Tag Archives: human evolution

Our ancestors may have always walked on two legs, 10-million-year-old ape suggests

Upright walking is one of the hallmarks of our species yet the origin of human bipedal locomotion is still a subject of heated debate among experts and scholars. How did our ancestors ever make the jump from walking on all fours to an upright gait? Well, what if our early ancestors were far more equipped to walk on two legs than we’ve given them credit for? This exciting possibility was recently proposed by researchers who studied the fossils of a 10-million-year-old small-sized ape.

Rudapithecus has a more flexible lower back than modern African apes, which probably allowed it to stand upright more like humans. Credit: John Siddick.

Carol Ward, an anthropologist at the University of Missouri, analyzed the pelvis bone belonging to a Rudapithecus specimen. The fossil was unearthed near Rudabánya, an old mining town in Hungary.

The pelvis was initially discovered by David Begun, a professor of anthropology at the University of Toronto. Previously, Begun had studied limb bones, jaws, and teeth belonging to Rudapithecus, showing that it was a relative of modern African apes and humans.

The new study now offers information about Rudapithecus‘ locomotion and posture.

“Rudapithecus was pretty ape-like and probably moved among branches like apes do now—holding its body upright and climbing with its arms,” said Ward, a Curators Distinguished Professor of Pathology and Anatomical Sciences in the MU School of Medicine and lead author on the study. “However, it would have differed from modern great apes by having a more flexible lower back, which would mean when Rudapithecus came down to the ground, it might have had the ability to stand upright more like humans do. This evidence supports the idea that rather than asking why human ancestors stood up from all fours, perhaps we should be asking why our ancestors never dropped down on all fours in the first place.”

The pelvis was not complete but using modern 3-D modeling techniques, the researchers filled in the blanks and digitally completed the bone. The reconstruction allowed them to then compare Rudapithecus’ pelvis to modern animals.

Modern African apes, such as chimpanzees and gorillas, have a long pelvis and short lower back. For this reason, they typically walk on all fours when they’re on the ground. Humans, on the other hand, have much more flexible lower backs, which allows them to walk on two legs without expending a lot of energy.

If humans evolved from an ancestor built like an African ape, significant changes would have had to be made to the pelvis and lower back. This is why Ward believes that it is plausible that we evolved from an ancestor that looked more like Rudapithecus — the transition to upward locomotion would have been more straightforward.

A Rudapithecus pelvis fossil, center, overlain on a skeleton of a siamang, compared with a macaque on the left and orangutan on the right. Credit: University of Missouri

“We were able to determine that Rudapithecus would have had a more flexible torso than today’s African apes because it was much smaller—only about the size of a medium dog,” Ward said. “This is significant because our finding supports the idea suggested by other evidence that human ancestors might not have been built quite like modern African apes.”

In the future, the researchers plan on conducting more 3-D models of the other Rudapithecus fossils in order to learn more about how it moved about, perhaps offering more insights into how our ancestors left the safety of canopies to bravely explore the world on two legs.

The findings were reported in the Journal of Human Evolution.

Here’s what the Denisovans might have looked like

Researchers have used patterns of methylation in ancient Denisovan DNA to predict their anatomical features.

This image shows a preliminary portrait of a young female Denisovan based on a skeletal profile reconstructed from ancient DNA methylation maps. Image credits: Maayan Harel.

The entire collection of Denisovan fossils features a pinky bone, three teeth, and a lower jaw — that’s it. From all that, we not only know that they were a distinct species, but we can also figure out some intriguing aspects about them.

Denisovans are a group of archaic humans in the genus Homo, alongside ourselves and the Neanderthals. A decade ago, we didn’t even know about their existence, until small fragments were discovered in the Denisova cave in Siberia (hence the name Denisovans). Since then, we’ve learned quite a bit about them, although in the grand scheme of things, they still remain a mysterious group.

They lived alongside humans and Neanderthals, interbreeding with both groups, even breeding with the ancestors of some modern groups. For instance, it’s estimated that three to five percent of the DNA of Melanesians and Aboriginal Australians comes from Denisovans.

However, we still have very little idea as to what they looked like.

