Lactose Tolerance Evolution: How Periodic Famine, Disease Outbreaks Led Ancient Europeans to Start Drinking Milk

Researchers recently reported that Europeans avidly tapped into milk drinking roughly 9,000 years ago when the so-called "dairying group" initially reached the southeastern corner of the continent.

As indicated in a ScienceNews report, ancient Europeans may have developed the ability to digest milk because of periodic famines, not to mention disease outbreaks.

Nonetheless, it took several thousands of years before huge numbers of Europeans developed a gene for digesting lactose, the sugar found in milk, according to the study authors.

According to Richard Evershed, a biochemist from the University of Bristol in England, and his colleagues, such discoveries, based on animal fat residue specimens from hundreds of archeological areas and a trove of DNA data, disable an influential notion that milk drinking dramatically increased the nutritional and health benefits of the product drove the evolution of lactose tolerance.

Lactose Tolerance Evolution

In their study published in the Nature journal, the researchers noted that Milk drinkers who cannot digest lactose are experiencing gas, bloating, diarrhea, and intestinal cramps.

The research specified that such reactions causing discomfort were extremely mild to move the evolutionary needle toward lactose tolerance on their own.

However, during periodic famines and infectious disease outbreaks, lactose-induced conditions like diarrhea for one turned fatal for many malnourished people in farming communities, the new study suggested. The study authors also explained that such recurring threats hotwired the evolution of lactose tolerance.

This report of Evershed rules out widespread milk consumption as the evolutionary force behind lactose tolerance, according to Oliver Craig, a bioarcheologist from the University of York in England.

Additional research needs to elucidate the scale and the extent of famines, or infectious disease episodes that may have affected how Europeans were digesting milk, Craig, who was not part of the new study, also said.

Frequency of Milk Use in Europe Mapped from 9,000 Years Ago

There is a need for researchers as well to keep in mind that cheese, as well as other low-lactose dairy products, date to around 7,400 years back in Europe.

If such foods were commonly available, it remains unclear why lactose tolerance Europeans would not have survived times of disease or famine, explained Craig.

The team mapped estimated frequencies of use of milk throughout Europe from approximately 9,000 to 500 years back by investigating previously published data from animal fat remnants extracted from over 13,000 pottery fragments at around 550 archeological sites, a related ScienceDaily report specified.

The team led by Evershed also followed the occurrence and spread of the main gene responsible for lactose tolerance through published ancient DNA data from almost 1,800 Asians and Europeans.

Lactose Tolerance in Other Parts of the World

In other parts of the globe, and for equally unexplained reasons, regular consumption of milk does not essentially promote the spread of lactose tolerance.

For example, lactose tolerance rarely occurs among milk-consuming Central Asian heders, although biological indications of lactose tolerance frequently appear in East African Hadza hunter-gatherers who do not drink milk.

Related information about the evolution of lactose tolerance is shown on Biointeractive's YouTube video below.

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