pnas | 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.
