Why do mammals (and probably some other vertebrates) seem to like affection so much? Is it an adaptation or a spandrel? If so, what is the adaptation(s) from which the spandrel emerged? I encourage people to use sources (preferably shying away from the field of evolutionary psychology) - this could easily be a highly speculative topic, so even if you can't find a paper that directly supports your claim, try to find some literature that at least indirectly supports it. My preliminary research turned up a lot of answers, maybe too many answers to know where to start. Thanks everyone!