Evolution of homosexuality in birds explained
When birds have help on the parenting front, it leaves wiggle room for homosexual behavior without sacrificing evolutionary efficiency.
By Bryan NelsonTue, Jul 13 2010 at 2:18 AM EST
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ALBATROSS LESBIANS: Up to 31% of pairings among some albatross species are female–female. (Photo: Manabu Ogasawara/Jupiterimages.com) A new study published this week may mark the end of the theory that homosexuality only has evolutionary disadvantages, according to Nature.
The findings, based on observations of 93 bird species that are known to engage in homosexual activity, revealed that the amount of time males or females put toward parental care was proportional to how often they engage in homosexual behavior.
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This means that homosexuality may not be costly for birds that have plenty of mating opportunities because of lower parenting demands, said Geoff MacFarlane, one of the study's principal researchers.
In other words, since some animals can devote more energy toward mating behavior than to raising offspring, there is wiggle room for homosexuality to become a common behavior without sacrificing evolutionary efficiency.
Previously, biologists struggled to explain how homosexuality could have evolved since it distracts animals from sexual activity that directly produces offspring. The fact that it had evolved was difficult to deny: more than 130 species of birds participate in homosexual activity. For example, among Laysan albatrosses, as many as 31 percent of all pairings are female-female. Among graylag geese, one in five pairings are male-male.
The research team reached its conclusion by scoring each bird species based upon the relative contribution of males and females to parental chores. They found that male homosexuality is more prevalent among bird species in which the female is more heavily devoted to parenting tasks (such as tending the nest or feeding and caring for chicks). Similarly, when females had more free time, female homosexuality was more frequently witnessed.
Overall, the research discovered that 38 percent of the species studied display female–female sexual behavior and 82 percent participate in male–male behavior. In total, 5 percent of all sexual encounters among all the species was homosexual in nature.
"This is one of the few studies that explains homosexual behavior from the evolutionary point of view," said Vincent Savolainen, a biologist at Imperial College London.
Although the study dispels of the theory that homosexuality is evolutionarily disadvantageous or unnatural, it cannot determine what the ultimate explanation for homosexuality is. As evolutionary geneticist Allen Moore points out, "this study suggests that when there's no cost, homosexuality can persist, which isn't the same as saying it's adaptive. It may be that when there's no parental care involved, it's like having a hobby."
Researchers have speculated, though, that homosexual behavior in birds may help them to practice courtship displays, form alliances, reduce social tension or solidify dominance.
"The next logical step is to see if similar patterns occur across other vertebrate species," said MacFarlane. His team has already reached some preliminary results that suggest the patterns are similar for primates.
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Comments
Albatross
04/23/2011 22:36 PM
From the point of view of evolutionary genetics, sibling animals are identical. Therefore if a homosexual "uncle" animal contributes to the reproductive success of its "brother" and "nephew" animals, its genetic success, including the genes for supportive homosexuality, are passed along as effectively as if the homosexual animal itself had reproduced. Failure to grasp this demonstrates either an inability to fully understand evolutionary theory, or possibly a wholly nonscientific refusal to.... More
SenseOfNature
08/08/2010 13:44 PM
How do we know that what the same-sex birds are doing is sexual in the slightest? How do we know that it is not the bird version of handshake, hug, or polite kiss (friendly, non-sexual)?
We don't speak Birdish, Birdanese, Birdin, or Bird.
Singe
07/22/2010 00:15 AM
...can't say homosexuality is "unnatural" any longer.
Yes, this is an article about birds not people, and the Christians might still want to say homosexuality is "morally wrong", and probably will keep saying this, but for ages they've also said it is unnatural and, well, clearly it's quite natural. There it is. Nature.
John
07/16/2010 16:47 PM
One point that never comes up. In the animal kingdom, there is no hate towards each other for being different. They help each other. Perhaps we could learn some thing from these "lower life forms"
Dave
07/16/2010 06:15 AM
It doesn't matter if you're talking about birds or humans they're still BENDERS!
TDub
07/15/2010 16:09 PM
the lack of a need to be a parent doesn't explain why birds OR people would be attracted to a same-sex mate over a opposite-sex mate. Think about it. Lots of gay people still want kids and want to be a parent, and they're still gay.
Nick
07/15/2010 08:09 AM
It means... This is an article about birds. It is only an article about birds. There may be inferences that can be made, but more study is needed.
eMale
07/14/2010 18:48 PM
I am a homosexual and I have never laid and Egg. What does that mean?
Nec
07/14/2010 17:04 PM
@WTF
I'm fairly positive that the article never mentions morality. It's merely concerned with how a behavior that seems to directly contradict sexual reproduction would evolve. You're the one who sees this as a definition of morality.
The commenter doth protest too much, methinks.
Guest
07/14/2010 16:57 PM
Did you even read the article? It doesn't say that it is justified, just that it happens and how it came to be.
WTF
07/14/2010 16:46 PM
So are we letting birds define our morality now? We have the ability to rise above our natural (or unnatural) tendencies and be evolved and enlightened people. If you wanna justify rolling around with sodomites, pornographers, pedophiles and perverts go right ahead... you are only fooling yourself.
Sodomite
07/19/2010 21:42 PM
Gays have risen above the natural tendency to be straight. Everyone knows that the majority of pornographers, pedophiles, perverts are heterosexual.
Awggie
07/15/2010 15:33 PM
Your hatred is transparent and vile.
Xina
07/15/2010 02:56 AM
homosexuality is natural, its apparent that u either aren't or are violently still in the closet, whichevr, morality? nature? sexuality is personal, as in if u don't like it don't do it, and mind ur own genitals... for the record, porn is for people who enjoy it, anal for the penis and anus that enjoy meeting, eating and greeting, no one invited u well smile ur anus can just hug ur poo instead... never ever compair consenting adults to pedophilians ever again k thats just abusive and.... More
Dave
07/14/2010 18:49 PM
I think you missed the point, it's about birds not people. If you wanna go rolling around with sodomites, pornographers, pedophiles and perverts it's entirely up to you. The birds don't care.
metaphid
07/14/2010 17:01 PM
Verily I say unto thee: Thou art a moron.
