Comments on: Sons and lovers

By: Statistical Modeling, Causal Inference, and Social Science

Statistical Modeling, Causal Inference, and Social Science — Thu, 27 Jul 2006 02:01:31 +0000

Homosexuality and the number of older brothers and sisters, or, the difference between “significant” and “not significant” is not itself statistically significant

This paper, “Biological versus nonbiological older brothers and men’s sexual orientation,” by Anthony Bogaert, appeared recently in the Proceedings of the National Academy of Sciences and was picked up by several news organizations, including Scientifi…

By: seth

seth — Mon, 10 Jul 2006 21:49:10 +0000

Point taken – people aren’t ants, and obviously operate in very different ways. I just wanted to bring up the idea that evolution isn’t always the zero-sum game it’s depicted as.

By: Frank Schmitt

Frank Schmitt — Mon, 10 Jul 2006 18:19:41 +0000

It’s a bit of a stretch to bring in the example of ants and other social insects. Sterile worker ants are so-called “supersisters” (sounds like a good name for a band) that share 75% of their genes, which is more than they would share with any sexually-produced offspring. Hence it is more advantageous for them, from a selfish gene perspective, to look after their sisters than to reproduce.

By: seth

seth — Mon, 10 Jul 2006 03:58:52 +0000

I know only children who are gay, so I tend to be skeptical that the older-brother effect is a necessary or sufficient cause.
However, I don’t have much doubt that there can be a genetic basis for homosexuality, despite the fact that in a zero-sum evolutionary game it would seem to be bred out.
Social animals have somewhat different evolutionary strategies than solitary ones. Termites and ants aren’t extinct, even though they have undreds of non-reproducing males and females. Scouting behavior in prairie dogs is suicidal from the individual standpoint but incredibly advantageous from the standpoint of colony survival. Humans, too, are social animals whose evolution has depended on cooperation within groups, and the potential for non-reproducing members of the tribe, to serve as protectors or caretakers for other members of the tribe, strikes me as plausibly advantageous.

By: Hamilton Lovecraft

Hamilton Lovecraft — Sun, 09 Jul 2006 16:52:24 +0000

Let’s run with this. In whose genetic interest would be this response? Not the mother’s or the father’s – their Darwinian interest is to have breeding sons. But it could well pay an elder son to have a younger brother who would not be a sexual competitor for females but remain a natural ally in his own reproductive strategy.
I favor what I call the Funny Uncle Theory.
Your own children carry 50% of your genetic material. Your nieces and nephews carry 25% of your genetic material. (These numbers increase slightly if there are additional ancestral relationships.)
If you’re a late-birth-order male in a subsistence environment, your own children will be competing for resources with your older siblings’ children, potentially reducing all their chances for success. If instead you invest effort in feeding and protecting your nieces and nephews, you can increase their chances of survival and success, which does mean that a birth-order-linked-homosexuality-gene (which obviously is expressed in the mother, not in the homosexual male) could get spread around.

By: James Wimberley

James Wimberley — Sun, 09 Jul 2006 09:46:28 +0000

PS: Many US soldiers believe that MRE chicken will make them gay, possibly because of the currants. http://www.washingtonmonthly.com/archives/individual/2006_07/009141.php

By: James Wimberley

James Wimberley — Sun, 09 Jul 2006 08:42:55 +0000

Brett: too strong an immune system is risky, and the threats it has to handle are very numerous, so I don’r buy that part of your objection. Your Haldane/Hamilton altruistic fitness point is stronger. A heterosexual brother is admittedly less of a competitor than an unrelated male, and other things being equal a male should welcome his kid brother’s reproductive success. But they are not equal; the pool of available females may be small, and the ally payoff large. We can’t go further from our armchairs.
Bruce: of course it’s complex. The facts that some firstborn sons are gay, and some daughters, alone rule out the vaccine theory as a one-shot explanation. But trying to grasp everything at once is an impracticable scientific strategy. Much better to get some hard data – as Bogaert invaluably has done – and worry at them. We now know from his work, not guess, that homosexuality has nothing to do with growing up with older brothers.
Coommonsense: thanks for the additional data point.
My wife has come up with the ingenious point that a homosexual younger son could be in his mother’s interest, as Paleolithic social security. The problem is that the benefit is personal, but not apparently reproductive.
I thought for a moment that the findings shed a new light on the account in Genesis 39 of the failure by Potiphar’s wife to seduce Joseph, “the son of [Jacob's] old age.” Perhaps Joseph just wasn’t interested? But Joseph was the first-born son of Rachel, Jacob’s second wife (Gen. 35:24).

