Scientists have compared the wrists of humans and apes - and found traces of a shared past

A new study shows that part of the answer is hidden not in the fingers, but in the small bones of the wrist. Scientists compared the wrists of modern humans, great apes and ancient human relatives, and saw that our hand holds traces of a shared past with African apes.

Details

The researchers studied the carpal bones - the small bones between the forearm and the hand. They're usually rarely talked about because all the attention goes to the thumb and fingers in general. But it is the wrist that helps the hand to be both stable, mobile and accurate.

The team compared bones in different primates and in 55 fossil hominins - ancient relatives of humans. To do this, they used 3D scans and computer analyses of the shape of the bones. This approach is needed because carpal bones are small, irregular and poorly described by simple measurements like length and width. Supplementary materials to the article confirm that the authors compared the shape of carpal bones of modern primates and fossil hominins using three-dimensional analysis.

The most noticeable similarity was found in two bones of the inner part of the wrist - semilunate and triangular. In humans, they are closer in shape to the bones of African great apes, especially chimpanzees and gorillas.

But that's only part of the story. While some bones retained ancient features, other parts of the wrist gradually changed. The side of the thumb became especially important - it is the side associated with precise grip and handling of objects.

Simply put, the human hand did not appear as a ready-made "tool". At first, our ancestors used the forelimbs less and less for locomotion, and then more and more for handling objects. The bones of the wrist changed piecemeal: some remained similar to the ancient condition, while others were rearranged to suit new tasks.

Why it matters

This study helps us understand how one of the most important human traits - the ability to work with precision with our hands - arose. Without such brushwork, there would be no sophisticated tools, crafts, writing, many technologies and everyday activities that seem commonplace to us.

The main point here is not that humans have a "monkey hand". On the contrary, the work shows a more interesting thing: evolution doesn't always erase the old and create the new from scratch. It often takes an existing design and gradually modifies it to suit new tasks.

That's why our brush is a mixture of ancient and new features. It has traces of the past, when hands were still important for locomotion, and more recent changes related to precise movements and implements.

Background

Scientists have long argued about how the distant ancestors of humans and African apes moved. Some hypothesise that they may have had traits associated with moving on their knuckles, like chimpanzees and gorillas. Others believe the story was more complex and different primate lineages followed different paths.

The new work doesn't close that argument definitively. It adds an important detail: the shape of the wrist in humans does retain similarities to African great apes, but human dexterity arose through more recent changes, especially in the part of the hand associated with the thumb.

Source

Laura E. Hunter et al, "Did modern human carpal morphology evolve from knuckle walking traits?", Proceedings of the Royal Society B: Biological Sciences, 2026.

In the study, the scientists compared the carpal bones of modern primates and 55 fossil hominins. They used 3D scans and computer analyses of the shape of the bones. The main conclusion: the human wrist is similar in some features to the wrist of African great apes, but the features associated with precise hand movements were formed gradually and are particularly noticeable on the thumb side.