Mapping the Effects of Testosterone

As I’ve detailed in the previous two posts, the testosterone system in males in responsible for quite a few behavioral and physical tendencies. Men with higher testosterone are more aggressive. They are more sexual. They are more socially dominant (actually, a man’s testosterone rises and falls in response to how dominant he is in a particular context). They have deeper voices, sharper facial features, broader shoulders, greater hand grip strength, and higher sperm counts. Interestingly, they are also more analytical, making them especially adept at engineering, and tactical games, like chess. Many of these traits also make them more attractive to females. A high testosterone male has great potential to accumulate resources—both social and material—and to be reproductively prolific, especially in societies that permit polygamy.

Take, for instance, Genghis Khan. The man’s insatiable desire to subjugate an entire continent is legendary. Few people have had greater impact on world history, and some argue that no man has had greater impact on the world’s gene pool. It’s estimated that about 1% of men alive today have his Y chromosome. That means that 1 in every 100 men on the planet is a direct, patrilineal descendent of Genghis Khan. And it’s all the outcome of a raging testosterone system. What else would compel a man to so avidly pursue opportunities to rape and pillage? This is an extreme illustration of the evolved purpose of the testosterone system: to drive males towards behaviors that will give them greater access to females who might bear their children.

When looked at from this perspective, you start to wonder about all of the other great emperors of world history. Julius Caesar. Alexander the Great. Xerxes. Napoleon Bonaparte. I’d venture to guess that, if we had access to blood samples for them, each and every one would have an overwhelming testosterone level. It’s interesting to note, though, some details about them that aren’t generally mentioned in our 9th grade history classes. For example, Julius Caesar was a particularly depraved individual. He tortured prisoners of war and was happy to massacre an opposing army. There are quite a few anecdotes about licentious activities with members of both sexes. He is also suspected to have been sleeping with the wives of many of the members of the Senate. And he was romantically linked to Cleopatra, arguably one of the most vaulted females in world history. All of this is consistent with a specific behavioral strategy that is testosterone driven.

My friend and colleague John Hinshaw is a professor of history at Lebanon Valley College in Pennsylvania, and we have recently been working on this idea. He is always quick to point out, though, that not all of these men had many—or even any—children. This is an important point because the behavioral strategy was selected for over time not because it always leads to greater reproduction, but because it does so on average. Can it account for the fact that Alexander the Great seems to have been more interested in male companionship than female consorts? Or that Napoleon was so obsessed with his ever-expanding power that he was somewhat indifferent to reproduction? No, those are individual quirks that are independent of the overarching correlation between testosterone and reproductive fitness. For every such example, though, there’s a Genghis Khan, or a Trujillo (dictator of the Dominican Republic) or a Ramses the Great representing the other side of the spectrum. Each had countless offspring.

One way or another, it’s amazing to think how this one behavioral system has helped to shape the course of history, and to guide the drawing and redrawing of countries and their borders. This is merely a hypothesis at this point, but John and I are brainstorming what types of “data” might be available to support it. The project is in its first stages, so I’m sure we’ll have more to say about it soon…

This brings the first week of posts to a close. As I write this I’m on my way to a meeting of urban researchers called the Promise Neighborhood Research Consortium. Next week I’ll be telling tales of the work that they are doing to improve the everyday lives of city dwellers.


About Dan

Daniel Tumminelli O’Brien, PhD, is the Project Manager of the Harvard Boston Research Initiative at the Radcliffe Institute for Advanced Study. He is also a Visiting Assistant Professor at Binghamton University where he has been a key player in the development of the Binghamton Neighborhood Project. Both projects bring together academic and city agencies in the development of innovative solutions for the everyday challenges of urban life. Amidst these efforts, his own research focuses on urban social behavior. As an educator, he has concentrated on pedagogical techniques that bring evolutionary theory to classrooms outside the biological sciences.
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