The Milk Tolerance Gene Emerged Independently in Asians

Science & Technology Science

Posted by AI on 2025-05-13 07:22:42 | Last Updated by AI on 2025-12-21 00:53:47

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Genes that allow for milk consumption past infancy appeared in East Asians before cattle domestication, a study published in Nature Genetics finds. Scientists discovered that the mutation for lactase persistencethe ability to digest lactose appeared in Asian populations independently from other populations and long before cattle domestication, with the exact timing being highly uncertain.

Lead: A study published in Nature Genetics debunked the long-standing hypothesis that East Asians evolved the ability to drink milk only after they began domesticating cattle. The team discovered that this mutation for lactase persistence appeared in Asian populations long before cattle domestication.

Many populations throughout human history lost the ability to digest lactose once they were no longer reliant on breastmilk, but evidence has shown that the enzyme lactase, which helps digest lactose, continues to be produced well beyond weaning in some populations. This is due to a mutation in the MCM6 gene, which scientists believe occurred somewhere between 14,000 and 7,000 years ago in populations that came to occupy Europe and parts of Africa. This mutation allowed these populations to consume dairy products from livestock, which was beneficial in climates where growing crops was more difficult.

However, this study found that the mutations that confer lactase persistence emerged independently in different populations. Their emergence in North European and African populations in particular appears to have coincided with the domestication of cattle, buffaloes, goats, sheep, and other livestock, which began about 11,000 years ago.

In contrast, the team discovered that the mutation for lactase persistence appeared in eastern Asia much earlier, dating somewhere between 24,000 and 19,000 years ago, long before the domestication of cattle. Instead, the authors suggest that the lactase persistence mutation appeared advantageous during a period of food scarcity when mammals such as bison, yaks, and deer, which all produce milk, were a valuable source of nutrition.

Although they acknowledge that the timing is highly uncertain, the authors suggest that the independent emergence of the milk-drinking gene in Asians preceded the expansion of agriculture and animal domestication.

Conclusion:

Scientists have long acknowledged that populations in Africa and Europe evolved the ability to digest milk later than those in Asia, but have often attributed this to the fact that Asians were raising animals other than cows, such as sheep and goats, that produced less milk and required less lactase to digest. This study's findings challenge that long-held belief, showing that the genes that allow for lactase persistence in Asians evolved independently from those in other populations and long before the domestication of cattle.

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