Science Uncovers Genes Governing Male and Female Behaviors

We tend to think of the differences between men and women in broad, comprehensive terms. Women are more nurturing, men are more aggressive, and on and on. Of course we rationally understand that these traits are influenced by our sex hormones, but on a deeper level we seem to regard the differences in our behavior as somehow fixed. But now new research is showing that, in fact, there are very specific genes that regulate male or female behaviors, and they can be turned on and off at will—which could drastically alter the way we think about what drives us to be who we are.

The connection between sex hormones and behavior has long been understood, but the relationship between hormone levels and gene expression in our brains was less clear. To better understand it, the research, which was conducted by scientists at the University of California, San Francisco, aimed to locate a number of genes that are influenced by testosterone and estrogen and in turn dictate specific sets of male and female behaviors in mice.

To do this, lead researcher Dr. Nirao Shah and his team analyzed sex differences in gene expression in the hypothalamus, a part of the brain that is involved with sensing hormones. They managed to locate 16 genes that were expressed differently in males and in females, and showed that the different expressions were regulated by the sex hormones.

But what they also found is that they could isolate parts of classic male and female behaviors and pinpoint them as being governed by their own particular genes. It's fascinating to think of all of our sex-specific quirks as connecting back to specific genes that can be turned on and off. EurekAlert offers a useful analogy for understanding the relationship between the hormones and genes. If you think of your brain as a house that's wired into the power grid, then,

A sex hormone is similar to the main breaker that connects the house to the utility pole and regulates electricity to the entire house. Individual genes influenced by sex hormones are like the light switches in each room, making it possible to turn the lights on in the kitchen while leaving the bedroom dark.

Shah explains how this plays out in the mice:

It's as if you can deconstruct a social behavior into genetic components. Each gene regulates a few components of a behavior without affecting other aspects of male and female behavior.

In other words, by flipping the switch, you could turn off a mouse's sex drive, willingness to spend time with their young, and even their desire to pick fights—while leaving every other behavioral element unaffected.

Imagine how crazy it would be if we could do that in humans. Don't like it that your boyfriend gets into fights at the bar? Just flip the switch. For now, Shah says that understanding the genes that drive male and female behavior can guide researchers to find the genetic basis for other complex social behaviors. And along the same lines, it could prove very useful in locating which genes are involved in diseases where a gender difference exist, such as autism, which affects four times as many males as it does females.

As good as all that sounds, there is something a bit unnerving about contemplating your genes as a collection of switches that govern your behaviors. On some level it would be a dream to be able to turn behaviors off and on at will—it would revolutionize the way we interact, but, on the more terrifying side of things, it would also totally change our conception of what makes us who we are. Fortunately, manipulating them is a complicated process. So it looks like we have a while until we're all going to need to start popping pills to fine tune ourselves. That's a relief, because for most of us managing the hormones we already have is a big enough job.

Male and female behavior deconstructed [EurekAlert!]

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