Nature, Nurture, DNA, Environment
The old phrase "nature versus nurture," is not (as often used) interchangeable with, "DNA versus environment."
We start out with a little critter with a certain set of DNA.
From that point forward, everything other than the ordering of Gs and Ts and As and Cs is subject to environment. Prenatal environment is perhaps the most important environmental variable.
Is there a "gay gene"? Probably not, as such... but in practical effect there is. Are there DNA sequences that are more or less likely to respond to certain hormones produced by the mother (or ingested by the mother) by forming brains with varying orientations, gender identities, gender-typical affects?
Yes. Almost certainly.
What we are usually looking for is "inborn"... not a product of education or upbringing. And if we short-hand "what a person is intrinsically, when born" as "DNA" then we won't be far off for many purposes.
Bu it is still a distinction worth drawing.
Different prenatal environment results in very different people. (Different post-natal environment also results in very different people.)
But much of that prenatal environment is a specific pre-natal parental contribution from the mother that is dictated largely by her DNA and thus behaves a lot like DNA in practice... mom's DNA keeps shaping how her and dad's DNA contributions are expressed.
And—here's a fun wrinkle—identical twins typically have almost identical prenatal environment, making DNA vs. environment questions even more challenging.
But now let us zoom ahead to birth, and the traditional meaning of Nature Versus Nurture.
By the time we get to birth we almost certainly do have some people who can be meaningfully said to be "born" gay or straight or musical or impulsive or good at symbolic reasoning, even though the will not be expressing all those things as newborns.
And even though those things can be advanced or retarded in nurture.
It is entirely possible that at birth baby X can never be a chess grandmaster. But there is no baby Y that is certain to be a grandmaster. A million effects in post-natal environment will shape the expression of that potential where it might exist.
We spent thousands of years thinking about nature versus nurture without knowing that DNA even existed, and knowing almost nothing about the effects of prenatal environment in the womb. (Beyond the most obvious things, like that malnourished moms were likely to have sickly kids.)
So for a lot of purposes (but not for prenatal care) we should think about nature as inborn traits as things we have at birth and think of "nurture" as the totality of post-natal environment.
The point of this OP is that what we usually think of as "nature versus nurture" is sometimes quite different from, "DNA versus environment," and that scientific purposes and public policy purposes and public health purposes will view these questions quite differently.
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