Homosexuality And Right Or Left Handedness

Queer handedness

Like most people, I’m right handed, while gay people are somewhat more likely to be left handed than straight people.

Handedness is interesting because we can see patterns in people, but don’t know what makes me right handed and some other person left handed (and we won’t even get into the ambidextrous). Current theories on handedness include genetics, birth stress, ultrasound, and prenatal testosterone. We also know body asymmetry correlates with gendered cognition, so we surmise there may be a relationship between cognition and handedness.

The other confusing thing is that varying studies have come up with conflicting results. One study only found the effect in gay women, while another only found it in gay men. Adding further confusion, the more older brothers a boy has, the more likely he is to be gay, but this is only true for right-handed males. Left-handed males are only more likely to be gay if they have no older brothers. Right-handed males without older brothers, and left-handed males with older brothers, were homosexual at about the same rate.

Clearly something is going on here, but more study is figure out exactly what!

Summary:

  • Gay Men: Tend towards left-handedness. No older brother effect for right-handed gay men.
  • Lesbians: Tend towards left-handedness.

Sources:

  • Lalumière ML, Blanchard R, Zucker KJ., Sexual orientation and handedness in men and women: a meta-analysis. Psychol Bull. 2000 Jul;126(4):575-92. A meta-analysis of 20 previous studies showing gay people are somewhat more left handed than straight people.
  • Mustanski, B. S., Bailey, J. M., & Kaspar, S. (2002). Dermatoglyphics, handedness, sex, and sexual orientation. Archives of Sexual Behavior, 31, 113–122. Found that homosexual women to be more left handed that straight women, but did not find the same effect in heterosexual and homosexual men.
  • Lippa, R. A. (2003). Handedness, sexual orientation, and gender-related personality traits in men and women. Archives of Sexual Behavior, 32 103–114. Found homosexual men more left handed than heterosexual men, but did not find the same effect in women.
  • Blanchard, R., Cantor, J. M., Bogaert, A. F., Breedlove, S. M., & Ellis, L. (2006). Interaction of fraternal birth order and handedness in the development of male homosexuality. Hormones and Behavior, 49, 405–414. Found the older brother effect in handedness.

This article is part of a series, Written on the Body, exploring the correlations between our body structures and sexual attraction.

Homosexuality And Fingertip Swirls

You already know that every individual has a unique fingerprint, but did you know these fingertip swirls are usually asymmetrical? Most of us have more fingertip ridges on our right hands than our left.

Gay people are different. We tend to have higher left hand ridge counts. 30% of us have more fingertip ridges on our left, whereas only 14% of straight people have more on their left hands.

Fingertip swirles seem an odd thing to count, but they tell us something important. Fingertip patterns are highly inheritable, with genetics accounting for 90%–95% of the variation. Our fingerprint swirls are also fully developed by the 4th month of pregnancy, meaning this trait is not affected by other factors in birth, childhood, or later in life.

Body asymmetry is important because it correlates with the ability to perform certain cognitive tasks. Those with higher right hand counts excelled at tasks where men typically excel, and those with higher left hand counts excelled at tasks where women typically excel. Knowing the link between asymmetry and cognitive functioning we learn that fingertip swirl counts tells us there are gender or sexual-orientation related cognitive patterns based in our DNA, factors determined at the moment of conception.

Summary:

  • Gay Men: Tend towards higher fingerprint ridge counts on the left hand indicating pre-natal differentiation.
  • Lesbians: Same effect as gay men.

Source:

  • J.A.Y. Hall and D. Kimura, Dermatoglyphic asymmetry: Relation to sex, handedness and cognitive pattern, (1994) Behavioral Neuroscience, 108, 1203-1206

This article is part of a series, Written on the Body, exploring the correlations between our body structures and sexual attraction.

Homosexuality And Finger Length

Preston left, Kamran right.

If I hold out my hand, I can see that my ring finger and my index finger are about the same length. That may be a sign of my body’s homosexuality. In general, men tend to have longer index fingers than ring fingers, while women’s index fingers tend to be the same size or slightly shorter than their ring fingers.

