Since lesbian and homosexual acts do not produce offspring, it would seem that they do not serve any genetic purpose and therefore should not exist.
Yet, they do exist. Every tribe and culture in the world has it, no matter how primitive, from the Australian Aborigines to the Amazon Jungle Indians. Moreover, it seems to exist in roughly the same percentage of the population everywhere.
Is this just an accident, an aberration or a deviation, or is there some greater purpose in this?
One theory is that male homosexuality has a militaristic purpose. Men bond together, join and form armies, go out and fight, risk their lives for their buddies and die in battle.
This obviously has a genetic purpose. Throughout history, victorious armies have taken over the land of their vanquished enemies, killed all the men, and copulated with the women, thereby producing a new generation of presumably improved genetic stock. Men who would fight for each other in battle would be likely to prevail over and conquer men who were not organized because they did not feel the need for male bonding.
Strangely, men who prefer the company of other men are often referred to as "real men" as opposed to those of us who prefer the company of females.
But, what is the need for lesbianism?
A study of the oystercatcher birds may hold the clue to this. The oystercatchers have an exceptionally long life span. They live to 40 years or more. They also pair off and form long standing relationships just as humans do. They are more like humans in this respect than many primates.
Like their human counterparts, if a female oystercatcher cannot find a mate, she will sometimes attack another female who has one. Sometimes, the interloper drives away the other female and takes away her male. More often, however, the original "wife" of the male bird prevails and drives away the intruder.
The males sometimes help the original mate, but more often they do not take sides and just let the two girl birds fight it out themselves.
Sometimes it happens that the two females fight each other for a long time and neither is able to prevail over the other. Then, a surprising thing occurs: The two females stop fighting and start having lesbian sex with each other. They will even switch positions, one getting on top and taking the male role with the other on the bottom and then visa-versa. Then, they will both take turns copulating with the male.
More than that, they form a family group. The two females start sharing the same nest and laying eggs together. The three of them together cooperate to drive away any intruders.
Statistics show that the newly arrived female has a better chance of reproducing if this happens then she would if she tried to find a single male. On average, a nonbreeding female floater has only a 9 percent chance of breeding the next year. By contrast, a female who has been in a cooperative troika has a 67 to 73 percent chance of breeding in the next season.
Thus, at least among these birds, lesbianism seems to increase the change of passing on genes to the next generation.
Only about 2 percent of these types of birds form lesbian relationships. Interestingly, the female human population also seems to have about 2 percent lesbians
Here is a link: Birds' Design for Living Offers Clues to Polygamy