Comments by "Jack Mac" (@TheEggmaniac) on "Your DNA and the Digestion of Milk…" video.

  1. Ive aways found it fascinating and also a bit weird that so many people, in some parts of the world, like Britain and Ireland (96%), have this genetic mutation, that allows them to be able to digest milk, after the normal period of weaning in humans. Until relatively recently, all humans were lactose intolerant, as they didnt need to be able digest milk, after they were weaned as a baby. Generally by one year of age. But a mutation somewhere back in time gave people who could digest milk, after this age and as adults a evolutionary advantage. Lactose tolerance is highest in the world in Ireland , and second highest in the UK. As you point out this wasnt always the case. If you go back 4000/ 5000 years ago the natives were lactose intolerant. Lactose tolerance/ or persistence, seems to have been there since the arrival of the Bell Beaker and other people, who were pastoralists and farmers and were very reliant on the milk of animal like cows, goats, horses and sheep. Why is it so high in theses countries? Archaeologists have speculated that there must have been times of great starvation, when all crops and most animals had died, which lead humans in Ireland and Britain, to be extremely reliant, on the milk of the domestic animals, to keep them alive. Thus pushing the evolutionary pressure even more in favour of people who had this mutation for lactose tolerance/persistence. At these times if you didnt have that gene you were much more likely to die of starvation. There was nothing else to eat.
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