In the nature vs nurture debate, the pure nature and pure nurture people are extremist views, and most people are somewhere in-between. The articles you have presented are talking about mild effects - and the first article is chock-full of weasel words... and ultimately talks about morality as being a way to controls our 'evolved selves' (where the author uses 'evolved' to mean 'genotypical').

I mean, let's keep it in context of the article: they began to find research suggesting wide cultural differences almost everywhere they looked: in spatial reasoning, the way we infer the motivations of others, categorization, moral reasoning, the boundaries between the self and others, and other arenas. These differences, they believed, were not genetic.

If moral reasoning were genetic, then you wouldn't have people losing or changing religions, and there'd be no such thing as social movements. The article isn't talking about subtle effects on individuals from serotonin levels, it's suggesting that it was generally accepted that 'wide cultural differences' were genetic, and that the researchers in question were taking an unusual path in thinking they weren't genetic.

"If moral reasoning were genetic, then you wouldn't have people losing or changing religions, and there'd be no such thing as social movements."

This might be true if genes completely determined morality, but I don't think anyone is saying that, as you allude to in your first paragraph. The fact that exercise can affect strength doesn't mean that genes don't play a very large part in the range of strength a species can have. The main thing I was objecting to in your initial comment was the idea that it's so obvious that genes and evolution have nothing to do with morality that even someone with no training (a layperson) can see that[1]. That is to say, you seemed to be advocating pure nurture, yourself.

[1] Not to mention the existence of lots of popsci books and essays on precisely the subject of morality being strongly affected by our evolutionary history.