[jennyp]

The likelihood that a random mutation actually improves functionality is incredibly small. Most mutations are harmeful. It still looks like man is de-evolving. And that the negative genetic mutation load vastly outweights the positive.

But the "negative genetic mutation load" does not increase if the people who get the negative mutations die off or have fewer kids! That's the beauty of natural selection: It ratchets the species as a whole towards fitness, even in the face of an overwhelming majority of negative mutations.

[DannyTN]

"But the "negative genetic mutation load" does not increase if the people who get the negative mutations die off or have fewer kids!"

Yes, but the over 600 inherited genetic diseases have already passed the second phase. So there is a huge negative load that has avoided dying off and is being passed down in the gene pool.

So it's not clear at all that natural selection is even preserving the gene pool. It looks like a slow degradation of the gene pool. It's also by no means certain that even if there was more pressure on the human race, so that natural selection could work better, that the gene pool would be preserved.

Natural selection will kill off the weakest members, but it looks like enough of the negative load gets transmitted from one generation to the next, that Natural Selection is still fighting a losing battle.