No, Humans Didn’t Evolve From the Ancestors of Living Apes

https://interestingengineering.com/no-humans-didnt-evolve-from-the-ancestors-of-living-apes

The last ancestor that we shared with apes had its own set of traits, and was different from both us and modern apes.By  Marcia WendorfMay 10, 2021No, Humans Didn't Evolve From the Ancestors of Living ApesMan-Half-tube/iStockPhoto

The truth is that we don’t know where we, homo sapiens, came from. In his 1871 work, In The Descent of Man, Charles Darwin speculated that humans originated in Africa, and that we evolved from an ancestor who was different from any currently living species.

Now, a new study by an international group of paleoanthropologists, with a wide range of specialties, have backed up Darwin by concluding that it is likely that the last ancestor that we shared with apes had its own distinct set of traits that are different from those of both modern humans and modern apes.

Who was this ancient ancestor?

Chimpanzees, with whom we share 98 percent of our DNA, are in genus Pan, while humans are in genus Homo. Humans diverged from chimpanzees between 9.3 and 6.5 million years ago.Top ArticlesEngineering Failure: Man Trapped on 300ft-High Bridge After Glass ShattersREAD MOREVoyager 1 Just Heard a Cosmic 'Hum' in the Depths of Interstellar SpaceTurn Your Favorite Hot Wheels Car into a Mini-RC ModelFacebook's User Data Enables Drug Companies to Target People with Health ConditionsFossil Fuel Emergency: US Races to Move Gasoline After a Pipeline HackEngineering Failure: Man Trapped on300ft‑High Bridge After Glass Shattershttps://imasdk.googleapis.com/js/core/bridge3.457.0_en.html#goog_1640365065https://imasdk.googleapis.com/js/core/bridge3.457.0_en.html#goog_2056904514https://imasdk.googleapis.com/js/core/bridge3.457.0_en.html#goog_562727021javascript:falseSKIP ADEngineering Failure: Man Trapped on 300ft-High Bridge After Glass Shatters

Historically, two major approaches have been used in analyzing human ancestry:

  • Top-down – uses living apes, especially chimpanzees, to reconstruct our origins
  • Bottom-up – uses the fossil record of both humans and apes; it shows multiple possibilities both for what the LCA looked like, and where he roamed.

In reviewing the studies surrounding these diverging approaches, the authors of the paper argue that there are limitations to relying on just one or the other of these opposing approaches. This is because the top-down studies often assume that modern ape species share habitat and features of earlier groups, while bottom-up studies tend to give individual fossil apes a more important evolutionary role than may be warranted.

In an attempt to reconcile these approaches to identifying our ancient ancestor, the scientists looked at what the environment must have been like for the Pan-Homo last common ancestor, or LCA. 

The Miocene epoch existed from around 23 to 5.3 million years ago, and a number of fossil ape genera from that era have been found. However, they show a combination of features common to both “orthograde” (upright) and “pronograde” (walking on all fours) body plan, which has led some scientists to exclude the Miocene apes from the human lineage, and there is no scientific consensus on the evolutionary role played by these fossil apes.

The journey from monkeys to us
The journey from monkeys to us. Source: Almécija/AAAS

Some scientists espouse the theory that some Miocene apes dispersed out of Africa and into Eurasia, approximately 16 to 14 million years ago, before the hominins diverged from apes. Some of these apes gave rise to the line that produced orangutans, and the European “Dryopith” apes, while others returned to Africa where they evolved into modern African apes and hominins. Others interpret dryopiths as broadly ancestral to hominids or as an evolutionary dead end.

During the late Miocene period in Africa, increased habitat fragmentation may have led to the evolution of African ape knuckle-walking, and hominin bipedalism, or walking on two feet, from a common orthograde ancestor who lived in the trees. Walking on two feet might have allowed our human ancestors to adapt their diets and locomotion, and escape the  “specialization trap” that kept other apes in an arboreal environment.

The study concluded that future research efforts should focus on looking for Miocene ape fossils in areas where they have yet to be found. The scientists also concluded that data-driven modeling should take precedence over trying to fit evolutionary scenarios to every fossil find.

Hominin fossils have been found in eastern and central Africa, and possibly also in Europe. Fossils of over 50 genera of ancient apes have been found in Africa and Eurasia, however, as Dr. Sergio Almécija, a researcher in the Division of Anthropology at the American Museum of Natural History told Sci-News “… there is no scientific consensus on the evolutionary role played by these fossil apes.”

Kelsey Pugh, one of the study co-authors, added that, “The unique and sometimes unexpected features and combinations of features observed among fossil apes, which often differ from those of living apes, are necessary to untangle which features hominins inherited from our ape ancestors and which are unique to our lineage.”

Locations of Miocene ape fossils
Miocene ape fossil locations. Source: Source: Almécija/AAAS

Where do we go from here?

