However, we can say from these simulations that selection removes the allele far more often than not. These simulations assume selection quite a bit weaker than the widely-cited cost of same-sex sexuality percent lower fitness instead of 80 percent--so you would expect selection to be even more effective against an allele that makes men gay and women lesbian. However, as I noted above, same-sex sexuality has been present in human populations for considerably longer than 50 generations. That suggests my simulations don't accurately reflect the real-world evolution of human sexual minorities--not because I've simulated weaker selection, but because I've simulated selection that works too well.
It could be that I've modeled the genetics incorrectly. Most of what I've discussed up to now assumes that there's only a single gene involved in determining sexual orientation. However, as the evolutionary biologist Douglas Futuyma has pointed out in his review of Roughgarden's book for the journal Evolution , if multiple genes are involved, they would "share" the selective costs associated with same-sex attraction.
Selection would then have proportionally less power to remove alleles for same-sex sexuality in the face of drift and mutation. Given that recent genome studies have not clearly identified a single gene region associated with sexual orientation, it seems likely that multiple genes are indeed involved. The other possibility, however, is that selection against same-sex sexuality is not as strong as I've made it in my simulations.
How is that possible? Well, simply put, the lives of gay men, lesbians, and transgendered people in Western societies over the last few decades might not be much like the lives we would live in other times and other places. And that could make all the difference. In the United States, the most well-known LGBT life story goes something like this: one discovers same-sex attraction in adolescence, and comes out of the closet before having much sexual interaction with members of the opposite sex.
For committed same-sex partners, having biological children is possible via surrogacy or sperm donation, but it's complicated by the lack of legal recognition and protection for the couple and for children they choose to have. All these factors tend to reduce the number of biological children gays, lesbians, and trans folks have--but they're also all phenomena of our current historical and political moment.
In different social contexts, LGBT fitness could very well be higher.
Before the gay rights movement, social expectations probably led many people who today would identify as gay or lesbian to enter into straight marriages and raise families. This kind of social pressure may explain why gay and lesbian couples are more likely to be raising children if they live in the conservative southern United States --not because adoption is more common in that region, but because in the South, gay men and lesbians are more likely to have heterosexual relationships, and children, before they come out.
On the other side of that coin, it's possible to imagine that in societies in which same-sex relationships recieve the same legal recognition as straight marriages, gay men and lesbians might eventually have biological children at substantially higher rates than they do today. So if oppression might reduce the fitness cost to being gay, equality probably could, too. Many non-Western societies, too, have accepted social roles for a "third gender" that can encompass identities approximating Western gays, lesbians, bisexuals, and transgendered folks.
The roles and behaviors of third-gendered individuals vary considerably, but in some cases they may have biological children even if their primary relationships are with members of the same sex. As Christopher Ryan and Cacilda Jetha describe extensively in their book Sex at Dawn , pre-agricultural human societies may have been highly polygamous by modern standards, with children raised communally. In that context, Ryan and Jetha propose, same-sex sexual interactions may have provided social capital that could help to support children produced in relatively infrequent heterosexual couplings.
This is consistent with the picture Joan Roughgarden paints in Evolution's Rainbow. Roughgarden's book describes widespread same-sex activity that usually fosters social relationships in support of reproductive sex rather than instead of it. To pick just one example out of dozens, some male bluegill sunfish look and behave like females, and "court" more masculine males--then help attract a female and share in the resulting three-way reproductive opportunity by fertilizing some of her eggs.
The wide range of non-reproductive sexual behavior in the broader animal kingdom suggests that human sexual minorities are just one manifestation of a phenomenon that could date back to the origins of sex itself. It has also been suggested that LGBT folks might make up for a lack of biological children by boosting the reproductive success of their close relatives. My brother shares half of my genetic material--so if I help him and his future wife support more children than they would have otherwise, those nephews and nieces "count" towards the children I'm not making myself.
This kind of indirect fitness might offset a lack of direct reproduction, but I doubt that it can cancel it out. Genetically, a nephew "counts" towards my fitness about half as much as a son does. Therefore, if I would otherwise have two children on my own, I have to help my brother to have four additional children to make up for them. I'd like to think I'll make a good uncle, but I won't be that good.
And, in fact, one survey of gay men has found that they aren't significantly more generous toward their nephews and nieces than straight men are. One objection you might make to this study is that it addresses our current societal context, not that in which humans originally evolved. A subtle twist on the indirect fitness idea that I haven't seen in the scientific literature could be to consider not the fitness of gay men and lesbians, but their mothers.
