Does homosexuality have to be an evolutionary dead end? Agony Aunt Carole Jahme from the Guardian shines the cold light of evolutionary psychology on readers' problems. This week: gay dads
From Joe, age 38
Dear Carole, I am a 38-year-old single gay man who is perfectly at ease with his sexuality, but I have this nagging feeling that I should be making an effort to perpetuate my genes. If I die without leaving any offspring surely I will have failed as a biological entity. I don't believe in life after death, so it will be as if I never existed.
Should I impregnate a friendly lesbian, or would it be simpler – and more efficient in evolutionary terms – to register as a sperm donor?
Carole replies:
Do you have any nephews or nieces? It has been theorised that homosexuality, which remains at a stable level in human populations of around 4% for men and 2% for women, survives from generation to generation due to a phenomenon known as kin selection. This is the evolution of behaviours that favour the reproductive success of genetic relatives and has been observed in many species, us included.
Nephews and nieces share 25% of their genes with their aunts and uncles. The quarter of your genes you have in common with your sibling's offspring is second only to the half of your genes you would have in common with your own children. Thus, gay, lesbian or childless heterosexuals can increase their own reproductive fitness by behaving altruistically towards their nieces and nephews – in other words by helping to ensure their survival and future reproductive success.
There are many examples of kin selection in nature. Our New World primate cousin, the endangered golden lion tamarin, is a highly cooperative breeder. Pairs of males (sometimes brothers) both mate with the same female. When the infant is born neither male knows which is the father, and yet both invest equal care in the progeny. The more carers an infant tamarin monkey has the better its chances of survival.
Humans are no different in this regard. For example, a child born as the result of an alliance between a gay couple and a lesbian couple has two genetic parents and two "alloparents". With four adult carers this infant is better placed to succeed in the game of life than a child born to a heterosexual pairing.
Read more : www.guardian.co.uk