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Scientists are trying to explain why people began consuming animals' milk before they developed genetic mutations which enabled them to digest it properly.
The mutations mean people produce lactase—an enzyme which breaks down milk sugars, called lactose—after they reach adulthood. Without the mutations, lactase production stops in childhood, which can lead to lactose intolerance.
"There is at least a 4,000 year gap between when we see the earliest evidence of dairying and when we see first the evidence of any mutations anywhere in the world," said Professor Christina Warinner, head of microbiome sciences at the Max Planck Institute for the Science of Human History in Jena, Germany.
Only about 35% of the world's population today have lactase persistence mutations. They exist mainly in European populations—especially northwestern Europe—and their descendants, and in parts of the Middle East, sub-Saharan Africa and South Asia.
"If we can work out the evolutionary history and mechanics of lactose intolerance (how diet, human genetics, and gut microbes interact), we will have a powerful model for how to tackle other complex digestive disorders and food allergies," said Prof. Warinner.
[...] "The reason people were able to eat dairy before we had the ability to process lactose is because of fermentation," said Cheryl Makarewicz, professor at the University of Kiel, Germany.
"It shows the power of this kind of processing and how it can impact how your body reacts to different foodstuffs," she said. Fermented foods contain microbes which may also play a part in people's digestion.
Microbes in people's guts may have also evolved to break down the lactose. "This hasn't been well studied … It's something we're trying to test," said Prof. Warinner.
To do this, Dairy Cultures scientists are exploring the microbiome, the genetic makeup of microbes that live in the gut, which include bacteria, viruses and fungi. They are studying samples from herders to see if they contain elevated levels of microbes that aid milk digestion.
"The more we can understand about how the microbiome functioned in the past and what it is capable of, the better we will understand how and why the microbiome is changing now and why it is associated with so many health problems today," she said.
(Score: 2) by Joe Desertrat on Sunday January 26 2020, @12:02AM (4 children)
This was my immediate thought. My guess would be that drinking animal milk started in more environmentally marginal areas where protein and food in general were somewhat scarce, and such places generally make it tough to raise cattle as well. I would think a small docile goat or sheep would be easier to try such an experiment with than larger animals.
(Score: 2) by JoeMerchant on Sunday January 26 2020, @02:55AM (3 children)
Run a life simulation, any kind. Restrict the food source to something "difficult" for the general population to handle, but allow mutations that can make handling it easier - see what happens in just a few generations.
When milk was readily available, those rare people with the lactase genes were clearly more attractive and more likely to mate and raise children to adulthood than the ones who were too malnourished to raise children, or constantly bitching about an upset stomach.
We're doing it again, with Roundup Ready (TM) soybeans, and whatever f-ed up selectively bred "short wheat" they've come up with that has taken the market by storm but made so much of the population gluten intolerant. Unfortunately, life is too easy these days and most people still get to breed and raise children even if they're suffering from these food challenges.
🌻🌻 [google.com]
(Score: 2) by Joe Desertrat on Sunday January 26 2020, @11:13PM (2 children)
That's true to an extent, but remember evolution works at a slow pace. First you get genetic drift to the limits, then the mutations start to have more and more effect. Who knows what we will end up with in the end.
(Score: 2) by JoeMerchant on Sunday January 26 2020, @11:27PM (1 child)
When it's an effect like modern gluten intolerance, that's true - maybe there's a 5-10% breeding prolificacy advantage when you're not whining about being gluten free, but when it's a matter of life and death by the age of 12 like the Ashkenazi Jews [newrepublic.com] it seems to happen within just a few generations.
🌻🌻 [google.com]
(Score: 2) by Joe Desertrat on Saturday February 01 2020, @01:43PM
That is natural selection operating on an outlier of genetic drift. Still a long ways from becoming a new species...