In order for my mother to have as many grandchildren as she would with two straight sons, I only need to help my brother and his wife support two additional children. That seems more achievable, and might work out in the context of the polyamorous, mutually-helping tribes described in Sex at Dawn. It's also consistent with the observation that men are more likely to be gay if they have older brothers --a woman who has already had several straight sons might, concievably, have more surviving grandchildren by giving them a helpful gay uncle.
Finally, there is some evidence that genes associated with same-sex attraction in men might provide a fitness boost in women. Since any given gene has about a 50 percent chance of ending up in one sex or the other, a gene that makes men more likely to be gay but makes women more fertile might, on average, have no selective advantage or disadvantage.
A study found that women related to gay men have more children , which supports this scenario.
- Online Strategy. 10 Essentials of Online Marketing, SEO, Social Media!
- Serious Online Dating.
- Social, Emotional and Academic Intelligence.
- Do Men Want to Date Intelligent Women? | Psychology Today?
- From Berlin to Beijing and London: A Look at TV & the Olympics.
- The Case for Reparations by Ta-Nehisi Coates - The Atlantic!
The biologists Sergey Gavrilets and William Rice used a mathematical model of selection on same-sex sexuality to consider this hypothesis in a paper, and found that a female fertility boost could indeed allow male same-sex sexuality to persist. In the end, however, this is mostly storytelling--lots of possibilities, but much less hard data. What we need to test many of these ideas is detailed records of the total reproductive fitness of sexual minorities in specific social contexts--especially societies approximating the ones formed by our earliest human ancestors.
The best we can say without this is that many societal contexts could have made the apparent fitness cost to same-sex attraction smaller than it appears at first glance. So where does all of this leave the evolutionarily-aware gay man, lesbian, or transgendered person?
As I noted at the start, figuring out the exact nature of our tenuous relationship with natural selection doesn't tell us much about our moral stature, our value to society, or the best way to live our lives. It does, however, offer to answer the question that evolutionary biology can potentially answer for all human beings, regardless of orientation, gender, or race: how did we come to be what we are?
The best answer we have so far is complicated--it may be that we're children of history and chance, not a clear-cut adaptive path. But easy lives and clear-cut answers aren't, I think, what we celebrate in the history of our LGBT forerunners, or remember at Pride rallies. If we queer folk live our lives in the tail of a probability distribution, the the good news is that the company here is pretty good.
Thanks or blame for this article is owed to Steve Silberman , who got me thinking about this topic in an e-mail conversation last year; and to Chris Smith , who gave me some invaluable suggestions on an earlier draft. Bogaert, A. Biological versus nonbiological older brothers and men's sexual orientation. USA DOI: Bailey, N.
Same-sex sexual behavior and evolution.follow url
The Best First Date Tips: 40 Tips From 40 Experts
Trends in Evolution and Ecology. Camperio-Ciani, A. Corna, and C. Evidence for maternally inherited factors favouring male homosexuality and promoting female fecundity.
Royal Soc. Eller, E. Hawks, and J. Local extinction and recolonization, species effective population size, and modern human origins.
Online Dating with EliteSingles
Human Biology Futuyma, D. Celebrating diversity in sexuality and gender. Evolution Gavrilets, S. Genetic models of homosexuality: generating testable predictions. B Haldane, J. A mathematical theory of natural and artificial selection. Part V: Selection and mutation.
Cambridge Phil. Hamer, D. Hu, V. Magnuson, N. Hu, and A. A linkage between DNA markers on the X chromosome and male sexual orientation.
- 1. Be Together For the Right Reasons.
- Visual Coloring: A Foolproof Approach to Color-Rich Quilts!
- Dictionary of biology.
- Expertise. Insights. Illumination.!
- Mr. Right?!
- Why the Smartest People Have the Toughest Time Dating.
Science Herbenick, D. Reece, V.
Serious Online Dating
Schick, S. Sanders, B. Dodge, and J. The Journal of Sexual Medicine. Pillard, R. Human sexual orientation has a heritable component. Human biology. PMID: Rahman, Q. An empirical test of the kin selection hypothesis for male homosexuality.
The 50 Most Daring Entrepreneurs in
Archives of Sexual Behavior. Ramagopalan, S. Dyment, L. Handunnetthi, G. Rice, and G. A genome-wide scan of male sexual orientation. Journal of Human Genetics.
Related Intelligent Dating for Smart Men--The Ultimate Guide to Being Successful With Women
Copyright 2019 - All Right Reserved