Intelligence and Genes: The Inconvenient Truth

Researchers have found that people with high intelligence scores tend to have certain regions of the cortex that are larger than average. Shaw expects that some of those patterns will turn out to be the result of the environment. But these regions of the cortex tend to be the same size in twins, indicating that genes are responsible for some of the difference as well.

In recent years, scientists have also published a number of studies in which they claim to have found distinctive patterns of brain functioning in people who score high on intelligence tests. Recently Haier and Rex Eugene Jung of the University of New Mexico surveyed 37 studies examining regional brain size or activity to look for an overall pattern to their results. As Plomin would have predicted, Haier and Jung found no one “intelligence spot” in the brain. Instead they identified a number of significant regions scattered around the cortex. Other studies have implicated each of these regions in different kinds of cognition. “It looks like intelligence is built on these fundamental cognitive processes, like attention and memory, and maybe language ability,” Haier says.

Along with describing the gray matter tissue that makes up the cortex, these studies also find the signature of intelligence in the white matter that links distant parts of the cortex to one another. People with high intelligence tend to have tracts of white matter that are more organized than other people. “The white matter is like the wiring,” Haier says. “If you think about it, you know, intelligence really requires processing power and speed; the white matter would give it the speed; the gray matter would give it the processing power.” _Intelligence In Genes SciAm

Despite the growing body of evidence linking genes and intelligence, there will always be cranks and still more cranks who cannot let go of their attachment to blank slate pretensions to knowledge. But evolution and genuine science care nothing for these political objections. If allowed to work, science and the truth will eventually out.

The genes are able to influence a person's intelligence via several distinct means. From the time that African pygmies split genetically from their African neighbors, 50,000 years ago, humans have been splitting genetic branches from the homo sapiens trunk. As distinct breeding populations separated, they adapted to their differing environments through natural selection. Natural selection can make important changes in human populations much more quickly than we previously believed -- sometimes after only hundreds of years.

Different populations of humans can have distinctly different genetic records, which reflect the vastly different experiences that the distinct populations passed through over the tens of thousands of years since they split from the main trunk. Science understands this, although political correctness continues to hysterically deny the obvious -- turning educated persons who might otherwise make reasonable scientists, into blathering cranks.

Russian scientists showed in the 1990s that a strong selection pressure (picking out and breeding only the tamest fox pups in each generation) created what was — in behavior as well as body — essentially a new species in just 30 generations. That would correspond to about 750 years for humans. Humans may never have experienced such a strong selection pressure for such a long period, but they surely experienced many weaker selection pressures that lasted far longer, and for which some heritable personality traits were more adaptive than others. It stands to reason that local populations (not continent-wide "races") adapted to local circumstances by a process known as "co-evolution" in which genes and cultural elements change over time and mutually influence each other. The best documented example of this process is the co-evolution of genetic mutations that maintain the ability to fully digest lactose in adulthood with the cultural innovation of keeping cattle and drinking their milk. This process has happened several times in the last 10,000 years, not to whole "races" but to tribes or larger groups that domesticated cattle.

Recent "sweeps" of the genome across human populations show that hundreds of genes have been changing during the last 5-10 millennia in response to local selection pressures. (See papers by Benjamin Voight, Scott Williamson, and Bruce Lahn). No new mental modules can be created from scratch in a few millennia, but slight tweaks to existing mechanisms can happen quickly, and small genetic changes can have big behavioral effects, as with those Russian foxes. We must therefore begin looking beyond the Pleistocene and turn our attention to the Holocene era as well – the last 10,000 years. This was the period after the spread of agriculture during which the pace of genetic change sped up in response to the enormous increase in the variety of ways that humans earned their living, formed larger coalitions, fought wars, and competed for resources and mates. _Edge.org

Indeed. The last 10,000 years have exerted enormous evolutionary pressure upon the various distinct breeding populations of Earth. Of course, some populations that existed in more remote areas of the world, may have evaded most of these evolutionary stresses -- until now. That, of course, is the rub. That is why leftist cranks must continue to deny what is directly in front of their noses. The inconvenient truth of intelligence and genes.