Sexually Oriented Fingers

Well this report from 2000 is interesting.

The level of male hormones in the womb can influence an unborn child’s future sexual orientation, according to new research from a University of California, Berkeley, professor who used an unusual technique – measuring finger length – to gather evidence.

Marc Breedlove, professor of psychology, also found that higher levels of these male hormones, or androgens, can create a greater than normal tendency for both males and females to develop a homosexual orientation.

“There is no gene that forces a person to be straight or gay,” said Breedlove, who studies the biology of sexual orientation. “I believe there are many social and psychological, as well as biological, factors that make up sexual preference.

“Having said that, these data do suggest that there are some people in the world who are gay because of fetal androgen levels.”

OK What about the fingers.

Breedlove looked at relative finger length because it is influenced by androgen levels in the womb and thus is an approximate measure of fetal androgen levels.

In most people, the index finger is very slightly shorter than the ring finger, but, at least in the right hand, the difference is accentuated by higher levels of androgens during fetal development. Typically, in women, the two fingers of the right hand are nearly the same length. In men, the index finger is obviously shorter.

Breedlove collected data on 720 people who attended three San Francisco Bay Area street fairs in the fall of 1999. Using a portable copy machine, his research assistants had subjects lay their hands flat on the machine to record finger lengths. Breedlove also administered a questionnaire that explored birth order and sexual orientation.

According to the data collected, homosexual women, on average, had a more masculine finger length pattern – an index finger considerably shorter than the ring finger on the right hand – than did heterosexual women.

“… this suggests that at least some lesbians were exposed to greater levels of fetal androgen than heterosexual women,” Breedlove and his colleagues wrote.

Men had more a complicated pattern: There was no direct relationship between finger length and sexual orientation. However, some gay men did appear, based on their finger lengths, to have been exposed to greater than normal levels of fetal androgens before birth.

“This calls into question all of our cultural assumptions that gay men are feminine,” said Breedlove. He said his findings are consistent with other, very sketchy indications that some gay men are hypermasculinized, having a greater average number of sexual partners in a lifetime than heterosexual men, higher than normal levels of testosterone circulating in the blood, and larger genitalia than heterosexual men.

Well what else does that finger set up predict?

It can predict math ability.

A quick look at the lengths of children’s index and ring fingers can be used to predict how well students will perform on SATs, new research claims.

Kids with longer ring fingers compared to index fingers are likely to have higher math scores than literacy or verbal scores on the college entrance exam, while children with the reverse finger-length ratio are likely to have higher reading and writing, or verbal, scores versus math scores.

Scientists have known that different levels of the hormones testosterone and estrogen in the womb account for the different finger lengths, which are a reflection of areas of the brain that are more highly developed than others, said psychologist Mark Brosnan of the University of Bath, who led the study.

Exposure to testosterone in the womb is said to promote development of areas of the brain often associated with spatial and mathematical skills, he said. That hormone makes the ring finger longer. Estrogen exposure does the same for areas of the brain associated with verbal ability and tends to lengthen the index finger relative to the ring finger.

That is amusing. I have math fingers. I did really well on my Math SAT. And a little better than that on my verbal SAT. Engineers who are also good writers are a rare breed. I’m one of them. So what happened to me? Estrogen and testosterone exposure? There is no good way at this late date to find out.

And just so we get the nomenclature correct the fingers are (starting with the thumb)

1st Thumb
2nd Index finger
3rd Middle finger
4th Ring finger
5th Little finger

Here is a page with a finger chart showing the length variations. Reading that page seems like reading a palmistry manual. It does correspond some with the above scientific study. At least in the parts where they overlap.

So what else do we think we know (all science is tentative) about womb hormones? A report from 1993 says:

Scientists realized that without testosterone the genetic blueprint for masculinity was essentially worthless. Indeed, they learned, for a male rat’s brain to become truly organized as male, the rat must be exposed to testosterone within the first five days of life. After the fifth day the masculinizing window of opportunity is closed, and the genetic male will grow up with a “female” brain. In contrast, the brain of a female needs no estrogen for organization; left alone, it will become female.

Thus it came to be understood that what one might think of as the “default brain” for both sexes of the rat is feminine, and that testosterone is as necessary in the creation of a masculine brain as it is in the creation of masculine genitals. This concept, which is the basis of one approach to the neurobiological search for the origins of sexual orientation, is known as the “sexual differentiation of the brain.”

