A set of scientists have proposed the controversial idea that hyperactivity and impulsivity may have had advantages in the ancestral state of man in nature, leading to the preservation of genes that increase ADHD risk. Interestingly, the 7R variant of the DRD4 gene is more common in populations that have migrated long distances, as well as those that are nomadic, compared with settled populations.
In 2008, a team of anthropologists genetically tested Ariaal tribesmen in northern Kenya, some of whom are nomadic and some recently settled. In the nomadic group — and only in the nomadic group — those with the 7R version of the DRD4 gene were less likely to be undernourished.