Senior Seminar in Neural and Behavioral Sciences
Bryn Mawr and Haverford Colleges, Spring, 2002
Session 5: The Genetics of Sex, Gender, and Mate Preference
Discussion
(Readings and Web Links)
Dictionaries define 'gender' as basically the equivalent to sex. However, if you would look at the anthropological definition, it would most likely say that gender is a product of culture.
It makes sense that empirical evidence would indicate that females do prefer male traits that would most strongly stimulate their senses. Certain traits and qualities attract certain people. We have heard the saying that "sex sells". We learn about people's preferences in psychology and how certain people find other people attractive because they feel that they can obtain those people. However, I agree with the article on "How Females Choose Their Mates" which said that the benefits and costs of being choosing when selecting a mate differ for different species, in different environments and sometimes at different times of day. People tend to mature as they get older and what they look for in a mate may change. We know if we ask women what the top qualities they look for in a man and men what they look for in a woman, the answers usually differ. We know that some men want someone who is like their mother, while others do not.
Genes and the brain play an important role in human behavior. Science becomes especially hard when emotions are involved. Is your DNA really your destiny? There is complexity of links between genes and human behavior. Behavior in general is very complex. I agree that particular genes might influence personality traits that could in turn influence the relationships and subjective experiences that contribute to the social learning of sexual orientation. I think there are both biological and experiential factors that contribute to sexual orientation. We know that people can grow up in a household with two gay parents and not grow up gay. There probably is some kind of correlation between structure of the AC and sexual orientation, whether or not the size of the INAH 3 nucleus of the hypothalamus correlates as well. However, with LeVay's studies, the homosexual brains he sliced all came from men who had died of AIDS, therefore the cells could have been significantly affected by AIDS or the medication they might have been taking for it. Researchers can sometimes be confused as to what they are studying when they assess sexual orientation in their research. Did LeVay really know what sexual orientation those people really were? People can be one sexual orientation and act another for various reasons. There was not a range. He also did not include lesbians in his study and the sample size was not that large. Did LeVay's studies really prove that anyone was born gay? Are men gay because of a smaller INAH-3, or was their INAH-3 smaller because of the activities they engaged in, their thoughts, or their feelings? Our brains change in response to changes in behavior and the environment.
However, what exactly are all these studies trying to say? Doesn't everyone have a right do what they want with their bodies? There are many studies being done to try and find out what causes someone to be a homosexual. However, is society itself saying that there is something wrong with being gay? If a gay gene is found, would the nature/nurture question finally be answered? Is it genetic? Is it a choice? Is it neither?There was even studies about the size of your index finger and your sexual orientation. What would exactly be done if we did find scientific evidence?
I think the best evidence for a biological (would not necessarily be genetic) basis would come from animal studies. Most studies of the biology of homosexuality are based on the theory that almost everyone is either almost exclusively heterosexual or almost exclusively homosexual.What about being bisexual? Does that even exist according to science? One study can show a strong genetic factor in male homosexuality while other studies can show that identical twins are more likely to both be gay than non-identical twins. This just shows that the nature-nurture debate will likely continue for awhile. Also, another important thing to keep in mind is that genetic influence does not equal complete determinism.
Like Rebecca, I feel that sex is chromosomally determined either XX or XY with some rare anomalies, but that gender is a social construct. Mate selection can be socially and genetically influenced, but the extent of each seems to be species-dependent. Although studies on guppies have showed that females can engage in rather complex discriminations between male guppies based on color preference, boldness and fitness, and social factors and imitation, it is unlikely that one could decipher similar patterns in female human beings. I do not deny that there may be a genetic or evolutionary draw to certain males, but this "chemistry" is hardly reason enough to pick a mate. I agree that factors such as education and socio-economic status override unconscious signals, but unlike Dr. Ober, I do not see this as a cause for high divorce rates. In fact, I think that making such a leap is somewhat ridiculous. Furthermore, I am not at all convinced by the arguments for MHC/HLA in modern-day mate selection. I would be willing to accept that MHC/odors may have played a role in mate choice pre-civilization (pre-showers and pre-deodorant), but not now. I did not find this to be a particularly valid line of research or one that is worth pursuing.
I do, however, find LeVay's research on the biology of sexual preference to be interesting. I agree with LeVay that this line of research should be carried out for the sake of knowledge rather than to gain social acceptance or to "fix" what some may perceive as being wrong. There is no denying the critical role that hormones play in the development of the brain, the SDN, and in mating behaviors in rodents. Also, LeVay's findings on the differences in the INAH 3 of heterosexual and homosexual men were notable, but do not imply any causation. This study probably raises more questions than it answers. LeVay failed to study many women, homosexual women, bisexuals, closeted gay men, or heterosexual men who had previous homosexual encounters. It seems that the boundaries of human sexuality and sexual preference may be too fuzzy to perform good scientific research on. Even if a genetic influence on sexual preference is found, I imagine that once again it will be "lemonade".
