{"id":16052,"date":"2022-08-15T00:00:00","date_gmt":"2022-08-14T22:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/?post_type=purple_issue&p=16052"},"modified":"2022-08-22T12:03:29","modified_gmt":"2022-08-22T10:03:29","slug":"lactose-tolerance-evolved-in-europeans-thanks-to-famine-and-disease","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/2022\/08\/15\/lactose-tolerance-evolved-in-europeans-thanks-to-famine-and-disease\/","title":{"rendered":"Lactose tolerance evolved in europeans thanks to famine and disease"},"content":{"rendered":"\n

LACTOSE TOLERANCE EVOLVED IN EUROPEANS THANKS TO FAMINE AND DISEASE<\/h3>\n\n

Wide-ranging evolutionary study overturns the long-held idea that the gene for lactose tolerance spread because it allowed dairy-farming humans to consume more milk <\/p>\n\n

Prehistoric Europeans were drinking milk as adults thousands of years before most of them evolved the gene necessary to digest lactose, a study carried out at University College London and the University of Bristol has found. <\/p>\n\n

By poring over DNA and archaeological records dating back 9,000 years, the researchers believe that it was bouts famine and disease periodically killing off the lactose intolerant that drove the protective gene\u2019s evolution. This overturns the widely held model that as we began to farm dairy, a novel genetic mutation occurred that allowed some to be lactose tolerant as adults, and from there this became positively selected for and spread throughout the population. <\/p>\n\n

\"\"
The people living on ancient agricultural settlements would have been likely to turn to dairy products in the event of crop failure <\/figcaption><\/figure>\n\n

In order to digest lactose, we need to produce an enzyme known as lactase in our guts. Almost all babies can do this, but the gene to produce lactase switches off in the majority of the global population as they mature into adulthood. The ability to continue producing the enzyme is known as \u2018lactase persistence\u2019 and exists in around one-third of adults in the world, including most of the population of Europe.<\/span><\/p>\n\n

When people without the enzyme drink milk, the lactose passes into their large intestine where it can cause cramps, diarrhoea and flatulence \u2013 a condition known as lactose intolerance. While this condition is unpleasant, it is rarely fatal. However, its effects can be magnified in those who are malnourished in times of famine or disease, the researchers say. This is what likely drove the evolution of lactose tolerance. <\/p>\n\n

\u201cWhen their crops failed, prehistoric people would have been more likely to consume milk\u201d <\/p><\/blockquote>\n\n

\u201cIf you\u2019re healthy and lactase non-persistent, and you drink lots of milk, you may experience some discomfort, but you\u2019re not going to die because of it,\u201d said co-author Prof George Davey Smith of the University of Bristol. \u201cIf you\u2019re severely malnourished and have diarrhoea, however, then you\u2019ve got life-threatening problems. When their crops failed, prehistoric people would have been more likely to consume unfermented high-lactose milk \u2013 exactly when doing so poses the greatest risk to them.\u201d <\/p>\n\n

The discovery depended on several teams working on different pieces of the puzzle. First, researchers led by Prof Richard Evershed from the University of Bristol put together a database of nearly 7,000 organic animal fat residues taken from fragments of pottery from more than 500 archaeological sites to find out where and when people were consuming milk. They discovered that milk was regularly consumed since the earliest dairy farming began around 9,000 years ago, but fluctuated across regions at different time periods.<\/p>\n\n

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Humans have been consuming milk and the products that can be made from it for over 9,000 years <\/figcaption><\/figure>\n\n

A second team led by Prof Mark Thomas from University College London looked for the presence of the lactase-persistence genetic variant in the DNA sequences of 1,700 prehistoric Europeans and Asians. <\/p>\n\n

They found it first emerged around 5,000 years ago and reached appreciable levels 2,000 years later. They also found that the gene was no more common during periods of greater milk consumption, overturning the long-held view that this was a factor in driving the evolution of lactase persistence. <\/p>\n\n

Finally, Thomas\u2019s team compared the presence of the lactase-persistence gene variant in times of suspected famine and disease. They found that the gene became more widespread during these times, indicating that famine and disease played a key part in its evolution. <\/p>\n\n

IMAGES: SCIENCE PHOTO LIBRARY, GETTY IMAGES<\/p>\n","protected":false},"excerpt":{"rendered":"

LACTOSE TOLERANCE EVOLVED IN EUROPEANS THANKS TO FAMINE AND DISEASE Wide-ranging evolutionary study overturns the long-held idea that the gene for lactose tolerance spread because it allowed dairy-farming humans to consume more milk Prehistoric Europeans were drinking milk as adults thousands of years before most of them evolved the gene necessary to digest lactose, a 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TOLERANCE EVOLVED IN EUROPEANS THANKS TO FAMINE AND DISEASE Wide-ranging evolutionary study overturns the long-held idea that the gene for lactose tolerance spread because it allowed dairy-farming humans to consume more milk Prehistoric Europeans were drinking milk as adults thousands of years before most of them evolved the gene necessary to digest lactose, 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