altruism is deeply seated in our behaviours and does go as far as collective child-rearing

Indeed. But it doesn’t preclude otherwise screwing people over.

Nothing you’ve said contradicts anything I’ve said. Ensuring one’s own survival by altruistically caring for infants doesn’t mean one sees those infants as carriers of one’s own genes. Genetic relatives, especially offspring, are always one’s primary concern. Because they share one’s genes.