Science of Love, Sex, and Babies

Do beauties inspire higher sperm counts?

Posted in news by jenapincott on July 24, 2009

HughHefner Not all orgasms are created equal. For instance, intercourse orgasms are known to trump masturbatory ones, as evidenced by the amount of dopamine and prolactin produced. For men, sexual excitement produces higher sperm counts. As I recount in BLONDES, men who felt jealous or threatened by the possibility of a cheating partner had higher sperm counts than men who did not. The same is also true of male porn-watchers masturbating to a threesome. When guys watched two men attending to one woman, they had higher sperm counts than when watching one-on-one sex.

Sperm competition is the reason, according to the notorious British biologists Baker & Bellis. Men produce more copious, higher quality semen in situations in which those sperm might compete with rival sperm from other males.

And now there’s more — speculation that beautiful women also inspire men to have better quality sperm.

Female beauty has been found to enhance male sperm quality in other species. The latest evidence comes from a study led by Oxford biologist Charlie Cornwallis on Gallus gallus, a species of bird. Cornwallis and his colleagues discovered that the comelier the chick — e.g., plump with an elaborate comb — the better the quality her partner’s sperm (more motile, higher velocity, with a higher sperm count). Interestingly, this was true of dominant males but not subordinate ones, who appeared to put everything they had into every copulation. From Cornwallis’ perspective, the most fit males invest their best loads in the most reproductively fit females.

No study has yet proven that the same is true in humans — it’s not exactly ethical to recruit a guy to have sex with both a beauty and a plain Jane and then compare the aftermath. A beauty bias that affects sperm count may be true only in a wildly polygamous species, which humans are not.

Even so, this theory applied to humans doesn’t sound so controversial if you think about it — after all, sperm counts in men are associated with sexual excitement. Beauty can spark frisson. Even more exciting to ponder is how in practice an alpha male would make a larger reproductive investment in the most desirable mate. How does a Hugh Hefner decide? And wouldn’t it be ironic if this were true?

What are “female hormones” doing in semen?”

Posted in news by jenapincott on March 29, 2009

It happened again to my friend C. — she had an affair with a dashing Moroccan guy two weeks ago and got her period early. She always experiences short or untimely cycles in the beginning of relationships, and do many women I know. One study found that one out of every three gals reports getting her period early in response to a new sex partner, or — as been found among Army wives — a visit from an existing one who lives far away. Even among women whose cycles are like clockwork, novel sex can make them cuckoo.

There are many factors that can throw off a cycle, including emotional excitement and stress. As I discuss in BLONDES, there’s evidence that sweat and semen can, too. Digging deeper into the psychobiology of semen, I stumbled upon a provocative theory. It all begins with the discovery that semen contains “female hormones” including follicle stimulating hormone (FSH) and luteinizing hormone (LH).

Why are these so-called female hormones in semen? The answer, according evolutionary psychologists Gordon Gallup and Rebecca Burch at SUNY Albany, is that they increase the man’s chances of impregnating the woman. Unlike females of other species, women don’t advertise when they’re ovulating. And because ovulation is concealed and the fertile window easy to miss, it may take many months of regular sex for conception to happen.

But what would happen if men could control the timing?

Turns out that hormones in semen may do exactly that — by mimicking the conditions of ovulation. The FSH in semen causes an egg in an ovary to ripen and mature. The LH in semen triggers ovulation and the release of the egg. If a woman is near ovulation — say, in the first week or so of her cycle — these seminal chemicals may be sufficient to induce an early release of the egg. By synchronizing ovulation with sex, a man improves his chances of conception in a casual encounter.

As a reason why female hormones are present in human sperm, the theory sounds plausible. Women conceal ovulation to prevent men from knowing when they’re fertile (for reasons I discuss in the book). Men, in an evolutionary tit for tat, developed ways to induce ovulation to increase the chances of conception. Indeed, when researchers analyzed the sperm of chimpanzees, which advertise ovulation rather than conceal it, levels of the female hormones LH and FSH were low to nonexistent.

Of course, questions remain: How do women’s cycles normalize a few months into the relationship despite ovulation-inducing hormones? Are FSH and LH hormones exclusively “female;” what other purposes might they have for men?

As for my friend C., she didn’t get pregnant from her fling. Fortunately, her cycle only accelerated. But the risk of a surprise pregnancy is one more reason why it’s a good idea to use a condom.

The “psych” in semen

Posted in news by jenapincott on March 25, 2009

hypnotize2My post on mind control properties in semen still attracts a disturbing amount of attention. So to appease your curiosity — and, I’ll admit it, mine — I’ve decided to do a little more investigation into the compounds in semen that may enter the bloodstream after sex. Some may have an indirect effect on the recipient’s hormones. A few may breach the blood-brain barrier, directly influencing mood and sex drive. Several, but not all, of the chemicals have been studied and proven to pass through the vaginal walls. From an evolutionary perspective, mood-modulating components in semen may give a woman an incentive to be in a committed relationship with regular, frequent sex. Apparently, the goo is bonding.

The information below comes from SUNY Albany evolutionary psychologists Gordon Gallup and Rebecca Burch, whose fascinating study on semen and depression I describe in BLONDES. Gallup and Burch wrote a chapter, “The psychobiology of human semen,” published in a compilation of research on sexuality. What they describe, I think, is fascinating.

The primary putative mind-altering ingredients in semen:

Luteinizing hormone: astounding concentration in semen; linked to high sperm count and motility. Absorption into female bloodstream may facilitate or even induce ovulation.

