“It is even harder for the average ape to believe that he has descended from man.” H.L. Mencken
There could be some good news after all coming out of the whole global warming (or ‘climate change,’ if you prefer) thing: it’s going to make humans a lot smarter. The down side is that we’ll be sporting heads the size of medicine balls. That’s just one of the theories presented in a new three-part series airing on the Public Broadcasting System program “Nova,” entitled “Becoming Human: Unearthing Our Earliest Ancestors.” Part 1, which aired November 3rd, opened with a discussion of the skull fossil found in Africa in 2000 called “Selam” (and also occasionally “Lucy’s Child” - a reference to the 3.2-million-year-old partial skeleton discovered in 1974 in Ethiopia). But the episode isn’t as interested in bones as it is in what bones can tell us: the size of humans’ (and other primates’) brains. From an evolutionary standpoint, the object of the show is to identify why we think like humans, while chimpanzees, for example, think like chimps.
The program notes that there was a long-term belief that humanness was a natural byproduct of the trait that most clearly differentiates us from monkeys: walking upright on two legs. In “Becoming Human,” a Harvard anthropologist, Daniel Lieberman, explains his theory that our bipedal natures developed as a way to save energy (an economy car compared with a monkey’s SUV). Says Lieberman of our chimpanzee relations: “It’s poorly designed to withstand the forces of gravity. It has to expend a lot of muscular effort to keep itself from collapsing into a little pile of chimp-ness, or whatever, with each step.” But being bipedal didn’t automatically translate to smarter: there were small-brained bipedal apes around for a long time which didn’t make much in the way of mental progress. The program’s narrator informs us: “As a group, they flourished for about 25 times longer than we’ve been around. They survived and thrived as brain size flat-lined for almost four million years.”
What stimuli finally made the brain grow? Rick Potts, a paleoanthropologist at the Smithsonian Institution, says it was caused by a wildly fluctuating climate. Around two million years ago, Africa experienced a period of instability during which things went back and forth from wet to dry to wet in back a relatively short period of time. Potts says, “Climate changed all the time. And so the idea that we’ve come up with is that variability itself was the driving force of human evolution.” Because only smarter creatures could survive under such conditions, brains got larger. The theory goes that global warming should have a similar effect, so we’ll soon be needing much larger hats to sport on our uber-massive heads. Makes you want to check out Part 2.
“Becoming Human: Unearthing Our Earliest Ancestors” airs Tuesday nights on PBS at 8 p.m., through November 17th.