Roger Gorski, a neurobiologist at the University of California at Los Angeles who has long been involved in research on sexual differentiation, looked back recently on the development of his field: “We spent much of our professional careers trying to understand this process of sexual differentiation, and what functions happen within it — male sex behavior, female sex behavior, control of ovulation, control of food intake, body weight, aggressive behavior, some aspects of maternal behavior. You know why male dogs lift their legs when they pee? Because the brain has changed. So this is really a fundamental concept, that the brain is inherently female and to develop as male it must be exposed to masculinizing hormones.”

It is a long article and well worth a read if you are interested in both the science and the social aspects of sexual orientation in humans. Like what was done in the past to humans with the “wrong” sexual orientation. Gruesome stuff mixed in with the science.

How about something more recent? This is from 2012:

From a strictly Darwinian viewpoint, homosexuality shouldn’t still be around. It isn’t the best way to pass along one’s genes, and to complicate the picture further, no “gay genes” have even been identified. According to a newly released hypothesis, the explanation may not lie in DNA itself. Instead, as an embryo develops, sex-related genes are turned on and off in response to fluctuating levels of hormones in the womb, produced by both mother and child. This tug of war benefits the unborn child, keeping male or female development on a steady course even amid spikes in hormones. But if these so-called epigenetic changes persist once the child is born and has children of its own, some of those offspring may be homosexual, the study proposes.

Evolutionary geneticist William Rice of the University of California, Santa Barbara, felt there had to be a reason why homosexuality didn’t just fade away down the generations. Research estimates that about 8% of the population is gay, and homosexuality is known to run in families. If one of a set of identical twins is gay, there’s a 20% probability that the other will be, too.

Furthermore, Rice notes, “homosexuality isn’t just a human thing.” Among California gulls, which he watches from his office window, about 14% of pairs are female-female. In Australian black swans, some 6% of pairs are male-male, and 8% of male sheep are attracted exclusively to male partners.

No doubt you are thinking of cheap sheep jokes. Well they are cheap dates. If you are into that sort of thing. With consenting sheep. Otherwise what ever happens when you take the sheep home is rape. There are laws against that. Well enough of that.

What about hormones? (insert another cheap joke here)

But testosterone doesn’t explain everything, the researchers found. For one thing, female fetuses are exposed to small amounts of the hormone from their adrenal glands, the placenta, and the mother’s endocrine system. At many key points of gestation, male and female fetuses are often exposed to similar amounts of testosterone. Levels of the hormone can even be higher than normal in females and lower than normal in males without any effect on genital or brain structure.

Rice and his co-workers were more intrigued by studies showing that male and female fetuses respond differently to the hormones that surround them, even when one hormone is temporarily higher. In their study, published online today in The Quarterly Review of Biology, the authors propose that differences in sensitivity to sex hormones result from “epigenetic” changes. These are changes that affect not the structure of a gene but when, if, and how much of it is activated—by chemically altering a gene’s promoter region or “on” switch, for example. Epigenetic changes at key points in the pathway through which testosterone exerts its effects on the fetus could blunt or enhance the hormone’s activity as needed, the authors suggest.

Although epigenetic changes are usually temporary, they involve alterations in the proteins that bind together the long strands of DNA. Thus, they can sometimes be handed down to offspring. According to the hypothesis, homosexuality may be a carry-over from one’s parents’ own prenatal resistance to the hormones of the opposite sex. The “epi-marks” that adjusted parental genes to resist excess testosterone, for example, may alter gene activation in areas of the child’s brain involved in sexual attraction and preference. “These epigenetic changes protect mom and dad during their own early development,” Rice says. The initial benefit to the parents may explain why the trait of homosexuality persists throughout evolution, he says.

I did a couple of posts on epigenetics about three years ago. You can find both by going to the post I titled (appropriately enough) Epigenetics.

Since the video link I left there is defunct I’ll repost the video here.

Well ok. I might as well go back to the article that I linked at my post “Epigenetics” – Maybe It Isn’t All In Your Genes – which discusses the heritability of addiction. You might also want to look up my recent DNA, PTSD, And Abused Children.

Cosmos Magazine discussed the subject further in Homosexuality starts in the womb.

