Well, since the tussle about epigenetics involves Brits, they’re really too polite to engage in a “smackdown.” Let’s just call it a “kerfuffle.” Nevertheless, two scientists have an enlightening 25-minute discussion about epigenetics at the Guardian‘s weekly science podcast (click the link and listen from 24:30 to 49:10). If you’re science friendly and have an interest in this ‘controversy,’ by all means listen in. It’s a good debate about whether “Lamarckian” inheritance threatens to overturn the modern theory of evolution.
Readers know how I feel about the epigenetics “controversy.” “Epigenetics” was once a term used simply to mean “development,” that is, how the genes expressed themselves in a way that could construct an organism. More recently, the term has taken on the meaning of “environmental modifications of DNA,” usually involving methylation of DNA bases. And that is important in development, too, for such methylation is critical in determining how genes work, as well as in how genes are differentially expressed when they come from the mother versus the father.
But epigenetics has now been suggested to show that neo-Darwinism is wrong: that environmental modifications of the DNA—I’m not referring to methylation that is actually itself coded in the DNA—can be passed on for many generations, forming a type of “Lamarckian” inheritance that has long been thought impossible. I’ve discussed this claim in detail and have tried to show that environmentally-induced modifications of DNA are inevitably eroded away within one or a few generations, and therefore cannot form a stable basis for evolutionary adaptation. Further, we have no evidence of any adaptations that are based on modifications of the DNA originally produced by the environment.
In the Guardian show, the “Coyne-ian” position is taken by Dr. George Davey Smith, a clinical epidemiologist at the University of Bristol. The “epigenetics-will-revise-our-view-of-evolution” side is taken by Dr. Tim Spector, a genetic epidemiologist at King’s College. Smith makes many of the points that I’ve tried to make over the past few years, and I hope it’s not too self-aggrandizing to say that I think he gets the best of Spector, who can defend the position only that epigenetic modification is important within one generation (e.g., cancer) or at most between just two generations.
But listen for yourself. These guys are more up on the literature than I am, and I was glad to see that, given Smith’s unrebutted arguments, neo-Darwinism is still not in serious danger. (I have to say, though, that I’d like to think that if we found stable and environmentally induced inheritance that could cause adaptive changes in the genome, I’d be the first to admit it.)
h/t: Tony
Davey Smith absolutely destroys the idea that epigenetic changes contribute significantly to inheritance. New technological discoveries do not change a century of studies showing phenotypic variation in isogenic lines does not breed true. (Both low and high extremes give offspring w/ exact same mean and distribution as parental generation). He also undermines conclusions from epidemiological studies supposedly showing transgenerational effects in humans, saying it is statistically impossible to control for confounding variables in such studies.
For more on the weakness of the supposed evidence for transgenerational effects, especially on behavioural traits in animals, see here: http://www.wiringthebrain.com/2013/01/the-trouble-with-epigenetics-part-2.html
Kevin Mitchell, Associate Professor of Genetics and Neuroscience, Trinity College Dublin?
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First sun was defective
. . . That’s why the Darwinian race left their first solar system . . . ?
Anyways, I’ve been digging through some books on epigenetics and agree with Coyne’s stance (I do not think I was fully following it all in the past). I will say that the claims made by epigenetics touches on many different cell reproduction systems, and the process of how genes (and the resulting cell structures) reproduce and create behaviors/traits seems endlessly complicated. To understand why a cell or organism behaves as it does it may be necessary to untangle all that tangled mess, but the idea about long-term inheritance following from that does seem questionable, to me. Though, any short-term process, such as cancerous growths, will necessary effect the reproduction of cells and the organism . . .
Good educational debate, but they hardly differed with each other. Epigenetics is in its infancy. Let’s see where it stands in 10 years.
Actually, its about three decades old with zero progress over all that time. It is a derailed bandwagon, a steamship rather than the Titanic but going down anyway.
Not to mention that epigenetics has been abducted by the “directed mutation” crowd who misread the evidence, ignore the rebuttals, and flounder around for a mechanism.
Ah yes, Darwinism is so dogmatic! And here we are, discussing options to bring it down, from it’s current state, where a man who regularly mocks evolution deniers treats the possibility respectefully, even as he denies it.
Even if Dr. Coyne turns out to be wrong, though, it’s still not creationism. While both incorrect, there is much more truth to a spherical earth than a flat one.
Readers of this column mike like to read a book on RNA, which does the real work on DNA before translating to protein. James Darnell, RNA Life’s Indispensable Molecule, Cold Spring Harbor Press, 2011. This work is in infancy. Darnell has worked on RNA since 1950’s. Since the RNA editor edits every DNA sequence in sexual organisms before translating into protein, perhaps we should know more about it than simply denying it does anything we need to know.
I believe that Dr. Robert Sapolsky covered quite a bit of this and the relations of these in his brilliant “Human behavioral biology” lectures. May want to take a look at those?
Added to my comment above about RNA. The sequencing of DNA is doing poorly on long streams of DNA. Many are trying new techniques on these long segments. Nature has an article on this precise question: Nature, The Genome Jigsaw, by Vivian Marx, Nature 12 September, 2013. None of it is precise. We need more time to evaluate the impact of RNA. So we cannot make a certain statement of epigenetics without more understanding.
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