The new study seems to put us back to square one as to where we came from. Every ancient religion has its own theory of how we came to be. Giorgio A. Tsoukalos, better known as “the hair guy,” who is a producer of the show “Ancient Aliens” on which he often appears, theorizes that humans arose due to visits made to Earth made by ancient aliens. Tsoukalos shares those opinions with others including Erich von Däniken, Zecharia Sitchin, and Robert K. G. Temple.

Scientists discover how humans develop larger brains than other apes

https://phys.org/news/2021-03-scientists-humans-larger-brains-apes.html

MARCH 24, 2021

by UK Research and Innovation

Scientists discover how humans develop larger brains than other apes
Human brain organoids grow substantially bigger than gorilla and chimpanzee (left to right). These brain organoids are 5 weeks old. Credit: S.Benito-Kwiecinski/MRC LMB/Cell

A new study is the first to identify how human brains grow much larger, with three times as many neurons, compared with chimpanzee and gorilla brains. The study, led by researchers at the Medical Research Council (MRC) Laboratory of Molecular Biology in Cambridge, UK, identified a key molecular switch that can make ape brain organoids grow more like human organoids, and vice versa.

The study, published in the journal Cell, compared ‘brain organoids’ – 3-D tissues grown from stem cells which model early brain development—that were grown from human, gorilla and chimpanzee stem cells.

Similar to actual brains, the human brain organoids grew a lot larger than the organoids from other apes.

Dr. Madeline Lancaster, from the MRC Laboratory of Molecular Biology, who led the study, said: “This provides some of the first insight into what is different about the developing human brain that sets us apart from our closest living relatives, the other great apes. The most striking difference between us and other apes is just how incredibly big our brains are.”

During the early stages of brain development, neurons are made by stem cells called neural progenitors. These progenitor cells initially have a cylindrical shape that makes it easy for them to split into identical daughter cells with the same shape.

The more times the neural progenitor cells multiply at this stage, the more neurons there will be later.

As the cells mature and slow their multiplication, they elongate, forming a shape like a stretched ice-cream cone.

Previously, research in mice had shown that their neural progenitor cells mature into a conical shape and slow their multiplication within hours.

Now, brain organoids have allowed researchers to uncover how this development happens in humans, gorillas and chimpanzees.

They found that in gorillas and chimpanzees this transition takes a long time, occurring over approximately five days.

Scientists discover how humans develop larger brains than other apes
After only 5 days, gorilla neural progenitor cells have matured into a conical shape (right), while human cells (left) remain cylindrical. Credit: S.Benito-Kwiecinski/MRC LMB/Cell

Human progenitors were even more delayed in this transition, taking around seven days. The human progenitor cells maintained their cylinder-like shape for longer than other apes and during this time they split more frequently, producing more cells.https://googleads.g.doubleclick.net/pagead/ads?client=ca-pub-0536483524803400&output=html&h=280&slotname=5350699939&adk=3784993980&adf=1857921027&pi=t.ma~as.5350699939&w=753&fwrn=4&fwrnh=100&lmt=1616608675&rafmt=1&psa=1&format=753×280&url=https%3A%2F%2Fphys.org%2Fnews%2F2021-03-scientists-humans-larger-brains-apes.html&flash=0&fwr=0&rpe=1&resp_fmts=3&wgl=1&uach=WyJXaW5kb3dzIiwiMTAuMCIsIng4NiIsIiIsIjg5LjAuNDM4OS45MCIsW11d&dt=1616607687425&bpp=117&bdt=2441&idt=771&shv=r20210322&cbv=r20190131&ptt=9&saldr=aa&abxe=1&cookie=ID%3D5d55f89f953c9743-22b6644a08c70033%3AT%3D1616607686%3ART%3D1616607686%3AS%3DALNI_MYBzRhJl1pJ2SevpeFZZcqkW-bxAA&prev_fmts=0x0&nras=1&correlator=1374116295303&frm=20&pv=1&ga_vid=185394846.1565457508&ga_sid=1616607688&ga_hid=522824615&ga_fc=0&u_tz=-420&u_his=1&u_java=0&u_h=640&u_w=1139&u_ah=607&u_aw=1139&u_cd=24&u_nplug=3&u_nmime=4&adx=263&ady=2425&biw=1123&bih=538&scr_x=0&scr_y=300&eid=44731609%2C21066435%2C21068083%2C44738185%2C44739387&oid=2&pvsid=839096735404007&pem=466&ref=https%3A%2F%2Fnews.google.com%2F&rx=0&eae=0&fc=896&brdim=0%2C0%2C0%2C0%2C1139%2C0%2C1139%2C607%2C1139%2C537&vis=1&rsz=%7C%7CpEebr%7C&abl=CS&pfx=0&fu=8320&bc=31&ifi=1&uci=a!1&btvi=1&fsb=1&xpc=ZHEPBo0JgA&p=https%3A//phys.org&dtd=M

This difference in the speed of transition from neural progenitors to neurons means that the human cells have more time to multiply. This could be largely responsible for the approximately three-fold greater number of neurons in human brains compared with gorilla or chimpanzee brains.

