Philosophers, scientists and writers have tried to define the essence of beauty for thousands of years. The plurality of their efforts illustrates the immense difficulty of this task. Beauty, they have said, is: harmony; goodness; a manifestation of divine perfection; a type of pleasure; that which causes love and longing; and M = O/C (where M is aesthetic value, O is order and C is complexity).

Evolutionary psychologists, eagerly applying adaptive logic to every facet of behavior and cognition, have speculated that the human perception of beauty emerges from a set of ancient adaptations: Perhaps men like women with large breasts and narrow waists because those features signal high fertility; symmetrical faces may correlate with overall health; maybe babies are irresistibly cute because their juvenile features activate the caregiving circuits in our brains. Such claims sometimes verge on the ludicrous: The philosopher Denis Dutton has argued that people around the world have an intrinsic appreciation for a certain type of landscape — a grassy field with copses of trees, water and wildlife — because it resembles the Pleistocene savannas where humans evolved. In a TED Talk, Dutton explains that postcards, calendars and paintings depicting this universally beloved landscape usually include trees that fork near the ground because our ancestors relied on their conveniently low branches to scramble away from predators.

Of course, it is undeniable that we, like all animals, are products of evolution. Our brains and sensory organs are just as biased as any other creature’s. Our inherited anatomy, physiology and instincts have undoubtedly shaped our perception of beauty. In their recent books, Richard Prum and Michael Ryan synthesize research on animals and people, exploring possible evolutionary explanations for our own aesthetic tastes. Ryan is particularly interested in the innate sensitivities and biases of our neural architecture: He describes how our visual system, for example, may be wired to notice symmetry. Prum stresses his conviction that in humans, as in birds, many types of physical beauty and sexual desire have arbitrarily co-evolved without reference to health or fertility. What complicates their respective arguments is the overwhelming power of human culture. As a species, we are so thoroughly saturated with symbolism, ritual and art — so swayed by rapidly changing fashions — that it is more or less impossible to determine just how much an aesthetic preference owes to evolutionary history as opposed to cultural influence.

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A male Mandarin duck.CreditKenji Aoki for The New York Times
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A male Mandarin duck.CreditKenji Aoki for The New York Times

Perhaps more than any other object of aesthetic obsession, flowers expose the futility of trying to contain beauty in a single theoretical framework. Consider how flowers came to be and how we grew to love them: 150 million years ago many pollen-producing plants depended on the wind to spread their pollen and reproduce. But certain insects, perhaps beetles and flies, began to eat those protein-rich pollen grains, inadvertently transporting them from one plant to another. This proved to be a much more efficient means of fertilization than capricious air currents. Plants with the richest and most obvious sources of pollen were especially successful. Likewise, insects that were particularly adept at finding pollen had an advantage over their peers.

Through a long process of co-evolution, plants and pollinators transformed one another. Some plants began to modify their leaves into proto-flowers: little flags that marked the location of their pollen. Bold colors and distinctive shapes helped them stand out in a tangle of green. Strong aromas and ultraviolet beacons played upon pollinators’ senses. Nectar sweetened the deal. Insects, birds and mammals began competing for access, evolving wings, tongues and brains better suited to the quest for floral sustenance. As the pressure from both parties intensified, plants and their pollinators formed increasingly specific relationships, hurtling each other toward aesthetic and adaptive extremes — a bird that hums and hovers like an insect, an orchid that mimics the appearance and scent of a female bee.

Many millions of years later, flowers enchanted yet another species. Perhaps the initial attraction was purely utilitarian: the promise of fruit or grain. Maybe we were captivated by their consonance of color, form and aroma. Whatever the case, we adopted numerous flowering plants into an expanding circle of domesticated species. We brought them into greenhouses and laboratories, magnifying their inherent beauty, creating new hybrids and tailoring their features to our individual tastes. We contracted orchid delirium and tulip mania, and we have never fully recovered. The flower began as a plea and became a phenomenon.

