The price of holding a baby

Last week I learnt from Ronald Noè that female chimps (and other primates) pay new mothers (in time spent grooming) for a go on their babies. Louise Barrett and Peter Henzi actually found that the 'price' of holding a newborn monkey responds, just like that of most consumer goods in human markets, to the level of supply. Fewer babies around in the troop equals more minutes spent picking fleas out of Chimpette's fur before you get to cuddle baby Chimporino.

What I adore most about this fact is its utter irreconcilability with all our usual assumptions about why adult animals do things, in terms of fitness maximisation etc. I see nothing a monkey stands to gain from squidging someone else's little 'un (maybe I'm wrong?) except good old-fashioned cuteness.

Babies are just nice. Fact.