The evolution of Homosexuality

Why did Homosexuality evolve?

Homosexuality is a natural phenomenon found throughout the animal kingdom, and can be seen not only in Humans, but in many animals such as Lions, Zebra, Penguins, Bears and even Lizards. But how did homosexuality evolve if the members involved cannot reproduce, and are therefore incapable of passing on the genetic components for this characteristic? And what evolutionary purpose does the gay characteristic have for the organisms involved?

Well, scientists do not have a definitive answer yet, but there are a few very interesting ideas that have accumulated substantial evidence.

Sexual antagonistic selection Hypothesis:

Say an allele or group of alleles are passed from a parent to their female offspring that gives them greater feminine features such as wider hips and/or larger breasts, making them more attractive to males.
These features would be beneficial to the female as she would attract more mates and have a larger number of offspring than she would have had without these features.
However, although these alleles are of great benefit to the females, it causes an occasional male sibling with the same alleles to be attracted to the same sex rather than the opposite sex.

Although this male will not be able to reproduce, the advantage to the females would be so beneficial that she will have a good number of offspring allowing this allele to be passed through the generations, leading to more gay men down the line.

Kin selection Hypothesis:

This hypothesis conveys the idea that gay humans greatly aid in bringing up the offspring of their straight, reproducing relatives. If gay people have no young themselves to look after, they can aid in the protection and feeding of nieces and nephews improving their chances of survival.

This benefit to their relatives would allow greater spread of the genes that code for the homosexual characteristic causing it to appear in future generations.

These are the two most popular evolutionary hypotheses for homosexuality in Humans.

There are other ideas to why this behavior develops in human’s .i.e. if a female has a particularly high level of testosterone or progesterone during her fetal stage, she may develop gay preferences, and the same goes for some males if they have a particularly low level of these hormones.

Also, many gay people have been known to have children at a younger age and gone on to become gay later on in their lives causing their genetic traits to be passed on through their offspring.

However this is still being studied and an absolute answer has not been formulated yet, although it is more than likely based on environmental as well as genetic factors.

In the rest of the Animal Kingdom, the reasons for homosexuality are quite different.

Bonobo’s are very promiscuous animals and will mate constantly with different members of their group, not just for reproduction but to cement social bonds, and homosexual behavior within these primate groups help with this.

The all female Whip-tailed lizard’s (left) no longer mate with males (who have disappeared from the population) and reproduce exact female clones of themselves.However, because they require the stimulation of mating by males to ovulate, they will act out the copulation ritual with each other to allow egg laying to occur. This evolved as a way for the female species to hold onto the genes that best helps them survive in their environment without the detrimental addition of genes that would be passed to their offspring by males.

Although homosexuality in many non-human animals is greatly understood, humans are apparently more complicated and the scientific community is still working on an answer.
Although it does seem that although gay people cannot reproduce, there is a true evolutionary benefit to their existence.

-Thomas Glen

Image: hands: Phil Hol
For more info visit: http://www.bbc.co.uk/news/magazine-26089486