ELI5 version: Those certain African and Asian cultures have their own version of lactose tolerance that’s not the same type as Europeans. European version is more an on/off switch ability, you either can drink milk or not. Asian/African are more of a dimmer switch, some have a stronger tolerance than others. It also is related to specific cultural groups who lived around cows so there was a reason to have it. Other cultures may have been neighbours but didn’t need to because they had other sources of food.
Longer explanation: Lactose intolerance is a fun mutation to teach in anthropology because it actually came up multiple times. It’s usually the example of convergent evolution we use in intro to bio anthropology. The genes that allow some people groups to digest milk are not necessarily the same that allow others. They also have different degrees of tolerance but the main driving factor is communities that did some sort of sheep/cow herding in the agricultural revolution, though it’s a bit of a chicken/egg situation. What is unique about the European version of this lactose persistence trait is thought to have emerged earliest, and distributed to the resulting generations relatively quick, compared to other traits. The European version is also monogenetic (one gene, on/off) and the other types (I think it’s 4 others), are polygenic so the tolerance there is more of a spectrum.
Side note, Africa is very genetically diverse. There is more diversity within the continent than outside of. So it’s unsurprising that some have the ability to digest milk when others do not. Pastoral, nomadic communities (such as Maasai) tend to be the ones who have the lactose persistence trait and unsurprisingly, they spend most of their lives with cows
ELI5 version: Those certain African and Asian cultures have their own version of lactose tolerance that’s not the same type as Europeans. European version is more an on/off switch ability, you either can drink milk or not. Asian/African are more of a dimmer switch, some have a stronger tolerance than others. It also is related to specific cultural groups who lived around cows so there was a reason to have it. Other cultures may have been neighbours but didn’t need to because they had other sources of food.
Longer explanation: Lactose intolerance is a fun mutation to teach in anthropology because it actually came up multiple times. It’s usually the example of convergent evolution we use in intro to bio anthropology. The genes that allow some people groups to digest milk are not necessarily the same that allow others. They also have different degrees of tolerance but the main driving factor is communities that did some sort of sheep/cow herding in the agricultural revolution, though it’s a bit of a chicken/egg situation. What is unique about the European version of this lactose persistence trait is thought to have emerged earliest, and distributed to the resulting generations relatively quick, compared to other traits. The European version is also monogenetic (one gene, on/off) and the other types (I think it’s 4 others), are polygenic so the tolerance there is more of a spectrum.
Side note, Africa is very genetically diverse. There is more diversity within the continent than outside of. So it’s unsurprising that some have the ability to digest milk when others do not. Pastoral, nomadic communities (such as Maasai) tend to be the ones who have the lactose persistence trait and unsurprisingly, they spend most of their lives with cows
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