Effect of Culture on Observable Genetic Traits

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In arguing for the unequal gene frequencies amongst continent based populations, I've come across a few counterarguments I'd classify as not entirely absurd. I'll respond to one of them here.

Most environment proponents (EP) distinguish between two types of human traits: those affected by the environment ('nurture' traits) and those that are not ('nature' traits). In general, they categorize 'nurture' traits as those corresponding with intelligence, behavior, and social interactions and 'nature' traits' as those corresponding with many physical chracteristics. They contend the 'nature' traits are much less responsive to environment than 'nurture' traits. For example, someone with genes for red hair will always have red hair, independent of the environment. Behavioral traits and intelligence seem to be more conducive to change influenced by the environment. EP's then conclude that the environmental hypothesis is more likely true because they've attempted to isolate intelligence from the genetic or 'nature' category.

This argument is flawed on a number of accounts. First, it's largely a myth that IQ and 'g' areheavily influenced by the environment. Some data follows.

Twin Study: IQ is Inherited

But these new findings suggest that "g" is not just a statistical abstraction, but rather, that it has a biological substrate in the brain. I'm convinced that there are genes.

The finding suggests that environment - their own personal experiences, what they learned in life, who they knew - played a negligible role in shaping it.

Article about IQ Misconceptions:

A 2004 longitudinal study of a Scottish sample, conducted by an Edinburgh team of scientists led by Ian J. Deary, shows that intelligence changes very little after the age of 11. The correlation between IQ measured at age 11 and IQ measured at age 80 is .73. The little-known fact that intelligence remains stable after childhood means, among other things, that there is very little individuals can do in their adolescence and adulthood to increase their intelligence.

So, it's clear IQ scores generally express one's innate and biological intelligence.

Second, by setting up this dichotomy, the EP's try to separate intelligence from those traits that are almost entirely dictated by genetics, like eye and hair color. Then, they can define intelligence as an 'nurture' trait instead of the 'nature' trait we know it to be. Yet, even by their own standards, this dichotomy fails. There are many traits that are almost universally accepted as genetic: like height, weight, build, strength, skin color.

But think about the above physical characteristics. While I agree that each person has a natural propensity towards either being tall or short or fat or skinny, it's ostensibly clear that environment can easily alter these characteristics. So even skin color, an important indicator of racial or ethnic origin, can be significantly altered by sun exposure, which is an environmental stimulus. Physique can be altered through intense exercise.

By setting up this false dual classification, the EP's offer up a strawman argument. No hereditarians espouse an entirely genetic exposition of the race/intelligence problem. Strong hereditarians like Jensen and Rushton have surmised intelligence is 70% inherited, leaving 30% for environmental or cultural factors. Thus, it's reasonable to place intelligence in the 'nature' category because, like weight and strength, it's largely defined by heredity, but not entirely so.