Are Our Sexual Brains From the Stone Age?

Aug. 27, 2002 -- Men aren't the only ones with cheating hearts, and scientists do not believe that there is any such thing as a battle of the sexes either, according to a new book that takes a scientific look at sex.

In her new book, Sex: A Natural History, science reporter Joann Rodgers debunks some previous sexual theories, as she explores the biology and psychology of what drives our sexual behavior, from why we find Hollywood star Brad Pitt attractive, to why we sometimes cheat on our mates.

The findings: Sex is a lot more scientific than you might think. Though often influenced by culture, Rodgers found that human sexual behavior, including flirting and courtship, is also determined by biology — and certain rituals are the same now as they were in the era of cavemen.

"A lot of sexual behavior — including what we're attracted to — is hardwired into our brains," Rodgers said. "A lot of it is conditioned by the way evolution formed our brains. Basically, our sexual brains are from the stone age."

The Mating Dance

Culture also plays a role, which leads to variation in sexual behavior among various people and varying ideals of beauty. But there are basic similarities that remain the same.

"Certain kinds of behavior are so universal that they appear to be biologically programmed," Rodgers said. "There is a mating dance."

When scientists studied flirting couples at a hotel bar, they saw some of the same things again and again — gestures that are part of our "brain chemistry," Rodgers said.

A couple that was "connecting" would look into each other's eyes. When they sat down together, the man would lean forward, thrusting out his chest, while the woman would start twirling her hair.

"The man makes the first touch, say pretending to brush something off the woman's blouse," Rogers said. The hands would eventually touch each other, and eventually, the couple heads off to one of the rooms, researchers found.

No Battle of the Sexes

Rodgers also concluded that there isn't really a "battle of the sexes" and that the "Men are from Mars, Women Are From Venus" theory is a misleading one, Rodgers said.

"Battles always have a winner and a loser," Rodgers said. "But in the so-called battle of the sexes both sides have to win or else everyone loses … Scientists will tell you there is no battle."

The ultimate goal of sexual relationships is cooperation and reproduction, despite the different strategies and behaviors employed by each of the sexes to reach it, Rodgers said. A woman for example might "play hard to get," a courtship ritual that her ancestors used, too.

"These are behaviors that have evolved over millions of years, as the ways males and females size each other up," she said. "Men and women aren't different species. Ultimately, the male and female get together and have children — and that's a win-win situation."

Many people believe that infidelity is more of a male trait — something that is part of their makeup, based on the theory that men have needed to spread their sperm, far and wide in the name of evolution.

But that doesn't explain why women cheat too, or whom the men are cheating with, Rodgers said.

"Until the advent of paternity testing, men just didn't have a reliable way of finding out," she said. "Women are probably more like men in this respect than we'd like to think."

Why Women Love Brad Pitt

Among cultures there are different preferences in terms of what is attractive. In the West, there is a lot of emphasis on female breasts, while in Oriental cultures, for instance, there is more of a preoccupation with a woman's neck. Some cultures prefer heavier women.

But the kinds of body types we are attracted to is also linked to another part of our anatomy — our stomachs.

If Arnold Schwarzenegger walked onto a stone age plateau looking as buff as he did when he starred as Conan the Barbarian, women would think "he'll take a whole lot more to feed" than the other men, Rodgers said.

"Our sexual brains evolved at a time when there wasn't that much to eat," Rodgers said. "Arnold probably would have had a hard time finding a mate. People are programmed to be suspicious of extremes — extreme fatness, thinness, or muscularity."

Studies show that even now, most women are not particularly attracted to body builder types. But a moderately muscular guy like actor Brad Pitt, who is also blessed with symmetrical features, is a hit with the ladies. Elizabeth Taylor, Denzel Washington and ancient Egypt's Nefertiti are universally recognized as being full of sex appeal, for the same reason, Rodgers said.

"The first thing we look for is symmetry. Symmetry is a sign of health," Rodgers said. A new study released last week, which found that asymmetrical people are more jealous than others, fits into the theory. Asymmetrical people are less attractive, and therefore more fearful of losing their mates.

Sex and Death

Sex plays a role in our lives until the day we die — and in fact, sex and death are intimately connected, Rodgers found.

"Scientists say that sex and death are intimately related. Bacteria, for example, never die," she said. "They just keep on reproducing — splitting — forever."

Humans are more complex organisms, and when we evolved and started exchanging genetic material, things got more complicated. With bacteria, its whole makeup — just one cell — is devoted to reproduction, and that's all it does.

But with humans, only our sex cells are involved in reproduction, and the rest of our cells, including those that make up our skins and organs, cannot reproduce indefinitely. Sex — or the lack thereof — leads to our demise.

"Our other cells can only divide a certain number of times, and then they die, which is why we die," Rodgers said.