I just started reading a controversial book called the 10,000-Year Explosion that posits that the conventional beliefs about human evolution are all wrong. The conventional belief is that about 70k to 50k years ago, 'biologically modern humans' arose in Africa and ventured into the world. They were basically 'just like us' on the hardware side, and not much has changed on that front since then.

Based on that, you get the logical conclusion that most of our evolved instincts, including sexual ones, are adapted to that period. And that the stone age is the best place to look for evidence of our actual instincts since (a) it is the vast majority of modern human 'history', (b) it is a stable period whose conditions closely match those that were in place while we were evolving significantly, and (c) the cultural and environmental impacts are simpler and easier to see and parse from the biology.

But if this book is correct, then the conditions since the agricultural revolution massively sped up evolution in terms of changes per unit of time. Moreover, this accelerated evolution was different in different places. This means that the whole project of evolutionary psychology gets much harder. You cannot focus too much on the stone age, for one. You will have to sample all sorts of periods. Moreover, you cannot necessarily use cross-cultural studies because they may involve people whose hardware is subtly to substantially different in various ways.

As a result, parsing nature from nurture is much harder. It is still a legit project and we always need to try. But the evo psych would at best be decent guesses as a basis for some trial and error experimentation. The degree of certainty you get in terms of really figuring out what is hardware and what is software will always be limited. In addition, universality is called into question. It is better to ask questions about specific populations than 'all men and women'.

Note: Yes, there are some obvious but very controversial corollaries to this controversial theory that go well beyond sexuality. Let's remember this is Reddit and step carefully to avoid getting anyone banned.