Investigating the Heritability of Homosexual Behavior in Wild Rhesus Macaques

Key Highlights :

1. Homosexual behavior is not limited to humans. Biologists have reported homosexual behavior in many species of wild animals, ranging from bats and birds to dolphins and primates.

2. Male SSB is not unique to this population of macaques. We saw similar behavior in wild rhesus macaque populations in northern Thailand. And there have been previous reports of SSB in this species from India, too.

3. The heritability of male SSB is 6.4%.

4. The potential rate at which the trait can evolve per generation through natural selection is 14.9%.

5. Heritability of SSB has also been found in some invertebrate species, including seed beetles and fruit flies.

6. For example, factors such as imperfect sex recognition are believed to influence the development of SSB in invertebrates.

7. Demonstrating that SSB is heritable and its potential for evolutionary response to natural selection is an important first step towards understanding the factors that influence variation in this behavior.

8. Society's moral obligation to strive for more inclusivity and acceptance of different sexual orientations ultimately does not rely on observations from the natural world.

     Homosexual behavior is not limited to humans. Biologists have reported homosexual behavior in many species of wild animal, ranging from bats and birds to dolphins and primates. This raises the question of how homosexual behavior manages to evolve and continue to exist within a population. To investigate this, researchers studied 236 male rhesus macaques living freely in a colony of 1,700 monkeys on the tropical island of Cayo Santiago, Puerto Rico.

     The researchers observed the monkeys for three years and found that male same-sex sexual behavior (SSB) was widespread. In fact, 72% of the males they observed mounted other males, while only 46% mounted females. They also had access to pedigree records that traced the parentage of each macaque back to 1956, which allowed them to explore the effect of relatedness (heritability) on their behavior.

     The researchers found that the heritability of male SSB was 6.4%, meaning genetics do account for a small proportion of SSB—the rest is environmental. They calculated "evolvability" to be 14.9%, giving the potential rate at which the trait can evolve per generation through natural selection. This indicates that SSB can evolve through selection.

     The researchers also found a genetic correlation between the number of times a male was observed mounting another male and the number of times he was mounted by other males. This suggests that different forms of SSB in these monkeys share a common genetic basis.

     The findings suggest that the costs associated with human SSB might arise from specific social factors unique to humans. However, more research is needed to explore this idea further. These results may help to challenge beliefs that SSB is rare or the product of extreme and unusual environmental conditions, and combat prejudice against homosexuality and bisexuality.

Continue Reading at Source : phys