West African monkeys' flexible feet challenge assumptions about human‑chimp ancestor

Scientists observing wild monkeys in West Africa have documented the animals’ ability to climb vertical tree trunks using a degree of foot flexibility that had not been recognized before. High‑resolution video footage captured the primates gripping the bark with their toes and adjusting joint angles to maintain balance on steep surfaces, a locomotor skill previously thought to be limited to a few specialized species. The research, conducted in the dense forests of the region, suggests that the anatomical adaptations enabling such climbing are more widespread among African primates than earlier studies indicated.

The findings call into question a longstanding assumption about the morphology and movement of the last common ancestor of humans and chimpanzees. If flexible foot mechanics were present in these West African monkeys, it implies that the ancestral primate may have possessed a broader repertoire of arboreal locomotion, including efficient vertical climbing, than the predominantly knuckle‑walking model traditionally portrayed. This new evidence could reshape reconstructions of early hominin evolution by highlighting the potential for diverse climbing abilities in the lineage that gave rise to both modern humans and our closest relatives.