In Some Ways, Human Hands Are More Primitive Than Chimp Hands

Humans like to think they're pretty dexterous with their sleek thumbs and strong grips. However, in some respects, our hands might actually be more primitive than those of our closest Great Ape relatives, chimpanzees. That’s what researchers report in a study published July 14 in Nature Communications.

Scientists have long thought that when humans and chimps diverged seven million years ago, natural selection shaped chimp and human hands differently, explains Michael Balter for Science. While chimpanzees grew longer fingers and slightly shorter thumbs, well adapted to their tree climbing lifestyles, humans developed smaller fingers and slightly longer thumbs—ideal for precisely gripping things like tools. 

But now, a growing body of evidence is starting to suggest that only one piece of that logic is sound, writes Balter. Chimpanzee hands certainly did evolve. But human hands have stayed quite similar for millions of years, tool use or not. Some early hominins that didn’t make tools and still appear to have hands that are more like those of modern humans.

To see if our last common ancestor was more like a human or a chimp, researchers measured how the proportions of human and chimp hands had really changed over the years. They sampled living species—humans, apes and monkeys—as well as extinct species, including Proconsul heseloni, Ardipithecus ramidus and Australopithecus sediba.

Based on their measurements they concluded that the ancient ancestor of chimps and humans likely had more human-esque hands. While human paws might seem more sophisticated, the researchers' analysis suggests that the basic structure has been around for a long, long time.

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Helen Thompson writes about science and culture for Smithsonian. She's previously written for NPR, National Geographic News, Nature and others.