Not at all. A better way of looking at it is "fitness": how many offspring will you produce and also how well will those offspring survive and reproduce. This is evolutionary "fitness", not exercise "fitness". Physical attractiveness, mood stability, etc. can be considered factors as well as health and fertility. (This is where evolutionary biologists start talking about sexual selection as well as natural selection as being important in changes within populations over time.) And your fitness is all completely relative to anyone else's fitness.


Probably not, if those genes really did start to become less frequent in the population they would be eliminated much more slowly and eventually just get stuck. Many recessive defects become "sheltered" in the heterozygote individual, once they reach a particular low frequency they just circulate around in the gene pool at that rate, unless of course some event occurs that increases their frequency again. The genetics of the Pima Indians are an example of that, where for centuries environmental conditions actually selected for the genes that now cause insulin resistance.