Brain size alone does not tell the whole story, of course. Here, too, the results of the Nature paper are telling. The good news is that the steeper decline in body mass over the past 50,000 years has raised our ratio of brain to body above Neanderthal levels, even though total brain mass has dipped. Calculating the size of our progenitors' brains and bodies from a few scattered bones is a tricky process. Many of the bones vary too much from one individual to another to use for such estimation.
Teeth wear differently depending on diet, for example.
Eye sockets have changed in proportion over the years, and skulls have grown thinner. Past estimates of the body masses of human ancestors have sometimes disagreed by as much as 50 percent. These disparities made it difficult to assess the changing nature of the human line. Measuring these dimensions for 163 fossilized hominids, the scientists were able to plot our genus's changes in brain and brawn. These improved data are already prompting anthropologists to re-evaluate their assessment of the environmental and cultural transformations that shaped human evolution.