Shenk begins to offer some support for Lamarck's much-ridiculed idea that personal experience can alter heredity. He states how certain lifestyle experiences, such as children being exposed to more rigorous mental activity, can give a genetic boost to future generations. "In other words, we may well be able to improve the conditions for our grandchildren by putting our young children through intellectual calisthenics now" (162). For example, "could a family's dedication to athletics in one or more generations induce biological advantages in subsequent generations?" (162) However, much of Shenk's early argument focuses on his idea that there is no such thing as inborn talent. "Talent is not the cause but the result of something," (60) he declares, that something being extensive deliberate practice that causes our "muscles and brain [to] adapt to the demands that we make of them" (67). Does this mean that, when Shenk says that practice changes the body (65), the same physiological changes that give people "talent" can also be inherited from previous generations that have done the work for us? Shenk does admit that genetics play some role in determining our full potential. Examine how much GxE development in one generation can give an advantage to future generations, and how much must be attained by one's own practice.
Vivian Wang (vivian.wang9895@gmail.com)
Traditionally, Lamarck’s idea has been thrown to the wayside. Genes are the sole medium of heritability has been the predominant mindset as “today, any high school student knows that genes are passed on unchanged from parent to child, and to the next generation and the next” (Shenk 157). We often sarcastically thank our parents for our ugly nose, but very rarely do we sincerely thank them for challenging themselves mentally at a young age. However, more and more, the genetic sequence is proven to be just one of the components we inherit from our parents. In addition, we inherit epigenetics. Epigenetics control what genes get turned on and off. Therefore, this can have a major role in whom we become. Only genes that are turned on will have RNA polymerase synthesize mRNA by linking together ribnucleotides by phosphodiester bonds. These mRNAs will be synthesized into proteins after processing and editing. Proteins carry out many functions in the body including catalyzing enzymatic reactions and transporting molecules across membranes. Therefore, the epigenome we inherit does have an influence on whom we become. However, we are not at the mercy of our parents’ decisions completely. More importantly, we are the mercy of own decisions. As Shenk argues, “with humility, with hope, and with extraordinary determination, greatness is something in which any kid - of any age - can aspire” (12).
ReplyDeleteEpigenetic inheritance has the potential to give an advantage to future generations. For example, one study supported the claim “higher rates of heart disease and diabetes in the children and grandchildren of people who were malnourished in adolescence” (http://www.sciencedaily.com/releases/2009/05/090518111723.htm). This study indicates that decisions well before pregnancy impacted the next generation. This can be explained since environmental influences such as diet and nutrition can alter our epigenome. This is a new idea. We cannot alter our genetic sequence, but we can alter “additional instructional material – known as epigenetic material – which helps guide how the genes will be expressed” (Shenk 118). As Shenk continues, “this means that we can alter our genetic legacy” (118). Then this epigenetic material that was altered by the environment will passed on to future generations. This sends chills to Darwin’s theory of evolution. Epigenetic inheritance implies changing traits and evolving the human race in a blink of an eye as compared with evolutionary time with random mutations causing selective advantages. Actually we can force the advantages by training harder and committing more not only for ourselves, but also for future generations.
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ReplyDeleteThis means the mentally stimulating math practice my grandfather did, can have a similar effect on me as it did on him without any “work” on my part. However, the substantial advantage epigenetics plays is probably small compared to the GXE factors of my own life. My current level of dedication will have much greater influence on my than my grandfather’s level of dedication, so to speak. For example, Ted William’s extraordinary talent is not owed to “giftedness” by genes or epigenetic material, rather “he insisted his great achievements were simply the sum of what he put into the game” (Shenk 6). There are countless examples of mathematicians, musicians, and athletes who worked hard, put the hours in, and trained intensely to achieve greatness. Our genes, including inherited epigenetics, gives us our potential and possibly a slight advantage, but in order to unlock greatness, we have to set up the right environment as Shenk explains with training, dedication, and mentors. For example, cab drivers in London have adapted to their demands in real time. The streets in London are very confusing and the average person can’t navigate them. Yet “these navigational demands stimulate brain development, concludes a study five years in the making” and “that their intensive training is responsible for the growth” (http://www.scientificamerican.com/article.cfm?id=london-taxi-memory). The body can respond to demands placed on it by biochemical changes that will “trigger the activation of dormant genes within the cells’ DNA” (Ericsson qtd. in Shenk 69). Therefore, most who we are is related to the GXE of ourselves in the present, and less on the GXE of generation before us even though epigenetic inheritance does serve an important role passing traits along generations.
