Despite the back pain, foot problems, and other stresses and strains humans feel when walking, we’re pretty good at it. That’s especially true when you compare humans to chimpanzees or other primates.
“Chimpanzees, our closest primate relative, use a lot of energy to walk around,” explained Matthew O’Neill, an instructor in the Anatomical Sciences Department at Stony Brook. “Their cost of walking is 75 percent higher than human walking.”
O’Neill is broadly interested in understanding what role energy use played in human evolutionary history. He believes part of what makes humans unique is the low energy we expend when we walk.
“The energy cost of walking is largely determined by the mechanics of how our pelvis and hind limbs work,” he said. He explores what is different about the way humans walk. If energy were the equivalent of a financial budget, spending less on walking and getting around would allow humans to use those resources in other areas.
“The less we have to use in a given day for locomotion, the more we can allocate to things like maintaining tissue health or on other aspects of living our lives,” O’Neill said.
O’Neill is interested in understanding when and why the human body began to look and work the way it does. Fossils, he said, tell him when humans might have changed the way they walked from our ancestors, while studying humans and chimpanzees may help explain why.
He looks at the forces humans and chimps apply to the ground and the way their limbs move. He uses musculoskeletal models to calculate how bones, muscles and tendons work while walking. He can then try to understand how these different tissues work. One of the areas where he’s collecting data is in how much energy individual muscles consume.
O’Neill’s colleague at Stony Brook, anatomical sciences professor Susan Larson, who has worked with him for five years, called his work “ground-breaking.” For many years, she said, “researchers have been compiling observations characterizing how primates walk, but we didn’t really have much in the way of mechanical explanations for why they display many of these characteristics.”
Larson said O’Neill’s work moves beyond simple descriptive studies to explore “potential underlying mechanical reasons governing their manner of walking.”
O’Neill was recently a collaborator on a broader study on energy use in humans compared with other primates. The main result from that study showed that humans, chimps and other primates use about half as much energy in a 24 hour period as do other mammals, such as mice, antelopes and sea lions. That, O’Neill said, may be information for understanding why primates seem to live longer than other mammals.“There’s simply less wear and tear on our bodies” because of the lower energy lifestyle than other animals have.”
In that study, O’Neill contributed data from research he had done in North Carolina when he was at Duke University on ring-tailed lemurs. There, he had measured daily energy use for these primates, who normally live in Madagascar.
O’Neill is involved in other collaborations as well, including one with Larson, two other Stony Brook faculty members and a researcher from the University of Massachusetts, on a project to develop a computational model of an ape walking on two legs. Once completed, they can use the model to run simulation studies to explore different suggested characteristics of the earliest form of bipedal locomotion, Larson said.
O’Neill is “one of a handful of a new generation of biological anthropologists who are bringing new rigor in the analytical methods applied to studying our own evolution,” Larson added.
O’Neill said he would like to know more about how walking and human walking capabilities evolved. “What I want to do is take information that’s available now and combine it with what we know of living species and get reliable predictions about how a [taxon] might have walked,” he said.
A resident of St. James, O’Neill lives with his wife, Karen Baab, an assistant professor in the Department of Anthropology at Stony Brook, and their infant daughter. The snow has kept them from enjoying rides out on the North Fork, which they hope to resume this spring.
As for looking out at how walking might change in humans, O’Neill, who described his own walk as “slow and lumbering,” said humans don’t need to walk the way we used to, when our “survivorship depended on walking.” As a result, he doesn’t see “a lot changing” in the foreseeable future in the way humans walk.