In 2015, Stanford biologist Paul Ehrlich coauthored a study declaring the
world’s sixth mass extinction was underway. Five years later, Ehrlich and
colleagues at other institutions have a grim update: the extinction rate is
likely much higher than previously thought and is eroding nature’s ability
to provide vital services to people.
Their new paper, published this week in Proceedings of the National Academy
of Sciences, indicates the wildlife trade and other human impacts have wiped
out hundreds of species and pushed many more to the brink of extinction at
an unprecedented rate.
For perspective, scientists estimate that in the entire twentieth century,
at least 543 land vertebrate species went extinct. Ehrlich and his coauthors
estimate that nearly the same number of species are likely to go extinct in
the next two decades alone.
The trend’s cascading effects include an intensification of human health
threats, such as COVID-19, according to the researchers. “When humanity
exterminates populations and species of other creatures, it is sawing off
the limb on which it is sitting, destroying working parts of our own
life-support system,” said Ehrlich, the Bing Professor of Population
Studies, emeritus, at the Stanford School of Humanities and Sciences and a
senior fellow, emeritus, at the Stanford Woods Institute for the
Environment. “The conservation of endangered species should be elevated to a
national and global emergency for governments and institutions, equal to
climate disruption to which it is linked.”
The study comes in the wake of an April 7 letter from a bipartisan group of
senators urging the Trump administration to close markets that sell live
animals for food and unregulated wildlife markets, among other measures to
stop the trade in illegal wildlife and wildlife products.
Human pressures, such as population growth, habitat destruction, the
wildlife trade, pollution and climate change, critically threaten thousands
of species around the world. Ecosystems ranging from coral reefs and
mangrove forests to jungles and deserts depend on these species’
long-evolved relationships to maintain their functioning and make them
resilient to change. Without this robustness, ecosystems are less and less
able to preserve a stable climate, provide freshwater, pollinate crops and
protect humanity from natural disasters and disease.
To better understand the extinction crisis, the researchers looked at the
abundance and distribution of critically endangered species. They found that
515 species of terrestrial vertebrates- 1.7 percent of all the species they
analyzed- are on the brink of extinction, meaning they have fewer than 1,000
individuals remaining. About half of the species studied have fewer than 250
individuals left. Most of the highly endangered species are concentrated in
tropical and subtropical regions that are affected by human encroachment,
according to the study.
In addition to rising extinction rates, the cumulative loss of
populations-individual, localized groups of a particular species- and
geographic range has led to the extinction of more than 237,000 populations
of those 515 species since 1900, according to the researchers’ estimates.
With fewer populations, species are unable to serve their function in an
ecosystem, which can have rippling effects. For example, when overhunting of
sea otters-the main predator of kelp-eating sea urchins-led to kelp die-offs
in the 1700s, the kelp-eating sea cow went extinct.
“What we do to deal with the current extinction crisis in the next two
decades will define the fate of millions of species,” said study lead author
Gerardo Ceballos, a senior researcher at the National Autonomous University
of Mexico’s Institute of Ecology. “We are facing our final opportunity to
ensure that the many services nature provides us do not get irretrievably
The loss of endangered creatures could have a domino effect on other
species, according to the researchers. The vast majority-84 percent-of
species with populations under 5,000 live in the same areas as species with
populations under 1,000. This creates the conditions for a chain reaction in
which the extinction of one species destabilizes the ecosystem, putting
other species at higher risk of extinction.
“Extinction breeds extinction,” the study authors write. Because of this
threat, they call for all species with populations under 5,000 to be listed
as critically endangered on the International Union for Conservation of
Nature Red List, an international database used to inform conservation
action on a global scale.
These findings could aid conservation efforts by highlighting the species
and geographic regions that require the most immediate attention.
Understanding what species are at risk can also help identify what factors
might be most responsible for rising extinction rates.
Among other actions, the researchers propose a global agreement to ban the
trade of wild species. They argue the illegal capture or hunting of wild
animals for food, pets and medicine is a fundamental ongoing threat not only
to species on the brink, but also to human health. COVID-19, which is
thought to have originated in bats and been transmitted to humans through
another creature in a live animal market, is an example of how the wildlife
trade can hurt humans, according to the researchers. They point out that
wild animals have transmitted many other infectious diseases to humans and
domestic animals in recent decades due to habitat encroachment and wildlife
harvesting for food.
“It’s up to us to decide what kind of a world we want to leave to coming
generations-a sustainable one, or a desolate one in which the civilization
we have built disintegrates rather than builds on past successes,” said
study coauthor Peter Raven, president emeritus of the Missouri Botanical
The sixth mass extinction of wildlife on Earth is accelerating, according to an analysis by scientists who warn it may be a tipping point for the collapse of civilisation.
More than 500 species of land animals were found to be on the brink of extinction and likely to be lost within 20 years. In comparison, the same number were lost over the whole of the last century. Without the human destruction of nature, even this rate of loss would have taken thousands of years, the scientists said.
The land vertebrates on the verge of extinction, with fewer than 1,000 individuals left, include the Sumatran rhino, the Clarión wren, the Española giant tortoise and the harlequin frog. Historic data was available for 77 of the species and the scientists found these had lost 94% of their populations.
The researchers also warned of a domino effect, with the loss of one species tipping others that depend on it over the edge. “Extinction breeds extinctions,” they said, noting that unlike other environmental problems extinction is irreversible.
Humanity relies on biodiversity for its health and wellbeing, scientists said, with the coronavirus pandemic an extreme example of the dangers of ravaging the natural world. Rising human population, destruction of habitats, the wildlife trade, pollution and the climate crisis must all be urgently tackled, they said.
Human society under urgent threat from loss of Earth’s natural life
“When humanity exterminates other creatures, it is sawing off the limb on which it is sitting, destroying working parts of our own life-support system,” said Prof Paul Ehrlich, of Stanford University in the US, and one of the research team. “The conservation of endangered species should be elevated to a global emergency for governments and institutions, equal to the climate disruption to which it is linked.”