While finger length sounds like a random data point, it isn’t. The length of our fingers is determined by the amount of testosterone we receive in the womb. Apparently I had less, resulting in feminized finger lengths, while Kamran had the normal amount. This jibes with the concept these are statistical probabilities or tendencies, not absolutes. Lesbians tend towards men’s finger lengths, a sign of a masculinized body.

Strangely, none of this applies to gay men with more than one older brother. As the oldest of five kids, this doesn’t apply to me.

I really enjoy how we learned all this. With serious funding of gay people blocked, researchers went out into public street fairs, asked participants to complete a questionnaire about their sexuality, and then photocopied their hands for measurement later. The triumph of the copying machine as scientific research tool.

Summary:

  • Gay men: Finger length tends towards female patterns, indicating lower testosterone exposure in the womb. The pattern is not seen in gay men with more than one older brother.
  • Lesbians: Finger lengths tend towards male patterns, indicating higher testosterone exposure in the womb.

Source:

  • S. Marc Breedlove et al, Finger-length ratios and sexual orientation, (2000) Nature, 404, 455 – 456

This article is part of a series, Written on the Body, exploring the correlations between our body structures and sexual attraction.

Written On The Body

Looking puzzled at about 12 years old

I hated my body growing up. I was pear shaped, depressed, didn’t enjoy sports, and was lost in the experience of an alternative sexuality blooming in my awkward teenage body. (That story here.) As an adult things got better in my zesty 20s, but then cancers, a burst appendix, and a list of systemic health issues developed, many linked to the trauma of my upbringing. Life has forced me to learn more about the mind-body connection than I wanted to know.

I bring all that up because I am gay through some amalgam of body and soul. How much of my sexuality is from a “gay spirit” and how much was a biological destiny written on my bones, I don’t know, or really care. I am what I am, regardless of how I got here.

That said, it is still pretty fascinating to see the correlations between gay bodies and sexual attraction. Keeping it simple, we can look at what is physically different about gay bodies, and consider why these differences occur. The current list of variations we’ve discovered includes:

For a list of all articles on gay bodies click here.

Homosexuality And The Older Brother Effect

Some of my ancestors floating in the Great Salt Lake around 1926. The guy in the back was a family friend. People use to take the train out to the Great Salt Lake for a day at the Saltair resort, therefore the matching swimsuits. No implication of anyones sexuality implied, I just enjoyed the photo of brothers.

As the oldest child this doesn’t apply to me, but the more older brothers a boy has, the higher the chance a boy will be gay. Younger brothers and sisters of any age have no correlation.

We don’t know why, but there’s an interesting theory. When a mother has a series of boys, and becomes pregnant with another male, her body may have an immune system response that affects fetal development, including sexual differentiation of the brain. This could be a reaction of her female body reacting to a series of male embryos or it could be an evolutionary adaptation to ensure there is a feminized boy in the family if girls fail to appear.

A later study validated the results, and added the calculation that each older brother increases the chances the next son is homosexual by 33%. At an average rate of homosexual orientation of 4%, it would take 9-10 older brothers to reach a 50-50 chance of being gay.

Summary:

  • Gay Men: The more older brothers, the more likely a son is gay.
  • Lesbians: No sibling effect observed.

Sources:
  • R. Blanchard and A.F. Bogaert, Proportion of homosexual men who owe their sexual orientation to fraternal birth order: an estimate based on two national probability samples, Am. J. Hum. Biol. 16 (2004), pp. 151–157.
  • R. Blanchard, Quantitative and theoretical analyses of the relation between older brothers and homosexuality in men, J. Theor. Biol. 230 (2004), pp. 173–187.

Female Ovulation Enhances Gaydar

A human female ovary, just before an egg is released...the moment when a woman's gaydar is most acute.

Huh. Women can more accurately discern whether a man is gay when they are ovulating. Proof here.

Some people say we are not all wired for this whole gay thing, yet it appears women are hard wired with some seriously practical gay awareness.

Girl-On-Girl Bonobo Action And The Location Of The Human Clitoris

How is this for provocative… the location of the human clitoris may be explained by lesbian sex in bonobos, a smaller form of chimpanzees and the animal species genetically closest to humans.

