Down from the Trees NOT Up from the Ground

Humans are the only habitually bipedal apes on the ground. However their ancestors and close kin show signs of adaptations to bipedalism going right back to a certain ape from 20 million years ago, Morotopithecus, as illuminated for us by Dr. Aaron Filler in his book The Upright Ape. One niggling contraindication to this theory is the presence of knuckle-walking in gorillas and chimps, our closest living relatives with whom we share a Last Common Ancestor. However the specific adaptations for knuckle-walking don’t appear in any of our fossil ancestors and now a new study has produced evidence that the adaptations in gorillas and chimps are distinct and likely to have evolved independently…

Upright Gait May Have Roots in the Trees

Bipedal humans came down from the trees, not up from the ground

Eureka-Alert on the new study

…so one particular objection to Filler’s theory has been removed. But is he right? And why did one particular line of arboreal bipeds walk on two-feet on the ground instead of knuckle-walking like their close kin?