What do we know about the long-term reproductive success of people who don't like music?
If music has a biological function, and in particular if listening to music has a biological function, then listening to music must somehow contribute to long-term reproductive success.
There exist people who don't like music. So if music does have a biological function, then we would expect to see some consequence of that, in the form reduced long-term reproductive success.
Actually, it is only very recently that science has studied the existence of people who don't like music.
The percentage of people who don't like music is somewhat uncertain, and it can depend on how one defines the boundary between people who do like music and people who don't.
The observed percentage is somewhere between 3% and 5%.
That is a fairly small minority. But it is at least 1 of every 30 people, which means that there are non-music lovers all around us.
Indeed I once met a person who knew someone who didn't like music.
But if 1 out of 30 people don't like music, then probably I am at least acquainted with a few people who don't like music, but it's just that I don't know that they don't like it. And when you walk down a busy street, there are non-music lovers walking down that same street. (Just like, for example, there are gay people walking down the same street, but many of them may not be openly advertising that fact to the rest of the world.)
My big question is: Do the minority of people who don't like music have fewer grandchildren, on average, than the majority of people who do like music? (You'll see here that I am using reproductive success over two generations as an approximation to "long-term" reproductive success, but for most purposes that's probably close enough.)
Of course there is no easy way to answer this question, at least not very quickly. We would need to have some way of identifying a group of people who don't like music, and then we would have to count the number of descendants that those people had two generations later.
Either we would have to identify such a group of people historically, which is in practice almost impossible, or, we would have to identify a group of such people now, and wait two generations to see what happens.
Another possible approach would be to observe non-music lovers in the present, but instead of waiting two generations for results, we could look for ways that their lives are significantly different from the lives of "normal" music lovers.
There would of course be some obvious differences, such as:
People who don't like music are less likely to hang out in places or situations where there is a lot of music.
People who don't like music won't spend time, effort or money on creating or consuming music, and they will spend that time, effort and money on other things.
If anything, the second item would be something that we might expect to increase long-term reproductive success, if those other things are things that increase long-term reproductive success.
There is also the question of what it means when a disinterest in music is caused by some type of disability, such as poor pitch perception. Such cases probably don't tell us anything, because poor pitch perception might cause a problem even in non-musical situations, so we are really just observing the consequences of the disability, and not the consequences of disinterest in music.
Ideally we want to find a group of people to study who don't like music, and where that is not caused by any obvious disability.
(Actually this paper describes the results of a study of a group of “healthy” people exactly like this. However that study focused mainly on whether of not people disinterested in music were or weren’t also disinterested in other things, ie “musical anhedonia” vs “anhedonia” in general. It did not attempt to explore the question of whether those people might have greater or lesser long-term reproductive success compared to normal “healthy” people, ie people who like music.)
As it happens, https://www.reddit.com/r/musiccognition seems to be full of requests for people to participate in studies on various aspects of music cognition and music psychology.
So maybe someone somewhere in an academic environment could start an self-observational study of non-music lovers. They could post a request something like:
We are looking for people disinterested in music to take part in a research study. The primary goal is to find out if there is anything that is different about people who don't like music, other than the fact that they don't happen to like music. The initial stage of research will simply involve asking self-identified non-music lovers to identify all other aspects of their own lives and personalities that they believe are significantly different from those of most other people.
Of course people who don't like music probably don't spend much time on https://www.reddit.com/r/musiccognition, so the request for participants might have to ask people to pass the message on to other people they know who happen to be non-lovers of music.
Theories of Equilibrium
It may be that the percentage of people who don’t like music is fairly constant - that it is ~4% now, and it was ~4% a hundred years ago, a thousand years ago or even ten thousand years ago. (Of course we have no way of directly measuring those numbers.)
In which case the basic question is more complicated. It’s not “Do people who don’t like music have more or less long-term reproductive success?”, but more “Do people who don’t like music have more or less long-term reproductive success as a function of the current percentage of people in the population who don’t like music?”.