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Proteomic Analysis of Ancient Teeth Points to Dairy Consumption in Africa Thousands of Years Ago

NEW YORK — People in northeastern and eastern Africa began drinking milk as early as 6,000 years ago, according to a new proteomic analysis of ancient dental plaque. The finding suggests dairy consumption started before lactase persistence alleles became widespread.

People often lose the ability to digest milk when they reach adulthood, but some populations have the ability to continue to break down lactose past childhood. Among European populations, there is one genetic alteration linked to lactase persistence, while African populations have four such alleles. However, the relationship between the adoption of dairy consumption and the emergence of lactase persistence has been unclear.

Using a proteomic approach, researchers from the Max Planck Institute for the Science of Human History in Germany, the National Museums of Kenya, and elsewhere analyzed hardened tooth plaque, called calculus, from dozens of ancient African individuals who lived thousands of years ago. As they reported on Wednesday in Nature Communications, the researchers found proteins within some of the calculus samples that indicated ancient Africans consumed dairy. 

First author Madeleine Bleasdale, a researcher at the Max Planck Institute, noted in an email that dairy fats found on pottery samples indicated people were drinking milk thousands of years ago in northern Africa, "but our study gives the oldest proteomic evidence for Africa."

She and her colleagues extracted proteins from the dental calculus of 41 ancient individuals from 13 sites in Sudan and Kenya for an analysis that used liquid chromatography-tandem mass spectrometry. They uncovered milk peptides in samples from eight individuals from two sites in Sudan and three sites in Kenya. Typically, the protein identified was the milk whey protein β-lactoglobulin, which in some cases they could trace to sheep, cows, and goats.

One individual from Sudan who harbored milk proteins lived about 6,000 years ago, pointing to an early start of dairy consumption. Another individual who lived about 4,000 years ago had milk proteins associated with goats, providing the earliest evidence of goat milk consumption in Africa, the researchers noted.

Meanwhile, the samples from Kenya with milk peptides came from individuals who were a little younger, dating back to the Pastoral Neolithic phase between 3,500 and 1,200 years ago.

The findings point to a long history of dairy consumption in this region of Africa and suggest that goats and sheep were key sources of milk for herders in the region, according to the researchers.

For some of the ancient samples, the researchers also had access to genetic data. Four of the ancient individuals from Kenya found to have dairy proteins on their teeth did not have any of the known lactase persistence alleles.

This suggests that dairy consumption began before lactase persistence became widespread, even a thousand years before it became more common. "It is a puzzle, but it's something we have now seen in other regions of the world like ancient Mongolia," Bleasdale said.

In their paper, she and her colleagues speculated these dairy-consuming individuals may not have drunk milk, but may have eaten yogurt or other processed dairy products that would have been easier to digest. This behavior then could have led to the spread of lactase persistence, reflecting an intertwining of culture and biology.