Скачать или смотреть Why Some Indians Can Drink Dairy and Others Can't?

Humans are the only mammals that drink milk after infancy. This is actually incredibly weird from a biological perspective. Every other mammal on Earth stops producing the enzyme lactase after weaning, making them lactose intolerant as adults. This makes perfect evolutionary sense - why waste energy producing an enzyme you'll never need again?

Think of lactase as molecular scissors that cut milk sugar (lactose) into digestible pieces. In most mammals, the lactase factory shuts down permanently after childhood. For most of human history, we followed this same pattern.

But around 7,500 years ago, something remarkable happened. A tiny genetic mutation occurred - literally just one letter change in our DNA from C to T at position -13910 in the LCT gene. This single letter change meant the lactase factory never received the shutdown signal. People with this mutation could continue digesting milk throughout their entire lives.

When cattle domestication began spreading, this genetic "glitch" became a massive evolutionary advantage. People who could digest milk had access to additional calories, protein, and nutrients. They were healthier, had more children, and this mutation spread rapidly through populations that adopted dairy farming.

What This Map Shows
Scientists analyzed DNA from over 2,000 people across 106 different populations in India, testing for this exact genetic variant. The results reveal a striking pattern.

In the red/orange regions (Punjab, Haryana, parts of Rajasthan), 40-70% of people can digest milk as adults. In the blue regions (Odisha, Bengal, much of South India), only 2-4% have this ability. That's a 17-fold difference within the same country.

The pattern shows a clear northwest-to-southeast decline. The highest frequencies are concentrated along the Pakistan border, then gradually fade as you move toward eastern and southern India.

Interestingly, pastoralist communities maintain much higher frequencies than their farming neighbors. The Ror herders of Haryana show 49% frequency, while nearby agricultural groups often have less than 10%.

This correlates quite unsurprisingly with per capita milk availability in states. One can wonder - but South India and East India consume so many dairy products like sweets and dahi!

The key difference lies in processing and quantity. Traditional South and East Indian dairy consumption was typically limited to fermented products like curd (dahi), where bacterial cultures have already broken down much of the lactose. The small amounts of paneer or ghee used in sweets concentrate proteins and fats while reducing lactose content.

Modern dairy consumption patterns are quite different. A Punjabi drinking multiple glasses of milk daily or consuming large quantities of fresh paneer would likely cause significant digestive issues for someone from Odisha with the same consumption pattern.

Map credits: iipmaps.com