Lizzy Ettleson, lettleson@gmail.com
Lamarck was wrong in the sense that he believed that inherited characteristics are the primary vehicle of evolution. However, his ideas that an individual’s experiences and decisions in his/her life can alter the biological inheritance of his/her descendants are correct. This idea makes the evolutionary process a more “interactive” one (Shenk, 161). Lamarck didn’t realize this at the time, but what he was referring to is now known as epigenetic inheritance. Chromatins, which are DNA of eukaryotic cells and proteins packaged together in an “elaborate complex,” packs a cell’s DNA in order for it to fit inside of the nucleus but it also assists in regulating gene expression (Campbell, 356). These chromatins can be modified, however. They do not cause a change to the actual DNA sequence, but these modifications could be passed on to future generations. This is the phenomenon known as epigenetic inheritance. So, yes, the way of life of an individual can have an effect on his/her descendants. In a study done by Dr. Bygren, a study of the effects of famine on a generation and that generation’s descendants which controlled for socioeconomic variations, it was found that the grandsons of boys who had overeaten died an average of 32 years earlier than those that had endured a poor harvest (http://www.time.com/time/magazine/article/0,9171,1952313,00.html#ixzz1rnCGAPJ2). What this demonstrates is that epigenetics can indeed have an effect on the lives of an individual’s descendants.
ReplyDeleteLizzy mentioned above that, “Only genes that are turned on will have RNA polymerase synthesize mRNA by linking together ribnucleotides by phosphodiester bonds.” She was referring to the idea that epigenetic inheritance is due to modifications in the chromatin that are passed down. However, these same modifications can be reversed (Campbell, 358). These modifications can be “turned on” or “turned off.” Thus, epigenetic inheritance only has a limited amount of influence over our lives, abilities, preferences, and such because it can be reversed in our lifetime as well according to our experiences. Epigenetics can only give us a small advantage at most, and even that is not certain. Most of all, it is the GXE factors in our lives that ultimately change who we are. They provide a far superior advantage for our lives than the epigenomes that we inherit. Humans are built with the ability to learn in many different ways from habituation to associative learning, cognition, and spatial learning. The last type of learning has been seen to even physically change our bodies. London taxi cab drivers were seen to have a larger growth of the hippocampus of their brains the longer worked as a taxi cab driver (http://news.bbc.co.uk/2/hi/677048.stm). Their brains did not enlarge because their ancestors passed down a specific epigenome but rather because of their own experiences. This demonstrates that it is, ultimately, practice and experience that gives us the “advantage.” This is because individual experience is ultimately more stimulating, and that will provide for the greater change and greater “advantage.”
A human brain and his/her body is “primed for plasticity; they were built for challenge and adaptation” (Shenk, 131). Our bodies and minds were built to change and adapt to the type of life we live, the things we do, the way we think. Epigenetics can have a minor effect on the type of person you are, but it isn’t permanent nor does it have as large of an influence that your own practice and experience can have. So, essentially this ties back into the Growth vs Fixed Mindset. Your genes place only very few restrictions on the things you can do and the person you can be. The rest can be decided by the time and practice you dedicate to a certain subject, sport, or musical instrument; the way you think; as well as the way you live.
(Yanfei Gao, feifeiyg@yahoo.com)