I'm reading Edward Wilson's excellent book "On Human Nature" which really marked the start of the research programme today called evolutionary psychology. (Wilson still prefers the term he coined - sociobiology).
Wilson would have loved a recent example of his thinking. On the BBC nature programme 'Planet Earth' the film crew 'broke the rules' on non-intervention to save the life of an Emperor penguin chick which had become trapped in an ice-hole. Viewers were invited to comment on the ethics of this - of course, overwhelmingly they were in favour. Who could not want to save this cuddly chick? (See picture)
So why the reaction? Do we love all animals so unreservedly? Or do those chicks look awfully like ... human babies?
Suppose the camera crew had been filming a nest of enormous black, slimy, blood-sucking leeches slithering around, and one had come a little too close and fallen into a hole. My vote would have been with the guy with the petrol can and matches!