Why do homosexuality exist

Already have an account? Log in. Log in through your institution. Founded in by Edward C. The Monist publishes quarterly thematic issues on particular philosophical topics which are edited by leading philosophers in the corresponding fields. As a result, each issue is a collected anthology of continuing interest. Oxford University Press is a department of the University of Oxford.

It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. The Pride parade in Brighton, UK. The findings, which are published on 29 August in Science and based on the genomes of nearly , people, shore up the results of earlier, smaller studies and confirm the suspicions of many scientists: while sexual preferences have a genetic component, no single gene has a large effect on sexual behaviours.

But she cautions that the results may not be representative of the overall population — a limitation that the study authors acknowledge. The people who contribute their genetic and health information to those databases are predominantly of European ancestry and are on the older side. The study authors also point out that they followed convention for genetic analyses by dropping from their study people whose biological sex and self-identified gender did not match.

Research from the s 2 showed that identical twins are more likely to share a sexual orientation than are fraternal twins or adopted siblings. Some studies suggested that a specific part of the X chromosome called the Xq28 region was associated with the sexual orientation of people who were biologically male — although subsequent research cast doubt on those results.

But these studies all had very small sample sizes and most focused on men, says Mills. In the recent study, Ganna and his colleagues used a method known as a genome-wide association study GWAS to look at the genomes of hundreds of thousands of people for single-letter DNA changes called SNPs. If lots of people with a trait in common also share certain SNPs, chances are that the SNPs are related in some way to that characteristic.

Then the researchers performed two separate analyses. In one, they evaluated more than one million SNPs and looked at whether people who had more SNPs in common with each other also reported similar sexual behaviours. For their second analysis, Ganna and his colleagues wanted to see which particular SNPs were associated with same-sex sexual behaviours, and found five that were more common among those individuals.

An even larger sample size could help to identify those missing variants, he says. One is near a gene related to smell, which Ganna says has a role in sexual attraction. Another SNP is associated with male-pattern baldness — a trait influenced by levels of sex hormones, which suggests that these hormones are also linked to same-sex sexual behaviour.

The results demonstrate the complexity of human sexuality, says Ganna. Typically, this question is posed as a paradox. In a paper published yesterday by myself and Duke University professor Brian Hare, we propose human sexuality including homosexuality evolved as an outcome of the evolution of increased sociability in humans.

We argue many of the evolutionary forces that shaped human sexuality were social, rather than based on reproductive ability. In our closest primate relative , the bonobo, straight and gay sex have vital roles in play, social transactions, barter of food, same-sex social bonding and bonding between mating pairs. We must also consider its social functions. This is called prosociality.

Early humans that could quickly and easily access the benefits of group living had a strong selective advantage. We believe this led to the evolution of a whole range of traits including reduced aggression, increased communication, understanding, social play and affiliation.

Read more: 'Gay gene' search reveals not one but many — and no way to predict sexuality. Species such as the bonobo, that evolved for high prosociality, evolved to use sexual behaviour in many social contexts.

This results in an increase of sex in general, greater diversity in the contexts of sex, and an increase in gay sex. We believe something similar happened in recent human evolution.