The article itself includes more than one example. E.g. the researchers hypothesized that, given some premises about evolution, poor women would have more kids earlier. This rules out them having fewer kids later.
Then they went and tested it.
Um, isn't this already well known? Did they not craft the hypothesis to fit their existing understanding?
> Then they went and tested it.
No comment.
No idea. The point is that it's a substantive claim that could be tested empirically.
> Did they not craft the hypothesis to fit their existing understanding?
I hope so. Using what you already know helps generate interesting hypotheses. They don't pop into existence asexually.
Another problem with your post is that you are conflating males and females sexual and reproductive interests. You speak of certain "families" having more children than other families, but a family is not a cohesive, unanimous group with common interests. It consists of two partners, a male and a female, who both have remarkably different sexual and reproductive interests. You are right in that males’ evolutionary goal-albeit they are often not conscious of it, or at least no more conscious than a frog is-is to propagate their genes which they do by inseminating as many females as possible. However, females do not benefit from such promiscuous behaviour, as they are the ones who have to bear the pregnancy for 9 months and then some. So the behaviour of each member of the family needs to be understood within the appropriate evolutionary context, and not just as a "family".
Now, onto to a theory which does take wealth into consideration when explaining human behaviour: A male is better able to monopolize being born into a wealthy family, that is, attract more mates and produce more offspring because females typically look for resources in a potential partner. Thus, we would expect parents to invest more time and resources in raising male children when they are living in good-i.e., wealthy- conditions, because males would be better able to translate those resources into mates, and, eventually, grandchildren. A female is limited in the number of offspring she can produce in her lifetime, something called reproductive value. But a male, given ample suxual opportunities, can produce pleny of offspring because he is not obligated to carry, give birth, and, in some cases, invest time.resources into raising children. Thus, the best way for wealthy parents to ensure they have plenty of grandchildren is to invest in their male children more than female. In fact, richer families beget more male children than poorer, who, in turn, beget more females. The explanation of this latter fidining is unknown, but several theories have been proposed.
In poorer conditions, however, we would expect the opposite to ring true. That is, parents would invest more time and resources in raising female children because they, of the two genders, are more likely to find a mate and produce grandchildren. A poor son is not a desirable mate, so he is less likely to attract a female with whom he can produce children. The saffer strategy for the parents in this situation is to invest more in their daughers.
So, contrary to what you mentioned above, evolutionary theories do offer predictions for the behaviour of the rich, not just the poor. You’ve just asked the wrong questions, and so have had difficulty finding the right answers.