Mr. Bonobo (photo by Ltshears via Wikimedia Commons)

Bonobos are fully bisexual in a matriarchal society, and about half of their sex is same-sex. Also, they have a lot of sex, averaging once every two hours, and twice that often if the relationship is new. Female bonobos are particularly sexual with each other. One female will wrap her arms and legs around another, face to face, staring into each others eyes as they rub their genitals together, screaming and grimacing until they climax. Females also have sex by rubbing their butts together or mounting the other from behind. Males have many ways to interact as well including fondling each other, performing oral sex, and engaging in the descriptively named “penis fencing” which lead to ejaculation.

Interestingly, numerous studies show that bonobos maintain a peaceful society by using sex as an alternative to conflict in their social relations. When researchers put a new and intriguing object into a cage with two female bonobos, they will often have sex with each other before they approach the gift, presumably for stress release.

Meanwhile, in humans, one of the puzzles of human physiology is why the female’s main sensory spot is located separately from the place of direct sexual contact. In males the pleasure center is at the end of the penis, which is why men can happily stick it into just about anything. This motivates men to have sex with women–he derives pleasure from putting his cock into a vagina. But the female is not similarly wired for direct pleasure in intercourse. The orgasmic functions are particularly complex, largely because of the clitoris’s location. But why?

One answer is that the male is already motivated for sex and the resulting procreation, leaving the female body free to evolve for other purposes. The famous primatologist Frans de Waal wrote in 1995, “The frontal orientation of the bonobo vulva and clitoris strongly suggest that the female genitalia be adapted for this [frontal] position.” In her book Evolution’s Rainbow, Stanford biologist Joan Roughgarden notes that,

From the standpoint of female reproduction, little is gained by placing the clitoral neurons near the vagina to further same-sex mating when males are well motivated for intercourse anyway. Instead, the pleasure neurons are shifted to a location that promotes same-sex mating and may yield more effective same-sex bonds, increasing overall Darwinian fitness at no reproductive cost.

(photo by Malloreigh via Flickr)

Roughgarden also notes that Bonobos are one of the few mammals that have heterosexual sex face-to-face. So from the location of the Bonobo female clitoris, we derive that Bonobos evolved bodies that promote same-sex bonding resulting in face-to-face heterosexual sex.

The mind reels. Could it be that human females evolved a frontal clitoral pleasure center because female-female sexual bonding was so vital to our development? Do human males favor the missionary position because of the ways lesbian bonding affected female bodies? And most importantly to men who want to please their partners, is the clitoris separated from the vagina for reasons that have nothing to do with men? This explains a lot of male frustration in chasing elusive female orgasms, as men are fighting a battle nature rigged for the other team. We can conclude that if men get pleasure wherever they put their penis, and women are designed to find pleasure each other, we end up with a same-sex twist on a classical formulation: men sow their seed, and women bond…with each other.

Overwhelming as it seems, every human female body may be a testament to the power and importance of same-sex bonding in women.

Semen, Source Of Mind Altering Chemicals

Jesse Bering

I fell in love with Jesse Bering at first reading. He was grappling with polyamorous relationships in his Scientific American column, and amid all the logical analysis about animal behaviors and the evolutionary relevance of human monogamy, he brought in his own experience of heartache. His point was that heartache itself may have an evolutionary function. Anyone who can talk hard science and heart at the same time has my attention. Plus he’s cute.

Mr. Bering is a research psychologist, and while the human issues he writes about are all over the map, he often focuses on human sexuality in a way that is both scientific and warm. This week’s column takes a fascinating look at the psychological effects of ingesting semen.

It turns out that semen (not sperm, which is the little swimmers, but semen, which is the white goo the spermies travel in) has got some pretty interesting ingredients:

Such anxiolytic chemicals include, but are by no means limited to, cortisol (known to increase affection), estrone (which elevates mood), prolactin (a natural antidepressant), oxytocin (also elevates mood), thyrotropin-releasing hormone (another antidepressant), melatonin (a sleep-inducing agent) and even serotonin (perhaps the most well-known antidepressant neurotransmitter).

No wonder women and gay men get hooked on the stuff, with profound implications about why we desire sexual congress. It makes me wonder about people with sex addictions. Read the whole article, fascinating.