Much of this research came from the mind and laboratory of Daniel Lieberman, professor of human evolutionary anatomy at Harvard University and author of the new book Exercised, which looks at movement and evolution. Initially, most of the work of his and other scientists focused on evolution and running on the lower body, since the legs play such an obvious role in how we get from one place to another.
Dr. Lieberman was also interested in the torso of runners and especially in their heads. As a long-time marathon runner, he knew that a stable head is crucial to running successfully, but that it is not necessarily easy to achieve. Running is driving. You push off, step up, and then forcefully brake against the floor with every step, putting forces on your head that could make it flop uncontrollably, like that rocking ponytail.
How we manage to keep our heads stable is not entirely clear, however. Like most cursor species or animals, including dogs and horses, we have a well-developed neck band, a tissue that connects the skull and neck. This is not the case with species that are not natural runners, such as monkeys or pigs.
As a young scientist, Dr. Lieberman, he lured pigs – who are inelegant runners – onto treadmills to study their biomechanics. Their heads shook like bobble heads as they were forced to walk, which Dr. Lieberman and his colleagues concluded that they were missing a neck band, a finding that has been confirmed by anatomical studies.
But we humans also have the challenge of being upright on two legs. Probably in order to balance ourselves while running, we eventually started swinging our arms. Dr. Lieberman suspected that the swing of the arms helped stabilize our heads. But if so, there should be coordination between the muscles in our forearms and shoulders, he thought, even though those muscles don’t physically connect. They would have to shoot together and with comparable force while running in order to successfully stabilize our heads.