To shed new light on that issue, researchers used a technique called DNA methylation, which has been used before to suggest anatomical features (and the evolution of such features) in groups of humans.

Quite human. Another predicted portrait of a Denisovan. Image credits:Maayan Harel

Essentially, DNA methylation is a process by which methyl groups are added to the DNA molecule. This changes the activity of the DNA strand without actually changing its structure. From that shifting gene activity, epigenetic patterns can be inferred, and these patterns are then traced back to anatomical features. Using this approach, researchers were able to identify 56 anatomical features in which Denisovans differed from modern humans and/or Neanderthals — in other words, 56 features unique to the Denisovans.

For instance, their skull appears to be wider than that of both humans and Neanderthals, and they also had a longer dental arch.

“We provide the first reconstruction of the skeletal anatomy of Denisovans,” says author Liran Carmel of the Hebrew University of Jerusalem. “In many ways, Denisovans resembled Neanderthals, but in some traits, they resembled us, and in others they were unique.”

“By doing so, we can get a prediction as to what skeletal parts are affected by differential regulation of each gene and in what direction that skeletal part would change–for example, a longer or shorter femur,” added first author David Gokhman.

Image credits: Maayan Harel.

While the method isn’t exactly a perfect predictor, it’s a pretty good approximation. In order to check their findings, the team first compared traits of Neanderthals with those of chimpanzees. They found that roughly 85% of the trait reconstructions were accurate in predicting which traits diverged and in which direction they diverged. Furthermore, while the research paper was in review, another study came out describing a Denisovan mandible — and it fit the prediction.

But while this is helping us make the first steps in truly understanding the ancient group, it may also teach us a bit about ourselves. We only have a general idea about where the Denisovans lived, and little information about what their lifestyle was actually like. The environmental pressure and their reactive adaptations could show us what made us a species survive when our closest relatives didn’t.

“Studying Denisovan anatomy can teach us about human adaptation, evolutionary constraints, development, gene-environment interactions, and disease dynamics,” Carmel says. “At a more general level, this work is a step towards being able to infer an individual’s anatomy based on their DNA.”

Journal Reference: Cell, Gokhman et al.: “Reconstructing Denisovan Anatomy Using DNA Methylation Maps” https://www.cell.com/cell/fulltext/S0092-8674(19)30954-7

Neanderthal extinction not caused by diet

By all standards, at some point, Neanderthals were better prepared for life than any other human species; however, in spite of all this, they were extinct, while ‘we’ fluorished; the reason why this happened is still pretty much a mystery, but as always, some theories have been made. One of the most accepted ones was that the Neanderthal extinction happened because of their diet, that relied too much on meat; however, researchers from George Washington University and the Smithsonian Institution have discovered evidence that prove this theory wrong, showing that Neanderthals ate a lot of cooked plants as well.

“Neandertals are often portrayed as very backwards or primitive,” said Amanda Henry, lead researcher and a post-doctoral researcher at GW. “Now we are beginning to understand that they had some quite advanced technologies and behaviors.”

Dr. Henry worked with Alison Brooks, professor of anthropology and international affairs at GW, and Dolores Piperno, a GW research professor and senior scientist and curator of archaeobotany and South American archaeology at the Smithsonian National Museum of Natural History, Washington D.C., and Smithsonian Tropical Research Institute, Panama; together, they studied Neanderthal teeth and found traces of starch, which clearly points towards a more sophisticated and balanced diet.

“Neandertals and early humans did not visit the dentist,” said Dr. Brooks. “Therefore, the calculus or tartar remained on their teeth, preserving tiny clues to the previously unknown plant portion of their diets.”

The most common belief was that due to the Neanderthal’s diet (that relied mostly on meat) they weren’t able to adapt when some significant climate changes occured, thus being outlived by other humans; but this discovery suggests otherwise. It indicates that the Neanderthals ate pretty much the same things humans did, so in order to find the answer to their extinction, we have to look elsewhere.

“This significant finding provides new insight on the plight of the Neanderthals,” said Peg Barratt, dean of GW’s Columbian College of Arts and Sciences. “It’s also an excellent example of our dynamic partnership with the Smithsonian to further advance learning and discovery.”