This is just a short and random list of links (articles and comments) about the biological basis for homosexuality, that I decided to collect after some heated discussion in Brazil about it.First a few articles that I found particularly interesting.
Male homosexual behaviour—although found in most extant clades across the Animal Kingdom—remains a conundrum, as same-sex mating should decrease male reproductive fitness. In most species, however, males that engage in same-sex sexual behaviour also mate with females, and in theory, same-sex mating could even increase male reproductive fitness if males improve their chances of future heterosexual mating. Females regularly use social information to choose a mate; e.g. male attractiveness increases after a male has interacted sexually with a female (mate choice copying). Here, we demonstrate that males of the tropical freshwater fish Poecilia mexicana increase their attractiveness to females not only by opposite-sex, but likewise, through same-sex interactions. Hence, direct benefits for males of exhibiting homosexual behaviour may help explain its occurrence and persistence in species in which females rely on mate choice copying as one component of mate quality assessment.
Research over the last decades has stimulated a paradigm shift in biology from assuming fixed and dichotomous male and female sexual strategies to an appreciation of significant variation in sex and sexual behaviour both within and between species. This has resulted in the development of a broader biological understanding of sexual strategies, sexuality and variation in sexual behaviour. However, current introductory biological textbooks have not yet incorporated these new research findings. Our analysis of the content of current biology texts suggests that in undergraduate biology curricula variation in sexual behaviour, sexual strategies and sexuality barely feature, even though sex is discussed in a range of contexts. In this aspect, biological teaching is lagging behind current research. Here, we draw attention to new findings in the biology of sex, and suggest how these might be incorporated in undergraduate teaching to provide a more contemporary and inclusive education for biology students.
Julie E. Elie, Nicolas Mathevon,Clémentine Vignal. 2011. "Same-sex pair-bonds are equivalent to male–female bonds in a life-long socially monogamous songbird". Behavioral Ecology and Sociobiology, 65: 2197--2208:
Same-sex sexual behaviors are well documented in both captive and wild animals. In monogamous species, these behaviors are often exclusive, each individual having only one same-sex partner. A bias in sex ratio has been proposed as a social context yielding same-sex pair-bonding, but this hypothesis has rarely been tested. Focusing on a life-long pair-bonding songbird, the zebra finch Taeniopygia guttata, we tested whether same-sex pairing results from a shortage of individuals of the opposite sex. By experimentally skewing the sex ratio towards members of one sex, we observed a greater proportion of same-sex pair-bonds of that sex. Moreover, we assessed whether the quality and stability of social interactions were equivalent in same-sex and male–female pairs. Male–male and female–female same-sex bonds display the same behavioral characteristics as male–female ones: they are intense, highly selective, and stable affinitive relationships involving the same behavioral displays already described in wild birds. Moreover, same-sex male bonds were sufficiently strong not to split up when individuals were given the opportunity to reproduce with females. Because the pair-bond in socially monogamous species represents a partnership that may give advantages for survival (e.g., resources defense, fighting against predators, etc.), we propose that same-sex pairing in the zebra finch may result from the pressure to find a social partner.
Same-sex sexual behavior has been extensively documented in non-human animals. Here we review the contexts in which it has been studied, focusing on case studies that have tested both adaptive and non-adaptive explanations for the persistence of same-sex sexual behavior. Researchers have begun to make headway unraveling possible evolutionary origins of these behaviors and reasons for their maintenance in populations, and we advocate expanding these approaches to examine their role as agents of evolutionary change. Future research employing theoretical, comparative and experimental approaches could provide a greater understanding not only of how selection might have driven the evolution of same-sex sexual behaviors but also ways in which such behaviors act as selective forces that shape social, morphological and behavioral evolution.
And then some links to commentaries that were on my feeds
- The Real Story on Gay Genes | Michael Abrams at Discover Magazine
- Suppressed records of “depraved sex acts” by penguins finally released after a century « Why Evolution Is True
- Female bonobos 'advertise' homosexual bonds | Ella Davies at BBC Nature
- La neuroendocrinologia de la homosexualidad | Sapere Audere
- The Genetic Fatality of What You Are « Into Oblivion
- Krauss does it again, so soon! | Rationally Speaking
- The Intelligent Homosexual’s Guide to Natural Selection and Evolution, with a Key to Many Complicating Factors | Jeremy Yoder at the Scientific American Blog Network
- 23andMe Studies the Genetics of Sexual Orientation | The 23andMe Blog
- What we know—and don’t know—about the biology of homosexuality | Kate Shaw at Ars Technica
update (a few minutes later...): In fact I was searching my feeds for an article criticizing the anthropomorphization of animal sexual behavior, but couldn't find it. Here it is.
"Consistently any scientific report of same-sex sexual contact in any animals is reported as gay or lesbian behaviour," says Barron. (...) "Gay and lesbianism is more than same-sex copulation in humans. Let's not turn this animal behaviour into something that it isn't," he says. "Scientists would never call it gay."
And Barron says in many cases the animals in the scientific study didn't even copulate but simply showed some form of atypical male or female behaviour.
And Leach says in some fields of research - for example evolutionary psychology - scientists are actively linking human behaviour to animal behaviour. "You read this stuff not just about gay behaviour but about female versus male behaviour and it's irritating," she says.
"I get really tired of evolutionary psychology explanations that my behaviour has to do with hunters and gatherers."
The original critique is this one: Andrew B. Barron and Mark J. F. Brown. 2012. "Science journalism: Let's talk about sex." Nature 488: 151-152.