It would be very interesting to know to what level different species can keep track of
who's done what to whom--to what level they will do somebody a favor,
repaying somebody else that has done a favor for them the day before.
And especially, it would be very important to know
if these different species and groups of animals have norms about it.
If the individual that doesn’t repay the favor knows to some extent
that it’s done something wrong--that, I think, is an exciting question,
a very important question for which we know very little.
And again, because we are interested in the evolution of humans,
and for humans this is so important, it would be very interesting to know
to what extent our closest living relatives are capable of doing this.
Is this something that our closest living relatives are already doing?
Or is it something that did evolve only very recently, perhaps within the last 200,000 years ago?