Harlequin frog. Photograph: Gerardo Ceballos/University of Mexico/PA
“We are facing our final opportunity to ensure that the many services nature provides us do not get irretrievably sabotaged,” said Prof Gerardo Ceballos of the National Autonomous University of Mexico, who led the research.
The analysis, published in the journal Proceedings of the National Academy of Sciences, examined data on 29,400 land vertebrate species compiled by the IUCN Red List of Threatened Species and BirdLife International. The researchers identified 515 species with populations below 1,000 and about half of these had fewer than 250 remaining. Most of these mammals, birds, reptiles and amphibians were found in tropical and subtropical regions.
Scientists discovered that 388 species of land vertebrate had populations under 5,000, and the vast majority (84%) lived in the same regions as the species with populations under 1,000, creating the conditions for a domino effect.
UN draft plan sets 2030 target to avert Earth’s sixth mass extinction
The researchers said their findings could aid conservation efforts by highlighting the species and regions requiring the most urgent attention.
Prof Andy Purvis, at the Natural History Museum in London, and not part of the new analysis, said: “This research provides another line of evidence that the biodiversity crisis is accelerating. The hardest problem [the researchers] faced is that we don’t know more about the history of species’ geographic distributions. They only had that information for 77 of the species on the brink, and we can’t know for sure how typical those species are.”
Española giant tortoise. Photograph: Gerardo Ceballos/University of Mexico/PA
“But that doesn’t undermine the conclusion,” he said. “The biodiversity crisis is real and urgent. But – and this is the crucial point – it is not too late. To transition to a sustainable world, we need to tread more lightly on the planet. Until then, we are essentially robbing future generations of their inheritance.”
What is biodiversity and why does it matter to us?
Prof Georgina Mace, of University College London, said: “This new analysis re-emphasises some startling facts about the extent to which vertebrate populations have been reduced worldwide by human activities.” But she said she was not convinced that simply having a population less than 1,000 was the best measure of a species being on the brink. A declining trend for the population is also important and both factors are used in the IUCN Red List, she said.
“Action is important for many reasons, not least of which is that directly and indirectly we rely on the rest of life on Earth for our own health and wellbeing,” she said. “Disrupting nature leads to costly and often hard-to-reverse effects. Covid-19 is an extreme present-day example, but there are many more.”
Mark Wright, the director of science at WWF, said: “The numbers in this research are shocking. However, there is still hope. If we stop the land-grabbing and devastating deforestation in countries such as Brazil, we can start to bend the curve in biodiversity loss and climate change. But we need global ambition to do that.”
Within the space of less than a month, two specimens of a vanishingly rare fish have been plucked from the waters of the Rioni River in Georgia.
Before these two juveniles were caught, conservationists had expressed fears that the critically endangered ship sturgeon might have already sunk without trace. This extraordinary, other-worldly fish—whose evolution dates back hundreds of millions of years—had not been seen alive in the wild for many years.
A lack of solid scientific research on the species means that very little is known about the ecology and distribution of the ship sturgeon, but no one disputes that it is in deep trouble. In that context, the capture of two juvenile fish in quick succession, each estimated to be less than three years old, is extremely exciting news, raising the prospect that this elusive and gravely imperiled species might still be reproducing in the Rioni.
Sturgeons were once widespread throughout Europe, but have been virtually wiped out by a lethal combination of overharvesting, poaching and the loss of traditional spawning grounds to habitat destruction. The Rioni is one of the last three remaining refuges of these dwindling denizens of the Danube and the continent’s other great river systems. Remarkably, it still harbors breeding populations of several sturgeon species.
Georgia on our minds
The first evidence of recent reproductive success came in 2018, when a tiny juvenile fish—tentatively identified as a stellate sturgeon—was caught by two female students working full-time for Fauna & Flora International (FFI) on a pilot project launched earlier that year in an effort to safeguard Rioni’s remaining riches.
Since conducting what were the very first baseline studies for sturgeons in Georgia, FFI and our in-country partners have set about combating the threats to their survival, in particular poaching and illegal trade. We have established monitoring teams comprising ‘citizen inspectors’ drawn from communities along the river, whose role is to inform governmental agencies about incidences of poaching. FFI works closely with these communities—from schoolchildren to fish traders—to raise awareness of the plight of the sturgeons in the Rioni—and their global importance.
The FFI research team continues to work on the river from early spring to autumn, gathering vital data on sturgeon recruitment and genetic diversity in Georgia’s territorial waters. In collaboration with Ilia State University, we collect samples from any captured sturgeons for genetic analysis, in order to aid identification and shed light on which species still survive in the Rioni.
Hook, line and sturgeon
Ironically, both ship sturgeons were accidentally captured by surprised anglers, the first in mid-March, and the second just three weeks later. All sturgeon species in Georgia are officially protected, and commercial fishing on the Rioni is severely restricted, but sport fishing with rod and line is permitted, provided that anglers release any sturgeons they catch.
The fact that both anglers contacted one of FFI’s citizen inspectors immediately after catching the juvenile sturgeons—thereby enabling photographs and samples to be taken before the fish were returned to the river—is a success story in itself, vindicating FFI’s efforts to engage with nearby communities and engender local support for the project.
A week after the second ship sturgeon was caught, the river yielded a third juvenile, this time captured by the FFI team and provisionally labeled as a Colchic sturgeon—although hybrids are known to occur and can be difficult to differentiate from the real deal without detailed analysis.
While the ichthyologists may be agonizing over the idiosyncrasies of sturgeon subcategories, one thing is certain: the latest revelations provide further irrefutable evidence that the Rioni is an absolutely crucial sanctuary—and possibly the last hope—for these armor-plated icons of the fish world.
Dammed to extinction?
Further studies will be required before we can confirm categorically that the ship sturgeon is still spawning in Georgia’s mightiest river, but it seems that there could be light at the end of the tunnel. Unfortunately, that glimmer of hope is in imminent danger of being snuffed out.
A significant new threat to the survival of Georgia’s sturgeons has recently surfaced. The proposed development of several hydropower plants upstream from our project site could have a potentially disastrous impact on the Rioni—and put paid to the recovery prospects of its flagship fish species.
