Lactose intolerance is not a new problem, in fact evidences suggest that Neanderthal DNA remains from 38,000 years ago that were test were in fact lactose intolerant. These Neanderthal cousins while not our direct ancestors were as close in DNA to us as any other species. This is no big surprise since the herding of animals and dairying did not begin till about 10,000 years ago. This means that up to 10,000 years ago humans did not drink milk after the age of weaning.

Up till recent history humans like all other mammals would experience a decrease in lactase production after weaning, since after that time all mammals cease to drink milk which is food for their infants. In fact most scientists now believe that the continuation of the ability to produce lactase is actually a mutation, which is why most all of African and Asian ethnicities have a near 100% rate of lactose intolerance.  Herding started in the European area, so it is no wonder that lactose intolerance in these races is now much less, about 10%.

Complaints of gastrointestinal stress in adults from milk are described in ancient Greek and Roman texts leading us to believe that lactose intolerance was present back at the beginning of herding. While there were a number of cases reported in the late nineteenth century and early twentieth century, the problem was not looked at seriously until the 1960s when new techniques to study enzymes became available. Milk drinking was not real wide spread in adults early in our history on partly because of the need to keep milk fresh, so milk would not be as commonly consumed as it is today.

Studies in the 1960s and 70s found lactose intolerance to be wide spread as milk consumption increased. Funny enough doctors and scientists described this condition as being somehow abnormal when in reality what was truly abnormal were those that could drink milk in adulthood, with the decline of the production of lactase actually being the normal state.