PROGRESSthe coding of genes that give people different characteristics. People
who have a long form of the DRD4 gene, such as the 7R allele, are
more likely to take risks. They pursue new experiences because they
have a low tolerance for boredom. They like to explore new places,
ideas, foods, drugs, and sexual opportunities. They are adventurers.
Worldwide about one in five people have the 7R allele, but there’s sub-
stantial variation from place to place.MORE DOPAMINE, MORE DISTANCEThe researchers obtained genetic data from the most well-known
migration routes in North America, South America, East Asia, South-
east Asia, Africa, and Europe. When they analyzed the data, a clear
pattern emerged. Among populations that remained near their origins,
fewer people had a long DRD4 allele compared to those who migrated
farther away.
One of the migration routes they evaluated began in Africa,
went through East Asia, across the Bering Strait to North America,
then down to South America. That’s a long way—and the research-
ers found that the group that made it all the way, indigenous South
Americans, had the highest proportion of long dopamine alleles, 69
percent. Among those who migrated a shorter distance and settled in
North America, only 32 percent had the long allele. Indigenous pop-
ulations in Central America were right in between at 42 percent. On
average, it was estimated that the proportion of long alleles increased
by 4.3 percentage points for every 1,000 miles of migration.
Once it was established that the 7R allele of the DRD4 gene was
related to how far a population migrated, the next question was why?
How did the 7R allele become more common in far-flung populations?
The obvious answer is that dopamine makes people seek out more.
It makes them restless and dissatisfied. It makes them long for some-
thing better. These are exactly the kinds of people who would leave an
established community to go out and explore the unknown. But there’s
another explanation as well.