By: CommonSense

CommonSense — Sun, 09 Jul 2006 03:52:04 +0000

Providing further evidence that male homosexuality is biological in origin, the Monell institute published findings from a study of straight and gay male and female response to the body scents of straight and gay male and females in September 2005. Summarized in the institute�s press release, �Gay men preferred odors from gay men and heterosexual women, whereas odors from gay men were the least preferred by heterosexual men and women and by lesbian women.� Also, if I recall correctly, others� perceptions of lesbian scents and lesbians� perceptions of others’ scents were not different in a statistically significant way from heterosexual women�s perception of scents and others� perception of their scents.
The press report can be found here- http://www.monell.org/files/news/martins_2005_pr.pdf
The journal article is online, but access is limited to those with a paid subscription. This is a Blackwell publication, so anyone fortunate enough to have access to internet-based university library materials can likely view the document in some form.
Psychological Science
Vol. 16 Issue 9 Page 694 September 2005
Preference for Human Body Odors Is Influenced by Gender and Sexual Orientation
Yolanda Martins, George Preti, Christina R. Crabtree, Tamar Runyan, Aldona A. Vainius, Charles J. Wysocki
f further evidence4

By: liberal

liberal — Sun, 09 Jul 2006 03:34:37 +0000

Bruce Wilder wrote, “The trouble with specifically seeking genetic/developmental explanations of homosexuality, per se, is that it leaves aside, as somehow settled or uninteresting, genetic/developmental explanations of sexuality.”
What makes you think that anyone doing serious research on these issues views the genetics/developmental issues behind sexuality as “settled or uninteresting”?
“…the homely are not being weeded out of the human population.”
Cf the theory of sexual selection.

By: jim

jim — Sat, 08 Jul 2006 22:39:47 +0000

No. It’s too early to play. You need to have a mechanism. You need some sense of causality before you can surmise where the causality came from.
At this point all there is is a correlation. You don’t know which way the correlation works. The hypotheses so far have been along the lines of “my mother made me a homosexual.” But it may not be that. It may be that women have a way of recognizing and selectively aborting gay fetuses, but the mechanism for doing that weakens with each boy carried to term. (It may, of course, not be that, either.) The evolutionary mechanism for developing that would be very different from a mechanism that developed encouraging homosexuality in later boys.

By: Grumpy

Grumpy — Sat, 08 Jul 2006 19:53:40 +0000

When this was summarized on 60 Minutes a couple of months ago, it included a further twist: the Older Brother Effect is nullified by left-handedness. Somehow.

By: Bruce Wilder

Bruce Wilder — Sat, 08 Jul 2006 19:29:48 +0000

The trouble with specifically seeking genetic/developmental explanations of homosexuality, per se, is that it leaves aside, as somehow settled or uninteresting, genetic/developmental explanations of sexuality.
If you think homosexuality is not, in part, genetic, then, do you think sexuality is not, in part, genetic? Ditto, for developmental explanations.
The notion that sexual attraction, as experienced by self-identified homosexuals, is globally different in its etiology from sexual attraction as experienced by self-identified heterosexuals, seems an odd premise to adopt at the outset of even a speculative investigation.
It would be more sensible to start by trying to analyze what constitutes sexual attraction/attractiveness and willingness/eagerness to engage in sexual intercourse with a particular individual. Even the most casual survey would suggest that there might be a number of discrete and variable elements.
Then, we might ask which particular element was involved in the birth order observations.
We might also begin to ask what combination(s) of discrete elements tend to lead an individual to identify as heterosexual or homosexual, in a culture in which such categories are available, keeping in mind that other cultures and eras seem to have done quite nicely with completely different schemes for categorizing sexual behaviors and identities.
I would not be so certain that there would be any particular evolutionary pressure against homosexuality. Being handsome is reproductively advantageous, but being handsome is a fortuitous combination of factors, genetic and developmental; the homely are not being weeded out of the human population.
You offer one notion of how a dominant elder brother might be aided by a less-heterosexually-inclined younger brother. But, in a complex sexuality in a social species, there are probably multiple strategies in play. Highly attractive (handsome, fit) males have the option of seeking out many partners, offering superior genetic fitness to females, but little committment; lesser mortals might offer a single female more committment and support. Highly dominant males might seek to accumulate many wives, while subservient males might choose to serve, and occasionally cuckold, their lord and master.
Since the reproductive “game” in a social species is very complex, and there are many possible winning strategies, sexuality might have evolved to be quite flexible, and be both developmentally and behaviorally malleable. When monogamy, poligamy and even polyandry have been recorded, when one generation of human family units typically wants 12 children and a few generations later, family units want, at most, two, one has to admire the flexibility implied.

By: Brett Bellmore

Brett Bellmore — Sat, 08 Jul 2006 18:57:47 +0000

If the maternal immune response theory is valid, the evolutionary advantage accrues to the mother, and is due to having a robust immune system, which balances the cost of an increased probablity of one of her offspring not reproducing. No direct advantage to anybody due to the homosexuality itself is required, just as RH disease doesn’t require that giving birth to a sick baby be beneficial, just a cost of something else that is advantageous.
Note that a younger brother isn’t much of a “competitor” from an evolutionary standpoint, because he shares half your genes, and his reproductive success is a partial substitute for your own.