does our common ancestor with apes had unspecialized hands like us or specialized hands to live on trees ?



does our common ancestor with apes had unspecialized hands like us or specialized hands to live on trees ?

In: Biology

Our hands are highly specialised.

They are built around the opposable thumb, which (afaik) is unique to apes and man. (And since we both have it, our common ancestor probably did too)

While I dont have a background in this I would suggest the opposable thumb to originally be aimed at grasping branches and later refined for finemotor control to facilitate tool usage.

So. I think we are basically still in tree mode, add a prehensile tail (can grip), lengthen the arm and we’d be right at home.

The common ancestor was likely to be a creature similar to a gibbon or orang-utan with similar hands for griping branches and picking fruit off trees.

Our closest ape relatives are chimpanzees and bonobos. They, like other apes, have hands fairly similar to our own. The proportions are different, but they work similarly. Significantly, they can control their fingers mostly independently. They can move one finger, or several fingers.

Monkeys also have opposable thumbs, but they can’t move their fingers independently. All the 4 fingers move together to grasp or extend.

Their hands and arms are much stronger than ours so they can hang from trees and brachiate from one tree to another. Brachiation is what it’s called when you extend hand after hand along “monkey bars”. We can do that due to the specifics of how our shoulder evolved, with a rotator cuff. Monkeys don’t have rotator cuffs so they can’t move in that way—they can’t swing their arms in that fashion.

We have lost a lot of hand strength over time. But there are residual instincts. If you’re around a baby, you will notice they like grasping things, like your finger. They can hold on pretty tightly. This is a remnant of how other primates behave. When a new baby is born, initially the mother carries the baby on her front, while the baby grasps her chest hair—but the baby isn’t yet strong enough to be the soul source of support. When they get a little older and can hold on by themselves, the mother puts them on her back and they grasp, supported by their own strength, their mother’s hair as she moves through the trees. So humans have a vestigial hand strength when a baby, but it’s not needed and they’re not strong enough to hold on for long.