In terms of sexual orientation, my opinion on all of the genetic research is basically contained in a brief paragraph at the end of LeVay & Hamer's 1994 article: "A second idea is that the hypothetical gene acts indirectly, through personality or temperament, rather than directly on sexual-object choice. For example, people who are genetically self-reliant might be more likely to acknowledge and act on same-sex feelings than are people who are dependent on the approval of others." In other words, there does seem to be some evidence that there is a genetic link to 'homosexuality' (i.e. the data on Xq28) However, as mentioned in other postings, I think that genetic research in general has a problem in that the level at which the effect is taking place is difficult to determine. Do the genes involved in 'homosexuality' lead to homosexual behavior? to same-sex attraction? to non-conformity/ antiauthoritarianism? At this point I don't think that we have the data to determine that.
As a side note, I was surprised to read the following in Byne's 1994 article: "Regardless of their genetic sex or the nature of their prenatal hormonal exposure, they usually become heterosexual with respect to the sex their parents raise them as, provided the sex assignment is made unambiguously before the age of three." Was this article published before the revelations about the blatant failure of John Money's Bruce/ Brenda/ David Reimer case? Although it's never a great idea to draw global conclusions from a case study, that case, combined with a great deal of other data about the effect of fetal androgens on sex-specific behavior in mice, for example, seems to me to blatantly contradict Byne's notion that gender in intersex babies is infinitely socially malleable.
I think that there is no clear cut answer in response to the question about the whether there is a genetic influence on sex, gender, and mate choice – although some of the articles stated that animal research seems to indicate a possible biological component in mate choice, I am not convinced that the methods employed in these studies necessarily apply to humans as well. Furthermore, several of the studies with humans suggesting a genetic influence on sexual orientation were twin studies, but these researchers failed to compare their data to twins reared apart (with the exception of one study with only 6 participants). The fact that these studies found higher concordance rates among the twins is not completely convincing of the genetic component involved and fails to examine the effects of the environment – perhaps monozygotic twins are treated more similarly than fraternal twins and thus the concordance rates for MZ twins was higher. Overall, given the articles, I suspect that there is a strong genetic influence on mate choice, but I remain uncertain about the validity of the animal data as applied to humans (consider the article that discussed how the sexual orientation of rats was determined). As I've stated, it also seems to me that some researchers have almost dismissed the possibility of the role of the environment in gender and mate choice, which seems problematic. I think that while we are certainly growing in our understanding of the influences on gender and mate choice, many more studies are required before we can feel that we have a complete understanding of these influences.
I'm not so sure that gender is socially constructed any more so than sex is. To the extent that when children are born with ambigious genitalia and choices are made about whether to perform surgery and which sex the child should be, society is constructing a sex dichotomy just as much as a gender dichotomy. Most people identify as either males or females, although there is a whole range of masculinity/femininity within these groups. A few identify as somewhere in between...but that doesnt seem so different as how some are somewhere in between the male and female sex. Of course, society has determined what goes into the two gender roles, but as far as there being two, I don't think the societal component of gender is much greater than that of sex. Using a third dimension of masculinity and femininity, which has a more normal distribution, allows people to be either male or female in sex and gender, yet still have an identity falling anywhere on this continuum of masculine/feminine.
I am not terribly convinced by LeVay's data and the rest on biological influences on homosexuality, for all the reasons mentioned in other posts. I've always been intrigued by Bem's Exotic Becomes Erotic theory of homosexual identity formation, where boys who are less aggressive like to play "girl games" and thus associate with girls, thus viewing their own sex as the strange one, and attributing the heightened autonomic reaction to foreign stimuli as sexual attraction (I don't think he was concerned with same-sex attraction in women). I haven't heard much about this theory lately, so maybe it's been pretty much debunked, but I still like it...it seems to correspond to the trendy stress-diathesis explanations of various things. A genetic (or other) predisposition (diathesis) to lower aggression may or may not lead to homosexual identity formation, depending on how the environment reacts/encourages/discourages sex discordant behavior ("stress") and how strong the predisposition is...and it seems that could be a more direct genetic influence on aggression than on same-sex attraction or homosexual behavior.
although i find studies on the sexual orientation interesting, i do not see a point in identifying the cause of homosexuality. what do people do if they find out that homosexuality is genetic? or that homosexuality results from pre-adolescent experience? are the studies done so that they can find ways to prevent homosexuality by discovering the cause? i don't like that these scientific studies treat homosexuality as a disorder of some sort. whatever the cause is, i think it is more important that the society will accept homosexuals as one of many differences that individuals have. if the scientific studies can lead the society in such a way, i think they should be continued. but if they stimulate the existing discrimination against homosexuals, i don't think they should be done at all.
