Tuesday, July 29, 2008

Epigenetics in New Scientist

As a general rule, the magazine New Scientist does an acceptable job of covering the issues that I'm familiar with. Sure, from time to time they screw up big time, but the good articles outweigh the bad.

The July 12-18 issue has one of the big time screw-ups. There is it on the cover, "Forget Genes: The strange inheritance from your parents." The article inside is by Emma Young, an Australian writer for New Scientist who has mostly specialized in stories about space. The title of the article in the magazine is "Strange Inheritance" and the title on the website is Rewriting Darwin: The new non-genetic inheritance
HALF a century before Charles Darwin published On the Origin of Species, the French naturalist Jean-Baptiste Lamarck outlined his own theory of evolution. A cornerstone of this was the idea that characteristics acquired during an individual's lifetime can be passed on to their offspring. In its day, Lamarck's theory was generally ignored or lampooned. Then came Darwin, and Gregor Mendel's discovery of genetics. In recent years, ideas along the lines of Richard Dawkins's concept of the "selfish gene" have come to dominate discussions about heritability, and with the exception of a brief surge of interest in the late 19th and early 20th centuries, "Lamarckism" has long been consigned to the theory junkyard.

Now all that is changing. No one is arguing that Lamarck got everything right, but over the past decade it has become increasingly clear that environmental factors, such as diet or stress, can have biological consequences that are transmitted to offspring without a single change to gene sequences taking place. In fact, some biologists are already starting to consider this process as routine. However, fully accepting the idea, provocatively dubbed the "new Lamarckism", would mean a radical rewrite of modern evolutionary theory. Not surprisingly, there are some who see that as heresy. "It means the demise of the selfish-gene theory," says Eva Jablonka at Tel Aviv University, Israel. "The whole discourse about heredity and evolution will change" (see "Rewriting Darwin and Dawkins?").

This is, of course, nonsense. The article is all about epigenetics but it's a very broad definition of epigenetics. One that makes you cringe when you read ...
Epigenetics deals with how gene activity is regulated within a cell - which genes are switched on or off, which are dimmed and how, and when all this happens. For instance, while the cells in the liver and skin of an individual contain exactly the same DNA, their specific epigenetic settings mean the tissues look very different and do a totally different job. Likewise, different genes may be expressed in the same tissue at different stages of development and throughout life. Researchers are a long way from knowing exactly what mechanisms control all this, but they have made some headway.
Some headway? That's quite an understatement isn't it? Emma Young then goes on to describe some of that mysterious headway. Turns out that methylation of DNA, histone modification, and RNAi are the prime suspects in the upcoming paradigm shift. Who woulda guessed?

According to the New Scientist article, there are a host of scientists who are ready to abandon the gene as the unit of evolution. These include Eva Jablonka from Tel Aviv University, Israel and Russell Bonduriansky, at the University of New South Wales in Sydney, Australia. But wait. What does Richard Dawkins have to say about this?
For Bonduriansky the accumulating evidence calls for a radical rethink of how evolution works. Jablonka, too, believes that "Lamarckian" mechanisms should now be integrated into evolutionary theory, which should focus on mechanisms, rather than units, of inheritance. "This would be very significant," she says. "It would reintroduce development, in a very direct and strong sense, into heredity and hence evolution. It would mean the pre-synthesis view of evolution, which was very diverse and very rich, can return, but with molecular mechanisms attached."

That needn't necessarily mean an end to the idea of the gene as the basic unit of inheritance, or Richard Dawkins's selfish gene, according to some. "I don't think it violates the basic concept that Dawkins articulated," says Eric Richards, at Washington University in St Louis, Missouri. "Epigenetic marks can also be viewed as part of that basic unit in a more inclusive definition of a gene," he says.

What does Dawkins himself think? "The 'transgenerational' effects now being described are mildly interesting, but they cast no doubt whatsoever on the theory of the selfish gene," he says. He suggests, though, that the word "gene" should be replaced with "replicator". This selfish replicator, acting as the unit of selection, does not have to be a gene, but it does have to be replicated accurately, the occasional mutation aside. "Whether [epigenetic marks] will eventually be deemed to qualify as 'selfish replicators' will depend upon whether they are genuinely high-fidelity replicators with the capacity to go on for ever. This is important because otherwise there will be no interesting differences between those that are successful in natural selection and those that are not." If all the effects fade out within the first few generations, they cannot be said to be positively selected, Dawkins points out.
That's a relief. All epigenetic phenomena are unstable and/or reversible and Dawkins isn't buying any of this pseudoscientific nonsense about its effect on evolution. Now if we could only convince the science writers to pay more attention to the skeptics and less attention to the self-serving "revolutionaries."


  1. As a science writer, I can say there is a tendency to make a mountain out of a molehill. A little blip in the literature, a few juicy quotes later, and you have yourself a feature article.

  2. any heritable influence on genes is therefore an influence on the selection process. the epigentic phenomenon of environment-gene interaction and the resulting influence on heritable gene expression can not be overestimated. DNA inheritance can respond to environment and cause changes in the "gene pool" on a generational basis. heritable epigenetic mechanisms respond continually throughout the lifespan of an organism, therefore much more sensitive to environment, and therefore should be given the major role in influencing the heritiability of traits across generations. the variability of human DNA, specifically its expression patterns, can lead to events as uniquely different as life and death.