I was inclined to agree with this until I noticed that the whole 'what is the purpose of' in this sentence is effectively retroactive guessing at whim without any real basis to do so. The majority of these 'scientific theories' of 'why people have nostalgia', 'why "men" look at "women's" breasts' et cetera are just largely guessing at whim, ask yourself, is there any way to truly verify your own hypothesis on such questions.Why does it have to serve a function? Seems to me that it could easily be an unintentional product of other inherant (human) capabilities.
A: The purpose of nostalgia is intrinsicly linked to the desire of man to create social inertia once it has found a working society.
B: Pfah! Nonsense, the purpose of nostalgia is all an experiment planted into us by Aliens from he planet No'rth-Kh'orea to observe us for scientific testing how we respond when one of us asks the question what it is for, can you not see this?
And there really isn't a way to falsify one or the other.
Then it's an evolutionary advantage not to believe it. There are more things which are 'true' which are an 'evolutionary advantage' to not believe. In fact, they are quite common, this is because ignorance is an evolutionary advantage 'ignorance is bliss', the mistake people often make with these things like 'the human genome is becoming weak' is that they fail to realize that their own opinion about 'good people' needn't concord with that of evolution. This is because evolution—of course—cares about one thing, ability to reproduce offspring that can again reproduce. I'm not sure about you but that's not really my own definite criterion on how much I value another man. The whole futuristic idea that man will evolve to startling intelligence is only fit for fiction, evolution does not lead to species who are 'advanced', it leads to species which are able to procreate in the environment they are put it. It's an evolutionary disadvantage to know a thing or two about physics it seems, physicists don't have that many children, I know few that even have a child wish.Hey, I'm gonna toss out this little paradox:
What if evolution is true, but it's an evolutionary advantage not to believe it?