I added the part about selection because its the followup that exacerbates this, yes, the paper stops short of that

It does say the other part, which you wrote as adverse environment and I wrote as culture. Because the paper points out that there are environments/countries that aren't gender unequal, the entire basis of being able to do this study

To me, that basis then suggests that the unequal countries are perpetuating it far beyond culture, since people grow up and are available for mating based on some attributes over others, but you’re correct that the paper itself doesn’t go there and we dont have confirmation that the brain aspects are sex linked traits