[BiffWondercat]

Thanks for the pings as always.

Some state that "99% of mutations are harmful"
Y'all are much more up to speed on this point.

I can give one example of where a 'harmful' mutation, was of a benefit. Sickle cell anemia. In the old areas of malaria, the mutation allowed the mutants to survive longer than the non-mutants who had no resistance to it. In the short term, it conferred a great benefit, in todays world, it is a miserable affliction. I thought Tay-sachs had something similar to it. What about Lactose-intolerance?

Any clues are appreciated!

[PatrickHenry]

I'm not an expert on mutations. I suppose there are as many possible mutations as there are possibilities for imperfect replication of genetic material. Many are irrelevant. Some are lethal. Some turn out to be beneficial. Natural selection is what sorts them out, like a filter, for the next generation.

[Dimensio]

I thought Tay-sachs had something similar to it.

Tay Sachs usually leads to a very early death, so I don't see any reproductive advantage to it, even if there are very short-term "benefits".

[Virginia-American]

[genetic diseases as adaptations to infectious diseases]

I don't have it in front of me, but Jared Diamond's Guns Germs and Steel discusses this. IIRC, sickle cell is to malaria as cystic fibrosis is to cholera as tay-sachs is to TB. I think lactose tolerance has more to do with culture than disease.

I'm pinging G3k because he always has something to say about this.

In the old areas of malaria, the mutation allowed the mutants to survive longer than the non-mutants who had no resistance to it. In the short term, it conferred a great benefit, in todays world, it is a miserable affliction.

Being heterozygous for hemoglobin-S still protects, being homozygous is real bad. Granted, American blacks don't get any benefit from it. Do a Google search on thalassemia, similar to sickle cell but found in Europe rather than Africa.

[jennyp]

Some state that "99% of mutations are harmful"
Y'all are much more up to speed on this point.

Actually most mutations are neutral. Of the mutations that have some kind of effect, most are indeed harmful. But not all of them. There's a list of several examples of beneficial mutations here.