Yet very few chemists could make a living as marriage counselors or political commentators. Analyzing social behavior in terms of molecules sounds harder than forecasting the U.S. economy by playing Monopoly. Knowing the brain's biochemistry is a long way from understanding sex, love, and the ratio of fighting to skating in ice hockey. Nevertheless, modern research methods for manipulating genes and scanning the brain's anatomy have enabled scientists to infer some intriguing links between social behavior and molecules in the nervous system. It shouldn't be surprising.
Molecules make the brain's nerve cells do what they do.
From fighting or fleeing to seeking mates, an animal's social behavior depends on what signals these brain cells send to organs and muscles. Ultimately those signals are under molecular control. Many of the molecules at work in the brain today are there because evolution selected them for their influence on social behavior. After all, social behaviors such as aggression and mating strategies developed in competitive environments. Evolution fine-tuned the brain chemistry underlying such behavior to enhance the prospects of surviving long enough to reproduce.