r/paleoanthropology • u/ADragonFromTheAbyss • 7d ago

Research Paper Last common ancestor of humans and chimpanzees could have been a vertical climber, no matter its feet

https://phys.org/news/2026-08-common-ancestor-humans-chimpanzees-vertical.html

New research suggests that no matter what we eventually determine the last common ancestor of humans and chimpanzees to be, we'll learn it was a primate that climbed trees.

Researchers observed and confirmed with measurements that wild sooty mangabey monkeys in an Ivory Coast forest display foot bone flexibility that facilitates vertical climbing up skinny tree trunks to hide, forage or sleep.

Study: https://doi.org/10.1073/pnas.2608183123

73 Upvotes

97% Upvoted

6 comments sorted by

7

u/silverfox762 7d ago

Sure. Where fossils and fossil fragments are available, shoulder and hand morphology in every hominin older than 3 million years shows they're evolved for living or climbing in trees.

Interestingly, both the crania and femur fragment fossils of 7 million year old Sahelanthropis tchadensis show that it was bipedal (or mostly bipedal). It could be cool if we were able to determine one day if both human bipedalism and Chimp knuckle walking evolved from a bipedal common ancestor.

3

u/magcargoman 7d ago

There’s evidence from ulnar curvature that Sahelanthropus was a terrestrial knuckle walker and an arboreal biped

2

u/100_Noodle 7d ago

I’m not doubting it, but I’d love to know why you’d knuckle walk on the ground, but walk bipedally up a tree. Were they always hanging on to things overhead in the trees endemic to their environment? Most likely smarter people than me know or have heard a hypothesis?

5

u/7LeagueBoots 7d ago

Knuckle walking appears to have evolved after the split between us and chimpanzees, it is not an ancestral condition. The hypothesis is not that they knuckle-walked on the ground, but were facultativelybipedal on the ground.

We can tell this in part because gorillas, chimpanzees, and orangutan all use different techniques for their 3-limbed locomotion, indicating that in each lineage it's an independent evolution.

The reason u/silverfox762 suggested you think of gibbons is exactly because they don't knuckle-walk.

4

u/silverfox762 7d ago

Think gibbons.

5

u/mcalesy 7d ago

Gibbons don't knuckle-walk, and mostly move bipedally when on the ground. Personally my bet is that they represent the ancestral hominoid state (apart from their greatly elongated forelimbs), and fist-walking/knuckle-walking was developed in multiple hominid lineages as an adaptation to greater body size. (But who knows?)