Lactase Persistence in AdultsApproximately 65 percent of the world's population is lactose intolerant. Most humans cannot digest lactose, the sugar found in milk, beyond childhood. Virtually all humans are lactose tolerant from birth to childhood. Only 35 percent of humans, mostly northern and central Europeans, continue to produce lactase, the enzyme that breaks down lactose, into adulthood. Although scientists are not sure why these populations evolved and developed lactase persistence in adults, it is hypothesized that the nutritional value of milk, as well as environmental factors, played a role in the development of Adult lactase persistence genes in specific human populations. Say no to plagiarism. Get a tailor-made essay on “Why violent video games should not be banned”? Get the original essay Populations of northern and central European origin have the highest percentage of individuals capable of digesting lactose at adulthood. The latest research shows that the genetic mutation causing lactase persistence in adults occurred between 2,000 and 20,000 years ago. Before that, most humans couldn't digest lactose after childhood. The fact that the gene arises and spreads rapidly through the population tells scientists that extreme evolutionary pressures caused this gene to develop rapidly. Milk contains a multitude of nutritious micronutrients, as well as high amounts of protein, fat, calcium and carbohydrates. . It stands to reason that individuals in the population who possessed the gene for adult lactase persistence would be able to continue drinking nutritious milk into adulthood and would therefore have a fitness advantage over to those who did not have this gene. Additionally, those who did not have the gene would suffer from diarrhea and other digestive disorders associated with lactose intolerance after drinking milk. Before modern water sources and pedialyte, many of these individuals lacking the lactase persistence gene could have perished from dehydration caused by diarrhea. This would only further accelerate the proliferation of the adult lactase persistence gene in a population. It is no coincidence that areas with a long history of domestication of dairy animals are correlated with high adult lactase persistence in their respective populations. European populations in particular were descendants of humans who migrated from the Fertile Crescent, where they brought with them crops like wheat and barley. These crops were difficult to grow during Northern Europe's short growing season. On the other hand, milk can be produced all year round. During the cold winter months, milk may have been a valuable source of nutrition and only adults with the adult lactase persistence gene could benefit from it. Keep in mind: this is just a sample. Get a personalized article from our expert writers now. Although there was likely rapid development of the gene that allowed adults to break down lactose as adults, exactly how this happened remains a mystery. Despite this, there is sufficient evidence to suggest that environmental factors contributed to the proliferation of the lactase persistence gene in adults. Milk would have been a source of nutrition thousands of years ago and could have contributed to the survival of certain human populations..