A much better way to put it is that 80-90% of our genome is accumulating mutations at a rate that is consistent with neutral drift which would indicate that the vast majority of mutations do not affect fitness to the point that natural selection can see the difference.
That may be perfectly fine as one way of looking at it. And I find that a very interesting number. Thanks for it.
However, I think the context here is the rate of all kinds of mutations at all points. That means not just in the germ line and not just in the living individuals we may study.
From a reasonable evolutionary perspective it is valid to say that the mutations mostly hover around neutral which your neutral drift information supports.
But we are discussing this with a creationist who claims that "all", "most", "many" or some such portion of mutations are harmful. And from one perspective they may be right. Maybe (I think we don't have the numbers ) harmful mutations are actually in the majority.
Maybe it is worth pointing that possibility out too. This now leads to the recognition of the effect of selection. If the failure of a large percentage of pregnancies is actually due to mutations it demonstrates the power of selection to weed out those mutations.
Without knowing the actual numbers it is clearly possible to conclude that if an individual starts off with a genome that contains a very seriously bad mutation they will obviously not pass the selection filter. In the case of humans we manage to thrive while loosing about half of all fertilization to spontaneous abortions. Since we can manage with that it seems clear that very deleterious mutations can be in the majority and still not be a long term threat to a species and not be of any concern to the evolutionary process.
Edited by Admin, : Fix quote.