Re: effect of potassium on evolution

You have a good point, but the problem has many dimensions to it, of which radiation is only one. True, reducing potassion concentrations would help to reduce radiation dose from internal radionuclides, but it would also reduce our ability to use this important element in our biochemistry. We use potassium for many purposes, and it appears to be more important to continue using potassium than not.

Remember, too, that radiation accounts for only about 1-5% of background DNA damage; even with our current potassium concentrations. The overwhelming amount of DNA damage comes from the leakage of free radicals from our mitochondria (for eukaryotic organisms - that is, those with a cell nucleus). Organisms living in an oxygenated environment also have a lot of DNA damage from the simple presence of oxygen in their cells. And other metabolic processes produce free radicals that damage DNA as well. These account for over 90% of DNA damage.

So - you are correct that reducing potassium in our bodies would reduce DNA damage and mutation rates, but apparently not enough to make this worthwhile on an evolutionary basis.