19 February 2012

DNA, Epigenetics & Identity

Discover Magazine has a terrific essay on epigenetics and environmental influences on individual development. Money quote:    
The even greater surprise is the recent discovery that epigenetic signals from the environment can be passed on from one generation to the next, sometimes for several generations, without changing a single gene sequence. It's well established, of course, that environmental effects like radiation, which alter the genetic sequences in a sex cell's DNA, can leave a mark on subsequent generations. Likewise, it's known that the environment in a mother's womb can alter the development of a fetus. What's eye-opening is a growing body of evidence suggesting that the epigenetic changes wrought by one's diet, behavior, or surroundings can work their way into the germ line and echo far into the future. Put simply, and as bizarre as it may sound, what you eat or smoke today could affect the health and behavior of your great-grandchildren.

All of these discoveries are shaking the modern biological and social certainties about genetics and identity. We commonly accept the notion that through our DNA we are destined to have particular body shapes, personalities, and diseases. Some scholars even contend that the genetic code predetermines intelligence and is the root cause of many social ills, including poverty, crime, and violence. "Gene as fate" has become conventional wisdom. Through the study of epigenetics, that notion at last may be proved outdated. Suddenly, for better or worse, we appear to have a measure of control over our genetic legacy.
On some level, these findings should not surprise us. Plant physiologists, for example, have long known that transcription changes in plants situated in nitrogen rich or nitrogen poor environments. That these changes should be expressed in progeny seems a likely - if somewhat Lamarck-ian - thesis. But notice the really important point: these changes in the environment lead to behavioral changes in the mammal's offspring. The implication is that the underlying neurobiological mechanisms are themselves highly plastic.

The lesson that I take away from this - this is totally conjecture - is that epigenetics will underpin a more devastating critique of many fMRI studies (and thus function implicitly as a larger critique of the widespread neuromania of the last few years). Largely the issue is going to be that fMRI studies will increasingly be seen as naive structural-functionalist accounts. They will be described as unable to account for changes over time, for failing to recognize that changes across generations are not uniform, and seen as classic examples of circular reasoning.        

1 comment:

  1. A good post. I too am a fan of the whole epigentics area simply because it unites quite a lot of nature/nurture findings. Lamarckism is also finding its niche there.

    As for the ultimate epigenetic influence, have a look at the Barker hypothesis (thin-fat bodies) and the Flemish/Netherlands studies of wartime famine effects: http://www.ncbi.nlm.nih.gov/pubmed/18955703

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