The neurotransmitter serotonin is known to be important in mood and behaviour; now researchers have shown that its function is also essential to the survival of baby mice.
Evan Deneris at Case Western Reserve University in Cleveland, Ohio, and his colleagues compared the reproductive success of normal mice with that of animals lacking many of the neurons that produce serotonin. Litters in the care of mothers with low serotonin levels died within a few days of birth despite adequate nursing.
The mothers' behaviour explained this: they built poor-quality nests and did not keep their offspring huddled together, leaving the litter exposed to the cold. When these mothers' young were fostered by normal mothers immediately after birth, their odds of living rose to normal.
SSRIs, the common drugs that inhibit the re-uptake of Serotonin (which makes it more present) are not available for rats. Jokes aside, I am stunned that the presence or absence of one molecule can so dramatically alter behavior and mood and therefore directly be a factor in selection. Mental illness is a terrible thing, but maybe mostly a chemical thing?
I strongly believe in better living through chemistry.