20721 정태준: 11월 2014

Is human still evolving?

When asked what evolution is, we may imagine primitive men like Australopithecus evolving into humans or dinosaurs which are believed to be ancestors of lizards or crocodiles. Most of us think of the evolution as a process that happened tens of thousands of years ago. But this is a misconception we often make. In fact, the evolution is still working today although the changes don’t appear significantly. Bacteria are one of the good examples which prove this. Since a nylon was invented in 1940s, nylon eating bacteria are nothing but new. The bacterium Pseudomonas can metabolize the nylon due to certain enzymes it has. Surprisingly, however, same thing happened to non-nylon eating bacteria when they were placed in an environment where nylon was the only available food source. Whenever the experiment was tried, the bacteria evolved until they could consume nylon. This example shows that most forms of life can adapt to their environment by evolving.

Then what about us; is human still evolving these days? My answer is yes: the human being is also evolving, and there are several evidences that support this. Then why should we concern about it? I believe that it has a same reason with why we should study history. By studying recent change and our development, we can somewhat predict how human being will evolve in the future. This would help us prepare for the future.

Before I start my confirmation, let's take a look at the history of evolution theory and what 'Natural Selection' is. Many people regard Charles Darwin as a father of the theory of evolution. He can be called in this way as he systematized evolution at his book‘On the Origin of Species’. However, the concept of evolution is much older. Ancient Greek philosopher Anaximander, believed as a precursor of the concept of evolution, supposed that mankind naturally originated from an early animal species. And in 1809, biologist Jean-Baptiste Lamarck asserted ‘The Theory of Use and Disuse’,insisting that traits of an organism are designed and inherited by effort, the environment, or by the use and disuse. However, it was Darwin who established the concept of modern natural selection and forever changed the theory of evolution.

In natural selection, one species’ possibility of survival can be determined by how well adapted it is to the environment. Natural selection doesn't generate new species. To help a species adapt better its environment, the process simply changes the genetic makeup and sends it to next generation. Also, the process can easily be predicted. If a certain trait which can solve the problem lacks, the species will develop the missing trait.

Today, many researches on human evolution are proceeding. In 2007, Researchers of Utah University discovered that a human evolution has not ceased and it is even accelerating.

"We used a new genomic technology to show that humans are evolving rapidly, and that the pace of change has accelerated a lot in the last 40,000 years, especially since the end of the Ice Age roughly 10,000 years ago,"says research team leader Henry Harpending. He says there are implications from the study.

"We aren't the same as people even 1,000 or 2,000 years ago. The dogma has been these are cultural fluctuations, but almost any Temperament trait you look at is under strong genetic influence. Human races are evolving away from each other. Genes are evolving fast in Europe, Asia and Africa, but almost all of these are unique to their continent of origin. We are getting less alike, not merging into a single, mixed humanity."

According to Harpending, the considerable increase in human populationover the last 10,000 years has speeded up the occurrence of evolution. It’s because we are now in new environments where we need to adapt and more mutations occur due to larger population. Therefore, thinking evolution has halted because of its invisibility is obviously a misconception.

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 which allowed grown up human 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 a genetic mutation were able to spread their genes, so now more than 95 percent of Northern European people carry the genetic mutation that 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 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 a meat apart. However, nowadays we can utilize utensils like forks and knives to cut food. Also, we have plenty of foods that are much softer and easier to chew. Therefore, jaws of modern humans became too small to contain all of them. That is why wisdom teeth disrupt the other when they are coming in. Like an appendix that lost its original function as we quit eating uncooked food, wisdom teeth have become a trace of our evolution. In fact, 35 percent of us are already born without wisdom teeth. Some even have 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 Hawks, professor of the University of Wisconsin–Madison,study of human genome has revealed that hundreds of our genes show evidence of change during the 10,000 years of human evolution. He also mentioned that particularly our brains are evolving recently. He said that our brains have 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 shrunked about 150 cubic centimeters: from 1,350cc to 1,200cc. Professor Hawks suspected that the shrinkage of human brains is related with the change of our lifestyle. Unlike in hunter-gather society, we now live in a huge society. We can rely on others in many parts of our lives and work together. 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 also made us stronger to endure diseases. You can see the most obvious evidence in mutation against malaria.Sickle cell anemia is an example of defense mechanism against malaria. Actually, sickle cell anemia is a disorder that deforms red blood cells into sickle shapes. It impairs blood flow and tissues. Surprisingly, this malady can also prevent the malaria parasite from infecting blood cells. Sickle cell is best known in Africa, but there is also an India-Pakistan variant that seems to have evolved very recently.Dr. Ian Barnes from the School of Biological Sciences at Royal Holloway says thatliving in cities has also produced a genetic variant that allows us to be more resistant to diseases like tuberculosis and leprosy.

