Examples Of Natural Selection

Natural selection is the process by which individual organisms with favorable traits are more likely to survive and reproduce than those with unfavorable traits. In order for natural selection to occur there must be heritable variation for a trait and there must be differential survival and reproduction associated with that trait. (C.Stated) Heritable traits become either more or less common in population as the inherited traits in the differential reproductive success of the better adapted organisms interact with their environment, and pass on their successful survival genes to the next generations. (M.Cummings) Lactose tolerance is a good example of natural selection. Lactose tolerance is the ability to digest milk and is a necessity for
Lactase splits apart the two sugars, galactose and glucose that make up lactose in the epithelium of the small intestine. Milk is not easily digested; most humans lose the ability to digest lactose and become lactose intolerant in early adolescence. Shortly after the infancy period, parents introduce the young to adult foods thus not drinking as much milk, to eventually none at all. Removing milk out of the diet causes the production of lactase to seize in mainly everyone. This is due to the ‘switching off’ of the lactase gene situated on chromosome two. (BioInteractive) However, some populations around the world are still able to produce lactase. Most populations in North Central Europe and East Central Africa have a mutation in the regulating gene of lactase production that causes them to have higher lactose tolerance levels than populations in South America and South of Africa.(BioInteractive) The difference between the two is the dairy consumption. Populations with high lactose tolerance are groups of individuals who rely heavily on pastoralism and are consuming dairy long after adolescent
A few of those domesticated animals was the cow and the goat that provided them with milk. Dairying provided the human body with many nutrients with its milk sugar. Domestication of cows and goats caused profound biological trait changes in our species. Lactase persistence increased in pastoralist regions as it provided a selective advantage. In case of famine and times of scarce “clean” water (not infested with insects or mixed with soil), milk would be the only alternative. Those individuals with the lactase enzyme would be able to digest milk and take in all its nutrients. Those individuals without the enzyme in a famine situation without many options available had no choice but to drink milk and experience the symptoms. Consuming toxic foods and not being able to hold in nutrition will only result in low chances of survival. Lactose intolerant individuals are the ones that are most likely not to survive and have no chance to pass on their biological traits. Individuals with the lactase enzyme have higher chances of surviving thus passing off those biological traits to the next generations to come.