April 22, 2010

Bye bye genetic determinism

How important are genes in determining how we are and become? Obviously, genes are quite important. Genes contain the instructions which lead to the formation of proteins, the molecules which play vital functions such as to help create cells. So, genes are definitely important. But how important are they? Or: how are they important?

Chapter 2 of David Shenk's  The Genius in All of Us: Why Everything You've Been Told About Genetics, Talent, and IQ Is Wrong is about genes. It describes how, until very recently, the dominant view of what genes do, was that they determine what we are and become. However, this popular conception of the gene as a simple and powerful causal agent is not valid. A new interactionist model which describes the role of genes more accurately is briefly summarized as 'GxE'.

The old view of genetic influence was an additive model in which genes (nature) and environment (nurture) each had a separate influence. The nature-nurture debates that got much attention tried to establish how great the relative influence of nature and nurture respectively were. This old view is visualized as follows (page 26):

The new interactionist (GxE) model describes how genes 'constantly respond to, and interact with, a wide range of internal and external stimuli - nutrition, hormones, sensory input, physical and intellectual activity, and other genes - to produce a unique, custom-tailored human machine for each person's unique circumstance.' The simple presence of a gene does not guarantee that specific types or numbers of proteins will be built. First, the gene has to be 'switched on' or expressed before this happens. According to Shenk, this interactionist view can be visualized as follows:

Briefly, this model shows how genes continuously interact with everything else that is happening in your life. This interaction shapes how we develop. 

3 comments:

  1. and the fact that the way genes operate is more complex than we thought means we can't talk about determinism? How is that?
    e.g. chaotic systems are unpredictable yet they are deterministic

    ReplyDelete
  2. I don't understand. How can we still talk about genetic determinism if the explanation in the post is true then?

    ReplyDelete
  3. Mind you I'm not saying 'determinism' but 'genetic determinism'. the explanation is that genes are not sole causal agents of traits

    ReplyDelete

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