Shenk’s of genetics multiplied by environment seems like the idea that we as a community grew up with. When we were asked, specifically in my AP Psych class, which determined a person’s identity, nature or nurture, most of us said both. Shenk’s formula, however, is much more interesting than genetics plus environment. Shenk described the experiments from the” temperature surrounding turtle and crocodile eggs determined their gender” (Shenk 30) to lizards changing color based on a blackened environment to locusts developing vastly more musculature than locusts in less crowded conditions. We thought that nature and nurture combined to form a person’s identity. Shenk explains that “nature/nature” must be replaced with a whole new term entirely, “dynamic development” (Shenk 33).
How would Shenk’s formula explain the process of natural selection? How would this influence Galton’s view on genetics? What makes gXe a more dynamic process than simply nature vs. nurture? How does this discovery influence the idea of intelligence or a lack thereof? Why are genetics and environment inseparable according to Shenk? Think of an example of dynamic development.
Gabriella Veytsel (geminizire@hotmail.com)
Historically, scientists have known that organisms can be influenced by their environment, as well as their heredity.
ReplyDeleteHowever, in the classical model of Nature vs. Nurture, these influences were entirely separate. According to what was known about genetics, mostly from the work of Mendel, this notion persisted up until the discovery of the true mechanism of inheritance.
Part of the reason environmental factors are so influential is because the mechanism for inheritance and trait expression is DNA, a huge molecule in the cell that is certainly not in isolation. It sits in the middle of a whirlwind of proteins, hormones, nutrients, and other cellular machinery. DNA is not in a locked safe in a cellular bank, it is extremely accessible, and because of this it is subject to influences from the outside.
As we discover more about DNA, the more we learn about the essential role of the environment on its function. The first model, G + E, was based on the notion that “genes directly determined traits” (Shenk 31), with the environmental factors added in after protein synthesis.
Shenk’s thesis, his model of G x E, strengthens the connection between genetics and environment. No longer can we consider genetics and environment independently – it simply does not make sense to do so, proven by new discoveries about the regulation of gene expression. Transcription factors present in the nucleus are regulated by outside factors, and mechanisms such as alternative RNA splicing can significantly change the way a cell operates, all due to environmental factors (Campbell 362-363). Gene expression can be further modified by the vastly larger epigenome – control of factors such as histone acetylation and DNA methylation that affect transcription, all regulated by environmental factors (Shenk 158).
The huge discovery, however, was the process of epigenetic inheritance, which according to Shenk is “perhaps the most important discovery in the science of heredity since the gene” (160). This means that epigenetic factors are not erased at birth, and environmental influences on previous generations are also important. Natural selection can now be affected by decisions made in previous generations, bringing in free will (http://learn.genetics.utah.edu/content/epigenetics/inheritance/).
All of these factors further solidify Shenk’s point that it is impossible for intelligence to be fixed, controlled by genetics, or completely in the hands of the environment, as per Locke’s tabula rasa philosophy. Instead, it is influenced by dynamic development, influence of environment on genetics and vice versa.
David Whisler (dwhis428@gmail.com)