I don't cite those names as authorities whose views on the historical influence of Christianity--which differ greatly in their particulars, by the way--demand acceptance. I'm presenting them as evidence that the subject is worth reading up on, whether by you or by someone else who happens to read these comments.

Thank you, that's an interesting paper. Looking at the "morality-as-cooperation codebook," though, I see a great deal that contradicts orthodox Christian doctrine--for example, Giving preferential treatment to (members of) your group. Assuming that the opposite belief--that you should "love your enemies, bless them that curse you," etc.--has gained any adherence in the West, that ethic must have originated in something else (maybe a religion?) besides the code of reciprocity your paper's authors have assembled.