Human evolution: “Ardipithecus ramidus (Introduction)

by David Turell , Thursday, June 17, 2021, 20:34 (1253 days ago) @ David Turell

A very strange pre homo:

https://www.sciencenews.org/article/evolutions-bad-girl

"Ardi’s unusual mix of apelike and monkeylike traits demolishes the long-standing assumption that today’s chimpanzees provide a reasonable model of either early hominids or the last common ancestor of people and chimps — an ancestor which some scientists suspect could even have been Ardi, if genetics-based estimates of when the split occurred are borne out.

"Second, the team concludes, Ardi trashes the idea that knuckle-walking or tree-hanging human ancestors evolved an upright gait to help them motor across wide ancient savannas. Her kind lived in wooded areas and split time between lumbering around on two legs hominid-style and cruising carefully along tree branches on grasping feet and the palms of the hands.

"One member of White’s team argues for a controversial possibility: that two-legged walking evolved because Ardipithecus males had small canine teeth. Many living and fossil male apes fight for mates by wielding formidable canines, but Ardi’s male counterparts had to band together and forage over long distances to obtain mates, his thinking goes.

'In a third slap at scientific convention, Ardi fits a scenario in which a few closely related hominid lineages preceded the larger-brained Homo genus that emerged around 2.4 million years ago, White says. In contrast, many anthropologists think of hominid evolution as a bush composed of numerous lineages that, for the most part, died out.

***

"Ardi sports a peculiar skeletal medley that pushes chimps and gorillas out of the evolutionary spotlight, says anthropologist Owen Lovejoy, a member of White’s team. Ardi’s ancient remains indicate that the last common ancestor of humans and chimps must not have looked much like living chimps, as many researchers have assumed, asserts Lovejoy, of Kent State University in Ohio.

"Since a split 8 million years ago or so, chimps and gorillas have evolved along evolutionary paths that eventually produced specialized traits such as knuckle-walking, he says.

"In his opinion, Ardi indicates that a human-chimp ancestor had monkeylike limb proportions and feet, a flexible and unchimplike lower back, and an ability to move along tree branches on all fours, rather than swinging chimp-style from branch to branch and hanging by outstretched arms.

“'Ardipithecus, not living chimps, offers a remarkably good perspective on the last common ancestor,” he says. “We can’t modify the truth to make chimps more important.”

"That conclusion leaves some scientists unimpressed. “It’s way too early to claim that we know what the last common ancestor looked like without actually finding its fossils,” remarks anthropologist Brian Richmond of George Washington University in Washington, D.C.

"Richmond holds that Ardi lived several million years after the last common ancestor, plenty of time for her kind to have evolved substantial skeletal changes.

"And those changes may not have been as substantial as White’s team claims, adds Richmond. Ardi’s curved toes, wide big toe and large body correspond pretty well to chimps, in his opinion.

"Other fossil evidence suggests that hominids came from a climbing and knuckle-walking ape ancestor that was unlike Ardi, Richmond argues."

Comment: An interesting variation. We still do not know how we exactly evolved. I think I presented this before, but search showed no reference.