Among the primates from whom we are descended, the victorious male in any encounter may have needed to maintain high testosterone levels in the expectation that his position in the pecking order would be challenged by the next guy coming up. But here it gets complicated. And aggressive behavior seems to require some testosterone in your system. But researchers have yet to show conclusively that adding a little more in males who already have a normal range of the stuff does much to make them more aggressive or confrontational. In one study, Dr. Christina Wang of UCLA found that men with low testosterone were actually more likely to be angry, irritable and aggressive than men who had normal to high-normal levels of testosterone.
Married men tend to have lower testosterone.
It's evolution's way of encouraging the wandering mate to stay home. They are just unmanageable. Dabbs, the author of Heroes, Rogues and Lovers, a book about the importance of the male hormone, is another researcher who believes that T counts for a lot in any number of male moods and behaviors. It's possible for the scientific community to come to such disparate conclusions on the stuff, not just because the research is slim but because the complexities of human behavior are deep. If we're verging on a moment when testosterone will be treated as one more renewable resource, we may soon all get to focus more clearly on just what it does.