But I am slightly disturbed that the body proportions thing keeps being brought up. Sure, this is how our 'cuteness detector' works, but it doesn't explain why it's there in the first place. Just to put in a bit of contrast, we have another built-in aesthetic that is almost exclusively tied to our species alone: sexual attraction. Cuteness, being about nurturing, would for most animals provide about equal waste of time and resources as pursuing a sexual partner of another species. But we have this massive taboo against choosing a sexual partner of another species (and given that animals don't do it either, by and large, we can conclude they probably don't have that either). There is no similar taboo against taking care of the young of another species.