The closest ancestors of modern humans first appeared 200,000 years ago in Africa. It seems that for 97 percent of the period of their existence, the human populations were lactose intolerant— they could not consume dairy products. In Southern Africa lactose intolerance is still fairly high. The country with the highest lactose intolerance is South Korea. In his book The Horse, the Wheel, and Language, David W. Anthony writes: “Recent genetic research on the worldwide distribution of the mutation that created lactose tolerance, which made a dairy-based diet possible, indicates that it probably emerged first in the steppes west of the Ural Mountains between about 4600 and 2800 BCE…”
This means that the Yamnaya could be the world’s first lactose tolerant population. Historians believe that they spoke a late Proto-Indo-European language which they implanted in the regions where they migrated: Europe, the Middle East, and South Asia. David W. Anthony conjectures that since the cows give more milk than any other herd animal (twice as much as the mares and five times more than goats), the Yamnaya developed the religious practice of revering their cows. In their culture, cows symbolized prosperity and the blessings of the divine. The Yamnaya probably counted their wealth in cows—those of high social status would maintain large herds. The Sintashta and the Andronovo cultures are also identified with the Yamnaya culture.
One of the implications of this finding is that the religious practice of revering the cow did not originate in South Asia (India) but somewhere in the Central Steppes. In my opinion, the problem with this thesis is that it is based on genetic research that is centered on European populations. The only reason the Yamnaya were intensely investigated by the geneticists is because they had a European connection. The Yamnaya invaded (or migrated) into Europe about 5000 years ago, and they completely replaced Europe’s original population of native hunter-gatherers. Hardly any trace of Europe’s original population, the population before the Yamnaya arrived, can be found. Currently the lactose intolerance level in Europe is between 18 percent to 26 percent.
The genome of the ancient populations of the non-European populations has not been extensively studied. There could be other ancient populations which became lactose tolerant at the same time or before the Yamnaya did.
The Yamnaya arrived in India between 2000 and 1600 BC. Their mingling with the natives of North India is believed to be the cause of the higher lactose tolerance in the North Indians vis-à-vis the South Indians. A study shows that lactose intolerance was 27.4 percent in a sample group taken from New Delhi, and it was 66.6 percent in a sample group taken from two South Indian centers at Trivandrum and Pondicherry. In East Indians lactose intolerance is higher—this is because of their mingling with the East Asian populations which are lactose intolerant. These inferences have been developed from the study of samples taken from a few urban centers. The countryside was not a part of the study.