Dr. Lancaster said: “We have found that a delayed change in the shape of cells in the early brain is enough to change the course of development, helping determine the numbers of neurons that are made.

“It’s remarkable that a relatively simple evolutionary change in cell shape could have major consequences in brain evolution. I feel like we’ve really learnt something fundamental about the questions I’ve been interested in for as long as I can remember—what makes us human.”

To uncover the genetic mechanism driving these differences, the researchers compared gene expression—which genes are turned on and off—in the human brain organoids versus the other apes.

They identified differences in a gene called ‘ZEB2’, which was turned on sooner in gorilla brain organoids than in the human organoids.

To test the effects of the gene in gorilla progenitor cells, they delayed the effects of ZEB2. This slowed the maturation of the progenitor cells, making the gorilla brain organoids develop more similarly to human—slower and larger.

Conversely, turning on the ZEB2 gene sooner in human progenitor cells promoted premature transition in human organoids, so that they developed more like ape organoids.

The researchers note that organoids are a model and, like all models, do not to fully replicate real brains, especially mature brain function. But for fundamental questions about our evolution, these brain tissues in a dish provide an unprecedented view into key stages of brain development that would be impossible to study otherwise.

Dr. Lancaster was part of the team that created the first brain organoids in 2013.


Explore further‘Mini brain’ organoids grown in lab mature much like infant brains

Secrets of the largest ape that ever lived

Jaw of the aoeImage copyrightPROF WEI WANG
Image captionLittle is known about the ape as only a few fossils are known, including this jawbone

A fossilised tooth left behind by the largest ape that ever lived is shedding new light on the evolution of apes.

Gigantopithecus blacki was thought to stand nearly three metres tall and tip the scales at 600kg.

In an astonishing advance, scientists have obtained molecular evidence from a two-million-year-old fossil molar tooth found in a Chinese cave.

The mystery ape is a distant relative of orangutans, sharing a common ancestor around 12 million years ago.

“It would have been a distant cousin (of orangutans), in the sense that its closest living relatives are orangutans, compared to other living great apes such as gorillas or chimpanzees or us,” said Dr Frido Welker, from the University of Copenhagen.

Artist reconstruction of the apeImage copyrightIKUMI KAYAMA
Image captionArtist reconstruction of the ape

Human evolution hopes

The research, reported in Nature, is based on comparing the ancient protein sequence of the tooth of the extinct ape, believed to be a female, with apes alive today.

Obtaining skeletal protein from a two-million-year-old fossil is rare if not unprecedented, raising hopes of being able to look even further back in time at other ancient ancestors, including humans, who lived in warmer regions.

There is a much poorer chance of being able to find ancient DNA or proteins in tropical climates, where samples tend to degrade quicker.

“This study suggests that ancient proteins might be a suitable molecule surviving across most of recent human evolution even for areas like Africa or Asia and we could thereby in the future study our own evolution as a species over a very long time span,” Dr Welker told BBC News.

Extinction clues

Gigantopithecus blacki was first identified in 1935 based on a single tooth sample. The ape is thought to have lived in Southeast Asia from two million years ago to 300,000 years ago.

Many teeth and four partial jawbones have been identified but the animal’s relationship to other great ape species has been hard to decipher.

The ape reached massive proportions, exceeding that of living gorillas, based on analysis of the few bones that have been found.

It is thought to have gone extinct when the environment changed from forest to savannah.

Borneo has lost half its orangutans due to hunting and habitat loss

‘Their forests homes have been lost and degraded, and hunting threatens the existence of this magnificent great ape’

Borneo has lost more than 100,000 orangutans in the space of just 16 years as a result of hunting and habitat loss, according to a new report.

Logging, mining, oil palm, paper, and linked deforestation have been blamed for the the diminishing numbers.

However, researchers also found many orangutans have vanished from more intact, forested regions, suggesting that hunting and other direct conflict between orangutans and humans continues to be a chief threat to the species.

The report published in the Current Biology Journal found more than 100,000 of the island’s orangutans vanished in the period of 1999 to 2015.

“Orangutans are disappearing at an alarming rate,” said Emma Keller, agricultural commodities manager at the Worldwide Fund for Nature (WWF).

“Their forests homes have been lost and degraded, and hunting threatens the existence of this magnificent great ape.

“Immediate action is needed to reform industries that have pushed orangutans to the brink of extinction. UK consumers can make a difference through only supporting brands and retailers that buy sustainable palm oil.”

Around half of the orangutans living on the island of Borneo, the largest island in Asia, were lost as a result of changes in land cover.

Researchers said the Bornean orangutan’s survival is dependent on forging successful alliances with logging companies and other industries and raising public awareness of the issue.

Looking at predicted future losses of forest cover and the presumption orangutans are ultimately not able to stay alive outside forest areas, the researchers predict that over 45,000 more orangutans will be lost in the space of the next 35 years.

The report comes after an orangutan was shot at least 130 times with an air gun before it died earlier in the month, according to police in Borneo.