David Shenk's main argument is that the model for human development over time is based on a Genetics x Environment model (GxE) in which genes and the environment interact equally instead of a Genetics + Environment model (G+E) where genes lay the concrete foundation for human development and don't interact with the environment until later.
Based on your reading of this book as a whole, do you personally agree with the GxE model in lieu of the G+E model? Why? How does the concept of GxE add legitimacy to the concept of Lamarckism or take away legitimacy from the concept of evolution? Can you think of different examples (other than those shared in the book) in which either GxE or G+E seems more plausible than the other? For what reason?
(Adithi Rao, adithi.a.rao@gmail.com)
Based on your reading of this book as a whole, do you personally agree with the GxE model in lieu of the G+E model? Why? How does the concept of GxE add legitimacy to the concept of Lamarckism or take away legitimacy from the concept of evolution? Can you think of different examples (other than those shared in the book) in which either GxE or G+E seems more plausible than the other? For what reason?
(Adithi Rao, adithi.a.rao@gmail.com)
I agree with the GxE model due to the specific evidence Shenk gives throughout his book "The Genius in All of Us". Specifically, Shenk gives an example of how "The changes in hippocampal gray matter...are acquired" (Shenk 35), this supports the model GxE because it shows that the body has adjusted to to the environment, therefore showing that environment has a just as much impact in traits as in DNA. This model also relates to to biological theme of interdependence in nature, but in a more indirect way. Based on a GxE model, the environment can influence the production of proteins that lead to the creation of traits. As opposed to the conventional idea of the theme interdependence in nature, where n organism adjusts is behavior due to environmental stressors, abiotic and biotic factors, and the carrying capacity (Campbell 1126), our bodies are actually even more dependent of nature than previously believed. I believe that Shenk shows that our bodies have a strong link to the environment through various examples relating to the GxE model.
ReplyDeleteLamark suggested that "organisms altered their behavior in response to environmental change. Their changed behavior, in turn, modified their organs, and their offspring inherited those "improved" structures." (http://www.pbs.org/wgbh/evolution/library/02/3/l_023_01.html). The model GxE supports part of Lamark's theories. The idea that an organism adapts to it environment seems to very true. For example, the cab drivers in London acquired a larger amount of hippocampal gray matter in their brains, and studies showed that more experienced cab drivers had a larger amount of hippocampal gray matter than less experienced cab drivers. This parallels the ideas of both the GxE and Lamarkism. Conversely, the model GxE does not overshadow the theory of evolution. The reason for this is because the model only suggests that an organism is interdependent in nature and that it will change accordingly in order to overcome challenges present in a specific environment. The GxE model does not suggest that the traits acquired through interaction with the environment will be passed down to other generations.
Another example of the GxE model is evident in exercise. Exercise in a sense is a type of environment that we impose on ourselves. Specifically, the kicking of a soccer ball is an action that when practiced creates an environment for the muscles to interact with and adapt to. The practicing of kicking a soccer ball is an action that will cause these muscle cells to need to be more efficient with their energy and the muscle itself will have to get stronger in order to adapt to the larger amount of strength needed for the environment. This causes the body to adapt in a sense, more muscle cells are created in order to satisfy the need for more strength and increased blood volume and blood flow will help the cells have a constant flow of oxygen. Also, the body will adapt and become more efficient in the breaking down of glycogen with glucagon (Campbell). The ability of the body to change for a change in the environment, exercise, shows that our body and our traits have an interdependence in nature and that traits are not only determined by DNA, but are also determined by environmental stimuli.
