The Early Man Gets the Big Brain
“Why are human brains so big?” asked Live Science. Why are our brains larger relative to body size than almost all other animals? Rachael Rettner reported on various answers. To her credit, she pointed out the fallacies of trying to test hypotheses when there is insufficient evidence.
Rettner evaluated three hypotheses about why early human ancestors developed large brains. She summarized ideas that revolve around climate change, the demands of ecology, and social competition. “But with several competing ideas, the issue remains a matter of debate.”
Can any of these theories be tested, to see which is stronger? She discussed skull analyses by David Geary (U of Missouri), published recently, that tried to tease out the most significant factors. His study favored the social competition theory.
How valid are conclusions like that? Ralph Holloway (Columbia U) commented that the social competition theory sounds good, but he asked, “How would you ever go about really testing that with hard data?” Presumably that is what science is supposed to do to make it stand apart from speculation.
He points out that the sparse cranium data “doesn’t tell you anything about the differences in populations for Homo erectus, or the differences in populations of Neanderthals.” For example, the number of Homo erectus crania that have been found in Africa, Asia, Indonesia and parts of Europe is fewer than 25, and represent the population over hundreds of thousands of years, he said.
“You can’t even know the variation within a group let alone be certain of differences between groups,” Holloway said. Larger skulls would be considered successful, but “how would you be able to show that these were in competition?”
By declaring that “larger skulls would be considered successful,” however, Holloway seems to be begging the question. The success of larger skulls (in evolutionary terms) is the question at issue. Question-begging seemed inherent in his own theory – that in order for brains to enlarge, they needed to have more time for neuron growth, and longer gestation. But why should that be a “driving force behind larger brains” when the success of larger brains has not been established? Presumably, Homo habilis and Homo erectus (and all other animals, for that matter) carved out successful niches for a long time without the increased brain-to-body size ratio.
Rettner considered two other evolutionary hypotheses before concluding. A diet high in shellfish “could have provided our ancestors with the proper nutrients they needed to grow a big brain,” she mentioned quickly, overlooking why other animals with high-shellfish diets did not follow suit. “And another idea is that a decreased rate of cell death may have allowed more brain neurons to be synthesized, leading to bigger noggins.” By now she seems to be grasping at straws.
All that was prelude to a last-paragraph wallop that should cast strong doubt on whether any of this speculating about the evolution of big brains belongs in science:
Ultimately, no theory can be absolutely proven, and the scant fossil record makes it hard to test hypotheses. “If you calculate a generation as, let’s say, 20 years, and you know that any group has to have a minimal breeding size, then the number of fossils that we have that demonstrates hominid evolution is something like 0.000001 percent,” Holloway said. “So frankly, I mean, all hypotheses look good.”
A corollary would be (assuming a level playing field) that “all hypotheses look bad.”
Lately, Live Science has made baby steps toward scientific integrity (compared to New Scientist’s plunge into abject folly – see next entry), so we must be grateful for their effort to walk upright (e.g., 06/25/2009). They still stumble often (06/30/2009). It takes time to learn a new motor skill.
That said, this article does not go far enough. Live Science still cannot think outside the box. It’s nice when Darwinians engage in a modicum of self-criticism (good grief, it’s about time), but when will they take seriously the roar of criticism from outside the camp? Think about it. If all the hypotheses within the Darwin camp are equally good, and therefore equally bad, isn’t it time to ask why the Darwin Team gets to be the only player in the Science Tournament? In what other area of serious inquiry can one viewpoint, that is admittedly bankrupt for ideas, and fouling out left and right with logical fallacies, call all the shots, and exclude from the game any criticisms and alternative ideas? Let’s use those big brains, humans! That’s what they were created for.