Brain Size Myth Won't Die
Evolutionists continue to push the idea that bigger brains offer better fitness, despite repeated empirical problems.
“It’s not the size of the dog in the fight, but the size of the fight in the dog,” an old proverb goes. Similarly, it’s not the size of the computer, but the wiring or programming that can make all the difference. Today’s cell phone chips have more ability than the room-sized computers of the early days. This seems so obvious; why, then, do some evolutionists get so focused on brain size? A bigger brain could offer more wiring, but if brain tissue mass were the main determinant of intelligence, elephants or whales would be solving differential equations and keeping us humans in their zoos. Yet crows have more problem-solving ability than chimpanzees, and tiny insects perform remarkable feats with brains smaller than a grain of rice (see Evolution News & Views).
In some sense, the larger brain in humans is a function of our mental abilities compared with those of apes, whose brains (on average) are 1/3 the size. But if it were a linear relationship, the biggest humans would be the smartest. We know that isn’t necessarily true. A small Asian female mathematician can out-think many a pro wrestler or NBA player. And there are cases of disabled humans with severely diminished brains—with even half of the brain missing—who, for most intents and purposes, were normal. Since large brains are costly to maintain metabolically, an evolutionist could make a case that miniaturization would provide a fitness advantage.
Three recent articles show that evolutionists have a hard time letting go of the notion that bigger brains are more fit—and these aren’t even from the field of paleoanthropology, where the myth is endemic.
Zebrafish: PhysOrg reports on Swedish researchers who measured brains of zebrafish and guppies. A single gene, they said, was responsible for the increase in size. The brief article says that bigger brains correlated with intelligence, but it doesn’t say how that was measured. The gene, Ang-1, seems mostly responsible for blood vessel formation in the brain. “We don’t yet know if Ang-1 is important in human brain development,” they say, making giant leaps from fish to mammals.
Guppies: Science Daily titles one of their articles “An evolutionary heads-up: The brain size advantage.” Viennese scientists bred guppies with 12% larger brains, then let them loose in a “semi-natural environment” where they had to survive predation. After about six months the larger-brained fish were more numerous. “We have provided the first experimental proof that a large brain offers an evolutionary advantage,” the lead author boasted (notice after all these decades of brain-size hype, they claim this is the “first” proof). But what does this really prove? The bigger brain might have only helped motor skills and escape speed, not intelligence. They merely assumed that bigger brains are more intelligent:
A larger brain brings better cognitive performance. And so it seems only logical that a larger brain would offer a higher survival potential. In the course of evolution, large brains should therefore win out over smaller ones. Previous tests of this hypothesis had relied on comparison studies looking at the intelligence and survival potential of species with large brains versus species with smaller brains. And species with larger brains do appear to have an advantage. But such studies are unable to show a causal relationship.
They did notice that size is not all good; any advantage had “to compensate for the fact that brain mass is very expensive to develop and maintain.” The results, however, were of dubious evolutionary use, because the larger brain hurt the males:
Large-brained females, whose brains were about 12 percent larger than that of the small-brained females, evaded their predators more often and so had a higher rate of survival. Larger brains did not provide any survival benefit for males. Ethologist Sarah Zala explains: “Male guppies are more colourful and more conspicuous than females and are therefore more easily caught by a predator. A larger brain does not appear to compensate this disadvantage.“
Obviously you’re not helping natural selection if you get eaten. If this were a sex-specific law of nature, we should expect conspicuous male birds, like peacocks, to have smaller brains than drab females. That seems unsupportable. The only conclusion that seems viable is that the larger-brained females of one guppy species in a partly contrived situation either (1) may have been able to dart away from predators faster or (2) had more offspring. That’s only if we can assume the experimental setup was unbiased, was reported honestly, and produced statistically significant results. In terms of neo-Darwinian theory, we don’t even know if the trait was passed on. “Genetic analysis should help provide clarity in this regard,” they say. Indeed; clarity was sorely lacking. Shed a tear, meanwhile, for the large-brained males.
Birds: Corina Logan, a biologist at UC Santa Barbara, got a wake-up call when studying brain size in birds. Everything was rosy one day as she embarked on proving the brain-size paradigm for great-tailed grackles:
“People love to study brain size,” said Logan, currently a Leverhulme Early Career Research Fellow in the Department of Zoology at the University of Cambridge. “It’s a huge topic. And there is growing interest in how brain size varies within a species, which can tell us what factors contribute to the evolution of large brains.“
She had this notion that measuring the skull should correlate other measurement technique, measuring the inside volume of the skull. That way, you didn’t have to kill the bird to get data. Problem: they didn’t sync. Measuring the skull with calipers cannot predict the actual internal brain size. PhysOrg (“The challenge of measuring a bird brain”) reveals the implications of her results:
According to Logan, it’s impossible to approximate brain size using the external skull measurement because it varies so much within this species. That was surprising to her on a couple of levels. “First, I was surprised that the external skull measurements did not accurately predict the actual endocranial volumes,” she said. “But I was also surprised that there was so much variation, particularly in males.”
There’s another more serious implication about the ethical practice of the scientific method that goes far beyond her own work:
Scientists don’t generally publish negative results—i.e. not finding what they’re looking for—but in this case, Logan’s unexpected result is quite interesting. She demonstrated that the Pearson product-moment correlation coefficient, which is commonly used to measure the degree to which two variables relate to each other (such as the two indirect measures of brain size), is not the right test to apply to these data. It overlooks differences in the individual data points, she noted, which was the whole point of the study.
Logan draws a wider net around science: “According to Logan, scientists can no longer take for granted what has previously been determined as accurate and correct,” the article says. In fact, “Statistical methods in biology are in flux right now,” she said. What does this imply about decades of previous studies that used p-values, Pearson coefficients or other then-popular methods to draw conclusions? What does it mean for brain size measurements on humans?
Junk the Myth
Social Darwinism left a dark stain on the history of anthropology. Stephen Jay Gould, in his 1981 book The Mismeasure of Man, recounted in damning detail the practice by racist evolutionists of measuring skulls to prove their belief in the superiority of white Europeans over other “inferior” races. Simplistically thinking “bigger is better,” they rigged their measurements to prove their foregone conclusions, finding ways to toss out measurements that didn’t fit their assumptions.
One would hope we know better now, yet Logan happily jumped into the skull-size game with birds because “It’s a huge topic” and “People love to study brain size.” And why is that? Because it “can tell us what factors contribute to the evolution of large brains.” It’s long past time to junk this myth. Brain size is just one factor among many; any increase in one trait will have tradeoffs in other traits; and quantity does not necessarily correlate with quality. Better a modern microchip than a 1951 Univac. All we can say scientifically is that each species has the brain it needs for its place in the system. It strains logic to assume that mistakes in a gene here or there will improve any trait, especially a brain.
You have the brain you need for your place in the system. Use it.