Science in Mind

8 percent of people found to have feet with chimp-like flexibility

Boston University anthropology professor Jeremy DeSilva, with replicas of fossils of primitive humans.
Boston University anthropology professor Jeremy DeSilva, with replicas of fossils of primitive humans. Credit: Jonathan.Wiggs

For over a year, people visiting the Boston Museum of Science took off their shoes for science. Visitors strutted their stuff on a 20-foot-long mechanized gait carpet and a special plate that measured various characteristics of how their feet landed and pushed off when they walked.

In total, Boston University anthropologist Jeremy DeSilva has measured how 650 museum visitors walk, amassing a database that shows the wide array of natural variation in human locomotion.

In a study published in the American Journal of Physical Anthropology, DeSilva has presented the first analysis of 398 adults, finding that 8 percent of those museum visitors had feet that retain a key characteristic of non-human primates—a flexible midfoot that can bend, and which may have helped with climbing trees.

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For years, researchers had wondered whether this particular characteristic—called a midtarsal break—existed only in non-human primates. The people whose feet had this feature not only had a more flexible midfoot, they also had flatter feet.

This line of research intersects with DeSilva’s other work, which tries to reconstruct how human ancestors walked. His recent work on fossils of Australopithecus sediba suggested that the species also had a flexible midfoot suited for climbing, but that would have meant it walked with a hyperpronated gait.

Next, DeSilva is planning a study that will try to connect the dots between form and function, examining both how people walk and what the bones in their feet look like. Starting this summer, he will do medical scans of people’s feet and analyses of their walking. Together, the data will help him understand in what ways their foot anatomy corresponds to nuances in gait. He will also use a 3-D printer to create casts of their foot bones—much like the ones he examines when he tries to understand what ancient bones indicate about how long-extinct creatures walked.

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