that was one of the theories of the study. also another study noted that people judged most "attractive" in terms of facial features were people who were "average" in terms of things like facial proportion, eye spacing nose size. one of the theories was that "average people" tend to be genetically the least likely to have issues.
all fascinating stuff.
when I was in HS charlie's angels was big. one survey had pictures of the three angels-one was their faces in what would be called photo shoot shots (ie if you were their agents and trying to get them work) and the other had each woman in a one piece tank suit (sort of like the famous red job FF was in)
they asked hundreds of men which girl they thought was most attractive
it was amazing, younger men, often without sexual experience and those with low rates of education invariably chose FF who had the biggest rack (both the head shot and the body shot). artsy guys often chose JS. the smartest guys tended to choose KJ when the pictures were shown
when they were shown in the tanksuits, JS was the biggest winner among the brightest guys
1) survival of the fittest is something of a misnomer. What it actually refers to is passing on genes. A person who lives 20 years but has 5 kids was better "fit" from an evolutionary standpoint than some one who lived 50 years and had 1. Some one who lived 100 years and had no children would be a complete failure evolutionarily. This is an oversimplification that does not take into account outcomes for the children, nor "passing on" genes by supporting relatives, and many other factors, but is basically true.
2) Your example would only work if those currently on welfare would pass on genes at a lower rate if welfare did not exist.
3) Welfare and such are such recent additions to the world that they have not had time to have an evolutionary impact.