Prolactin: influences maternal behavior, oxytocin secretion; mediates bonding

Estrone and estradiol: assists in recipient’s absorption of other compounds such as progesterone; may boost woman’s sexual motivation and mood

Testosterone: may increase sex drive and motivation; the more intercourse, the higher the testosterone levels in women, and the stronger the sexual desire. More than half the amount of testosterone in sperm has been found to be absorbed by the vagina.

Cytokines: these are the “warriors,” they suppress immune reaction to semen invading the vagina and cervix and therefore increase likelihood of pregnancy

Enkephalins: these opioids may contribute to orgasmic experience. They may decrease anxiety and cause drowsiness after sex.¬† There’s also speculation that they assist in immune function and “reinforcing effects” — making a woman come back for more, i.e. addiction¬† (although the absorption rate in female bloodstream is unknown)

Oxytocin: assists in stimulation of ovulation, increases production of other hormones, initiates bonding, facilitates orgasmic contractions; may strengthen bonding and make sexual activity more rewarding

Placental proteins, including human chorionic gonadotrophin (hcg) and human placental lactogen: associated with sperm motility; may increase chances of pregnancy

Relaxin: made in the prostate, this hormone may facilitate fertilization, implantation, and uterine growth. The role of relaxin suggests that women should keep having a lot of sex during pregnancy because sperm has pregnancy-maintaining properties. Relaxin also facilitates implantation and prevents preterm labor.

Thyrotropin-releasing hormones: potential anti-depressive; works by stimulating the release of thyroid-stimulating hormone, which in turn triggers hormone production in the mood-mediating thyroid gland. In pill form, it’s used to treat PMS and depression.

Serotonin: increases sperm motility.¬† It also mediates mood, although not much known yet about vaginal absorption. Even if it doesn’t make it to the brain, it may indirectly alter behavior and emotions by contributing the building blocks of serotonin

Melatonin: increases effects of steroid hormones; induces sleepiness and fatigue, which may help the woman relax after sex; may stimulate reproductive function, also mood mediator; low melatonin levels are associated with depression and “reality disturbance”

Tyrosine: a precursor of neurotransmitters such as dopamine, the hormone of reward and addiction, and norepinephrine, involved in attention and arousal

Oh, and there’s also sperm in there, the DNA-bearing courier. Sperm is less than 3 percent the total volume of semen. But as it turns out, the bath water is nearly as important as the baby.

n.b. Although not yet studied, researchers suspect that these chemicals in semen may also enter the bloodstream through mucous membranes when having oral and anal sex. If so, straight women aren’t the only lucky recipients.

Semen has mind control properties

Posted in news by jenapincott on January 8, 2009

hypnotism-0250-pg1The more a woman has sex with her partner, the more committed she becomes, and the less attracted she is to other men — at least in the short-term. I blogged about this study several weeks ago and offered explanations both hormonal and psychological. But another theory came to my attention today in the form of a study on fruit flies.

For decades, scientists have known that female Drosophila refuse sex for a period of time after contact with seminal fluid. This may give a reproductive edge to the first male with whom a female has sex. A study led by Geoffrey Findlay at the University of Washington has finally shed some light on the phenomenon. It turns out there are proteins in seminal fluid, many of which transfer to the female after sex. Some of these proteins are warrior-like — they fight the sperm of rival males. Other proteins are like hypnotists — entering the female’s circulatory system, they may hormonally dampen her interest in sex with other males. Somewhat disturbingly, the more semen a female is exposed to, the more influence the male has over her reproductive tract and her mating behavior. Semen, it seems, has mind control properties.

So what does this mean for humans? The same study hasn’t been done on men and women, but researchers speculate that many of the same proteins are in the semen of human males. “Does semen make you happier?” is one of the questions posed in BLONDES. In answering it I describe a fascinating study at SUNY Albany that found that, yes, women who are regularly exposed to their partner’s semen are less depressed than women who use condoms most of the time. Hormones and proteins are absorbed through the vagina, enter the bloodstream, and possibly breach the blood-brain barrier. Might these factors in men’s semen manipulate women’s minds (and bodies) in the way that fruit fly spunk affects female fruit flies? Perhaps, but it’s hard to prove. Women’s love lives (and psyches) are a little more complicated than those of Drosophila. After all, a woman in love with the man with whom she has unprotected sex would be happier and more faithful anyway. It’s a puzzle for all scientists who study human sexuality: Where to draw the line between chemical love and Eros? The seminal and the sacred?

n.b. Here is a list of the potential mind-altering “ingredients” in sperm.

A smart man is just sperm’s way of spreading more sperm

Posted in news by jenapincott on November 6, 2008

super_spermEvolutionary psychologist Geoffrey Miller, author of The Mating Mind and the famous stripper study described in BLONDES, recently found another interesting connection: smart men have better sperm.

Analyzing the data of 425 veterans who took IQ tests and submitted sperm samples, Miller found a statistically significant link between men’s IQ and their sperm quality (higher scorers had higher sperm count and motility). Miller is the biggest propagator of the theory that intelligence is a sexually selected trait. Women, the choosier sex, are attracted to intelligence — expressed in anything from problem-solving to songwriting — because it’s a sign of “sexy” high-quality genes and overall developmental fitness. And because a woman can’t test a man’s sperm directly for these qualities, she has to judge him by what comes out of the head sitting on his shoulders.

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