zlacker

Plenty of genes spread that are neutral to net negative for fitness. Sometimes those genes don't kill the germ line, and they persist.

There is no evolution == better/more fit, as long as reproduction cascade goes uninterrupted, genes can evolve any which way and still survive whether they're neutral or a negative.

>>heavys+(OP)
Technically correct but not really. It's a biased random walk. While outliers are possible betting against the law of large numbers is a losing proposition. More often it's that we as observers lack the ability to see the system as a whole and so fail to properly attribute the net outcome.

It's true that sometimes something can get taken along for the ride by luck of the draw. In which case what's really being selected for is some subgroup of genes as opposed to an individual one. In those cases there's some reason that losing the "detrimental" gene would actually be more detrimental, even if indirectly.