We risk having to bear witness to the tragedy of a rediscovered species being pulled back from the brink of extinction by conservationists only to be knowingly pushed over the precipice in the name of economic progress. Let’s hope that day never arrives.
These members of the genus Homo have long occupied two different branches on the family tree. But now that researchers think these groups interbred, scholars are giving serious consideration to whether we are the same species after all.
Around 200,000 years ago, in what is now northern Israel, a small band of tech-savvy humans dragged home and dismembered a bounty of wildlife. Using exquisitely pointed flint spearheads and blades, they hunted and butchered myriad prey, including gazelles, deer, and now-extinct aurochs, the ancestors of modern cattle.
In the cool, humid climate of the coastal plain, these early Homo sapiens foraged for acorns in nearby forests of oak, olive, and pistachio. They ate the saline leaves of shrubby saltbush and lugged ostrich eggs back to the cave, where they slurped down the yolks.
This vision of the past comes from Haifa University archaeologist Mina Weinstein-Evron. In 2002, she and her colleagues discovered the upper jaw and teeth of a H. sapiens that dated to between 177,000 and 194,000 years old in Israel’s Misliya Cave, with animal bones and sharp tools nearby.
It’s probable, Weinstein-Evron explains, that these humans migrated to the Arabian Peninsula more than 200,000 years ago, trekking along lush corridors out of Africa. “We don’t know how many crossed, and how many of them perished, and how many went back. We only know that these people arrived,” she says.
We also know that they were likely not alone. Based on small finds of teeth and bones from local caves, “we know that the area was inhabited by Neanderthal-like creatures,” or the predecessors of Neanderthals, at that time, says Tel Aviv University anthropologist Israel Hershkovitz, an expert on modern human origins.
While out foraging, H. sapiens may have mated with these Neanderthal-like inhabitants. In this land that later birthed the Bible, they likely knew each other in the Biblical sense.
The humans* who lived in the Misliya Cave were part of a population that, many scholars suspect, ultimately died out. Later waves of H. sapiens that left the African continent succeeded in reproducing and spreading out. But braided into the story of those human migrations is that of Neanderthals, hominins—members of our family tree closest to modern humans—who may have first evolved in Europe from African ancestors some 400,000 years ago.
Many scientists now suspect that H. sapiens and Neanderthals met and mingled their genes multiple times. Geneticists have documented how Neanderthal genes survive today among modern humans, evidence of some earlier instances of interbreeding.
New studies, made possible in part by computational techniques that enable researchers to analyze huge quantities of genetic data, show that H. sapiens and Neanderthals interbred far more than previously imagined. Indeed, their proclivity for pairing off has led many researchers to question the old dictum that Neanderthals and H. sapiens were separate species.
Such ideas raise questions as to what it really means to be a distinct “species.” They also raise the possibility that perhaps H. sapiens did not outcompete Neanderthals into extinction, as some scientists have suggested. Rather, one species may have simply absorbed the other—and so, Neanderthals, in a sense, could survive in us.
In 1856, in the Neander Valley of Prussia (now Germany), limestone cutters discovered the partial skeleton of a thick-boned, brow-ridged hominin in a cave. A German anthropologist named Hermann Schaaffhausen examined the bones.
Schaaffhausen realized that the skull differed from that of modern humans but concluded it could nonetheless belong to what he called a “barbarous and savage race” of human. However, his contemporary, Irish geologist William King, disagreed.
King noted that the skull of this fossil, with its “strong simial [apelike] tendencies” was “generically distinct from Man.” In 1863, King declared it a new species, which he named Homo neanderthalensis.
Scientists have been arguing over whether H. sapiens and H. neanderthalensis are truly separate species ever since. By appearances alone, Neanderthal fossils resemble ours—they are clearly members of our hominin family tree. But on closer examination, Neanderthal features are also quite distinct.
“There was debate back and forth: Was this just a weird variant of us—a more primitive, brutish-looking thing than living humans—or was it really something different?” asks physical anthropologist and evolutionary biologist Jeffrey Schwartz of the University of Pittsburgh.
Schwartz can rattle off a raft of anatomical differences between H. sapiens and Neanderthals: H. sapiens are flat-faced; the Neanderthal face sticks out. Neanderthals had boxy, stout bodies, and their major arm and leg bones were thick. H. sapiens, by contrast, have thinner, gracile bodies. Neanderthals had different teeth and thumb lengths, as well as longer collarbones.
The argument might have been confined to questions of anatomy had it not been for a singular discovery in 2010. A team led by evolutionary geneticist Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, extracted bits of DNA from Neanderthal fossils and published an early version of the Neanderthal genome.
By comparing portions of the Neanderthal genome with the genomes of five modern-day humans—from Southern Africa, West Africa, Papua New Guinea, China, and France—they found that Neanderthals share more genetic snippets with humans in Europe and Asia today than with people living presently in much of sub-Saharan Africa.
Pääbo and his team’s findings showed that between 1 and 4 percent of the genomes of modern non-African humans consist of Neanderthal DNA. That overlap suggested, for the first time, that our H.sapiens ancestors could have had intimate encounters with Neanderthals.
That study would be the first of many to indicate that these two hominins interbred. And such studies matter to the question of whether Neanderthals and H. sapiens are one or two species because, by biologist Ernst Mayr’s “classic definition,” Hershkovitz explains, “if two organisms can breed and produce fertile offspring, it means that they belong to the same species.”
Genetic research has long faced a challenge in scale. There are an estimated 21,000 genes in the human genome that code for proteins, complex molecules that do most of the work in cells and play crucial roles in the body. Sequencing these genes involved studying the 3 billion DNA base pairs that make up the human genome.
Every advance that makes studying an individual genome cheaper, more accurate, and faster is a major step forward in understanding how individuals—whether H. sapiens, Neanderthal, or other—compare. For all of those reasons, the development of artificial intelligence (AI) techniques, which enable researchers to set computers to solving problems and conducting analyses, has been a game changer.
