Did Human Ancestors Walk on Their Knuckles Like Today’s Chimpanzees? New Research Adds More Evidence to the Debate

After investigating thousands of wrist bones, scientists suspect the last common ancestor species of humans and chimpanzees may have navigated the world on its knuckles

Sarah Kuta | Daily Correspondent

June 2, 2026 11:36 a.m.

Share

Copy linkEmailSMSFacebookXRedditLinkedInBlueskyPrint

Add as preferred source

Walking upright all the time is one of the unique features that sets Homo sapiens apart from other primates still around today. But, before we stood up and started strolling, how did our ancestors move through the world? As they ambled around on all fours, did they navigate on their knuckles, like bonobos, chimpanzees and gorillas do, or did they clamber about with flat palms, like macaques and capuchins?

New research, published May 20 in the journal Proceedings of the Royal Society B, seems to strengthen the case for knuckle walking. But the study’s co-authors caution their results are not conclusive and, until scientists find fossils of the common ancestor species we shared with nonhuman apes, we may never fully solve the mystery of our ancestors’ gait.

Roughly eight to six million years ago, an unknown common ancestor species roamed around the planet. That species eventually split into hominins, such as Neanderthals, Denisovans and H. sapiens, and nonhuman apes, such as chimpanzees and bonobos.

Because the fossil record is scarce, researchers still haven’t been able to determine the identity of that shared common ancestor species. As a result, they don’t know how it behaved or what it might have looked like—but they’d like to find out.

“We became the human lineage, but understanding where we started from is what tells you how we got here,” lead author Laura Hunter, a paleoanthropologist at the University of Chicago, tells Science’s Olivia Maule.

For the new study, scientists compared CT and 3D laser surface scans of 2037 wristbones from numerous extinct and living species, including Homo naledi, Homo floresiensis, gorillas, orangutans and chimpanzees.

Their investigation revealed that hominin wrists share similarities with African apes that may have evolved in response to the biomechanical demands of knuckle walking.

For example, two bones on the thumb side—the scaphoid and centrale—are fused together in both hominins and African apes, an adaptation that researchers think may have helped stabilize the joint during knuckle walking. Two other bones, the lunate and the triquetrum, also show “striking” similarities that suggest “these bones have not changed appreciably since the [two lineages] shared a common ancestor,” the researchers write in the paper.

“Put simply, carpal morphology inherited from an African ape-like, possibly [knuckle walking] ancestor probably facilitated the evolution of the modern human wrist,” the researchers write in the paper.

Even though hominins eventually began walking upright, these shared wrist traits might have persisted because they gave hominins other advantages, such as the ability to manipulate objects like tools, the researchers hypothesize.

The study is the “most comprehensive analysis of the wrist that we’ve seen yet,” Tracy Kivell, a paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology who was not involved with the research, tells Scientific American’s Jackie Flynn Mogensen.

However, Kivell points out that the paper has a few limitations. For one, it focused only on the wrist, which is just one of the many body parts involved in knuckle walking. The findings also don’t definitively prove that the common ancestor walked on its knuckles, as the similarities between hominin and African ape wrists might have evolved in response to some other type of movement, such as climbing.

“We won’t ever know this answer until we find fossils from that time period,” Kivell adds.

Philip Reno, an anatomist at the Philadelphia College of Osteopathic Medicine who was also not involved with the research, also notes that hominins and African apes may simply have similar wrist bones because they are closely related.

“Showing morphological similarity of humans with our closest relatives is kind of the null hypothesis you would expect,” Reno tells Science. “You need differences to really tease out whether there has been actual selection.”

Still, he adds, the study is “impressive” and brings up “many interesting kinds of questions that relate to the mosaic of hominid evolution.”

Sarah Kuta | Read More

Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.