Human Brain Size Varies Twofold

We’re all human, but some of us have brains twice the size of others. And areas inside the brain can vary, too. What does this mean?

P. K. Reardon and a team of neuroscientists, publishing new research in Science, studied the brains of 3,000 individuals and found a lot of variation. To evolutionists, this should be surprising, because we’re all members of the same species, Homo sapiens, and all humans are interfertile. We can all learn to eat the same food, we can learn each other’s languages, and we can make children. The same variability we see in body shapes and sizes, hair types, eye color, skin color and other outward traits extend inside our brains as well. Reardon’s team tried to bring evolution into the picture, but how successful are they?

Brain size variation over primate evolution and human development [growth from the embryo] is associated with shifts in the proportions of different brain regions. Individual brain size can vary almost twofold among typically developing humans, but the consequences of this for brain organization remain poorly understood. Using in vivo neuroimaging data from more than 3000 individuals, we find that larger human brains show greater areal expansion in distributed frontoparietal cortical networks and related subcortical regions than in limbic, sensory, and motor systems. This areal redistribution recapitulates cortical remodeling across evolution, manifests by early childhood in humans, and is linked to multiple markers of heightened metabolic cost and neuronal connectivity.

Their use of “recapitulates” sounds awfully [literally ‘awful-ly’] like Haeckel’s discredited Recapitulation Theory, which has been thoroughly debunked by Jerry Bergman in his new book Evolution’s Blunders, Frauds and Fallacies, ch. 10. The organization of human brains today has nothing in common with evolution from a presumed ape-like ancestor. It is not retracing evolutionary steps. Certain human brain regions are larger than others, but Reardon’s team presents no transitional forms on which to base that claim, and watching a baby grow doesn’t reveal what mythical path an ape took on the road to humanity. He doesn’t even mention any archaic humans in his paper—not Homo erectus, not Neanderthal Man, not Homo naledi or the Hobbits.

Writing a Perspective piece about Reardon’s paper for Science, David Van Essen, too, tries to drag evolution into the picture. He also links the evolution of the human species to the embryonic development of the individual, implying some kind of recapitulation.

What makes humans unique as a species and as individuals? Our uniqueness stems from language, tool use, reasoning, and other cognitive abilities that are largely mediated by specialized regions of the cerebral cortex. These regions of higher cognitive function have expanded disproportionately during human evolution (compared with nonhuman primates) and during postnatal maturation, when cortical surface area expands threefold between infancy and adulthood. Our uniqueness as individuals reflects countless differences in brain structure, function, and connectivity. One basic anatomical difference between similarly aged individuals is a more than 1.5-fold variation in total brain size (and total cortical volume). On page 1222 of this issue, Reardon et al. bring this aspect of individual variability under the umbrella of “differential scaling” by showing that human brains of different sizes do not scale uniformly across all regions. Rather, larger brains show greater expansion in regions associated with higher cognition and less expansion in regions associated with sensory, motor, and limbic (emotion- and affect-related) functions.

Van Essen and Reardon’s team both try to associate IQ with brain size. This cannot be the case, or else large men would always be smarter than petite Asian women. Any math professor can tell you that is not necessarily the case; perhaps the converse is true! Reardon’s team did not draw any correlations, in fact, between body size and brain size. They did, however, submit every participant to a Wechsler IQ test, a highly dubious measure that is subject to criticism by other scholars (e.g., a paper in the Journal of Psychoeducational Assessment). Even though they only said that everyone scored at least 80 on the test, whatever use they made of IQ should be tossed out. Human beings are far too complex and individualistic to be rated on a linear scale, and definitions of intelligence are also subject to cultural and linguistic biases. Van Essen shares other reasons for doubt about brain evolution:

A simple a priori hypothesis is that brains of different size might be linearly scaled versions of one another. However, there is already evidence against this hypothesis, insofar as the cerebral cortex is a mosaic of many cortical parcels (areas) that each show more than twofold individual variability in size. But are individual differences in the size of various parcels correlated systematically, for example, according to function? Reardon et al. analyzed data from more than 3000 healthy individuals, drawn from three independent cohorts: the Philadelphia Neurodevelopmental Cohort (PNC) and National Institutes of Health (NIH) cohort (each comprising children and young adults), as well as the Human Connectome Project (HCP) cohort (comprising young adults only). By using in vivo structural magnetic resonance imaging (MRI) scans of individual brains, surface models of the cerebral cortex were generated and aligned to a surface-based cortical atlas. Local cortical surface area was then expressed in relation to individual differences in total cortical surface area (see the figure). Notably, both age and sex were ruled out as confounding factors, even though average brain size differs by age and sex. Areal scaling maps show broad similarities across the three cohorts in terms of which regions are expanded in larger brains (positive scaling) and which are less expanded in larger brains (negative scaling). However, there are many differences across the three cohorts, and regions that pass statistical significance for only one or two cohorts might not reflect genuine neuroanatomical effects. Given concerns about reproducibility, it is notable that Reardon et al. carried out what is effectively a multicohort reproducibility analysis.

Real brains do not come with dotted lines around regions, like a “cortical atlas” might. The methods and findings indicate a great deal of subjectivity and assumption. The only sound conclusion from this study of 3,000 individual brains (people who responded to an advertisement) is that the humans show a large amount of variation in size and shape of their brains, and yet they are all members of the same species.

The paper could get by easily without any reference to evolution. Reardon et al. could simply show differences between human and ape brains, and show the extent of variability between human brains. That would be science. Asserting any Darwinian connection between apes and humans, without demonstrating how blind chance could have crossed that chasm, goes far beyond the data.

Evolutionists continue to show fascination with brain size, and yet they know from past blunders to be politically correct and not rank humans by race or ‘fitness’ (whatever that is). Creationists can draw different conclusions. Knowing that brain size can vary twofold among living humans, what about dead humans? When you find a small skull in Homo naledi, or the Hobbit, does that imply they were less intelligent, or less human? Absolutely not. There are small people with small skulls today, and large people with large skulls. One cannot predict their intelligence except by getting to know them. And a ‘dumb’ person, with a little education and time, can get smarter. For all we know, the small-stature humans were intelligent even with fewer cubic centimeters of skull size.

Another important conclusion we can draw is that humans, unlike other species, show tremendous individuality. Look at one minnow, or one crow, and you’ve seen pretty much all of them. No two human faces are alike. No two human personalities are alike. And now, we see that no two human brains are alike. This is more evidence that we are each unique beings made by God for His glory. Use your brain for that, not for sacrificing to the Bearded Buddha.