Darwin himself held that tribal solidarity wins out as natural selection.

Evidence

It must not be forgotten that although a high standard of morality gives but a slight or no advantage to each individual man and his children over the other men of the same tribe, yet that an advancement in the standard of morality and an increase in the number of well-endowed men will certainly give an immense advantage to one tribe over another. There can be no doubt that a tribe including many members who, from possessing in a high degree the spirit of patriotism, fidelity, obedience, courage, and sympathy, were always ready to give aid to each other and to sacrifice themselves for the common good, would be victorious over other tribes; and this would be natural selection. — Norenzayan, Ara, Big gods - how religion transformed…, 454

Categorization

• XREF: Group selection at the scale of whole tribes echoes the reader’s Big God mechanism, since the tribe-level selection pressure rewards costly commitment and devotion to a group-wide moral system.