As far as I'm aware, the hedonic treadmill is a culture-bound theory. Has anyone actually done serious research about it outside of the 'developed' world? Also, by my understanding, it doesn't state that long-term lifestyle changes won't make you happier, just that our happiness levels stabilize quickly after sudden changes.

Genetics may be one factor, but relative differences in wealth is another huge factor that I know has been observed extensively outside of dominant western culture. In HG societies, there are almost no differences in wealth. Everyone considers themselves pretty well-off because there are very few things (or experiences) in their world that they could want but not have.

And even by the objective standard, a HG is better off than someone in the industrial world who has no job, family, home, or love prospects. An average HG has meaningful work, a large and close family, a mate, and considers their entire territory to be their family's "home". It isn't a miserable or unfulfilling life at all. The only way you could come to the conclusion that you're still better off is if you held really stereotypical and inaccurate views of how HGs live. Which leads like things like groups of us deciding that we have a moral obligation to nose in on what few HG societies still exist and bestow the gifts of technology and capitalism on them, so that they can live in slums for the rest of their lives and the lives of most of their descendants. Which doesn't exactly make them happy, because they go from being the richest people in their society to the very bottom of the ladder in ours.

I'm not going to live my life maximizing my standard of living because money and wealth aren't the same thing. Call it fulfillment instead of happiness if it makes you feel better, but having the biggest pile of money isn't the way to get there.