Famine and Disease may have Driven Ancient Europeans’ Lactose Tolerance

 

Scientists have used DNA from fat samples in archaeological sites to determine that Ancient Europeans evolved a gene that allowed them to digest lactose, a sugar that is found in milk. There were many famines around 9,000 years ago, but it took Europeans a few thousand years to evolve the gene for lactose tolerance. Drinking milk was a way for people to get their nutrients when crops failed in famines. A common symptom of lactose intolerance is diarrhea. Since medicine was not advanced during this time, people that could not digest lactose suffered from diarrhea, which led to dehydration, which could lead to death. 

Scientists extracted 1,800 samples of ancient European and Asian DNA. They found a gene from about 6,000 years ago that improved the function of lactase, the enzyme responsible for digesting lactose. This gene wasn’t common until about 3,000 years ago. In times where there were famines and diseases, there were more traces of the genes for increased function of lactase. 

If someone is lactose intolerant, drinking a lot of milk will not suddenly make them able to digest lactose. Their situation would be worse, and they would get sicker. I think that since Pasteurization was not performed on milk at the time, people drinking milk also could have been drinking harmful bacteria and getting sick from that. This could have also caused deaths, whether someone had a lactose tolerant gene or not. It doesn’t make a lot of sense to me how these people survived. Medicine was not advanced at that point in history, and consuming bacteria was deadly. 

Asians and Europeans; Lactose-Intolerant 5,000 Years Ago

     Studying ancient DNA has always been a big part of genetics as it gives insight into the past history of humans. What was generally already found is that around 5,000 years ago, Europeans and Asians are generally light-skinned and - surprisingly - lactose intolerant. During the Bronze Age, which ranged from the years of 3,000 - 5,000 years ago, was a time of mass human migrations throughout the region of Europe and Asia. Because of these large migrations, the present-day demographic structure has been developed. 

     Researchers have sequenced genomes from 101 unearthed ancient humans from Europe and Asia. Although DNA sequences have previously been studied using ancient DNA, the new technology that is available makes for clearer data. It has recently been discovered by Morten Allentoft of the University of Copenhagen’s Natural History Museum and his colleagues that light-skinned Europeans were present at a high frequency already in the Bronze Age, thus implying that light-skinnedness was first developed previous to 5,000 years ago. Another conclusion from their data tells that during the Mesolithic hunter-gatherer age, the presence of blue eyes was already established. 

     These data are set to answer the question, could there be a greater distribution of Neanderthal DNA in the genomes of Europeans and Asians? This is still unclear, however the findings suggests that these humans were settled into Europe and Asia before the Bronze Age.

     Something also interesting about the data is that 5,000 years ago, humans had not evolved the enzyme to break down lactose - the sugar found in milk. In an evolutionary perspective, this makes sense because ancient humans and - in fact, mammals in general - do not need to drink milk to survive after infancy, thus the lactose intolerance. When humans began to produce the enzyme to break down that indicated the start of domestication of animals which did not occur much before 5,000 years ago thanks to the data. 

     I personally think that this article is interesting because there are people who today are still lactose intolerant. The article tries to explain this as their ancestors did not drink much milk, thus never needing the enzyme to break down lactose. It is amazing how using the preserved DNA from bones that have been under the earth for so long can lead to vast discoveries like this. This discovery tells a lot about the time line of when humans became what we are today.

Original Article

More about the Bronze Age

University DNA Swabs Incoming Freshman

On May 18, 2010, The New York Times published an article titled, "College Bound, DNA Swab in Hand". For the first time, a university will offer DNA testing. At the University of California, incoming freshman of 2014 will be offered to have their cheeks swabbed and their DNA sent out for testing. Three genes that regulate the metabolism of alcohol, lactose, and folates are being analyzed. Some students may have genetic markers that would indicate if they need more or less of the three substances. Jasper Rine is the genetics professor at the University of California. Jasper stated that this is an opportunity to improve the student's health and their eating habits. The testing will be confidential. Students will learn if they should drink less alcohol and dairy products, or if they should increase the amount of green, leafy vegetables they consume. Bioethicists are uneasy about offering genetic testing outside of a medical environment without counseling available. Professor Jasper Rine will be giving a lecture to the entire campus about the three genetic markers being tested.

University of California offers genetic testing of three genes.

Besides testing for lactose, I think that testing for alcohol and folate genetic markers is a waste of time and money. Some people cannot drink dairy products and this is a real concern. People who ingest dairy products and cannot digest them get stomach pains from gas buildup. Alcohol is dangerous to consume in large quantities. Everyone should drink in moderation. The opposite goes for leafy greens. The majority of Americans are not eating enough green, leafy vegetables. Freshman should not need a genetic test for them to know that they should drink less alcohol and eat more leafy vegetables.

Drink less alcohol, eat more green, leafy vegetables.