Apparently hiccuping is a throwback

there is no obvious evolutionary disadvantage to keeping it

But wouldn’t that mean that we’d find more people around that don’t ever get hiccups? I don’t believe there are many people around who don’t ever get hiccups but I don't know for sure. Both our kids had hiccups pretty often when they were younger. If I’m right in thinking that everybody gets hiccups, that would surely suggest that it serves a purpose, or that it’s tied to something else that serves a purpose.

But wouldn’t that mean that we’d find more people around that don’t ever get hiccups?

Why would it? If your reasoning is that evolution needs a reason to keep a feature of an organism, that’s not true (just look at the human appendix, or our vestigial tail bones, or for that matter the webs on our hands and feet). There needs to be an advantage or disadvantage in order for evolution to “make a change”, as it were (though IMO those kinds of descriptions make it sound like evolution is an active process, which I don’t believe it is).

I also don’t believe you can necessarily make assumptions about the likelihood of adding or removing a particular feature from an organism, particularly with something like hiccuping that (if the theory is true) would have been strongly selected-for in the past. That is, without an evolutionary advantage, you would expect a trait to be present randomly, but I don’t think you can easily guess what kind of distribution you would find.

Anyway, it’s an interesting point… I wonder whether there are people who never hiccup, and if so how many there are. I’m not sure we’d notice them wandering around, so you’d have to do some sort of survey.

Why would it?

Well, there‘s surely a probability, albeit small, that someone would be born that didn‘t hiccup. Given that, over time the number of people that don‘t hiccup would increase. Obviously, the time it would take for the change to be visible could vary on a great number of factors as I imagine there are parts of our genetic make-up that mutate very slowly.

just look at the human appendix, or our vestigial tail bones, or for that matter the webs on our hands and feet

It‘s interesting that you should mention the human appendix. According to Wikipedia there are some people that do not have an appendix which would lend some credence to the idea that it serves no purpose.

There seems to be some doubt as to whether or not our vestigial tail bones are useful. Nine muscles attach to it which are useful and that suggests the chances of there being a mutation that didn’t affect something else would be small.

As for the webbing between our fingers and toes: any variation there would be visible which would, I suspect, have consequences (as much as I‘d like to believe it wouldn‘t).

One thing that’s different about your examples to hiccups is that hiccups appear to be a brain function rather than physical. I don‘t know the answer but that leads to me to wonder whether such features are more or less easily mutated.

There needs to be an advantage or disadvantage in order for evolution to “make a change”

This is slightly misleading. If at one point in time, a particular feature was an advantage but then was to become unnecessary (neither an advantage or disadvantage), you‘d find that the proportion of people with the feature would decrease.

That is, without an evolutionary advantage, you would expect a trait to be present randomly, but I don’t think you can easily guess what kind of distribution you would find.

Well, if the trait is independent from everything else, it would have to be 50/50. Having said that, I very much doubt that many, if any, of our features are genetically independent from other features which could mean that hiccups are dependent on, say, the heart (genetically that is) which would be a reason we still have them (or rather this would decrease the probability of not having them to negligible levels).

Well, there’s surely a probability, albeit small, that someone would be born that didn’t hiccup. Given that, over time the number of people that don’t hiccup would increase.

The number, sure, but not the proportion (to any significant degree).

According to Wikipedia

:-) That well known reliable source of information. (I’m sure it’s right in this case though.)

This is slightly misleading. If at one point in time, a particular feature was an advantage but then was to become unnecessary (neither an advantage or disadvantage), you‘d find that the proportion of people with the feature would decrease.

The trouble with this kind of statement is that you make it sound like there is some sort of intelligence behind evolution.

Because there isn’t active selection against such a feature, and because it was strongly selected-for in the past, I think what you would find is that any increase in the proportion of the population without that feature would be quite small and relatively slow. I don’t disagree that it would happen, but I think without natural selection you’re really talking about random chance (and even then, you might expect that the genes that code for a feature that conveyed a significant advantage would be dominant genes, making the chance of the lack-of-feature spreading smaller still).