Biology

Chimp study refutes prevailing theory on origins of bipedalism

Chimp study refutes prevailing theory on origins of bipedalism
Despite living in a mixed woodland/grassland environment, the chimpanzees observed in the study spent just as much time in the trees as chimps living in tropical forests
Despite living in a mixed woodland/grassland environment, the chimpanzees observed in the study spent just as much time in the trees as chimps living in tropical forests
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One of the chimpanzees carries her infant on her back, as she makes her way through the trees
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One of the chimpanzees carries her infant on her back, as she makes her way through the trees
Despite living in a mixed woodland/grassland environment, the chimpanzees observed in the study spent just as much time in the trees as chimps living in tropical forests
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Despite living in a mixed woodland/grassland environment, the chimpanzees observed in the study spent just as much time in the trees as chimps living in tropical forests

It has long been believed that our prehistoric ancestors started walking on two legs as they moved from the trees into the more open environment of the African savanna. A new study of chimpanzees, however, suggests that such may not have been the case.

Known as the Savanna Hypothesis, the prevailing theory suggests that as tropical forests began receding due to natural climate change, the early hominins that lived in the trees of those forests started venturing out into the savanna. Because the savanna consisted of a mix of woodlands and grasslands, the apes gradually began walking upright, in order to better traverse the open spaces.

All of that having been said, not everyone completely buys into the hypothesis. Among those who now question it are scientists from University College London, the University of Kent, and Duke University in North Carolina, who conducted the recent study.

Over a 15-month period, the researchers observed a group of 13 wild adult chimpanzees living in the Issa Valley of western Tanzania. The "savanna-mosaic" landscape of that region is very similar to that of our early ancestors, consisting of a mix of dry open land and patches of forest. Because chimps are humankind's closest living relatives, it seems likely that over the millennia, the Issa population would adapt to their landscape in a manner similar to that of prehistoric hominins.

One of the chimpanzees carries her infant on her back, as she makes her way through the trees
One of the chimpanzees carries her infant on her back, as she makes her way through the trees

Refuting the Savanna Hypothesis, it was found that the Issa chimpanzees spent just as much time in the trees as their counterparts living in dense forest environments, rarely going out into the grasslands. Additionally, even when they did make their way across the open ground, they still tended not to walk upright. In fact, over 85% of the occurrences of bipedalism that were observed took place when the apes were in the trees.

"Our study suggests that the retreat of forests in the late Miocene-Pliocene era around five million years ago and the more open savanna habitats were in fact not a catalyst for the evolution of bipedalism," said University College London's Dr. Alex Piel, co-author of a paper on the study. "Instead, trees probably remained essential to its evolution – with the search for food-producing trees likely a driver of this trait."

The paper was published this week in the journal Science Advances.

Source: University College London via EurekAlert

6 comments
6 comments
DavidB
It's laughable that educated, intelligent university researchers seem to think that evolution is the same as adaptation, concluding that early hominids must not have EVOLVED over hundreds, thousands, or millions of years to walk upright, simply because a group of closely related hominids did not ADAPT over a few weeks, months, or years to walking upright.

I'd have expected such ludicrous research conclusions to have been published on April 1.
Cymon Curcumin
DavidB:
I agree with your point.
White Rabbit
DavidB, The chimps were OBSERVED for 15 months to see if thousands of years of living on the savanna had produced more/less bipedal behaviour than in chimps living in denser forest. The 15 months does NOT refer to how long the chimps lived on the savanna, but how long they were studied. Nobody expected them to adapt (or evolve) while being observed!
The troll-like failure to understand the research premises is exactly why it takes "educated, intelligent university researchers" to conceive and conduct such research, and why reading comprehension is an important part of both education and intelligence.
akarp
@DavidB: LOL, Evolution IS Adaptation...over time, that leads to changes that can be inherited through successive generations. By studying 'similar' environments that cause adaptation (if we observed bipedalism behavior), we would hypothesis these environments lead to the evolutionary changes of bipedalism.
ARF!
speaking of, "tool use" by chimps contrasted against footage of fish cracking shells against rocks (something they could have been doing for millions and millions of years without ever evolving to do that better, cause, y'know... FISH) never convinced me that they were ever entering any kind of actual stone age. yet, anyways.
guzmanchinky
Yet again we have so many "experts" on here who with one fell swoop of a keystroke stating their FACTS, seek to inflate themselves above researchers and scientists who spend their lives pulling together data and observations to make a THEORY on how things MIGHT have been different.