If there is a universal truth about beauty — some concise and elegant concept that encompasses every variety of charm and grace in existence — we do not yet understand enough about nature to articulate it. What we call beauty is not simply one thing or another, neither wholly purposeful nor entirely random, neither merely a property nor a feeling. Beauty is a dialogue between perceiver and perceived. Beauty is the world’s answer to the audacity of a flower. It is the way a bee spills across the lip of a yawning buttercup; it is the care with which a satin bowerbird selects a hibiscus bloom; it is the impulse to recreate water lilies with oil and canvas; it is the need to place roses on a grave.

New Research Suggests Octopuses Have Extraterrestrial Origins

Octopuses are known to be intelligent, advanced creatures, able to create their own shelter, change color in an instant and even adapt well to climate change.

In a new study, a group of 33 international scientists suggest these unique traits may have an unearthly origin. They investigated the theory that octopuses may have evolved from life forms that came to earth on ancient comets.

This isn’t a new concept. Scientists have been grappling with the origins of life on our planet for centuries. And this study adds an intriguing look into the theory of panspermia, that suggests the evolution of life on Earth has, and continues to be, influenced by the arrival of organisms from space.

The study has faced some criticism, but the scientists have also supported their claims with well-established research. Let’s take a closer look at their findings.

THE THEORY OF PANSPERMIA

In the 1980s, astronomer Fred Hoyle teamed up with astrobiologist Chandra Wickramasinghe to propose that life didn’t originate on earth. In fact, life was seeded on our planet by comets carrying space-hardy bacteria, viruses and perhaps even fertilized eggs and plant seeds. This concept is scientifically known as “panspermia”.

The earliest microbial life found on Earth was discovered in Canadian rocks and is estimated to be about 4.1-4.23 billion years old. This was during the Hadean epoch, when the earth was still forming its core and crust, as well as its atmosphere and oceans. Our planet had frequent and violent collisions with asteroids and comets during that period, and the surface was still extremely hot and unstable.

The study’s researchers propose that it was impossible for life to have formed on Earth during this time. The first microbes found in Canada were most likely delivered by comets and meteorites that impacted with our planet, and these microbes went on to become the basis of terrestrial life on Earth.

WHAT CAN ACTUALLY SURVIVE ON A COMET?

Comet-hopping life forms may sound far-fetched, but research is starting to show this may be a distinct reality. Evidence has found that comets would have contained vast amounts of water in their interiors when they were first formed billions of years ago at the dawn of our solar system. These protected, watery environments would have provided ideal conditions for early bacteria and viruses to grow and multiply.

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The discovery of a wide variety of ancient organic particles in comets also supports this theory. Organic particles are important precursors for the creation of molecules that are the foundation of life, such as sugars, amino acids and DNA bases.

Once comets had cooled down and after millions of years in space, evidence suggests the primitive bacteria and viruses living on them became embedded in rock, carbonaceous material or ice. This effectively protected them from the intense radiation and sub-zero temperatures encountered in space.

Although not proven, it is also possible that more complex life forms, such as fertilized eggs and plant seeds, could also have survived in similar conditions.

Masters of disguise - Mediterranean Octopus

Masters of disguise – Mediterranean Octopus

WHAT OCTOPUSES CAN TELL US ABOUT EVOLUTION

Octopuses are actually related to slugs and snails. They belong to a group of mollusks known as cephalopods that developed about 500 million years ago during what’s known as the Cambrian Explosion. This was a time when life in the earth’s oceans went through a dramatic stage of diversification and evolution, and most of the ancestors of modern life were born.

The new study, titled “Cause of the Cambrian Explosion – Terrestrial or Cosmic?”, investigated panspermia and how it may relate to the Cambrian Explosion, and the rise of life forms like octopuses. They made a few important conclusions.

