The Molecule of More

PROGRESS

Tribes that kept going, however, would experience unfamiliar envi-

ronments generation after generation after generation. The repro-

ductive advantages of 7R would continue, and 7R carriers would live

longer and have more children. Over time the 7R allele would become

more and more common among these long-distance travelers. And

that’s what we do see. The farther a population migrated, the greater

the frequency of the 7R allele. It didn’t start them moving, but it did

help them survive as they went along.

IMMIGRATION

Movement across the  globe today is  different from what our  prehistoric 
ancestors experienced. Emigration away from one’s native country is a
personal decision rather than a tribal decision. And although the rea-
son may be similar—seeking better opportunities—the 7R allele of the
D4 dopamine receptor doesn’t seem to play a role. Immigrant popu-
lations have about the same percentage of the 7R allele as the people
who remained in their home country. Nevertheless, dopamine seems to
be involved, but in a different way.
In chapter four, when we discussed the role of dopamine in cre-
ativity, we  compared creativity to  schizophrenia, a  mental illness char-
acterized by  excessive dopamine in  the  desire circuit. We  discussed 
ways in which psychotic delusions have things in common with highly
creative ideas and  even ordinary dreams. But  schizophrenia is  not  the 
only  illness characterized by  excessive dopamine activity. Bipolar disor-
der, sometimes called manic-depressive illness, also has a dopaminergic
component, and the condition seems to be linked to immigration.

BIPOLAR MANIA: ANOTHER CONDITION

OF TOO MUCH DOPAMINE

Bipolar refers to two mood extremes (like bicycle refers to two wheels).
People with bipolar disorder experience episodes of depression when