This morning brought notification of yet another delightful editorial by Gerald Weissmann in the FASEB Journal (which I don’t otherwise read much), entitled, Fashions in Science: From Philosophers’ Camp to Epigenetics.1
The idea that there are fashions in science is nothing new whatsoever. Who among us has not lamented the fact that one’s subject of predilection is not the easy sell and draw for money and personnel that we might have believed anything “-omics”, related to human disease-causing viruses, or string theory is?
Many interesting debates about how organisms develop and acquire form and function seem to revolve around an artificial, easy dichotomy between nature and nurture, and Weissmann exposed them for the specious simplifications they are.
Aristotle proposed that humans developed from the interplay of nature, or “preformation,” and nurture, which he called “epigenesis.” Once genetics became a science, and “evo” joined “devo,” nature and nurture were revived in the guise of Mendelian vs. non-Mendelian heredity; Weismann’s immortal germ plasm vs. mortal protoplasm; and Mayr’s “soft” inheritance vs. the “hard” kind. More recently, Dawkins’ selfish gene (nature) has been countered by E. O. Wilson’s altruistic biology (nurture). Right now the epigenetic style is in high fashion with us and, like all high fashions, attracts the attractive. Dame Honor anticipated this sentiment in her presidential address to the First International Congress of Cell Biology in Paris:
Sartorially speaking we are probably not an outstandingly fashionable group, but where our research is concerned, we can be as fashion-conscious as the most elegant woman in this City. In science, as in the world of dress, fashions recur … .
I have few quibbles with following fashion. We scientists only heap scorn on it because it implies a certain passivity of thought, and an expenditure of limited energy on an apparently futile endeavor. (At least with respect to clothing, or to emulsions at the dinner table.) It’s not for me (well, clothes are, but not necessarily fashionable ones), yet I spend my time in other, arguably futile endeavors like writing blog entries, so I am ill-equipped to criticize.
It is de bon ton as well as relevant to cite Conrad Hal Waddington’s The Strategy of the Genes (Geo Allen & Unwin, London 1957) and the now-famous schematic describing fate acquisition in a progressively more restrictive environment, his “epigenetic landscape”. As Jonathan Slack explains the concept in his biography of Waddington 2,
…Up to a certain threshold, any genetic variation or environmental noise will be ‘buffered’ and not affect the pathway, but above this threshold, the cell would flip over into an adjacent pathway. By representing a pathway as a valley in a surface, Waddington provided a simple mechanical analogy for the rather complex biochemical-genetic buffering that occurs in organisms during development.
Weissmann’s summary of Waddington’s major insight is this:
Successive generations of the same phenotype will tend to seek the same path and the phenotype will become fixed regardless of the variability of its environment or genotype.
With a somatic mutation, for example, there can be enough impetus for a cell to roll out of one trough and enter another. The cell can react (or not) quite differently to its environment and its endogenous (epi)genetic state of affairs, which had “canalized” it so well until then. In the case of some cancers, it might go careening across the valleys as if the billiard ball had been given a hard lateral hit, and not really enter any of them for long.
During normal development, a cell will embark upon a path of differentiation that is progressively restricted over time. If you take it out of that context, as in innumerable experiments carried out by the legatees of Wilhelm Roux, Ethel Browne, Hans Spemann, Hilde Mangold, and Nicole Le Douarin, it often long retains the potential to go on and do other things, and that potential can wane over time at a variable rate depending on the cell type. Whether the potential is ever revealed is a matter of circumstance.
Which can apply to people, as well.
Insight that has brought us to another scientific fashionable concept in which I happily participate, stem cells. But woe be to anyone who tried to define a stem cell once and for all! Like the term’s object, “stem cell” is context-dependent.
I wish Weissmann did not reserve his insights for his readers at FASEB J but also opened up the editorials, at least, to Open Access and eventually to comments, such that they could double as blog posts. I am sure the discussions would be fascinating.
I have printed this out but didn’t yet get around to reading it. Thanks for pointing it out – promise to read soon! I enjoyed his piece on limericks – Martin Fenner alerted me to your post on that.