Wednesday, December 24, 2003

IQ and Genetics

Just a quick note. I've been carrying on a conversation elsewhere with one individual who's been notable for his commitment to the notion that the International HapMap Project would soon provide the answer to the question to which he presumes to know the answer, namely "are differences in IQ measurements between 'racial' groups a reflection of historical events, or an indicator of fundamental, genetically-mediated, intellectual limitations of some groups by comparison with others?"

This fellow would say "yes," and he expects to be able to say so soon, but the fact is when it comes to attempts to link most complex human traits to particular genetic markers, the record has been a dreadful one. As soon as we go beyond the simple framework of "one gene = one disease" to thinking about complex, multigenic traits, the task of establishing valid correlations between genes and behavior becomes exponentially harder. The embarrasing retraction of Robert Plomin's much ballyhooed claim to have linked extremely high IQ to the IGF2R gene is a case in point. Cases like this lead me to be sceptical that anyone will establish to general satisfaction that certain gene combinations are more common in group A than group B, and that the people in A are therefore indisputably, genetically capable of more intellectual heavy-lifting than those in B.