Despite these scientific bases, some argue that evolution of humanity is now over. Recently Sir David Attenborough, the famous naturalist, said that humans have stopped physical and genetic evolution, during an interview with week's Radio Times.

“We stopped natural selection as soon as we started being able to rear 90-95% of our babies that are born. We are the only species to have put a halt to natural selection, of its own free will, as it were.”

His argument seems plausible at first glance as we have achieved astonishing advancement in reducing infant mortality and in combating many diseases. However, children’s survival is not assured as Attenborough said and it is not consistent across the world. Still, a lot of people cannot have basic healthcare and continue to die because of diseases and malnutrition. Moreover, even if we do reach the point of “being able to rear 90-95% of babies that are born”, that will only counter one of the conditions necessary for natural selection.

Attenborough is right in that natural selection requires variation. It needs some people to prosper more than others. So the improved survival prospects around the world might have decreased the potential for natural selection to work in those who are not threatened by natural tragedies. However, it may sound ironically, natural selection doesn't really care about survival. As I said, natural selection does help species to survive. But not every natural selection is related with survival. Natural selection only helps the emergence of gadgets that can solve the problems efficiently. What it is ultimately interested in is sending variations to next generations in order to increase effectiveness. Therefore the argument that our natural selection has stopped due to our increased survival prospects is flawed.

In fact, humanity has not abandoned its ability to make genetic variation. The human genome shows that recent population explosion made more variations within the last 200 generations. Thus, we may be evolving faster than ever before. Among them are mutations like lactose tolerance, smaller jaws and carrying the sickle-cell anemia.

Until now, evolution and civilization was considered as discrete thing. Human developed civilization after the process of evolution and society kept changing in the civilization was a universal thought. However, many scientific evidences prove that humans are still evolving, and our evolution is progressing faster than ever before due to the rapid development of civilization. Evolution is not a story of hunched primitive man anymore. It is a story of us. Theory of evolution is still a primary object of study to biologists and even today ground breaking hypothesis is ready to emerge. As we have seen how human being has recently adapted to new surroundings, I believe that we can somewhat predict how we will evolve in the future. This will not only give enjoyment of imagining future of humanity but also make us prepare for an upcoming future.

BIBLIOGRAPHY

http://www.discovery.com/tv-shows/curiosity/topics/10-examples-natural-selection.htm

http://mentalfloss.com/article/30795/5-signs-humans-are-still-evolving

http://www.mnn.com/earth-matters/wilderness-resources/stories/projecting-human-evolution-5-traits-we-might-possess-in

http://www.telegraph.co.uk/science/evolution/10297124/Sir-David-Attenborough-Humans-have-stopped-evolving.html -

http://www.nbcnews.com/id/33916577/ns/technology_and_science-science/t/humans-still-evolving-our-brains-shrink/

http://www.thehindu.com/sci-tech/sorry-attenborough-humans-still-evolve-by-natural-selection/article5141928.ece

http://www.theguardian.com/commentisfree/2013/sep/10/david-attenborough-humans-still-evolving

http://unews.utah.edu/old/p/120607-1.html

http://www.discovery.com/tv-shows/curiosity/topics/10-examples-natural-selection.htm

http://www.biology-online.org/dictionary/Lamarckism