While the study of genetics looks at the structure of DNA, ‘epigenetics’ concerns the way in which genes are switched ‘on’ or ‘off’, as a consequence of either external or internal stimuli – from nutrition and environment to specific biological molecules – called epigenetic switches.

The researchers focussed on sex-specific switches that are stimulated by sex chromosomes. These epigenetic switches are ‘erased’ between generations and produced anew in a foetus, with the purpose of regulating exposure to natural variations in testosterone during development. As a result, foetuses with XX chromosomes are less sensitive to male hormones, while XY foetuses are more sensitive to male hormones.

However, on occasion, the switches “escape erasure”, the researchers said, and are passed on to the developing foetus. When the switches are passed from mother to son, or father to daughter, the result can influence sexual preference and feminisation or masculinisation in offspring.

“Once we came up with the idea, different pieces of information started to fit nicely together and everything started to make sense,” Gavrilets said, adding that experimental evidence is still required.

One such piece of the puzzle was the finding that two distinct sexual development traits – when one or both testes fail to descend into the scrotum, and the development of the male urethra opening on the underside of the penis – showed similar epigenetic patterns to those seen in homosexual people.

“It was more of a satisfaction with finding a solution to a puzzle rather than a surprise,” Gavrilets said of the findings, which he adds are “fully compatible with existing data”.

Ryszard Maleszka, a geneticist at the Australian National University in Canberra, said the idea that homosexuality is not genetic is “not exactly new”.

Of course not. But not everything in science needs to be new. Confirmation of existing ideas are important. Either from replication of previous experiments or by a different experimental approach.

Let me finish with something about culture from Time Magazine.

For now, the work is still controversial. Gavrilets says he and his colleagues have been criticized both by conservatives, who weren’t happy with people searching for a biological basis to homosexuality, as well as by some in the gay and lesbian community, who feel they shouldn’t require a scientific investigation to justify who they are.

“It’s been a controversial topic,” Gavrilets says. “There is a lot of misconception in the world about the topic of homosexuality.” Still, he says, “One of the roles of science is to clear up misconceptions, to explain different phenomena or different patterns.”

I have a few more links on the subject that might be of interest. And of course you can find more if you start looking.

Preventing Homosexuality (and Uppity Women) in the Womb?

wiki – Prenatal hormones and sexual orientation

Homosexuality Might Develop in the Womb Due to Epigenetic Changes

From 2005: What Makes People Gay?

My Genes Made Me Do It! – Chapter 7 – Hormones – pdf. The thesis of this book (all the chapters can be found here) is that homosexuality is a choice and neither genetics nor hormones affect that choice. At least not to a degree that can’t be “overcome”. The author discusses the recent epigenetic findings and finds them unpersuasive. He also discusses changing orientation. My take on all this? Sexuality is to a certain extent fluid and some people are more fluid than others.

I was deprived of any contact with females (aside from very long distance looks – 100 yards or more) in Navy boot camp for 3 months. Near the end of that time the guys in the shower started looking good to me. But that was the first and last time something like that ever happened in my life. I’d have to say that as long as there are females around my sexuality is not very fluid. When I was aboard ship (all male crew) port calls monthly or oftener did the trick.

Update:

The “changing orientation” chapter (which I’m still reading) brings up something Camille Paglia (who I adore) said:

…fascist policing of public discourse in this country by nominal liberals who have become as unthinkingly wedded to dogma as any junior member of the Spanish Inquisition. Why should the fluidity of sexual orientation threaten any gay secure in his or her identity?

When identity becomes a religion… On the other hand when religion persecutes some identities, group solidarity might seem critical for self defense. Maybe it is past time we got past persecution. Hopefully another generation or two will solve the problem. One can hope.

Let me add that where I part ways with the author is his aggressiveness in trying to change people from gay to straight. If a person is happy the way they are why is there any need to change them? And if they want to change what is wrong with helping them without coercion? I don’t get his need to have everyone conform to his preferred model. He strongly wants homosexuality to be a disorder. I don’t see it that way. I would suggest that if he needs to change others sexual orientations that he start with sheep. If he can obtain their consent.

Further update:

I’m going to do a post specifically on the “changing orientation” chapter once I have finished reading it, I have reflected some, and my thoughts are gathered. I’m not at all happy with his take on the matter. I think he gets close to a correct understanding at some points but is too uneducated to make all the required connections to properly inform his understanding.