Rare 10 million-year-old fossil unearths new view of human evolution

Rare 10 million-year-old fossil unearths new view of human evolution
Rudapithecus was pretty ape-like and probably moved among branches like apes do now -- holding its body upright and climbing with its arms. 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. Credit: John Siddick

Near an old mining town in Central Europe, known for its picturesque turquoise-blue quarry water, lay Rudapithecus. For 10 million years, the fossilized ape waited in Rudabánya, Hungary, to add its story to the origins of how humans evolved.

What Rudabánya yielded was a pelvis—among the most informative bones of a skeleton, but one that is rarely preserved. An international research team led by Carol Ward at the University of Missouri analyzed this new pelvis and discovered that bipedalism—or the ability for people to move on two legs—might possibly have deeper ancestral origins than previously thought.

The Rudapithecus pelvis was discovered by David Begun, a professor of anthropology at the University of Toronto who invited Ward to collaborate with him to study this fossil. Begun's work on limb bones, jaws and teeth has shown that Rudapithecus was a relative of modern African apes and humans, a surprise given its location in Europe. But information on its posture and locomotion has been limited, so the discovery of a pelvis is important.

"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 stood up from all fours, perhaps we should be asking why our ancestors never dropped down on all fours in the first place."

Modern African apes have a long pelvis and short lower back because they are such large animals, which is one reason why they typically walk on all fours when on the ground. Humans have longer, more flexible lower backs, which allow them to stand upright and walk efficiently on two legs, a hallmark characteristic of human evolution. Ward said if humans evolved from an African ape-like body build, substantial changes to lengthen the lower back and shorten the pelvis would have been required. If humans evolved from an ancestor more like Rudapithecus, this transition would have been much more straightforward.

"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."

  • Rare 10 million-year-old fossil unearths new view of human evolution
    A fossil pelvis from Rudapithecus. The pelvis is among the most informative bones of a skeleton, but one that is rarely preserved. Credit: Carol Ward
  • Rare 10 million-year-old fossil unearths new view of human evolution
    Carol Ward, a Curators Distinguished Professor of Pathology and Anatomical Sciences in the MU School of Medicine, and her team used new 3D modeling techniques to digitally complete the fossil's shape, then compared their models with modern animals. Credit: University of Missouri
  • Rare 10 million-year-old fossil unearths new view of human evolution
    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

Ward teamed up with Begun to study the along with MU alumna Ashley Hammond, Assistant Curator of Biological Anthropology at the American Museum of Natural History, and J. Michael Plavcan, a professor of anthropology at University of Arkansas. Since the fossil was not 100% complete, the team used new 3-D modeling techniques to digitally complete its shape, then compared their models with modern animals. Ward said their next step will be to conduct a 3-D analysis of other fossilized body parts of Rudapithecus to gather a more complete picture of how it moved, giving more insight into the ancestors of African apes and humans.


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Human ancestors were 'grounded,' new analysis shows

More information: Carol V. Ward et al, A late Miocene hominid partial pelvis from Hungary, Journal of Human Evolution (2019). DOI: 10.1016/j.jhevol.2019.102645
Journal information: Journal of Human Evolution

Citation: Rare 10 million-year-old fossil unearths new view of human evolution (2019, September 17) retrieved 23 October 2019 from https://phys.org/news/2019-09-rare-million-year-old-fossil-unearths-view.html
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Sep 17, 2019
"human ancestors might not have been built quite like modern African apes".

Well, duh, the two modern apes - humans and chimps - evolved from a common ancestor. Which incidentally looked a lot more like us in hands and feet for instance than the rather specialized knuckle walk capable chimps.

Sep 18, 2019
Huh, not quite sure what you're talking about, @torbjorn. Proconsul was the last one I knew about, and they're 25 million years old, so Rudapithecus at half that would be a much younger species. Tell me more. Do we know what the common ancestor of chimps and us was? And how close are gorillas and orangutans? I noticed you didn't include them as "modern apes."

Sep 18, 2019
Humans *are* apes, you nincompoop.

Sep 19, 2019
Well, duh, the two modern apes - humans and chimps - evolved from a common ancestor.
You forgot orangutans, gorillas, and bonobos.

Sep 19, 2019
@CirclesBeginning: I did not forget, but I wrote poorly since I thought the context was clear. Similarly you forgot that bonobos are a chimp lineage (again, in some contexts, analogous to that we have several species of gorillas, orangutans and gibbons) and that gibbons are apes as well (c.f. see the link below). ;-)

@Da Scneib: Rudapithecus was at 10 Myrs before or possibly at the later human/other apes split that the article describes (see the tree in the link below). So the tree is (IIRC dates) gibbons split at 15 Myrs, orangutans at 15-10 Myrs, gorillas at 10 Myrs, chimps at 6 Myrs; chimps and humans are more closely related to each other than each are to other apes. Nice tree drawing here: https://whyevolut...nt-apes/ . Re my poor wording, see my response to CB above, sorry for that.

Re morphology, it's a huge subject. But chimps and gorillas evolved different type hand walk independently, say.

Sep 19, 2019
- ctd- That is, chimps are less massive and have evolved a special "knuckle walk" tendon lock. Gorillas are massive and walk on hands.

Neither gibbons nor orangutans walk much, but when they do at least gibbons walk like us because they can balance with their arms. And when you project that forward or chimps/humans back towards the common fossil ancestors the two chains meet at a less specialized walk mechanism.

Early humans are mosaic, but a chimp/human common ancestor skeleton, hand and feet, looked more like us than chimps. Chimps have been ten times as successful (populous) during bottlenecks than humans and likely in general until recently, so they have been under a lot of selection for differences. Humans have idled along under random drift, to and fro as chance would have it (c.f. mosaicism). C.f. how chimp chromosome organization and gene transcription factors are much more changed in chimps than in humans vs the common ancestor.

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