Joseph Hugener (jah1112@comcast.net)
Like Joseph said, I agree with the GxE model that Shenk has proposed. Within the book, Shenk uses multiple experiments and examples that accurately lead to his conclusion. One example is Cc the cat. Shenk explains a cat, Rainbow, that was successfully cloned in 2001. The prediction for Cc (the carbon copy of Rainbow) was that the two cats would have not only the same genes, but the same appearance and personality. However, Cc had a different fur color and was more slender than Rainbow, despite their identical “nuclear DNA” (Shenk 74). The two cats grew up in different environments, thus creating the difference in their appearance. Another experiment that proves Shenk’s GxE model would be the test the Rod Cooper and John Zubek performed on rats in 1958. The two men had two groups of rats: “Maze-bright” rats and “Maze-dull” rats. These rats were then split into three groups: one group was in an environment that stimulated both their bodies and minds with by colorful walls, exercise, and numerous toys; one group was in an environment that had an average amount to stimuli with a few toys with ordinary walls; and the final group and a lacking environment that had no stimuli with only food and water pans (Shenk 28). It was expected, based on the idea that genes affect intelligence alone with little influence from the environment, that the “Maze-bright” rats would have much fewer errors than the “Maze-dull” rats. However, after the rats went through the maze it was discovered that both “Maze-dull” and “Maze-bright” rats that were in the highly stimulated environment performed equally well. While both “Maze-dull” and “Maze-bright” rats that were in the lacking environment performed equally poorly. The only difference seen in the rats were the rats in the average environment: both types of rats had roughly the predicted outcome (Shenk 29). This clearly proves the GxE model since the rats’ performance was dependent on the environment that they were in. These two experiments, along with many others that Shenk references, back up Shenk’s claim about how the environment, not just genetics, shape living organisms into who they are.
ReplyDeleteJoseph is also correct when he identifies that Lamarckism backs up Shenk’s GxE model. Joseph used a quote from pbs.org that explains Lamarck’s idea that organisms will change their behavior or appearance in response to an environmental stimulus. There are two main ideas behind Lamarckism: “(1) the fixed genetic potential of the organism (…the specific qualities of its genetic material, or DNA [deoxyribonucleic acid]); and (2) the environmental conditions which an organism experiences as it grows” (http://science.jrank.org/pages/3795/Lamarckism.html). The ideas behind both the GxE model that Shenk created and Lamarckism are very similar, and can be shown by workers at a Baltimore dairy plant. In the dairy plant, the carton packers have very little education. However, although their education is low, they are able to do complex math in their heads that limits the amount of physical stress and energy needed while they do a day’s worth of work. If the white-collared workers were to come in and try to do the carton packers’ jobs, they would exert much more energy since they are unable to do this complicated math in their heads (Shenk 48-9).
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(Alexis Bauer, abauer9182@gmail.com)
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ReplyDeleteThis backs up both ideas in the two models by showing how the environment affected the workers. The carton packers were uneducated, and seemed to have very little “book smarts.” However, when they are presented in an environment that is like the one that they work in, they are able to use knowledge that they have, while acquiring new knowledge, and limit the amount of energy needed in a day of work. The workers responded to the environmental stimulus of having a lot of heavy lifting in a day, and they were able to expand their knowledge to limit the energy used. This relates to the biological theme of continuity and change because the workers went into the job with a very low education that was continuous throughout their life. But when the environment shifted, the worker’s mentalities changed, and it enabled them to increase their intelligence. The workers adapted to their work, and were able to minimize the amount of lifting they did.
The fact that GxE is more plausible that G+E is shown in cross-fostering studies that have been done for animals. In the textbook, a behavioral experiment is conducted using male California mice and male white-footed mice. Male California mice are aggressive and provide a lot of parental care, while male white-footed mice are less aggressive towards others and therefore provide less parental care. When male pups are switched in both species (white-footed pups brought up by California mice and vice versa) the behavioral patterns of the parental figures were observed in the pups. In other words, the California mice (that were pups) were less aggressive, while the white-footed mice were more aggressive (Campbell 1129). Although the aggressive genetics of the California mice were present is the cross-fostered mice, the environment had shifted the personality of the mice to be more like the white-footed mice. The environment played a large role in the mice’s genetics by influencing the genes that were expressed in a mouse’s behavior.
Shenk’s theory of GxE is greatly supported in not only his book, but the world around us. One can see how the environment affects genetics on a daily basis. Shenk was right when he said that the phrase “nature vs. nurture” should not be used anymore and that it should now be “dynamic development” (Shenk 33).
(Alexis Bauer, abauer9182@gmail.com)