Human evolution; first walking ancestor (Introduction)

by David Turell , Thursday, August 25, 2022, 22:21 (603 days ago) @ dhw

Seven million years ago:

https://www.livescience.com/when-human-ancestors-first-walked-upright?utm_campaign=368B...

"The oldest known human-like species likely walked on two legs as far back as 7 million years ago, a new study finds, and the discovery sheds light on what first set humans apart from our ape relatives.

"Researchers analyzed a thigh bone (femur) and a pair of forearm bones (ulnae) from Sahelanthropus tchadensis, which may be the oldest known hominin — a relative of humans dating from after our ancestors split from those of modern apes — according to the Smithsonian National Museum of Natural History(opens in new tab). First unearthed in Chad in north central Africa in 2001, the remains are about 7 million years old.

"The examination of the femur and ulnae indicated that S. tchadensis not only walked on two feet but also climbed trees, adding evidence that this enigmatic species was bipedal, as an earlier analysis of its skull anatomy suggested.

***

"The partial skull of S. tchadensis that the scientists found revealed that the species was probably close to a chimpanzee in size and structure. Although its brain also appeared chimp-size, its face and teeth more closely resembled those of hominins, suggesting it may have been a close relative of the last common ancestor of humans and chimps, the researchers said.

"Judging by the thick, prominent brow ridges of the skull, the specimen, which the researchers nicknamed "Toumaï," was probably male.

***

"Perhaps the most interesting feature that Toumaï shares with other hominins is the anatomy of the opening at the base of the skull where the spinal cord emerges. In four-legged animals, this opening is normally located toward the back of the skull and is oriented backward. However, in S. tchadensis, this opening is positioned near the middle of the skull and is oriented downward. This suggests that S. tchadensis was bipedal, meaning it walked on two legs, Daniel Lieberman, a human evolutionary biologist at Harvard University...

***

"'Our study shows that the Chadian species has a set of selected anatomical features that clearly indicate that our oldest known representatives were practicing bipedalism, on the ground and on the trees," study co-author Franck Guy, a paleoanthropologist at the University of Poitiers in France, told Live Science.

***

"All in all, "the key finding is that the earliest hominins were bipeds of some sort, reinforcing the evidence that the evolution of bipedalism is what set the human lineage on a separate path from the apes," Lieberman said in the email. "But, like our closest living chimpanzee relatives, early hominins still retained abilities to climb trees.'"

Comment: the driving force for these early hominins was for terrestrial walking. There is no obvious natural driving need for this, so why did it happen? Apes and monkeys have continued to this day happily in an arboreal existance. Why did some folks try to switch? Or did God design the change?