In his book “How Sex Works,” Dr. Sharon Moalem answers questions about the evolution of sex. In this excerpt, he breaks down the cause of spring fever and shares the origin of the kiss.
Imagine for a second it’s a beautiful spring day, and a woman sees a good-looking man across the aisle at the grocery store — you know ... tall, dark, handsome, and symmetrical. She catches his eye, and she gets that familiar tingle. Why does that familiar tingle seem to be so familiar every spring?
Spring fever, of course. It’s directly related to the increased sunlight that follows winter. The explanation for spring fever is actually pretty straightforward. Increased sunlight, which is detected by your eyes and via the optic nerve, and a group of neurons in the brain called the suprachiasmatic nuclei, eventually communicate to the part of the brain known as the pineal gland. The reporting of sunlight prompts your pineal gland to cut down its production of melatonin. Discovered in the late 1950s by a team of Yale researchers led by dermatologist Dr. Aaron B. Lerner, melatonin is a hormone that our body produces naturally which is involved in the regulation of circadian rhythms. This is the cycle of bodily chemistry and behavior that you follow from day to day — the most basic, of course, being awake and asleep. Melatonin has gotten some fair attention as an over-the-counter aid for long flights, supposedly helping people find midair sleep easier and jet lag less of an issue. And naturally occurring melatonin in our bodies is certainly linked to the desire to sleep and changes in mood. So, as we bask in spring’s sunlit glow, we’re also tamping down on the flow of melatonin, waking us up, lifting our mood, and, in many cases, possibly turning us on. Of course, after a long winter, the fact that it’s finally spring doesn’t hurt either.
Back to the guy across the grocery store aisle. She’s now holding his gaze, and tilting her neck to one side. Her mouth is curling in a not terribly subtle hint of a smile. Is he staring right back at her, maybe raising his eyebrows a bit? Yes, they’re flirting.
Flirting is the body language call and response of the mating game, and its vocabulary and grammar are deeply ingrained in our subconscious. “Flirting is a way of testing one’s mate-value and the possibility of alternatives — actually trying to see if someone might be available as an alternative,” says Arthur Aron, a psychology professor at the State University of New York at Stony Brook. When Irenaus Eibl Eibesfeldt filmed African tribes in the 1960s, he found women doing the exact same tilt of the head and little smile we just imagined a woman offering the man in the grocery store. Of course, flirting is not the sole domain of heterosexuals, everyone does it.
You see somebody who looks attractive. You flirt with them. They flirt back. At some point, you’re probably close enough to smell them. You keep flirting. So do they. And whether it’s another ten minutes, or over a series of dates, if you keep responding favorably to each other and things proceed, eventually it happens.
The first kiss. Why do we kiss in the first place? Zoologist and author Desmond Morris proposed in the 1960s that kissing might have evolved from primate behavior termed prechewing. This is the practice in which a mother would begin masticating or chewing food (prior to the modern convenience of commercial baby food), before passing it off to her young, using her mouth.
Regardless of how the practice of kissing arose, it is important to mention that it’s not totally cross-cultural. In The Expression of the Emotions in Man and Animals, published in 1898, Charles Darwin wrote in reference to kissing: “It is replaced in various parts of the world, by the rubbing of noses.” This behavior possibly refers to the practice of kunik, historically practiced by the Inuit and somewhat similarly by the Maori; it’s part sniff, part nuzzle, not the commonly mistaken “rubbing of the noses.”
In the majority of cultures where kissing is practiced, it can be a very important test of a relationship’s potential. In fact, a study published in 2007 says the first kiss is so important it can kick a budding relationship into higher gear or cut it off altogether. In the study, 59 percent of the men and 66 percent of the women reported having been initially attracted to someone, but losing interest when the first kiss just didn’t feel right. Why? The study’s author thinks it’s because you’re still playing the mating game — gathering information, making judgments, assessing this person’s suitability as a potential mate and possible partner—and you’ve just raised the stakes. And, when you kiss, you exchange all kinds of information with the person you’re kissing. In an article in Scientific American, author George Gallup of the State University of New York at Albany said:
Kissing involves a very complicated exchange of information — olfactory information, tactile information and postural types of adjustments that may tap into underlying evolved and unconscious mechanisms that enable people to make determinations ... about the degree to which they are genetically incompatible.
To put it in the most straightforward terms, if you kiss somebody who tastes unpleasant, it’s likely to turn you off. Which makes me think that the odds are that bad taste means something; it could be a sign of a microbial infection — for example, the bacterium Helicobacter pylori that’s associated with ulcers — or other parasites and even diseases. Or it might just mean all is not right.
Excerpted from “How Sex Works” by Dr. Sharon Moalem. Copyright (c) 2009. Reprinted with permission from HarperCollins. To read more from this book, .