Reciprocal altruism is pretty rare in nature, as Tit-for-tat behaviour requires brain power.
Humans practice it. Though not all of them have any significant brain power.
Vampire bats practice Reciprocal Altruism… They have larger brains than other kinds of bats. (For example, my cricket bat has a negligible brain)
Reading about vampire bat tit-for-tat led me to wonder if this commonality had anything to do with our fascination for Vampires.
But then this entire verbiage could have been for the purpose of saying “bat tit” earlier.
What can I say, its a dark night!