AI has not only helped to confirm earlier genetic findings that H. sapiens and Neanderthals interbred, but also suggested their sexual encounters occurred to a degree that scholars never anticipated. All of this builds the case that the two could be the same species.
In 2018, for example, research published by population geneticists Fernando Villanea and Joshua Schraiber, then at Temple University in Philadelphia, made use of an AI tool called a deep learning algorithm, which seeks patterns in complex layers of data and is inspired by the brain’s approach to acquiring knowledge.
Computer scientists “train” algorithms by instructing them to identify specific patterns based on previously assembled data. In this case, Villanea and Schraiber used an algorithm to spot Neanderthal ancestry.
The pair then analyzed the distribution of Neanderthal DNA in the genomes of about 400 contemporary East Asians and Europeans, people whose ancestors have lived in these regions for a long time. This data came from the 1000 Genomes Project, an international collaboration to catalogue human genetic variation.
By the “classic definition,” explains anthropologist Hershkovitz, “if two organisms can breed and produce fertile offspring, it means that they belong to the same species.”
Schraiber and Villanea found fragments of Neanderthal ancestry: about 1.5 percent in each individual and 1.7 percent among people in East Asia specifically. Fabrizio Mafessoni, an evolutionary geneticist at the Max Planck Institute for Evolutionary Anthropology, reviewed Schraiber and Villanea’s findings and argued that the proportion of Neanderthal fragments among modern humans was a bit higher than would be expected if there had only been one episode in which these two populations mated.
“The intuitive explanation,” Schraiber says, “is that there were multiple episodes of interbreeding and that [populations in East Asia] interbred more.”
A 2019 study, co-led by Oscar Lao, who studies population genomics at Spain’s National Center of Genomic Regulation, and Jaume Bertranpetit, an evolutionary biologist at Pompeu Fabra University in Barcelona, used deep learning algorithms to identify a hitherto-unknown human population, a hybrid of Neanderthals and Denisovans. (The Denisovans are archaic hominins identified from the Denisova Cave in the Altai Mountains of Siberia.)
Their data showed that—given the distribution of Neanderthal DNA in various living human groups—Neanderthals interbred with Denisovans in East Asia, creating the Neanderthal-Denisovan population, and their hybrid descendants did the deed with modern humans before their arrival in Australia some 60,000 years ago.
That evidence for “admixing” between Neanderthals, Denisovans, and modern humans, Bertranpetit says, indicates “that all of these populations belong to a single lineage.”
Still other research, published in 2017, indicates that gene flow from early H. sapiensinto Neanderthals might have occurred earlier in humanity’s story—around the time that the Misliya Cave H. sapiens were sucking the yolks of those ostrich eggs.
That study, led by Cosimo Posth, an archaeogeneticist at the Max Planck Institute for the Science of Human History in Jena, Germany, examined DNA collected from an approximately 120,000-year-old femur bone excavated in a cave in southwestern Germany.
Specifically, they turned to mitochondrial DNA, genetic information handed down from mother to child and found within the cells’ energy-generating structures called mitochondria. The analysis concluded that the ancestors of Neanderthals and H. sapiens interbred at some point between 270,000 and 220,000 years ago, most likely in the Levant.
Taken together, these studies strengthen the case that H. sapiens-Neanderthal pairings occurred and that such mating was by no means unusual. Rather, H. sapiens, Neanderthals, Denisovans, and their hybrids all interbred (hinting, yes, that all three were the same species). And that mixing may have occurred as early as some of the first forays of modern human ancestors out of Africa.
“For hundreds of thousands of years, modern humans as well as archaic humans, such as Neanderthals and Denisovans, have been … crossing modern-day borders that, of course, were not existing in the past and multiple times admixing and exchanging genetic material,” Posth says. “This was not the exception but was the norm.”
If “species” is defined in large part by the ability to breed and have young who can also reproduce, one might argue that Neanderthals and H. sapiens are indeed one species. And many of the scientists who work on these studies agree. Yet some experts still contend otherwise.
Approximately 75 kilometers south of the Misliya Cave, Hershkovitz is sitting in his tiny office in Tel Aviv. Around him, the skulls of H. sapiens—the oldest dating back 15,000 years—jostle with one another on shelves lining the walls.
These skulls, which belonged to living, breathing human beings, evoke an aura of a long-forgotten world. And once, earlier still, such humans coexisted with other hominin species. Yet determining how different these species were from each other is difficult. Hershkovitz, for example, sees H. sapiens and Neanderthals as “sister populations” within the same species.
But Mayr’s “classic definition” of a species, based on interbreeding, is riddled with exceptions. For instance, if members of two different species happen to reproduce, they can have offspring but that new generation of “hybrids” may not be able to reproduce.
A horse and a donkey’s offspring, the mule, is typically sterile, for example. But lions and tigers, separate species that in the wild live on different continents, can sire “ligers” or “tigons” in captivity, and those hybrid felines can rarely or occasionally reproduce. In other words, scientists recognize instances where two species remain separate despite interbreeding—and some researchers extend that exception to H. sapiens and Neanderthals.
New York University biological anthropologist Shara Bailey believes H. sapiens and Neanderthals reproduced but remained distinct species—just like lions and tigers. She describes the two hominins as morphologically separate species who diverged from each other at least 800,000 years ago.
“For all intents and purposes, they were separate species,” Bailey says, “but they maintained the ability to hybridize.” Their offspring, she argues, would have been rare and, though able to reproduce, less successful in reproducing compared with their parents. The genetic record, then, indicates that some hybrids did sometimes succeed, contributing Neanderthal DNA to the modern human gene pool.
Bailey’s not alone in this viewpoint. Anthropologist Chris Stringer, at the Natural History Museum in London, also concludes that these populations both were separated long enough in terms of their evolution and were physically distinct enough in their features to remain separate species that occasionally hybridized.
Given the complications in Mayr’s definition, some scholars argue it ought to be replaced. To that end, there are now 20 different conceptions of what a “species” could be—and no strong consensus on which should take center stage. Some scientists subscribe to the theory of species mate recognition, in which members of the same species “recognize” one another as mates through courtship rituals, breeding seasons, or protein compatibility.