1. Virus-bearing comets fueled the Cambrian Explosion.

Viruses are the smallest living organism on earth, and they reproduce by attaching themselves to a host cell in another living organism and inserting their own genetic material into the cell. This changes the genetic structure of the host cells, which can cause disease in the host.

This also means that a viral infection can alter the host’s genetic code, and potentially change its course of evolution. Retroviruses are a specific type of virus that first appeared and multiplied just before the Cambrian Explosion.

And the researchers believe these retroviruses came from cometary bombardment the Earth was experiencing around the same time. As the comets broke up and left debris trails in the Earth’s atmosphere, dormant retroviruses were released and spread across our planet’s surface.

This wide-spread introduction of new genetic material in the form of viruses affected the development of life in our planet’s oceans, and potentially all land-dwelling life forms that came later.

2. Octopuses appeared too abruptly to have evolved on Earth.

The introduction of interstellar viruses may have increased the genetic diversity of life on our planet, but octopuses have some unique genetic traits that simply don’t make sense from an evolutionary stand point.

Genetically, octopuses are significantly different than most other life forms on Earth. Their large brains, sophisticated nervous systems, flexible bodies and ability to instantly switch color and shape are still very unique compared to other modern life forms.

And these striking traits appeared very suddenly on the evolutionary scene about 270 million years ago. The research group concluded that this sudden “great leap forward” would be impossible in such a short time frame.

“Thus the possibility that cryopreserved squid and/or octopus eggs, arrived in icy bolides several hundred million years ago should not be discounted,” the researchers say.

HOW DOES THIS RELATE TO LIFE ON EARTH TODAY?

We may never know whether or not octopus eggs actually arrived on Earth from outer space, but the theory of panspermia does hold the potential for a radical shift in our world view.

The research group concluded their study by discussing the need to change from our outdated view of life originating exclusively on Earth to one incorporating “cosmic biology,” which recognizes the scientific evidence that life on our planet may have been, and continues to be, influenced by organisms that arrive from outer space.

They also point out the vast number of Earth-like planets and other life-friendly planetary bodies that exist in our galaxy, and the potential for billions of exchanges of material between them through meteorites, cometary bolides and even space dust.

“One is thus forced in our view to conclude that the entire galaxy (and perhaps our local group of galaxies) constitutes a single connected biosphere,” the researchers write.

What do you think? Is Earth part of an intergalactic web of life? Or are we alone in the universe? Please share your thoughts in the comments!

Related on Care2

A Convenient Rationalization

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Here’s part of a comment I received from a hunter the other day: “I love animals, but fully understand that all living things have their place in God’s plan and on His Earth. He gave us domain over animals. Read Genisis [sic] and wake up!”

How convenient. But do people really still believe that kind of crap?

Sadly, the answer appears to be yes.

A staggering 46% of Americans believe that god created humans in their present form within the past 10,000 years, according to a USA Today/Gallup survey conducted this year from May 10th to the 13th. Not only has that number not changed much in the past 30 years since Gallup first asked the question on Creationism vs Evolution, it’s actually gone up 2%, from 44% in 1982 to 46% in 2012!

Gallup’s Frank Newport told CNN, “Despite the many changes that have taken place in American society and culture over the past 30 years, including new discoveries in biological and social science, there has been virtually no sustained change in Americans’ views of the origins of the human species since 1982. All in all, there’s no evidence in this trend of a substantial movement toward a secular viewpoint on human origins.”

So, why do I care what people believe? Why won’t I just let them have their fun?

Because such dogma can directly affect how non-humans are treated.

The literal belief that humans have some kind of god-given authority over every other species of animal bestows undeserved power into unreliable hands. Creationist claptrap that favors one species over another perpetuates speciesist doctrine devised to demean and control our fellow animals in the same way that notions of racial superiority were used against our fellow humans.

The second most common view of those polled—held by 32% of respondents–is that humans evolved with god’s guidance. Again, a very convenient conviction that can be used to put humans on top.

