Monday, 4 August 2008

Evolution and homosexuality (2)

(Continued)

"OK", retorts the homophobe, "If homosexuality is part of nature and evolution, surely they'd have died out, seeing as gay people are far less likely to have children!"

To which we have to go right back to the start, to our ancestors, the bonobo, who live on the south-side of the Congo River and chimpanzees who live to the north.

The delightful thing about bonobos is, basically, they shag all day long, no holds barred, regardless of gender, age, familial relationship or anything. The chimpanzees, on the other hand, are more aggressive and are omnivores rather than vegetarians.

Now think about these two small tribes; which one is more likely to have some sort of sense of 'collective purpose' or 'social cohesion'; the ones that fight with each all the time, or the ones that shag each other all the time?

More anon.

6 comments:

Andy Cooke said...

I was under the impression (though I can't reference it) that it was an "uncle effect". The argument goes as follows:

If you have a particular collection of genes that every so often throws up someone naturally homosexual, their nephews/nieces (who carry the genetic code recessively) will have an advantage, as rather than concentrating their resources on their own reproduction, they'll be available to assist their brothers/sisters with their own children.
Thus prolonging the line which has the said gene complex.
They'd also be great for warfare without risking the line, having no children of their own.

Could be bull (I'm no geneticist) but it seems to hold together as an argument. There would only be a marginal increase in resources for the nephews/nieces, but as economics teaches us, the margins are where it all* happens.

(*For an arguable value of "all", of course :) )

Anonymous said...

I like the sound of the bonobo lifestyle. Where can I sign up.

It's interesting to speculate how the blind force of natural selection can produce a certain proportion of gays generation after generation without the trait being bred out of the gene pool.

Like you Andy, I don't know what the explanation is for sure, but if the presence of gays is a selected trait (which it must be for it to persist) and if gays do not reproduce (which generally they do not) then their survival value to the genotype must operate through the preferential survival of their close relatives.

Mark Wadsworth said...

Andy, see post #3.

Andy Cooke said...

Mark,
Cool. Your Honour, I would like the record to reflect that my post was before Mark's "episode 3" post :-)

Anonymous said...

Mark, it's simple relatedness. As a member of a sexually reproducing species, I am the product of two parents so I am 1/2 related to each, in that there is an even chance that any gene of mine, gay or otherwise, is found in a particular one of them. My relatedness to myself is 1, to my siblings is 1/2, to my children is 1/2, to my grandchildren is 1/4, to my nephews/nieces is 1/4, to my cousins is 1/8.

Thus looking after your brother or his kids can be easily as advantageous as looking after your own. As the famous geneticist Haldane remarked when asked if he would sacrifice himself for his family, "I would lay down my life for two brothers or eight cousins"

Anonymous said...

Oops, Andy got my comment confused, it should have been on post 3.