As continually emphasized as a central theme of
Shenk’s proposal, the GxE model incorporates elements of both the blank slate
thesis (individuals begin life with an equal capability for intellectual
development) and the blueprint thesis (the intellectual capability of an
individual is strictly dictated by their genetic inheritance). Shenk’s GxE
model incorporates elements of both of these theses by claiming that it is the direct interaction
between external stimuli and genetics that dictate the intellectual capability
of individuals. Use the GxE model to disprove both the blank slate and blueprint
models of intelligence using evidence provided by Shenk throughout the Argument
section. Major sources of evidence for GxE come from: twin studies (Chapter 4),
examinations of savant syndrome (Chapter 5), examination of maze-bright and
maze-dull rats in enriched and restricted environments (Chapter 1), and other
sources within the Argument. Relate your proposals to Chapter 51 of Campbell,
specifically analyzing Section 51.3, which claims that genetic makeup and
environment contribute to development of behaviors.
Nick Sotos (nsotos13@gmail.com)
Shenk's GxE moel for human development disproves the blank slate method because genes do play a major role in shaping the person someone will become. This does not mean genes determine if a person will be funny, motivated, strong, intelligent, etc. However, genes do play an important and substantial role in giving someone the ability to be any of these traits and more. For example, Shenk describes how through evolutionary history, "West Africans...are endowed with shorter trunks and smaller lungs, longer arms and legs...Meanwhile, East Africans...[have] smaller physiques, narrow shoulders, lean legs, much less muscle mass" (298-299). This evidence does not support a complete control by the genes because the higher altitudes help with endurance in East africans, whereas West Africans are stronger because of economic hardships. However, the evidence does support many common traits for a group of people. The given attributes for a different group of people allows them to be affected by the environment. East Africans "lean legs" and "less muscle mass" gives them a higher endurance over most other groups in Africa and throughout the world. Furthermore, the Campbell textbook describes the ways in which genes and DNA affect courtship in male fruit flies. A study showed, "That a single gene called FRU controls the entire male courtship. Males lacking a functional FRU gene fail to court and mate females" (1130). The "FRU gene" completely controls a fruit flies ability to find a mate and reproduce-the primary goal of an organism. This evidence directly disproves the "tabula rasa" idea or blank slate because genes do have complete control over basic characteristics and some behavioral traits. The functioning FRU gene in a fruit fly is a major selective advantage enabling a male fruit fly to survive and reproduce. The action of courting and mating is hardwired into a fruit fly, which allows the whole species to survive by natural selection because they do not need to learn the behavior of mating-their genes have complete control.
ReplyDeleteThe GxE theory disproves the blueprint model because the environment plays a critical role in shaping a person. Genes do not control a person's personality or body type. Instead, the environment-altitude, weather, disease exposure, temperature, etc.-is important in development. For example, Shenk shows in a study of taxi cab drivers, "That...the longer the driving career, the larger the posterior hippocampus" (35). The environment, in this case the length of the taxi driving career, directly correlated to the size of the posterior hippocampus. This means that the more a taxi driver goes around a city, the more intelligent he is on the roads and ways to get to specific places. The posterior hippocampus functions in long-term memory, so the longer a cab driver's career, the more he or she knows the streets. Along the same lines is a study of the interactions between tuna fish and billfish from PNAS. The two species of fish were studied and "the patterns of variations in fisheries time series of tuna and billfish only poorly reflect the underlying dynamics of these fish populations; they appear to be shaped by several successive embedded processes, each interacting with each other" (Rouyer). The experiment explains how interactions between the two fish were underestimated in the role the symbiosis played on behavior. When many fish from both species are together, the scientists realized that the fish attack smaller fish as food in groups. Likewise, when there were few fish, they seemed to catch food individually. The environment-the amount of fish-controlled the behavior of the fish.
http://www.pnas.org/content/105/14/5420.full?sid=15c844e0-6282-4c41-bcb6-371f1b55e160
Josh LeVay (blevay@comcast.net)
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DeletePart 2:
ReplyDeleteThe two theories of blank slate and blueprint models do not act mutually exclusive, but rather they work together in a GxE world. Genes lay the groundwork and the environment then shapes the genes to create the person that everyone is. This relates to the biological theme of evolution and interdependence in nature. Gene expression lays the changeable "blueprint" of an organism. In the case of the fruit fly, the FRU gene had complete control over the fly's ability to mate. This is a selective advantage because the fly does not have to learn this important behavior, which allows reproduction of new fruit fly generations. On the other hand, the environment changes a person dramatically because of different factors. An organism depends on the environment for food, shelter, etc.
Josh LeVay (blevay@comcast.net)