Newport goes on to say, “It would be hard to dispute that most scientists who study humans agree that the species evolved over millions of years, and that relatively few scientists believe that humans began in their current form only 10,000 years ago without the benefit of evolution. Thus, almost half of Americans hold a belief [in creationism] that is at odds with the preponderance of scientific literature.”

To their benefit, and to the detriment of every other living thing on the planet, I might add.

Wildlife Photography Copyright Jim Robertson

Has humankind driven Earth into a new epoch?

 

https://www.knowablemagazine.org/article/sustainability/2018/has-humankind-driven-earth-new-epoch?utm_source=TrendMD&utm_medium=earned&utm_campaign=TrendMD_Credit

Our mark on Earth is so profound that some argue it’s time to bid goodbye to the current geological time period — the Holocene — in favor of a new one: the Anthropocene.

In the thousands of years that modern humans have trod the Earth, we have wreaked stunning changes on the planet — the rising CO2 levels fueling climate change, novel and long-lived radioactive particles from nuclear activity, depleted water resources, toxic waste buildup, desertification and more. To reflect our impact on the globe, some geoscientists and biologists have advanced the concept that we are living in a new geological time period: the Anthropocene, or the epoch of humankind.

The current geological epoch, the Holocene, began 11,700 years ago, after the last major ice age. But in the last 15 years, geologists and other Earth scientists have debated whether we have left enough of a mark on the world that it makes sense to bid the Holocene goodbye.

One proponent of the Anthropocene concept is Yadvinder Malhi of the University of Oxford in England, whose research on tropical forests has revealed the cascading ecological consequences of human-caused pressures such as logging, fires, invasive species and climate change. He reviewed the history of the Anthropocene idea, and debates that surround it, in “The Concept of the Anthropocene” in the Annual Review Environment and Resources.

This conversation has been edited for length and clarity.

What’s your definition of the Anthropocene?

It’s a term for a new geological epoch that signifies an age where the planet is dominated by human influence. But others wouldn’t agree. They say any significant modification of the environment would count — it doesn’t have to be complete domination.

And so one big debate is whether the Anthropocene is recent, say, starting in the mid-twentieth century, or whether it’s been going on for centuries or even millennia. The debate pivots on whether it’s a continuation of a process where humans have been altering the environment since we started using fire, or with early farming, or whether something dramatic has happened more recently where we started dominating and rupturing the environment in fundamental ways. Something so significant that it’s altering geological records.

For example, the spread of wet rice farming in Asia thousands of years ago may have increased global concentrations of methane, and this may have delayed the onset of the next ice age. Others argue that the extinction of megafauna, like mammoths, in which human hunters probably played a role, may have caused reflective and snow-covered high-elevation grasslands to be replaced by dark, heat-absorbing forests, leading to local warming. These would suggest human alteration of planetary processes, but not the domination of them that we’re seeing today.

What more recent changes would you point to that argue for a distinct Anthropocene epoch now?

The underlying issue is that human activity is so large because there’s so many humans and because of how active they are in consumption and waste production. We’re over-harvesting fisheries and the ocean, and we’re converting large parts of land from natural ecosystems to croplands or pasturelands. Part of it comes from our waste products. Climate change comes under that, through excess CO2 in the atmosphere, swamping the natural capacity of the carbon cycle to absorb it.

Excess plastics in the ocean are starting to alter food chains of ocean ecosystems, and excess nitrogen in our fertilizers is causing dead zones in lakes and estuaries.

Humans have always affected local environments, depleting resources or putting too much waste into it. There’s little evidence that early civilizations were more sustainable than contemporary ones; they just worked on a smaller scale. The challenge now is that we’re a global, interconnected civilization, so our activities are starting to alter planetary functioning.

Are there geological arguments against formally designating our current period as the Anthropocene?

Some geologists question whether geological time scales are the best forum for what is essentially a political framing or advocacy term. It’s also a challenge that a mid-twentieth-century start date is so recent that a clear stratigraphic signal is hard to distinguish.

