Anthropologists: humans born to run

The Globe and Mail

By Oliver Moore
The Globe and Mail

The need to run was crucial to the evolution of the modern human body, a pair of researchers in the United States proposed Wednesday.

According to their theory, the human body is different from its progenitors in a number of ways — including strong buttocks, long legs, shoulders "decoupled" from the skull and a general lack of body hair — because these traits allowed our ancient forebears to run long distances.

This ability let them hunt animals or scavenge carcasses, giving them access to more protein-rich meat than Australopithecines who could walk upright but not run. That access to protein in turn allowed humans to grow the large brains that help define our species.

"These esoteric anatomical features make humans surprisingly good runners. Over long distances, we can outrun our dogs and give many horses a good race," Harvard anthropology professor Daniel Lieberman said in a statement Wednesday.

"Running made us human, at least in an anatomical sense," University of Utah biology professor Dennis Bramble argues. "We think running is one of the most transforming events in human history. We are arguing the emergence of humans is tied to the evolution of running."

The research, published Wednesday in the journal Nature, suggests that Bruce Springsteen may have been right all along — humans really were born to run. But the trade-off was that the humans are less capable of climbing trees and swinging from their branches.

The researchers argue that the genus Homo (which over time included Homo habilis, Homo erectus and, eventually, Homo sapiens) is rooted in a breakaway group of Australopithecines whose characteristics were more suited to running. Natural selection perpetuated and extended those traits, leading to the human features that make long-distance running possible.

"We explain the simultaneous emergence of a whole bunch of anatomical features, literally from head to toe," Dr. Bramble said. "(Our theory) gives a functional explanation for how these features are linked to the unique mechanical demands of running, how they work together and why they emerged at the same time."

Dr. Bramble and Dr. Lieberman began their research 13 years ago, curious why pigs were such poor runners. They noticed that swine lack the nuchal ridge at the base of the skull which allows stronger runners, of both the human and animal variety, to keep their heads steady as they rush along.

Study of fossils showed that the earliest pre-humans did not have this ridge, and nor did chimpanzees.

"As we started to think more about the nuchal ridge, we became more excited about other features of bones and muscles that might be specialized for running, rather than just walking upright," Dr. Lieberman said.

Other features that allow strong running include the Achilles tendons which store energy between strides, a mostly hairless body that allows for sweat evaporation and muscular buttocks which stop the forward momentum of a run from getting out of control.

"Have you ever looked at an ape?" Dr. Bramble asked. "They have no buns."