Researchers have analyzed a pelvis of the 10 million-year-old fossil ape Rudapithecus hungaricus and found that human bipedalism might possibly have deeper ancestral origins than previously thought.
Rudapithecus hungaricus was pretty ape-like and probably moved among branches like apes do now. However, it would have differed from modern great apes by having a more flexible lower back, which would mean when Rudapithecus hungaricus came down to the ground, it might have had the ability to stand upright more like humans do. Image credit: John Siddick.
Rudapithecus hungaricus lived approximately 10 million years ago (Miocene period) in what is now Hungary.
The fossil ape was a relative of modern African apes and humans, a surprise given its location in Europe.
But information on its posture and locomotion was limited, so the discovery of the recently-discovered pelvis is important.
Since the fossil was incomplete, University of Toronto’s Professor David Begun, University of Missouri’s Dr. Carol Ward and their colleagues used new 3D modeling techniques to digitally complete its shape, then compared their models with modern animals.
“Rudapithecus hungaricus was pretty ape-like and probably moved among branches like apes do now — holding its body upright and climbing with its arms,” said Dr. Ward, the corresponding author of a paper published in the Journal of Human Evolution.
“However, it would have differed from modern great apes by having a more flexible lower back, which would mean when Rudapithecus hungaricus 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.”
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.
“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,” Dr. Ward said.
“If humans evolved from an ancestor more like Rudapithecus hungaricus, this transition would have been much more straightforward.”
“We were able to determine that Rudapithecus hungaricus 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.”
“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.”
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Carol V. Ward et al. A late Miocene hominid partial pelvis from Hungary. Journal of Human Evolution, published online September 17, 2019; doi: 10.1016/j.jhevol.2019.102645