The Anthropocene Working Group, a collaboration of mostly scientists, recommended in August 2016 to the International Commission on Stratigraphy, the authorities who decide on geological time periods, that Anthropocene should be a formal epoch, and they suggested traces in rocks and sediments to mark it — things like radioactivity and plastics. What’s the status of this?

The working group has converged on a starting date of the Anthropocene in the mid-twentieth century, often termed the “great acceleration,” and the group is spending the next few years building up a strong stratigraphic case for this. If you look at concentrations of atmospheric CO2, the amount of tropical deforestation, numbers of rivers dammed, the amount of fish harvested, as well as the total human consumption of food and raw materials, they all show an increase over time but an uptick in the mid-twentieth century.

Would you say the Anthropocene concept has been more useful for scientists or in a public, cultural sense, drawing attention to the impact we’re having on the planet?

I think both. The Anthropocene provided for the sciences a unifying framework that didn’t exist before, drawing together multiple fields to describe the processes changing the Antarctic, tropical forests, the climate, biodiversity, and the ozone layer.

Culturally, it’s even more useful than framing issues just around climate change because it brings in the underlying issue: the metabolic signs of humanity. Our activities, relative to the size of the planet, have become so large that they’ve changed the way we think about ourselves and our history and future. That’s got a huge cultural and political resonance. It’s the zeitgeist, it’s hit a raw nerve of something people felt was there, but needed a way to describe it.

The Anthropocene framing recognizes the world is finite. A century ago, when London and the river Thames were polluted, it led to the realization that the river isn’t infinite, you can’t just dump waste and forget about it. It comes back to bite you. With climate change, if you keep pouring waste into the atmosphere, at some point it feeds back.

This is a way to think about the world around you in a really fundamental way. That’s where you can start imagining different futures. It leads to challenges like, how can an economic model built on perpetual growth fit within a finite planet?

When you’re thinking of global problems, like climate change or species extinctions, which ones could cause the most damage?

It depends on what you think is a threat. For human civilization, I’d say it’s climate change. If we pass some threshold, like if we see Antarctic ice sheets melting and other irreversible tipping points, that would have a huge negative impact on much of humanity.

For the biosphere, the acidification of oceans could prove critical. On land, it’s the loss of large areas of forests, especially tropical forests.

Have you thought about global solutions, whether it be changing consumption patterns in industrial countries, or things like geoengineering to tackle climate change?

There’s a whole gamut of solutions. For me, an ideal mix includes changes in the fundamental economic model, the mass consumption society, coupled with behavioral change at the societal level, along with redesigning our energy systems — with renewables replacing the fossil-fuel economy. Technology plays a role, but also rethinking our priorities as a society.

I’m cautious about geoengineering. It may be necessary at some stage, but it presumes we know more about Earth’s systems than we do. It carries a bit of hubris around it. We could inadvertently do more damage, rather than reverse it.

Are there sociological or moral criticisms you’ve come across of the concept of the Anthropocene?

Some argue that the Anthropocene is a broader environmental concept that concerns us all, rather than just a geological one. It’s about how we think about our relationship with the natural world, how we manage living on a human-dominated planet.

There are criticisms within the social sciences. Political scientists ask, what is this “anthropos”? It creates a sense of all of humanity in this together as a force altering nature, and the term’s ignoring that only a subset of humanity caused the Anthropocene. People outside the West and industrialized Asia played little role in creating it. It diffuses responsibility away from the core that’s responsible.

Others argue that it creates a sense of inevitability, like this geological age was going to come to pass, ignoring that perhaps political or economic decisions, such as the creation of the capitalist world system, lie behind this, by creating a resource-intensive exploitation of the world.

What are the next steps for research on the Anthropocene?

The really interesting questions are not how we define the Anthropocene, but how do we navigate it?