And at least one researcher still questions the genetic evidence for interbreeding. Schwartz says he has seen and studied almost every specimen of the entire human fossil record and notes that “Neanderthals are clearly a different species from us: They are so morphologically unique.”
Schwartz doubts the interpretation of genetic evidence thus far. Although dozens of hominins once existed, Schwartz points out, scientists have only sequenced the genomes of three specimens whose species they could clearly identify by their morphology: modern H. sapiens, the Neander Valley Neanderthal, and a 400,000-year-old hominin called Homo heidelbergensis. (Researchers have endeavored to identify the species of other, fragmentary specimens, primarily using genetic clues derived from the definitively identified Neanderthal and H. sapiens fossils.)
Because we don’t know how many hominin species there were—and because the vast majority have not had their DNA sequenced—we can’t know how many of these hominins had genes that were specifically “Denisovan” or “Neanderthal,” Schwartz argues. Therefore, he says, there is no way of knowing whether the DNA sequences extracted from Neanderthals were exclusive to Neanderthals.
“Pääbo and his group are very good technicians,” Schwartz says. “I don’t doubt that they have really worked hard to make sure these sequences are not contaminated.” Still, he says, we lack the DNA of many other hominins. The evidence that the sequenced DNA is specific to Neanderthals is therefore unreliable, he argues, and so claims that they interbred with H. sapiens are also dubious.
“I’m not saying that the comparisons are incorrect or that the sequences are incorrect,” Schwartz says. “I’m saying that the conclusion is not that solid.”
Schwartz doubts that Neanderthals and H. sapiens would have recognized each other as mates: “Neanderthals don’t look like us; we don’t look like them; they wouldn’t move the same way we did,” he says. Also, “they probably smelled different than we do.”
For the moment, then, the answer to whether or not H. sapiens and H. neanderthalensis were the same species is still up for debate (along with the entire messy concept of “species”). But the larger message that comes through with each wave of findings is simple: Despite a long history of derogatory “cave man” descriptors, H. neanderthalensis was probably a lot like us.
The first time H. sapiens and Neanderthals met was likely in the region that is now Israel. Just as the Misliya Cave helps establish how long anatomically modern humans were present in the region, tools associated with Neanderthals, such as spearheads and knives, have been found in other caves in Israel.
But many mysteries remain. Did H. sapiens and Neanderthals whisper sweet nothings to each other beneath the leaves of a pistachio tree? Was there some secret lure, facial or pheromonal, that attracted one to the other? We can only speculate.
Neanderthals were intelligent; they were skilled toolmakers. We don’t know whether they had spoken language, because even though they had vocal anatomy similar to H. sapiens, the soft tissue associated with the vocal box—the area of the throat containing the vocal cords—has not been preserved.
Some scholars suspect that fierce competition between H. sapiens and Neanderthals pushed the latter from the warmer Levant into an ice-covered Europe. “The world was almost empty,” Hershkovitz says. “The way I personally see this—probably most people would not agree with me—the European Neanderthals had no other choice.”
Though Hershkovitz declines to conjecture as to whether female Neanderthals were forced into sex—rape has been used as a weapon of war through the ages to punish and terrorize—he does offer, “I don’t think it was a happy marriage.”
Others, including Schraiber, posit more peaceful encounters. “I imagine that when humans ran into some vaguely human-like thing, they were like, ‘This is cool,’” he speculates. But, he demurs, “I really don’t know, Did they whisper sweet nothings beneath the leaves of a pistachio tree? We can only speculate.especially since I’m not an anthropologist, I’m a geneticist.”
At least one researcher, computational biologist Rasmus Nielsen of the University of California, Berkeley, goes further. He hypothesizes that Neanderthals never went extinct: They, or their genes, were simply absorbed into modern humans. In other words, instead of dying out through violence or starvation, the Neanderthal population hybridized with H. sapiens.
Using mathematical models, Nielsen and his colleague Kelley Harris have argued that at one point, the proportion of Neanderthal DNA in humans alive today was as high as 10 percent—and that proportion later dwindled. That 10 percent figure is significant because other researchers have estimated H. sapiens outnumbered Neanderthals 10-to-1, so perhaps, Nielsen contends, the two species interbred to such an extent that they merged together.
Over time, however, modern humans lost significant amounts of Neanderthal DNA, perhaps because it carried harmful mutations. Indeed, another research team, which included Pääbo, found that most Neanderthal genes survive in H. sapiens in regions of non-coding DNA. “The regions that are most important for function—the protein-coding genes—are depleted of Neanderthal DNA,” Nielsen says.
In a Q&A for the journal BMC Biology, Nielsen and Harris write: “It is possible that Neanderthals did not truly die off at all but simply melted together with the human species. One could perhaps argue that Neanderthals did not disappear due to warfare or competition—but due to love.”
If they are right, then whether we were once one species or two does not matter because we are all one now.
*Editor’s note: Many anthropologists use the term “human” to not only mean modern Homo sapiens but also many other hominin species on our family tree. (In other words, for some scholars, Neanderthals have always been “human,” as members of the genus Homo.) In our story, we use “human” broadly while using “H. sapiens” to refer to the only living species of the Homo lineage and “modern humans” to point to “all humans living today.”
Beijing — Scientists say a giant fish species that managed to survive at least 150 million years has been completely wiped out by human activity. Research published in the Science of The Total Environment this week says the giant Chinese paddlefish, also known as the Chinese swordfish, is officially extinct.
The monster fish, one of the largest freshwater species in the world with lengths up to 23 feet, was once common in China’s Yangtze River. Due to its speed it was commonly referred to in China as the “water tiger.”
Study leader Qiwei Wei of the Chinese Academy of Fishery Sciences called it “a reprehensible and an irreparable loss.”
Zeb Hogan, a fish expert at the University of Nevada, Reno, told National Geographic that it was “very sad” to see the “definitive loss of a very unique and extraordinary animal, with no hope of recovery.”
