A genetic variant associated with ADHD has been found at higher frequency in more nomadic populations and those with more of a history of migration. Consistent with this the health status of nomadic Ariaal men was higher if they had the ADHD associated genetic variant (7R alleles). However in recently sedentary (non-nomadic) Ariaal those with 7R alleles seemed to have slightly worse health.
Science and the hunter vs. farmer hypothesis
The hunter vs. farmer hypothesis proposes that the high frequency of ADHD in contemporary settings "represents otherwise normal behavioral strategies that become maladaptive in such evolutionarily novel environments as the formal school classroom." An important view, with considerable genetic backing, is that some of these genetic variants may have value in certain kinds of social groups, such as those that have migrated. Genetic variants conferring susceptibility to ADHD are very frequent—implying that the trait had provided selective advantage in the past.
A 2008 New Scientist article by Tim Callaway reports that research of ADHD and related traits in different cultures offers some support for the hunter vs. farmer hypothesis. According to evolutionary anthropologist Ben Campbell of the University of Wisconsin–Milwaukee, studies of the Ariaal, an isolated nomadic group in Kenya, suggest that hyperactivity and impulsivity—key traits of ADHD—have distinct advantages to nomadic peoples. Additionally, nomadic Ariaal have high rates of a genetic mutation linked to ADHD, while more settled Ariaal populations have lower rates of this mutation. Henry Harpending of the University of Utah reports that with this genetic mutation, "You probably do better in a context of aggressive competition."