I’ve been reading work on “doughnut economics” by Kate Raworth, who describes herself as a “renegade economist.” She thinks about how we can reach this goal of getting enough people out of deprivation — the hole of the doughnut is the inner circle of deprivation — while staying within the outer ring. It’s this challenge of reconciling human improvement and welfare while maintaining the environmental stability of the planet and leaving enough space for other organisms that live on it. How do we stay in that doughnut? It’s a mixture of research and policy action.

Will the Anthropocene just continue indefinitely?

At least for some time in the future. We’re currently in the Cenozoic Era, which started with the asteroid that killed the dinosaurs. That was planet-altering. Perhaps the alterations we’re doing now, if they played out for a century, if we pushed climate change beyond tipping points so that it accelerates, then “Anthropocene” — an epoch — is too modest a designation. People argue that what’s happening now is so substantial and profound it should be something like the “Anthropogene” [a period] or the “Anthropozoic” [an era], since the scale of the change may be so large that “epoch” is too low in the geological hierarchy of time scales to be appropriate. It’s too soon to decide that.

Controversial study suggests earliest humans lived in Europe – not Africa

Controversial new research suggests that modern humans evolved from apes in the Eastern Mediterranean — not from ancestors in Africa, as long believed by the majority of scientists.

The researchers’ bold, potentially paradigm-shifting claims were published in two studies Tuesday in the journal PLOS One.

The researchers base their arguments on analysis of two Graecopithecus freybergi ape fossils, a lower jaw found in Greece and an upper premolar found in Bulgaria, dating back 7.24 and 7.175 million years, respectively.

The team argued that several dental features from these fossils — in particular, partially fused premolar roots on the lower jaw fossil— make a convincing case that the Graecopithecus freybergi is the earliest known human ancestor. Scientists have seen partially fused premolar roots in several fossils throughout the human lineage.

If the fossils mark the earliest moment of humans’ differentiation, it would significant change the human origin story. The researchers believe these fossils are several hundred thousand years older than the ancient hominin known as Sahelanthropus, a 6- to 7-million-year-old pre-human which was unearthed in Chad.

However, the study has been met with widespread skepticism from other experts in the field.

Critics say that the research is not strong enough to undercut the widespread consensus that evidence shows hominins originated in African and migrated north.

“The idea that hominins (human ancestors, defined largely by upright posture, the predominance of bipedal walking, and small canine teeth in both males and females) first emerged in Europe has little to support it,” paleoanthropologist Richard Potts, who leads the Smithsonian Institution’s human origins program, told CBS News over email. Potts was not affiliated with the study.

The researchers did little to back up the claim that a “fairly isolated place in southern Europe” could have been home to an ancestor of the African hominin, Potts said.

He criticized the researchers’ claim that the Graeco fossil’s canine root reduction clearly indicates the Graeco’s status as an early hominin, arguing the researchers did not have enough contextual evidence to draw real conclusions from the single canine root (for instance, there was no canine crown to accompany the root).

“I really appreciate having a detailed analysis of the Graecopithecus jaw – the only fossil of its genus so far.  But I think the principal claim of the main paper goes well beyond the evidence in hand,” Potts said.

Speaking to The Washington Post, anthropologist Susan C. Antón echoed Potts’ skepticism. The long line of later hominins found in Africa suggests “an African origin,” Antón, who teaches at New York University, said.

Jay Kelley, a paleontologist at Arizona State University’s Institute of Human Origins, also questioned the researchers’ conclusion that the fused premolar roots strongly indicate a connection to hominins. Fused tooth roots are not a constant feature across different hominin fossils, he told The Washington Post.

The team behind the new research included scientists from Germany, Bulgaria, Greece, Canada, France and Australia.

Darwin apparently right about the first life on Earth

May 10, 2017

Tara Djokic
Posted with permission from Newsweek

This article was originally published on The Conversation. Read the original article.

Fossil evidence of early life has been found in old hot spring deposits in the Pilbara, Western Australia, that date back almost 3.48 billion years.

