An article by David Graeber I first saw here, where he argues the utilitarian evolutionary view (every action witnessed in animals is there to somehow increase changes of survival) is a relic of the industrial revolution. Instead, he says, playing is a key feature of life.
https://thebaffler.com/salvos/whats-the-point-if-we-cant-hav...
A behaviorist maybe, but an ethologist?
* an ethologist surely knows that gene mutations can be advantageous for the family/group as well as the individual
* an ethologist surely knows that a previous advantage for survival can persist as a vestige
* an ethologist can surely rinse and repeat to find all kinds of fascinating combinations in living organisms which-- while they may not disadvantage the organism-- cannot be explained in the present as construing any clear survival advantage
Those alone are enough to develop an incremental path out of the narrow rational view that Graeber ascribes to Ethology's history. I can't imagine Ethology didn't already get there.
Ethologists: what say you?
Edit: Related process in an unrelated field-- early 20th Century German comparitive musicology eventually became the perfectly reasonable and relativist field of Ethnomusicology. AFAICT Ethnomusicologists kept the instrument taxonomy and the ethnologies, and then got off the "gold standard" of high-Romantic German art music. :)
“Debt: The First 5000 Years” is mind boggling and I hold it as high as Sapiens. In some ways it’s actually better when explaining what people actually did instead of our idealized views.
I think this[1] would be your definitive resources but if you can just search for "evolution of play" then you'll find a lot of stuff. Wikipedia has a hodgepodge of perspectives in section on the purpose of play [2] but you might be better off tracking down those citations.
1. https://www.cambridge.org/core/books/abs/cambridge-handbook-...
2. https://en.wikipedia.org/wiki/Play_(activity)#Development_an...
How did animals come to play? Because it allows them to explore their environment and increases their evolutionary fitness. Why do animals continue to play? Because they enjoy it.