I thought I should share about a talk i went to earlier this semester because it relates to this week's topic a little. i can't remember the name of the lecturer or the title of the talk, but it was about social monogamy and sexual polygamy in birds. many birds are socially monogamous, but they actually mate with different partners! this observation came from one study that performed vasectonomy in birds - female birds became pregnant even though their partners had vasectonomy done. since the surgery was carefully performed, the females must have copulated with those males that did not get the surgery. although, having affairs is "wrong" in the human society, the lecturer discussed both positive and negative aspects of sexual polygamy. for males, the advantage seems clear. by mating with multiple females, males can spread more of their offsprings. For females, however, copulating with multiple males does not lead to a bigger number of offsprings because the number of eggs are limited. sexual polygamy seems disadvantageous in females because it increases the risk of STD infection, and if caught by their social monogamous partners, the females may be severly injured or killed by the male. but, there are adavantages, too. mating with different males assure fertility; if the actual partner is infertile, the female cannot produce offsprings without getting fertile sperms from other males. Also, it increases genetic diversity. Moreover, females may be able to receive "better genes" by mating with a cuter/wealthier male than their husband so that their offsprings will have a better chance of producing more and healthier offsprings. in spite of all the advantages of sexual polygamy, birds, like humans, stick to monogamy socially because both parents are needed to raise their offsprings.
do genes play a huge role in mate selection in humans? the study of HLA alleles suggest that they do. however, in humans, there are a lot of environmental factors that drives one's decision. i believe that smell is very important in attraction. but when it comes down to mate selection, humans think about more. personality, wealth, intelligence, family background, and so on. and i also think that mate seletion depends on one's experience with many people or events that affected one's personality development. since i don't think personality is not simply genetic, i think mate selection depends on more than genetics.
The article on finches seems most appropriate to answer whether or not there is a relationship between sex, gender and mate choice. Mate choice may also be termed sexual orientation I believe. Sex is determined by genetics and physiology. I disagree that gender is a 'social construct'. I instead think that mate choice/sexual orientation is the real 'social construct' that is defined by intereactions with other individuals around you. Gender simply seems to refer to the morphological traits of sex. The way sexual traits are expressed does seem to be able to be controlled by hormone injection and living arrangement (which also influences hormonal levels, just ask any Mawrtyr). These both seemed to influence mate selection, though sex seemed to take over when placed in a colony environment. What does this mean? Gender and sex both play a role, but it is hard to transcend genetically assigned roles. Research on the differences between heterosexual and homosexual brains was very interesting, showing perhaps a unique difference in homosexual gender.
Sexuality is almost completely tied to natural selection in my mind. The entire point of sexuality is reproduction. Therefore, it seems only natural that we would study the genetics of this process. I think the exploration is very useful in understanding how evolution works and the basics of human behavior as well. Mate selection is a large issue for all of us, and understanding better what makes us do the things we do is beneficial for our self-knowledge. Considering that most literature centers on love and relationship, I think that biology should not ignore this field.
The genetic link to mate selection seems obvious, especially given the sort of selection cascade phenomenon. An individual chooses a mate not only because he has the most desirable characteristics, but also because her progeny will more easily find mates. Thus, desirable traits become entrenched. How else do we determine what is desirable than what are genes pre-dispose us for. There seems to be good evidence that humans are very drawn to certain MHC sites in smells, which correlate to their genes. Other factors, such as imitation play a role as well. But, genetic predisposition to colors for example rules the day when the differences are easily discernible.
And just like, say, how we can not test certain aspects of language on some animals I don't think that animal studies on sexual orientation can completely explain the phenomenon. Le Vay's findings are intriguing but there are so many confounds. The disease itself, the fact that the difference could be consiquence not cause, etc.
I just feel like we are So far away from finding anything truly conclusive, if even insightful about the topic. The brain has yeilded few other secrets in other topics that have much more extensive research (the most hopeful I think would be memory). As for whether we should even research this and that controversy: I feel that we should research anything and everything. What we do with the knowledge is a question we should ask when we come to it. I think that's a basic benefit of free will-- choice rather than blind ignorance and inactivity.