In our genes

A detailed molecular portrait of world diversity at the DRD4 locus is provided, showing that the allele associated with ADHD has increased a lot in frequency within the last few thousands to tens of thousands of years, although it has been present in the authors' ancestors for hundreds of thousands or even millions of years.

Abstract

The D4 dopamine receptor (DRD4) locus may be a model system for understanding the relationship between genetic variation and human cultural diversity. It has been the subject of intense interest in psychiatry, because bearers of one variant are at increased risk for attention deficit hyperactivity disorder (ADHD) (1). A survey of world frequencies of DRD4 alleles has shown striking differences among populations (2), with population differences greater than those of most neutral markers. In this issue of PNAS Ding et al. (3) provide a detailed molecular portrait of world diversity at the DRD4 locus. They show that the allele associated with ADHD has increased a lot in frequency within the last few thousands to tens of thousands of years, although it has probably been present in our ancestors for hundreds of thousands or even millions of years. A survey of world frequencies of DRD4 alleles has shown striking differences among populations.