The Rational Animal: How Evolution Made Us Smarter Than We Think Read Online Free PDF Page A

make his annual trek from Baltimore, Maryland, to Bogota, Colombia, the bird does not need to be aware of the connections between day length, seasons, survival, and mating.Likewise, it’s a safe bet that we bird-watching hominids are usually unaware of most of the connections between the proximate triggers for our decisions and the ultimate evolutionary reasons behind them.To make decisions right here and now, you don’t need to understand how your choices connect to your ancestors’ success, any more than you need to know the history of the automobile or the principles of the combustion engine to turn the ignition key and drive to the supermarket.But just because you’re not always aware of the ultimate reasons for your behavior, that doesn’t mean they’re not influencing your choices at a subconscious level.
    THE SUBCONSCIOUS INFLUENCE OF THE OVULATORY CYCLE
    Imagine you’re a woman shopping online for clothing.Do you think you will buy different outfits on days when your body’s physiology makes you more likely to become pregnant?
    A woman’s ability to become pregnant depends on her menstrual cycle, which in humans typically spans about four weeks.A woman can become pregnant during roughly one week of the cycle, known as the ovulatory phase .Whereas female chimpanzees advertise their ovulatory phase with a bright red swollen rump, for humans the signals are not so obvious.Without specific education or equipment, most college-age women do not even know when they themselves are ovulating.But if a woman is unaware that she is ovulating, does that mean it can’t influence her behavior?
    To dig a little deeper, marketing professor Kristina Durante and her research team recruited women who were not on hormonal contraception.When the women arrived for the study, they were given a urine test, which involved a trip to the restroom to pee on astick.Although the women were told this test was a measure of their general health, the actual purpose was to determine whether they were experiencing the hormonal surge associated with ovulation.Ovulating and nonovulating women were then sent on an online shopping spree—to a website designed to look like The Gap or Old Navy.The virtual store had over one hundred clothing items and fashion accessories, including pants, skirts, shirts, shoes, handbags, and purses.But the products were strategically preselected.Half the items were sexier, flashier, and more alluring, while the other half were more conservative and demure.Even though none of the women in the study knew whether or not they were ovulating, those in the fertile phase of their cycle chose sexier and more revealing clothing—shorter skirts, higher heels, and sheerer blouses that revealed a lot of skin.
    It turns out that ovulation alters women’s behavior even when they aren’t wearing any clothing at all.In another study, Geoffrey Miller, Josh Tybur, and Brent Jordan recruited a rather unusual team of research assistants—eighteen women who made their living as professional lap dancers in “gentlemen’s clubs.”The women recorded their tips over a sixty-day period, during which the researchers monitored each woman’s phase in her cycle.When the dancers were least fertile, they made an average of $185 per five-hour shift.But when they were ovulating, they made almost twice as much: $335.The researchers speculated that ovulation subconsciously led the women to act sexier, leading an invisible change in the women’s hormonal condition to have a very visible economic effect.
    If you were to ask a woman who is currently ovulating why she chooses to buy a sexy dress, she might offer a proximate explanation, such as “I’m feeling adventurous” or “I’m in a party mood today.”Such explanations are useful for understanding what’s going on at the surface, but they say nothing about why ovulation leads women to feel more adventurous in the first place.At a deeper, ultimate level, the reason why ovulation alters