Debating the relative import of nature or nurture on human development seems to be one of the perennial conversations that springs up at late night family get togethers. This can be instigated by a recent headline someone has read 'Researchers find genes for intelligence' or some similarly problematic claim. I find myself both energized and agitated by these conversations. Energized as I enjoy conversations around ideas, agitated as I object to the framing at the outset.
To give an example of what I mean by a problematic framing, I have taken an example originally proposed by the evolutionary biologist Richard Lewontin (1991) and recast it as a pedagogical metaphor to help students understand why the analogy is flawed:
“You may have heard people in the media talking about the importance of nature and nurture and debating which of the two is more central in how a person develops. You may have heard some people say, “it’s 75% nature” and another person disagreeing, “no, its mostly nurture”. To understand why that approach to understanding development is not helpful to biologists, imagine someone who has never seen a brick house asking you whether the bricks or mortar were more important. You could answer that the house is mostly brick, and some mortar, or that bricks and mortar are equally important. In doing so, however, what you would be missing is the pattern of the house in which each layer of brick alternates with a layer of mortar. In the same way, at each point in an organism’s development there is an interaction between the genes and the environment. Biologists seek to understand all of the different processes in which genes and the environment interact in the growth of an organism from an embryo to an adult.”
Beyond this point research on the genetic basis of intelligence is further complicated by the contested nature of defining intelligence. The basic rationale for assuming a singular intelligence goes like this: aptitude across domains tends to be co-linear. In other words, if you do well on math in exams, chances are you will do pretty well in reading too. Thus, both math and reading skill must be informed by a superordinate capacity called IQ. The challenge to this logic as presented by Howard Gardner in the Theory of Multiple Intelligences is that scores are co-linear across domains because they are being assessed through standardized tests. And standardized tests mostly measure a particular intelligence concerned with manipulating symbols.
It seems to me a great deal of skepticism is warranted in considering claims about the genetic basis for intelligence and strictly attributing it to 'nature' versus 'nurture'. The interaction between nature and nurture is dynamic since conception and this idea 'Intelligence' is not so easy to define and measure.