“Other animals fight over limited resources and desirable mates, but humans fight for both biological and cultural reasons. We alone will go to war to defend our honour and values. … What’s more, conflict seems to be an integral part of our social organisation. … Paradoxically, these antagonistic tendencies may be intimately linked with another, much more noble side of human nature: our unparalleled capacity for large-scale cooperation and altruistic self-sacrifice.”