CNN
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The ability of humans to walk. standing on two legs may have evolved in trees, rather than in the soil, according to scientists who study nature chimpanzees in Tanzania
This contradicts the widely accepted theory that prehistoric human relatives evolved to walk on two legs because they lived in an open savannah environment, according to a study published Wednesday in the journal. Progress of science.
Researchers from University College London (UCL) spent 15 months observing the behavior of 13 wild adult chimpanzees in the Issa Valley of western Tanzania, which is home to a mix of dry open terrain and areas of dense forest. Known as a “savanna mosaic,” this type of environment is similar to what our earliest human ancestors lived in.
The team recorded each time the chimpanzees were upright, and whether it happened while they were on the ground or in the trees.
They then compared this to cases of standing on two legs. by chimpanzees living in heavily forested areas in other parts of Africa, and found that Issa Valley chimpanzees spent as much time in trees as their forest-dwelling cousins.
This means that they were not more ground-based, as existing theories suggest, given the more open environment in which they live. Also, more than 85% of the times chimpanzees walked upright occurred in trees, rather than on the ground.
Study co-author Alex Piel, an associate professor of anthropology at UCL, told CNN that the widely held theories follow a certain logic.
“A long-standing assumption has been: fewer trees means more time on the ground, more time on the ground means more time upright,” Piel said.
However, his team’s data doesn’t confirm this, but instead suggests that more open environments were not a catalyst for encouraging bipedalism, Piel said. “It’s not this pretty logical story,” he said.
The next question for researchers is why Issa Valley chimpanzees spend more time in trees despite being near fewer trees than other chimpanzee communities, Piel said.
One explanation could be that the food-producing trees encourage them to spend time there to eat, he said, while there could also be a seasonal component.
In the rainy season, the grass in the Issa Valley grows to around 6.5 feet tall, Piel said, meaning chimpanzees are more vulnerable to ambush predators such as leopards if they spend time in soil.
“It could be that there is a dramatic seasonal signature to this,” he said.
Early human ancestors would also have faced predation in a similar environment, according to Piel.
“It’s a really analog system,” he said.
However, Piel stressed that the study does not draw a direct comparison between chimpanzees and our earliest human ancestors, but instead provides theories that need to be tested against the fossil record to see what it tells us about early hominin anatomy.
