Just a different perspective to answer this (and I am open to being wrong): competition b/w societies is decreasing. We live in an increasingly bureaucratic, interconnected, globalized world, and I think it is an undiscussed reason for this.
The incentives and disincentives to care for your neighbour or not, or to care for your group, decreased, and it will keep decreasing if this trend continues.
The incentives and disincentives to care for your neighbour or not, or to care for your group, decreased, and it will keep decreasing if this trend continues.