According to the researchers, no giant paddlefish have been sighted in the Yangtze since 2003, and there are none in captivity. They estimate that the last of the fish likely died between 2005 and 2010.
The species had been deemed “functionally extinct,” or unable to reproduce enough to maintain itself, since 1993.
The main causes of the ancient species’ demise have been listed as over-fishing and the construction of a major dam in 1981 that split the Yangtze, and the Chinese paddlefish population along with it, in two.
The 3,900 mile Yangtze River ecosystem has seen half of the 175 species unique to its waters go extinct, according to Chinese media.
Two other species native to the river have also been declared functionally extinct: the reeves shad and the Yangtze dolphin.
Last week China announced a 10-year fishing ban on some areas of the Yangtze in a bid to protect its beleaguered biodiversity.
Nine human species walked the Earth 300,000 years ago. Now there is just one. The Neanderthals, Homo neanderthalensis, were stocky hunters adapted to Europe’s cold steppes. The related Denisovans inhabited Asia, while the more primitive Homo erectus lived in Indonesia, and Homo rhodesiensis in central Africa.
By 10,000 years ago, they were all gone. The disappearance of these other species resembles a mass extinction. But there’s no obvious environmental catastrophe – volcanic eruptions, climate change, asteroid impact – driving it. Instead, the extinctions’ timing suggests they were caused by the spread of a new species, evolving 260,000-350,000 years ago in Southern Africa: Homo sapiens.
The spread of modern humans out of Africa has caused a sixth mass extinction, a greater than 40,000-year event extending from the disappearance of Ice Age mammals to the destruction of rainforests by civilisation today. But were other humans the first casualties?
We are a uniquely dangerous species. We hunted wooly mammoths, ground sloths and moas to extinction. We destroyed plains and forests for farming, modifying over half the planet’s land area. We altered the planet’s climate. But we are most dangerous to other human populations, because we compete for resources and land.
History is full of examples of people warring, displacing and wiping out other groups over territory, from Rome’s destruction of Carthage, to the American conquest of the West and the British colonisation of Australia. There have also been recent genocides and ethnic cleansing in Bosnia, Rwanda and Myanmar. Like language or tool use, a capacity for and tendency to engage in genocide is arguably an intrinsic, instinctive part of human nature. There’s little reason to think that early Homo sapiens were less territorial, less violent, less intolerant – less human.
Optimists have painted early hunter-gatherers as peaceful, noble savages, and have argued that our culture, not our nature, creates violence. But field studies, historical accounts, and archaeology all show that war in primitive cultures was intense, pervasive and lethal. Neolithic weapons such as clubs, spears, axes and bows, combined with guerrilla tactics like raids and ambushes, were devastatingly effective. Violence was the leading cause of death among men in these societies, and wars saw higher casualty levels per person than World Wars I and II.
Old bones and artefacts show this violence is ancient. The 9,000-year-old Kennewick Man, from North America, has a spear point embedded in his pelvis. The 10,000-year-old Nataruk site in Kenya documents the brutal massacre of at least 27 men, women, and children.
The incompleteness of the fossil record makes it hard to test these ideas. But in Europe, the only place with a relatively complete archaeological record, fossils show that within a few thousand years of our arrival , Neanderthals vanished. Traces of Neanderthal DNA in some Eurasian people prove we didn’t just replace them after they went extinct. We met, and we mated.
Elsewhere, DNA tells of other encounters with archaic humans. East Asian, Polynesian and Australian groups have DNA from Denisovans. DNA from another species, possibly Homo erectus, occurs in many Asian people. African genomes show traces of DNA from yet another archaic species. The fact that we interbred with these other species proves that they disappeared only after encountering us.
But why would our ancestors wipe out their relatives, causing a mass extinction – or, perhaps more accurately, a mass genocide?
Further growth, or food shortages caused by drought, harsh winters or overharvesting resources would inevitably lead tribes into conflict over food and foraging territory. Warfare became a check on population growth, perhaps the most important one.
Our elimination of other species probably wasn’t a planned, coordinated effort of the sort practised by civilisations, but a war of attrition. The end result, however, was just as final. Raid by raid, ambush by ambush, valley by valley, modern humans would have worn down their enemies and taken their land.
Today we look up at the stars and wonder if we’re alone in the universe. In fantasy and science fiction, we wonder what it might be like to meet other intelligent species, like us, but not us. It’s profoundly sad to think that we once did, and now, because of it, they’re gone.
A Tasmanian tiger, which was declared extinct in 1936, displayed at the Australian Museum in 2002.
(CNN)The Tasmanian tiger, a large striped carnivore, is believed to have gone extinct over 80 years ago — but newly released Australian government documents show sightings have been reported as recently as two months ago.
Tasmania’s Department of Primary Industries, Parks, Water and Environment (DPIPWE) recently released a document detailing eight reported sightings of the Tasmanian tiger, or thylacine, in the last three years.
The thylacine, a marsupial that looked like a cross between a wolf, a fox, and a large cat, is believed to have gone extinct after the last known live animal died in captivity in 1936. It had yellowish brown fur, with powerful jaws and a pouch for its young, according to the Australian Museum.
While stories abound that some continue to live in the remote wilds of Tasmania, an island state off Australia’s south coast, there has been no hard evidence to support this — only claims of sightings, like the ones newly released.
One report last February said that two people, visiting Tasmania from Australia, were driving when an animal with a stiff tail and striped back walked onto the road.
The animal “turned and looked at the vehicle a couple of times” and “was in clear view for 12-15 seconds,” the report read. Both people in the car “are 100% certain that the animal they saw was a thylacine.”
Another report filed the same month described a striped “cat-like creature” moving through the mist in the distance.
“I am accustomed to coming across most animals working on rural farms … and I have never come across an animal anything close to what I saw in Tasmania that day,” the report read.
In 2017, another driver reported seeing a possible thylacine near the Deep Gully Forest Reserve in northwestern Tasmania. He didn’t see stripes, but he was about 150 meters (492 foot) away — likely too far to have seen that level of detail. He “seemed certain that if it was a cat it was a bloody big one,” the report said.
