Hazeema Hazeema
SBI 3UB
Mrs. Quinlan
Dec. 10, 2018
How do we know that humans are still evolving?
Humans’ life span is not as short as other species so it can be hard to see our evolution overtime but the fact of the matter is that like all other species humans are still evolving. Evolution is caused by natural selection which is labile. Today, many long-term studies, such as the Framingham study, have identified trends that have altered different communities overtime. Evidence that humans are still evolving includes human’s ability to digest milk beyond infancy, variation in skin colour and height, birth patterns and resistance to malaria.
Humans are still evolving and one of the evidences that supports this claim is human’s ability to digest milk. Before humans began to domesticate animals and rely on dairy farming as a source of obtaining energy, adult humans were unable to digest lactose, a sugar found in milk. Essentially our bodies start tolerating the food source that is most abundant in our region. Lactose which was only digested by animals and infants before, can now be digested by adult humans. Lactose is broken down into two subunits; galactose and glucose by an enzyme called lactase. Today, humans from areas that have a long history of dairy farming such as Europe are able to digest milk better than those originating from areas where dairy farming wasn’t as popular such as Asia. As a result, some people of European descent and many people of Asian descent are lactose intolerant. Human adults began to digest milk because short patches of DNA outside the lactase gene started regulating its activity. About 7000 years ago, people started domesticating cattle, sheep, goats and camels for the purpose of dairy farming in Europe. Before that the ancient Europeans relied on energy from food obtained by hunting, fishing and gathering. Lactose tolerance is increasing substantially in the British population. By being able to obtain energy from lactose which makes up 30% of the calories found in milk, women who are lactase-persistent are able to use this energy in order to have a healthier children at a young age. Since women who are lactase-persistent have children at a young age, they are able to give birth to overall more children in their lifetime than those who are lactase-resistant. Slowly, mutations affecting the lactase gene became dominant and in every generation the population of those with lactose tolerance grew by 10%. Along with lactose tolerance, variation in skin colour and height are also pieces of evidence that prove that humans are still evolving.
Skin colour is a very obvious physical difference between different communities. More than 24 genes are involved in the production of melanin and its regulation in different tissues. When these genes are altered the production of eumenalin, the dark pigment, is affected and the skin contains mostly the reddish skin pigment, pheomelanin. As a result many skin tones and patterns...
