The Jinniushan fossil is "the first thing that we have that has a body size and a brain size estimate from one individual," notes anthropologist Karen Rosenberg of the University of Delaware, whose team conducted the new study. "Other estimates are made from bones that come from different specimens: body size based on a bunch of long bones and brain size from a bunch of skulls. That wouldn't be such a bad thing if we had big samples, but these were tiny samples."
Based on what they had, scientists' best guess was that brain size was increasing relative to body size during the Pleistocene. The Jinniushan specimen bears this out: her brain was large for her body size, even though she was larger-bodied than more primitive peoples. In fact, the lady from Jinniushan is the biggest woman yet found from the Pleistocene, weighing in at an estimated 173 pounds or so and standing some five feet tall. This led some researchers to classify her as a male specimen, but the shape of her pelvis suggests differently. "If we use modern sexing criteria, it looks clearly female," Rosenberg says.
The size and apparent strength of the Jinniushan woman may have been an adaptation to a cold climate. Much like elk or bears, these cold-adapted humans grew larger but with shorter limbs than those of their tropical peers in order to conserve heat more efficiently, the team posits. The research appears online this week in the Proceedings of the National Academy of Sciences. --David Biello