Epigenetics confirm people are born gay

The argument

The argument proceeds by elimination. If sexual orientation were fixed by a particular gene, identical twins, who share genetic sequences, would be expected to share an orientation almost without exception. On the evidence cited here they do not: where one twin is gay, the other is more likely to be straight than also to be gay. Proponents take that discordance to rule out a straightforward genetic account, since a shared sequence cannot by itself produce divergent outcomes. Yet the heritable pattern does not disappear. There is evidence that homosexuality runs in families, which is hard to reconcile with an explanation treating orientation as a matter of environment or choice alone. The argument therefore has to accommodate two findings that pull in opposite directions: something is being passed down, and yet it is not being passed down as a gene that settles the trait. Epigenetics, on this view, is what resolves the tension, and it is the account the evolutionary geneticist William Rice, of the University of California, set out in a paper published in 2013. Epigenetic marks govern how genes are expressed rather than what the underlying sequence says; they can be inherited, and they can differ between two individuals carrying the same sequence. A mechanism of that kind can be transmitted through a family, which accounts for the familial clustering, while still coming apart between two people with identical genomes, which accounts for the twins. Proponents press this as the decisive point: it is, they argue, the only possible explanation that accommodates both observations at once. If that is right, orientation is set by inherited regulation of gene expression rather than by anything a person does or decides, and it is in place before any of that could operate. On this account, people are born gay.

Context

The same genetic code can be expressed in different ways. Chemical changes that alter the way the genetic code is expressed can cause two people with the same genetic construct to behave in very different ways.

Premises

Counter-arguments

The argument from epigenetics is nothing more than a theory. It has never been supported by empirical data. Just because there is an absence of evidence for other theories does not mean that there is evidence for epigenetics.

Rejecting the premises

[Rejecting P3] There is no evidence for this.