A man naturally loves his children better than his nephews, his nephews better than his cousins, his cousins better than strangers, where every thing else is equal.” And we care more about ourselves than any single other individual on the planet (even if we might sacrifice ourselves for two brothers or eight cousins.)
As a nitpick, that isn’t necessarily true. People do sacrifice themselves for other individuals. Sometimes it even makes evolutionary sense—if they have a terminal illness, for instance.
As a nitpick, that isn’t necessarily true. People do sacrifice themselves for other individuals. Sometimes it even makes evolutionary sense—if they have a terminal illness, for instance.