Homosexual selection: The power of same-sex liaisons

Source

07 December 2009 by Kate Douglas

NOT long ago, the news was full of reports about two male Humboldt penguins at a zoo in Germany that adopted an egg, hatched it and reared the chick together. It seems like every time you turn around, the media spotlight has fallen on another example of same-sex liaisons in the animal kingdom.

In the past few years, the ubiquity of such behaviour has become apparent. This summer evolutionary biologists Marlene Zuk and Nathan Bailey from the University of California, Riverside, published a paper on the subject that included examples from dozens of species ranging from dung flies and woodpeckers to bison and macaques.

That is just the beginning of the story. The burning question is why same-sex behaviour would evolve at all when it runs counter to evolutionary principles. But does it? In fact there are many good reasons for same-sex sexual behaviour. What’s more, Zuk and Bailey suggest that in a species where it is common, it is an important driving force in evolution.

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The Times: Lesbian albatrosses and bisexual bonobos have last laugh on Darwin

17 June 2009
The Times (UK)
Source

Lesbian albatrosses and bisexual bonobos have last laugh on Darwin

Chris Smyth

Charles Darwin argued that sexual preferences can shape the progress of evolution, creating displays, such as the peacock’s tail, that are inexplicable by natural selection alone.

It’s safe to say, however, that he did not anticipate the lesbian albatrosses of Hawaii. Nor bisexual bonobos. Let alone sadomasochistic bat bugs or the gay penguins of New York.

Homosexual Activity Among Animals Stirs Debate

Source

James Owen in London

for National Geographic News

July 23, 2004

Birds do it, bees do it, even educated fleas do it. So go the lyrics penned by U.S. songwriter Cole Porter.

Porter, who first hit it big in the 1920s, wouldn’t risk parading his homosexuality in public. In his day “the birds and the bees” generally meant only one thing—sex between a male and female.

But, actually, some same-sex birds do do it. So do beetles, sheep, fruit bats, dolphins, and orangutans. Zoologists are discovering that homosexual and bisexual activity is not unknown within the animal kingdom.

Roy and Silo, two male chinstrap penguins at New York’s Central Park Zoo have been inseparable for six years now. They display classic pair-bonding behavior—entwining of necks, mutual preening, flipper flapping, and the rest. They also have sex, while ignoring potential female mates.

Male transsexual gene link found

Source: BBC
26 October 2008

Male transsexual gene link found

Australian researchers have identified a significant link between a gene involved in testosterone action and male transsexualism.

DNA analysis from 112 male-to-female transsexual volunteers showed they were more likely to have a longer version of the androgen receptor gene.

The genetic difference may cause weaker testosterone signals, the team reported in Biological Psychiatry.

However, other genes are also likely to play a part, they stressed.

The evolution of homosexuality: Gender bending

Source: The Economist magazine
23 October 2008

The evolution of homosexuality
Gender bending

From The Economist print edition
Genes that make some people gay make their brothers and sisters fecund

THE evidence suggests that homosexual behaviour is partly genetic. Studies of identical twins, for example, show that if one of a pair (regardless of sex) is homosexual, the other has a 50% chance of being so, too. That observation, though, raises a worrying evolutionary question: how could a trait so at odds with reproductive success survive the ruthless imperatives of natural selection?

Various answers have been suggested. However, they all boil down to the idea that the relatives of those who are gay gain some advantage that allows genes predisposing people to homosexual behaviour to be passed on collaterally.

New Scientist: Evolution myths: Natural selection cannot explain homosexuality

Evolution myths: Natural selection cannot explain homosexuality

18:00 16 April 2008
NewScientist.com news service
Michael Le Page

There are numerous evolutionary mechanisms that might explain homosexual behaviour, which is common in many species of animals

“Simple reasoning shows that evolution cannot explain homosexuality – how would a homosexuality gene get selected for?” “Why have the genetic traits predisposing to homosexuality not been eliminated long ago?”

Such arguments are surprisingly common – and completely wrong.

Homosexual behaviour has been observed in hundreds of species, from bison to penguins. It is still not clear to what extent homosexuality in humans or other animals is genetic (rather than, say, due to hormonal extremes during embryonic development), but there are many mechanisms that could explain why gene variants linked to homosexuality are maintained in a population.

The real story on gay genes

Source: Discover Magazine
5 June 2007

The Real Story on Gay Genes
Homing in on the science of homosexuality – and sexuality itself
by Michael Abrams

Some conservatives argue that homosexuality is a personal choice or the result of environmental influences. Some gay rights activists insist that homosexuality is genetic, hoping that proof from that domain will lead to greater acceptance. Still others, backing the same cause, discourage any investigation into the biological origins of sexual orientation, fearful that positive results will lead to attempts to rid the world of potential homosexuals. A handful of scientists, though, are just curious. For them, the discovery of how an individual becomes gay is likely to shed light on how sexuality-related genes build brains, how people of any persuasion are attracted to each other, and perhaps even how homosexuality evolved.