Most recently in July, a man in southern Tasmania, near the state capital of Hobart, reported seeing a footprint that seemed to match that of the Tasmanian tiger.
These reports reflect just how large the thylacine still looms in the collective imagination. Native to Tasmania and the Australian mainland, it was the only member of the Thylacinidae family to survive into modern times, according to the Australian Museum.
This thylacine was the last of its kind to be captured and died in Hobart Zoo on September 7th, 1936.
European colonists killed thousands of thylacines for attacking sheep.
Today, the thylacine still remains a major component of Tasmanian culture. It maintains almost Loch Ness Monster status, with regular claims of unsubstantiated sightings. In 2002, scientists at the Australian Museum even replicated thylacine DNA, opening the door to potentially bringing back the species with cloning technology.
Over the past half-century, North America has lost more than a quarter of its entire bird population, or around 3 billion birds.
That’s according to a new estimate published in the journal Science by researchers who brought together a variety of information that has been collected on 529 bird species since 1970.
“We saw this tremendous net loss across the entire bird community,” says Ken Rosenberg, an applied conservation scientist at the Cornell Lab of Ornithology in Ithaca, N.Y. “By our estimates, it’s a 30% loss in the total number of breeding birds.”
Rosenberg and his colleagues already knew that a number of bird populations had been decreasing.
“But we also knew that other bird populations were increasing,” he says. “And what we didn’t know is whether there was a net change.” Scientists thought there might simply be a shift in the total bird population toward more generalist birds adapted to living around humans.
To find out, the researchers collected data from long-running surveys conducted with the help of volunteer bird spotters, such as the North American Breeding Bird Survey and the Audubon Christmas Bird Count. They combined that data with a decade’s worth of data on migrating bird flocks detected by 143 weather radar installations.
Their results show that more than 90% of the loss can be attributed to just a dozen bird families, including sparrows, warblers, blackbirds and finches.
Common birds with decreasing populations include meadowlarks, dark-eyed juncos, horned larks and red-winged blackbirds, says Rosenberg. Grassland birds have suffered a 53% decrease in their numbers, and more than a third of the shorebird population has been lost.
A horned lark
Larry Keller/Getty Images
Bird populations that have increased include raptors, like the bald eagle, and waterfowl.
“The numbers of ducks and geese are larger than they’ve ever been, and that’s not an accident,” says Rosenberg. “It’s because hunters who primarily want to see healthy waterfowl populations for recreational hunting have raised their voices.”
Applied ecologist Ted Simons of North Carolina State University says that trying to enumerate bird populations and tracking them over time is a daunting task with a lot of uncertainty.
“People are doing a wonderful effort to try and understand our bird populations, but the actual systems that we have in place to try and answer really tough questions like this are really far short of what we need,” says Simons. “We’re certainly far from having the tools and having the resources to have real high confidence in our estimates of these populations.”
Still, he says, “I think it is very likely that we are seeing substantial declines in our bird populations, particularly migratory birds.”
Enlarge this image
A red-winged blackbird
Other researchers say this continentwide decrease in bird numbers is about what they expected.
“I think that I buy the magnitude of loss,” says Kristen Ruegg, a biologist at Colorado State University in Fort Collins. “Overall, the conclusions weren’t necessarily surprising. I mean, they were depressing but not surprising,”
Ruegg says there have been hints that the loss was this large from a variety of sources over the past few decades. But in most cases, these were species-specific accounts of local extinctions or models of projected losses resulting from things like climate change.
This study, she says, “really sort of wakes people up to the idea that this is happening.”
A dark-eyed junco
Elise Zipkin, a quantitative ecologist at Michigan State University, says the loss of individuals can be a big problem.
“Just because a species hasn’t gone extinct or isn’t even necessarily close to extinction, it might still be in trouble,” she says. “We need to be thinking about conservation efforts for that.”
The researchers cite a variety of potential causes for the loss of birds, including habitat degradation, urbanization and the use of toxic pesticides, notes Zipkin.
“And so I think this kind of lays the gauntlet,” she says, “for people to be thinking about ‘All right, how can we estimate maybe the relative contributions of these things to individual populations and their declines.’ ”
CorrectionSept. 19, 2019
An earlier version of this story misspelled Kristen Ruegg’s first name as Kristin.
New species related to humans discovered in cave01:15
(CNN)Ancient bones and teeth found in Callao Cave in the Philippines have led to the discovery of a previously unknown species related to humans called Homo luzonensis, according to a new study. The fossils belonged to two adults and one child who lived between 50,000 and 67,000 years ago.
This time frame means luzonensis would have lived at the same time as Neanderthals, Denisovans, Homo sapiens and the small-bodied Homo floresiensis. Like other extinct hominins, luzonensis is more of a close relative than a direct ancestor.
In 2007, a single foot bone was found in the cave and dated to 67,000 years ago. During excavations in 2011 and 2015, researchers found 12 additional hand and foot bones, including a partial femur and teeth, in the same layer of the cave. The researchers have named the new species luzonensis because of where it was found on the island of Luzon.
They are now the earliest human remains found in the Philippines. Previously, Homo sapiens remains were found on Palawan island and dated to between 30,000 and 40,000 years ago.
But what makes luzonensis different from other species? It’s all in the distinct premolar teeth, which vary considerably from anything identified in the other species belonging to the Homo genus.
Callao Cave on Luzon island, where the fossils were discovered.
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The seven premolars and molars are smaller and more simplified than those of other species. Although some of the characteristics can be compared to Homo erectus and Homo sapiens, the teeth and jaw features remain distinct as far as the odd features they combine.
This factor, along with the fact that the researchers haven’t been able to remove DNA from the fossils, makes it difficult to determine where luzonensis fits, evolution-wise.
The two hand bones and three foot bones also show a unique anatomy.
Although separated by millions of years of evolution, luzonensis’ toe bone strongly resembles that of Australopithecus afarensis, or the famed “Lucy” fossil. Australopithecus lived between 2.9 million and 3.9 million years ago.