This extends the known evidence of life at land-based hot springs on Earth by about three billion years.

Not only is the find exciting for what it might say about the evolution of early life on Earth, but it also has implications for the search for life on Mars.

Our understanding of these deposits would not be possible without the foundations laid by earlier researchers.

Ancient stromatolites

In the late 1970s, fossilised stromatolites—rock structures built by communities of microorganisms—were discovered within these Pilbara deposits.

These were interpreted as once living in a quiet, shallow water coastal environment much like we see in the modern setting of Shark Bay.

But extensive research over the past 20 years has led to a much better understanding of the environment that suggests it was actually part of an ancient volcano.

In modern volcanic settings, hot fluids circulate in the rocks underground and manifest as hot vents at the bottom of the salty ocean, such as the black or white smokers, or terrestrial hot springs on land where fresh rainwater is available.

What was unclear about the volcanic setting in the Pilbara was whether these hot circulating fluids were indeed discharging on land, producing hot springs—such as those we see in Rotorua, New Zealand—and could we link these hot springs to signs of life?

The smoking gun

Our recent findings from the Pilbara, published today in Nature Communications, provide a smoking gun to a terrestrial hot spring scenario in the form of a particular rock type called geyserite. This was found alongside a variety of textures that indicate life.

Geyserite only forms around the edges of terrestrial hot spring pools and geysers. These are found actively forming today in New Zealand, Yellowstone National Park and Iceland to name a few.

The biological signatures that we’ve found include stromatolites, but also some newly identified microbial textures. This includes a microbial texture (called palisade fabric) that represents microbes that grew upon the ancient sinter terraces —the rocks that form around hot spring pools.

We also found evidence of gas bubbles that must have been trapped in a sticky substance (microbial) in order to be able to preserve the bubble shape.

Importantly, all of these textures are comparable to fossil textures found in modern hot spring settings such as Yellowstone National Park or Rotorua, New Zealand.

Ancient life on land

The Earth’s geological and fossil record is like a thousand-piece puzzle, but we only have a few pieces. Every missing piece we discover helps us to better shape our understanding of life.

But these new findings don’t just extend back the record of geyserite and life living in hot springs on land by three billion years, they also indicate that life was inhabiting the land much earlier than previously thought, by up to 580 million years.

Before these findings, the world’s oldest evidence for microbial life on land was from ancient, organic matter-rich soils from South Africa, aged between 2.7 billion and 2.9 billion years.

The new discovery has implications for the evolution, and perhaps even the origin, of life on Earth.

Scientists are currently considering two hypotheses regarding the origin of life: that it began in the ocean in hot vents, or alternatively that it began on land in a version of Charles Darwin’s “warm little pond” which was connected to a hot spring system.

The discovery of biological signatures and fossil preservation in such ancient hot springs provides at least a geological perspective of the types of environments available and inhabited by life very early on in Earth’s history.

This may lend weight to the hypothesis that life originated on land and then took a downhill adaptive evolutionary pathway to the salty ocean, whereas the opposite is typically proposed.

Life on Mars

These findings have major implications regarding the search for life elsewhere in the universe, or at least our solar system. Our neighbouring planet, Mars, has long been a target in the search for extraterrestrial life.

It is widely accepted that the red planet was likely similar to Earth once upon a time, in that it had liquid water flowing on its surface and active volcanoes.

Recent data from the Spirit rover has even identified ancient hot springs, of a similar age to early Earth, in an area called Columbia Hills.

In fact Columbia Hills is one of the top three potential landing sites chosen for NASA’s upcoming Mars2020 rover that’s includes a primary objective to search for fossil life on Mars.

Our findings imply that if life ever developed on the red planet, and it is preserved in ancient hot springs on Earth, then there is a good chance it could be preserved in ancient hot springs on Mars too.

Tara Djokic is a PhD Candidate studying Earth’s earliest evidence of life at the University of New South Wales