Therefore, it begs the question: are humans still evolving? Have there been overall developments in our genetic code that provide for characteristics that humans centuries ago did not possess?
Shenk's book focuses primarily on human development through a single lifespan, but near the end mentions that "everything we do - everything we eat or smoke - can affect our gene expression and that of future generations" (Shenk 160), ultimately implying that human genetics truly are developing. Even Campbell brings up the idea of sociobiology, which touches base on the idea that there exists an "evolutionary basis for certain kinds of human social behavior...that have been perpetuated by natural selection," (Campbell 1142) which all too clearly suggests human evolution if certain behavioral tendencies could be tracked in a specific area or time.
In your response, please refer to a study that may suggest possible evolution in humans, along with what environmental conditions caused that development to occur. In addition, make sure to assess whether the study points towards epigenetic evolution (Lamarck) or mutation evolution (Darwin).
Humans are still evolving. The Scientific American reports that the agricultural evolution actually sped up human evolution, as previously unnecessary genes became advantageous for survival and reproduction as farmers instead of hunter-gatherers (http://www.scientificamerican.com/article.cfm?id=culture-speeds-up-human-evolution). For example, the LCT gene that codes for enzymes to enable the digestion of lactose, provided some immune protection and allowed humans to utilize milk as a new source of food. The mutation allowed humans to thrive in a new niche as farmers and to survive disease by the Plasmodium falciparum parasite. The Scientific American also discusses the OCA2 gene, a relatively new mutation from about 10,000 years ago, which codes for blue eyes.
ReplyDeleteThere is no evidence of LCT and OCA2 genes being the products of epigenetic evolution, and are most likely examples of the random mutations characteristic of Darwinian evolution. However, a study reported by Science Daily discusses the effects of cultural life on genetics, which could be a case of epigenetic evolution. Urban populations, being the perfect place for disease to spread because of the large number of people in a small space, have genetic mutations that increase their resistance to disease (http://www.sciencedaily.com/releases/2010/09/100923104140.htm).
While cities can be dangerous, genetic mutations that allow humans to survive in urban centers increase the selective advantage of living in large cities. The social benefits of city living, such as easier access to food and community as well as a larger pool of potential mates for a more varied gene pool, could also contribute to the continued success of human populations in urban centers. Sociobiology supports the idea of humans living in groups, because the genes that led early primates to live and find food in packs would be passed down and expressed in the humans, who would feel inclined to inhabit large cities (Campbell 1142).
Therefore, the genetic tendency of humans to live in cities could have contributed to the prevalence of disease-resistance genes, both because the large populations in cities would increase the rate of evolution, and because natural selection of humans with stronger immune systems would happen more quickly in disease-prone cities.
Mackenzie Levy (GinnyFan@comcast.net)