Week 8 Confirmation

1. What is my thesis?

Humans are still evolving.

2. What types of source am I using to defend my thesis? 

I am using experts’ opinions and relevant science articles.

3. Are my arguments mostly based on evidence, logic or emotion?
My arguments are mostly evidence. I have quotes from famous people, and a good example. There are no emotional appeals but I don't think those would be useful. I’m going to look for more statistical evidences.

 Now let’s take a look at the several evidences that prove my argument. The fact that we can drink milk is important evidence that people are still evolving. When our ancestors made a living through hunting-gathering ways, most of humans’ ability to digest lactose shut down during their childhood. The gene regulated producing enzyme called ‘lactase’ which can digest lactose because human beings’ only available dairy food was mothers’ milk at that time. However, when they began to domesticate cows, sheep and goats, people could drink milk gained from those animals. But many new diseases also began to appear as our eating habits had changed. This problem was solved by creating genetic mutation that allowed them to digest lactose. According to experts of Broad Institute of MIT, this mutation is presumed to appear 7,500 years ago in Europe. People with the genetic mutation were able to spread their genes, so now more than 95 percent of Northern European people carry genetic mutation which can digest milk.

 The fact that we are losing wisdom teeth is other evidence. Most people think of wisdom teeth as an irritating medical annoyance. Interestingly, however, the reason why wisdom teeth grow much later than other teeth has something to do with evolution. Our ancestors had much larger jaws than we do. It must have helped them to chew tougher foods like roots and nuts and tore meat apart. However, nowadays we can utilize utensils like forks and knives to cut food. Also we have plenty of foods which are much softer and easier to chew. Therefore, jaws of modern humans became too small to contain them without disrupting the other teeth. Like appendix which lost its original function as we quit eating uncooked food, wisdom teeth have become trace of our evolution. In fact, 35 percent of us are already born without wisdom teeth. Some are even born with just one, two or three wisdom teeth. It’s no surprise because evolution tends to eliminate a trait to save on the needless energy expenditure it takes to develop it when that trait is no longer necessary.

Human brains are shrinking due to the evolution. According to John Hawkes, professor of University of Wisconsin–Madison, study of our genome has revealed that hundreds of our genes show evidence of changes during the past 10,000 years of human evolution. He also mentioned that particularly our brains are evolving recently. He said that our brains have actually been shrinking, not growing, over the last 5,000 years in comparison to archaeological data discovered in Europe, China and Australia. The average volume of the human brain has decreased from 1,350 cubic centimeters to 1,200 cubic centimeters. Professor Hawkes suspected that shrinkage of human brains is related with the change of our lifestyle. Unlike in hunter-gather society, we now live in huge society. We can rely on others in many parts of our lives, allowing us to work together to solve problems. Therefore, smaller space would be enough for brains to take up. Also smaller brains are more efficient as it can be rewired to work faster.

Evolution makes us become stronger to diseases. You can see the most obvious evidence on mutation against malaria. Since the disease often targets humans early in life, there was a strong pressure to evolve defenses from malaria — any genetic factor that confers resistance against it would give descendents a chance to have offspring, while those without such protection were more likely to not reproduce. There are lots of examples of defenses against malaria. Sickle cell anemia is the best known —the disorder deforms red blood cells into sickle shapes, which can impair blood flow, thus damaging tissues, this malformation also prevents the malaria parasite from infesting blood cells. Although sickle cell is best known in Africa, there is also an India-Pakistan variant of it that seems to have evolved separately,” Hawks explained. “Both variants have evolved very recently, in the last three or four thousand years, and in that time have risen to as much as 10 to 15 percent of the populations. That’s pretty rapid change. Living in cities has produced a genetic variant that allows us to be more resistant to diseases like tuberculosis and leprosy. "This seems to be an elegant example of evolution in action," says Dr. Ian Barnes from the School of Biological Sciences at Royal Holloway. "It flags up the importance of a very recent aspect of our evolution as a species, the development of cities as a selective force."

Originally, we all had brown eyes. But about 10,000 years ago, someone who lived near the Black Sea developed a genetic mutation that turned brown eyes blue. While the reason blue eyes have persisted remains a bit of a mystery, one theory is that they act as a sort of paternity test. “There is strong evolutionary pressure for a man not to invest his paternal resources in another man’s child,” says the lead author of a study on the development of our baby blues. Because it is virtually impossible for two blue-eyed mates to create a brown-eyed baby, our blue-eyed male ancestors may have sought out blue-eyed mates as a way of ensuring fidelity. This would partially explain why, in a recent study, blue-eyed men rated blue-eyed women as more attractive compared to brown-eyed women, whereas females and brown-eyed men expressed no preference.