A new genetic study suggests that 1 in 4 East Asians have a different version of the lactase gene from those found in Europeans and Africans. There is a possibility that the gene variant was inherited from Neanderthals. (Image credit: Peter Adams via Getty Images)
New research suggests that a significant proportion of East Asian populations carry unique forms of the lactase gene, which allows people to digest the sugar found in milk.
These genetic variations were likely inherited from extinct Neanderthal ancestors tens of thousands of years ago, according to a study published March 10 in the journal PNAS. The variants may have provided an evolutionary advantage by helping early hunter-gatherers cope with infections, according to new data.
In some people of European or African descent, the lactase gene allows carriers to digest the sugar known as lactose found in milk after breastfeeding has ceased; this phenomenon is called “lactase resistance.” Many carriers of alternative forms of the gene cannot continue to break down lactose after infancy, resulting in lactose intolerance.
The lactase gene versions responsible for lactase resistance are thought to have arisen in populations in Europe and Africa between 5,000 and 10,000 years ago, around the time people on those continents began raising animals and drinking their milk.
This led the scientists to hypothesize that lactose-tolerant variants were selected for in these populations, meaning they became more common during evolution, because they provided certain advantages. In this case, they may have increased survival chances by allowing adults to absorb nutrients from milk.
However, until now little was known about the genetic mechanisms underlying lactase resistance and lactose intolerance in East Asians. It is estimated that about 65% of adults worldwide are lactose intolerant, but among East Asian populations, the figure ranges from 70% to 100%.
In the new study, scientists compared thousands of genomes from modern humans, including those of East Asian, European, and African descent. The data was collected from people in countries as diverse as China, Japan, Spain, Italy, and Nigeria.
The analysis found that about 25 percent of people of East Asian descent carried versions of the lactase gene that are not found in European or African populations. This is roughly the same as the proportion of people with lactase resistance among East Asian groups. These genetic variants increase the activity of the lactase gene in the body, the researchers found.
At first glance, this suggests that these genetic variants may have been selected for during evolution for dietary reasons, the researchers said. However, further analyses in the same study showed that this may not be the case.
Sourse: www.livescience.com
