Even if brain size accounts for just 10 to 20 percent of an IQ test score, it is possible to conjecture what kind of average scores would be made by a group of people with 30 percent larger brains. We can readily calculate that a population with a mean brain size of 1,750 cc would be expected to have an average IQ of 149.

This is a score that would be labeled at the genius level. And if there was normal variability among Boskops, as among the rest of us, then perhaps 15 to 20 percent of them would be expected to score over 180. In a classroom with 35 big-headed, baby-faced Boskop kids, you would likely encounter five or six with IQ scores at the upper range of what has ever been recorded in human history. The Boskops coexisted with our Homo Sapiens forebears. Just as we see the ancient Homo Erectus as a savage primitive, Boskop may have viewed us in somewhat the same way.

They died and we lived, and we can’t answer the question why. Why didn’t they out-think the smaller-brained hominids like ourselves and spread across the planet? Perhaps they didn’t want to.

Longer brain pathways lead to larger and deeper memory hierarchies. These confer a greater ability to examine and discard more blind alleys, to see more consequences of a plan before enacting it. In general this enables us to think things through. If Boskops had longer chains of cortical networks—longer mental assembly lines—they would have created longer and more complex classification chains. When they looked down a road as far as they could, before choosing a path, they would have seen farther than we can: more potential outcomes, more possible downstream costs and benefits.

As more possible outcomes of a plan become visible, the variance among judgements between individuals will likely lessen. There are far fewer correct paths—intelligent paths—than there are paths. It is sometimes argued that the illusion of free will arises from the fact that we can’t adequately judge all possible moves, with the result that our choices are based on imperfect, sometimes impoverished, information.

Perhaps the Boskops were trapped by their ability to see clearly where things would head. Perhaps they were prisoners of those majestic brains.

There is another, again poignant, possible explanation for the disappearance of the big-brained people. Maybe all that thoughtfulness was of no particular survival value in 10,000 B.C. The great genius of civilization is that it allows individuals to store memory and operating rules outside of their brains, in the world that surrounds them. The human brain is a sort of central processing unit operating on multiple memory disks, some stored in the head, some in the culture. Lacking the external hard drive of a literate society, the Boskops were unable to exploit the vast potential locked up in their expanded cortex. They were born just a few millennia too soon.

In any event, Boskops are gone, and the more we learn about them, the more we miss them. Their demise is likely to have been gradual. A big skull was not conducive to easy births, and thus a within-group pressure toward smaller heads was probably always present, as it still is in present-day humans, who have an unusually high infant mortality rate due to big-headed babies. This pressure, together with possible interbreeding with migrating groups of smaller-brained peoples, may have led to a gradual decrease in the frequency of the Boskop genes in the growing population of what is now South Africa.

Then again, as is all too evident, human history has often been a history of savagery. Genocide and oppression seem primitive, whereas modern institutions from schools to hospices seem enlightened. Surely, we like to think, our future portends more of the latter than the former. If learning and gentility are signs of civilization, perhaps our almost-big brains are straining against their residual atavism, struggling to expand. Perhaps the preternaturally civilized Boskops had no chance against our barbarous ancestors, but could be leaders of society if they were among us today.

Maybe traces of Boskops, and their unusual nature, linger on in isolated corners of the world. Physical anthropologists report that Boskop features still occasionally pop up in living populations of Bushmen, raising the possibility that the last of the race may have walked the dusty Transvaal in the not-too-distant past. Some genes stay around in a population, or mix themselves into surrounding populations via interbreeding. The genes may remain on the periphery, neither becoming widely fixed in the population at large nor being entirely eliminated from the gene pool.

Just about 100 miles from the original Boskop discovery site, further excavations were once carried out by Frederick FitzSimons. He knew what he had discovered and was eagerly seeking more of these skulls.

At his new dig site, FitzSimons came across a remarkable piece of construction. The site had been at one time a communal living center, perhaps tens of thousands of years ago. There were many collected rocks, leftover bones, and some casually interred skeletons of normal-looking humans. But to one side of the site, in a clearing, was a single, carefully constructed tomb, built for a single occupant—perhaps the tomb of a leader or of a revered wise man. His remains had been positioned to face the rising sun. In repose, he appeared unremarkable in every regard...except for a giant skull.

Source: Discover, 28.12.2009