The most common pattern here is that a wide number of studies show evidence of a difference, but on the basis of possible doubts, the opponents stick to a religious-like belief that there is no difference until proven otherwise. But that's a positive claim, not a negative one.
If you have no strong evidence
either way, then the working hypothesis should rationally default to a 50/50 position on nature vs nurture / difference vs no-difference, not veer
all the way to nurture because there's a possibility that the observable data might be mistaken. Otherwise, the position is no more rational than saying we can't know for sure how the first lifeforms evolved, therefore its must be the God of the bible which did it.
There's no reason that biology needs to adhere to our political correctness feel-good shit, really is there? e.g. your fellow anthropologists hold that
brain size has absolutely nothing to do with intelligence, because that would go against political correctness. You have to
explain why brain size and intelligence
wouldn't be correlated. It's actually a quite extraordinary claim, and certainly shouldn't just be assumed to be a scientific truth
in the absence of evidence.
e.g. one article is titled "
Why Brain Size Doesn’t Correlate With Intelligence" in the Smithsonian Magazine and 100% of the arguments are terrible, e.g. saying "well whales have big brains and they're dumber than us, aren't they?" And emotional counter-factual reasoning:
Consider the humble dog, Canis familiaris. The brain of a wolf-size dog is about 30 percent smaller than that of an actual gray wolf, its ancestor. Has the dog become less smart since it went its own evolutionary way thousands of years ago? Judge for yourself: When the mere gaze from the dewy eyes of a member of this species causes you to get up from the couch, repair to the refrigerator and retrieve a hunk of cheese for your charge—well, you tell me who is smarter.
God that's a shit argument for "brain size doesn't matter". Domestic dogs are like overgrown babies who don't even need to properly take care of their own young, since we've intervened in everything. Wolves have to be self-sufficient, raise their young to do the same, and coordinate pack hunting without human help.
Meanwhile, the "correlation" part of the headline is
not explored at all in the article. You can google the topic and wikipedia holds the "contrary" position that almost all research on the matter agrees that brain size is strongly correlated with intelligence, at at around a 0.4 correlation:
https://en.wikipedia.org/wiki/Neuroscience_and_intelligence#Brain_volumeSo, brain size strongly predicts intelligence yet popular accounts hold that there's no gender difference in intelligence despite a difference in brain size. If that's the case, that would need to be
explained by something like a
biological difference between men's and women's brains which
exactly compensates for their average brain size being smaller. A "just so" biological mechanism, if you will. And then you'd have to explain why that same biological trick
didn't also evolve in men's brains ...
This logical conundrum is why the "nurture" / "no gender difference" people cling to the lifeboat of saying "brain size doesn't matter
at all" against all the odds and scientific evidence. Because if you
accept the science then the rest of the ideology starts to unravel.
An alternate explanation is that there
are compensatory adaptations in women's brains that increase their bang-for-buck ratio compared to an equal-weight of men's brains, but that they're
not cost free. Otherwise men would have evolved them (any cost-free adaptation will spread to everyone). So women's brains tend to be really good - but at slightly different things to the "average man", which allows IQ tests to exist and be
ideologically calibrated to weight the questions such that they achieve "gender neutrality" on the tests.
And this isn't sexism. It's just saying that people with larger brains tend to have better cognition - which is backed by science. If it ends up supporting some "uncomfortable truths" then - sucks to be humans I guess? The universe never promised to adhere to our various ideologies.