Individuals vary a lot in wealth, and so do populations. Many factors influence wealth – income, the payoff for saving, historical experience, etc – but people likely vary in their innate propensity to save. This may be partly due to differences in time preference, but that assumes that people save for rational reasons, and that may not be the whole story. It could be that people, at least some people, just feel like saving, and would do so even if it were economically irrational. And other people may not feel that way, and don’t save much even when saving has a big payoff.
It looks as if saving has had a bigger payoff in recent millennia than it typically did in the distant past. I’m not say that as an iron law, more as a tendency. There may have been ways of saving food for hard times (winter, mainly) quite a while ago, at least in cold climates… at least you’d think so. On the other hand, there is almost no sign that Neanderthals had any means of preserving food.
It is at least true that a number of new ways of saving have been developed since the end of the Ice Age.
Farming must have favored low time preference. At minimum, people have to wait a few months for the payoff from their efforts in almost any kind of farming. Some crops, like olives, have high productivity but take several years to mature.
Grain crops can be stored, and seed must be saved for the next growing season. In some societies, private property was reasonably secure, so people could save wealth in the form of land or other assets.
In these new situations, where saving had higher payoffs, individuals that had a greater innate propensity to save ought to have had higher fitness. Having lower time preference, acting more like homo economicus , may have been favored, but surely a simple hoarding tendency, more like a squirrel burying nuts for the winter, would have been favored as well. Maybe there was selection for being more of a squirrel…
Of course there is a distribution of such traits, ranging from a little to a lot. In a population with a greater mean amount of tendency-to-save, some would do so to a ridiculous extent. Hoarders. They may not be equally common in every population.
If I had to guess, I would say that extreme hoarders ought to be rarer among populations that had a shallow experience of agriculture and/or no winter. I have long wished that someone would discover a cave once occupied by the Neanderthal version of the Collyer brothers, but this line of thought suggests that alas, that may never be.