[stremba]

When was the last positive, advantageous mutation in humans?

Sickle cell trait is actually a mutation that conferred a survival benefit to humans who had it, at least in a specific environment, namely an environment in which malaria is prevalent. In homozygous individuals it is harmful, but in heterozygous individuals it gives increased resistance to malaria. Remember, beneficial is not an absolute term, but rather is relative to the environment. Also remember, harmful and beneficial are relative only to reproductive success. A hypothetical trait that always caused death in humans between the ages of 40 and 50 would be considered a neutral trait in evolutionary terms, although a person affected with it would certainly not see it that way.

[Oberon]

Sickle cell trait is actually a mutation that conferred a survival benefit to humans who had it, at least in a specific environment, namely an environment in which malaria is prevalent.

I can see that...but the appearance of the mutation is prehistoric. We can presume that it first appeared in a single individual at a fixed point in time, but that (admittedly compelling) presumption isn't the same as being there and documenting when the mutation appears.

Others have supposed that the pronounced tendency of certain native american populations to Type 2 diabetes is also a survival adaptation, namely to periods of famine. Again, I can see it, but also again, it's not the same as being there and watching it happen.

[Dataman]

That's like saying being born without eyes is an advantage because it prevents myopia.