The finger bone also resembles that of Australopithecus, as well as early Homo species. The finger and toe bones are curved, like those of early hominins, likely suggesting that climbing was important to their lifestyle and survival.
“If you take each feature one by one, you will also find it in one or several hominin species, but if you take the whole combination of features, no other species of the genus Homo is similar, thus indicating that they belong to a new species,” said Florent Détroit, study author and paleoanthropologist at the National Museum of Natural History in Paris.
Complications in the evolutionary tree
Luzonensis presents a bit of a mystery because, as with the discovery of Homo floresiensis, previously unknown hominin species complicate the evolutionary tree. This also shifts the idea of which species migrated.
Given that Africa is regarded as the “Cradle of Life” and Homo erectus was found on the Indonesian island of Java, the idea is that erectus migrated out of Africa and helped disperse the species.
Floresiensis, nicknamed the “hobbit” species, have been found only on the island of Flores near Indonesia and were discovered in 2003. They lived between 100,000 and 60,000 years ago. And although they stood only around 3½ feet tall and had brains about one-third the size of a modern human’s, they made stone tools and hunted elephants.
It is believed that floresiensis was more diminutive in stature due to its island environment and limited resources. The same may be true for luzonensis, the researchers said.
Both of these species lived on islands that would have been reachable only by crossing the sea. And there is evidence of animal butchery on Luzon that dates back 700,000 years, but the researchers don’t know whether luzonensis is responsible.
The finding does build the case that hominins were already present on the island. They could have been luzonensis or the species descended from them, or perhaps they descended from another unknown group, the researchers said.
Seafaring could have happened by accident as they drifted on rafts or due to intentional navigation, the researchers said.
“We have more and more evidence that they successfully settled on several islands in the remote past in Southeast Asia, so it was probably not so accidental,” Détroit said. “Another important thing to have in mind is that you cannot successfully settle on an island with a single event of arrival of only few people, you need several individuals of course, and you need several arrivals, at least at the beginning, so that you have enough founders settled on the island.”
More exploration to come
So how did they evolve, and why do they share such varied characteristics with more ancient hominins? The answer may lie in more excavations and discoveries yet to be made on the islands of Southeast Asia.
“Our picture of homin evolution in Asia during the Pleistocene just got even messier, more complicated and a whole lot more interesting,” Matthew Tocheri wrote in an accompanying News and Views article. Tocheri, the Canada Research Chair in Human Origins at Lakehead University in Ontario, did not participate in this study.
The researchers are planning studying the biomechanical aspects of the fossils and how they may have moved, as well as more excavations of the cave or identifying new potential sites.
“As we can see now, Southeast Asia, and especially their islands, is a fantastic place for studying hominin evolution, and conducting fieldwork to find more sites with ancient archaeology and hominin fossils,” Détroit said.
Examples of how human societies are changing the planet abound – from building roads and houses, clearing forests for agriculture and digging train tunnels, to shrinking the ozone layer, driving species extinct, changing the climate and acidifying the oceans.
Not everyone is sure that today’s industrialized, globalized societies will be around long enough to define a new geological epoch. Perhaps we are just a flash in the pan – an event – rather than a long, enduring epoch.
Others debate the utility of picking a single thin line in Earth’s geological record to mark the start of human impacts in the geological record. Maybe the Anthropocene began at different times in different parts of the world.
For example, the first instances of agriculture emerged at different places at different times, and resulted in huge impacts on the environment, through land clearing, habitat losses, extinctions, erosion and carbon emissions, forever changing the global climate.
If there are multiple beginnings, scientists need to answer more complicated questions – like when did agriculture begin to transform landscapes in different parts of the world?
This is a tough question because archaeologists tend to focus their research on a limited number of sites and regions and to prioritize locations where agriculture is believed to have appeared earliest.
To date, it has proved nearly impossible for archaeologists to put together a global picture of land use changes throughout time.
Global answers from local experts
To tackle these questions, we pulled together a research collaboration among archaeologists, anthropologists and geographers to survey archaeological knowledge on land use across the planet.
We asked over 1,300 archaeologists from around the world to contribute their knowledge on how ancient people used the land in 146 regions spanning all continents except Antarctica from 10,000 years ago right up to 1850.
More than 250 responded, representing the largest expert archaeology crowdsourcing project ever undertaken, though some priorprojects have worked with amateur contributions.
Our work has now mapped the current state of archaeological knowledge on land use across the planet, including parts of the world that have rarely been considered in previous studies.
Even when these data are shared by archaeologists, they use many different formats from one project to another, making it difficult to combine for large-scale analysis.
Our goal from the beginning was to make it easy for anyone to check our work and reuse our data – we’ve put all our research materials online where they can be freely accessed by anyone.
Earlier and more widespread human impacts
Though our study acquired expert archaeological information from across the planet, data were more available in some regions – including Southwest Asia, Europe, northern China, Australia and North America – than in others.
This is probably because more archaeologists have worked in these regions than elsewhere, such as parts of Africa, Southeast Asia and South America.
Our archaeologists reported that nearly half (42 percent) of our regions had some form of agriculture by 6,000 years ago, highlighting the prevalence of agricultural economies across the globe.
Moreover, these results indicate that the onset of agriculture was earlier and more widespread than suggested in the most common global reconstruction of land-use history, the History Database of the Global Environment.
This is important because climate scientists often use this database of past conditions to estimate future climate change; according to our research it may be underestimating land-use-associated climate effects.
Our survey also revealed that hunting and foraging was generally replaced by pastoralism (raising animals such as cows and sheep for food and other resources) and agriculture in most places, though there were exceptions.
Global archaeological data show that human transformation of environments began at different times in different regions and accelerated with the emergence of agriculture.
Nevertheless, by 3,000 years ago, most of the planet was already transformed by hunter-gatherers, farmers and pastoralists.
To guide this planet toward a better future, we need to understand how we got here. The message from archaeology is clear. It took thousands of years for the pristine planet of long ago to become the human planet of today.