The lactose persistence gene variant found in Europeans is a one time mutation. It has evolved independently in Africa a few times too, but these variants are not found in ethnic Europeans.
Far less than 35% of the worlds population is lactose tolerant as an adult. I will take a look at the review linked on wiki and try to see how robust this number is.
Edit. Ok trekking back through the literature the estimate is based on old measures of the lactase persistence phenotype which is not very reliable, not on genetic data. It is likely to be wrong just on demographic growth alone in the last 40 years. My guess is around 15% of the worlds population is actually able to digest lactose in adulthood.
Far less than 35% of the worlds population is lactose tolerant as an adult. I will take a look at the review linked on wiki and try to see how robust this number is.
Edit. Ok trekking back through the literature the estimate is based on old measures of the lactase persistence phenotype which is not very reliable, not on genetic data. It is likely to be wrong just on demographic growth alone in the last 40 years. My guess is around 15% of the worlds population is actually able to digest lactose in adulthood.