An analysis of ancient human skeletons finds that an increase in size and weight in some regions coincided with increased lactose tolerance
20 January 2023
People in northern and central Europe increased in size between 7,000 and 4,000 years ago, while people elsewhere stayed the same height or got smaller, according to a study.
The growth of some Europeans was likely because they developed lactose tolerance earlier, the researchers say.
The ability to produce the enzyme lactase in adulthood and digest milk is thought to have played a significant role in the health and evolution of ancient humans.
Studies have suggested that those who were able to consume milk without health complications were able to overcome acute famine, causing lactase persistence to spread through natural selection.
To measure the impact of lactose tolerance on human size, Jay Stock of Western University in Toronto and colleagues collected data from 3,507 skeletons from 366 archaeological sites in seven regions, dating back 30,000 years.
The researchers used skeletal measurements to estimate the height of the specimens and the size of the weight-bearing joints to estimate their weight.
They found that the global mean height for males and females decreased from 30,000 years ago, reaching its minimum between 8,000 and 6,000 years ago. But in central Europe, height increased between 7,000 and 4,000 years ago, while in northern Europe it increased between 8,000 and 2,000 years ago. Similar trends were observed for body mass.
The earliest evidence of dairy production is from about 9,000 years ago in western Asia, from where it spread across the globe, reaching central Europe at least 7,400 years ago.
The authors theorize that the exceptional growth was due to those European peoples becoming lactose tolerant, allowing them to get more nutrition from milk. In other parts of the world at the time, people only ate fermented milk products, such as yogurt and cheese, which contain less lactose.
Although the data cannot prove that lactose persistence was the cause, the researchers argue that it is a convincing explanation. “We are showing that the timing and geography of increased body size corresponds to what we see in lactase persistence, and lactose is such an important component of the diet, providing very, very rich food sources of energy and nutrients. says Stock.
However, the study found that people in Britain actually got smaller in the same period, despite the fact that people in Britain were early milk drinkers.
“The authors have done some pretty fantastic things about height, estimating body mass and how it has changed over time. But I don’t see any systematic numerical analysis to suggest that it’s much more of a guess that the selection was stronger on lactase at this time when we see increases in body mass,” says Mark Thomas of University College London.
Previous research suggested that humans got smaller when they abandoned a hunter-gatherer lifestyle to grow crops, as relying on just one crop would have been less nutritious.
But the new study found strong evidence that people were actually getting smaller before turning to agriculture, suggesting there was another cause for their decreasing stature, Thomas says.
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