However this relatively recent biological imperative is at odds with a much older imperative: selfishness.
I'm not sure how well this contention holds up. There is plenty of evidence for social and co-operative behaviours throughout the animal kingdom. It may be recent in terms of the entire history of life, but then so is multi-cellularity. In fact even in terms of unicellular organisms we can see that co-operative strategies evolve.
TTFN,
WK