Saturday, March 27, 2010
Gene Culture Coevolution
On page 215, Coyne explains "gene-culture coevolution." Explain the relationship between human culture and how it has come to affect our genes. Also, gene-culture coevolution has already changed our genes, sometimes for the worse. Coyne points out several examples of incidences in which we have "de-evolved." Explain this occurrence. Is gene-culture coevolution affecting natural selection and our ability to evolve? Will we continue evolving in the future, even though our culture may alter evolutionary pressures?
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Gene-culture coevolution is a theory that delineates the effect that culture has had on the evolution of humans. Coyne mentions this to explain the striking visual differences between the races even though there has been such little divergence among humans, such as the almond eyes of Asians and the longer noses of Caucasians. Our ability to change culture so rapidly has, in effect, allowed us to create culturally introduced sexual selection; ie, a certain trait may be seen as more favorable than another, such as the example given by Coyne about the possiblity of one Asian empress' penchant for almond shaped eyes in her partner causing a cultural shift and subsequent sexual selection disposing of those individuals with round eyes. This phenomenom is definitely affecting our ability to evolve and natural selection on our species, introducing new environmental pressures far faster than nature could ever introduce.
ReplyDeleteHowever, it is also important to note that this gene-culture coevolution does not necessarily have to work against the evolution of nature. In fact, according to an article in Scientific American (http://www.scientificamerican.com/article.cfm?id=culture-speeds-up-human-evolution), this process could actually be aiding in increasing the speed to which our species evolves. Consider the many things that humans have evolved to fit our needs through cultural changes - a movement to an agricultural diet caused the introduction of new alleles, for example, to digest that type of food. Our evolution driven by cultural change doesnt just stop there; over the years, the gene for milk digestion has become activated for adults as well, perhaps again to attune to a cultural shift to a new diet. Even now in the present day this spurring of evolution toward more favorable traits may be arising in our cultural preference for more healthy, fit individuals rather than the affinity for the obese seen in earlier times. Thus,although gene-cultural evolution sometimes seems to be introducing superfluous traits to our species, in the long run it is actually propelling humans forward in the evolutionary tree as we introduce more and more new evolutionary pressures and we become adapted to our modern environment based on cultural norms.
The idea of gene-culture coevolution is described by Coyne as "the idea that change in cultural environment leads to new types of selection on genes- that makes the idea of sexual selection for physical differences especially appealing" (215). He also states the valid point that humans have the ability to change their culture much faster than their genetics. Because of racism problems and all the controversies that can arise with this issue, Coyne avoids saying anything bad and simply sticks to the idea that physical traits are what separate the races of the world. There is no scientific data supporting that evolution has produced different populations of people to display different behaviors, have different IQs, and different abilities. Jerry sums up the present scenario by claiming the idea that it may in fact be too early in our evolutionary history to distinguish important differences in "Intellect and behavior" and "Our genetic differences among human populations are minor" (216).
ReplyDeleteLater on in the the chapter, Coyne refers to a great example of humans ability to produce an enzyme (lactase) that breaks down lactose, which is found in the dairy products we consume. Today although many humans are born with the ability to digest milk and other dairy products, according to AskMen.co, up to 75% of adults worldwide show a decrease in lactase activity during adulthood. Coyne explains the evolution behind the production of this enzyme when he says "There are two alleles on the gene- the 'tolerant' (on) form and 'intolerant' (off)- and they differ in only a single letter of their DNA code" (217). The presence or absence of one allele or the other correlates with whether populations use cows. Evolution is guided by natural selection and allowing a species to survive and reproduce the environmental stress. This example is great because if our ancient ancestors had no source of milk after weaning the newborn, why would they produce a costly enzyme that wasn't necessary to have?
Lastly, gene-culture coevolution is indeed affecting our natural selection and our ability to evolve because science and medicine have come a long way. Without these things, dying would be natural and inevitable (it still is), but today we are able to fight diseases and conditions that would have wiped out different populations in the past. Cultures adopting these techniques are increasing the expected lifespans of the individuals belonging to them and with this evolving due to the stresses of the environment. It is hard to observe evolution on the micro level, but our culture will continue to bring more evolutionary pressures among us that will help us become even more efficient in the future.
We see that the way a person is born into this world affects being, and the people around him or her. Our culture is obsessed with creating beings with the best possible genes, and manipulating natural selection. We want to do what is favorable to ourselves. As Bkim said, "We create culturally introduced sexual selection." We are creating the perfect beings by choosing the people with the correct genes, and making them reproduce. Though when I mean perfect, I'm talking about those that we see are perfect, but not evolutionary perfect. We can't control evolution, but we can control those forces that affect evolution, and one of those is natural selection. We are controlling it by having people with blue eyes mate only with blue eyed people in order to ensure that their kids have blue eyes. They want there children to have certain characteristics that they view as good. So yes we are affecting natural selection, but not evolution because we can't stop evolution. It will keep on going, but with different results than it was intended. So certain genes might become more favorable than other genes. So essentially we could be giving ourselves the genes that are not favorable to natural selection, but to us they are. We can't really figure out what organs are part of this de-evolving part because we do not know what is favorable.
ReplyDeleteWe will keep evolving in the future like I said, but with different results than intended by nature. We will always have mutations that happen, and other things that will affect what evolution intends. Even with all the pressure, we will still be able to evolve because it is something that we cannot control, we could only control the forces that control evolution.
Though by doing this we can actually speed up evolution. By helping natural selection pick the favorable genes, we will be able to eliminate those bad genes from our lives, and live with only good genes. So in the future we will have really favorable genes, and we will be asking ourselves how far can we go before we reach a limit with what we can pick to be favorable or not.
Sources:
Bkim's comment
http://en.wikipedia.org/wiki/Genes
http://en.wikipedia.org/wiki/Evolution