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> Epigenetics is "how the genome is read" I'm not a molecular biologist, so take this all with a grain of salt. There are two things which get confused when discussing epigenetics. First, you have gene expression which is mediated by the environment. That is what you are talking about with your turtle example. This is pretty common. After all, being able to respond to environmental stimuli is useful. But there is another phenomena that gets labelled as epigenetics: stuff in the environment which modifies the DNA of the germ line cells (eggs and sperm) of an organism. The part about it being germ line cells is important, because that means that the changes to DNA will be passed on to the offspring, whereas epigenetic changes in any of the other cells of the body will not. People are in love with this aspect of epigenetics because, frankly, there's a certain type of person who is enamored with the idea that this might "disprove" Darwinian evolution (OMG Lamarck was right!). It's extremely frustrating because this second phenomena is, as far as we know, extremely uncommon. I mean, it almost has to be. Large organisms are like a house of cards; if you make too many changes, everything comes crashing down. So, if there were epigenetic changes to germ line DNA happening all the time, there would be unfeasible levels of mutation happening from one generation to the next. But the fact that it is extremely uncommon does not stop people from hearing about how this second meaning of epigenetics is a weird end-run around Darwinian evolution, then hearing about how common the first meaning of epigenetics is, and coming to the conclusion that Darwinian evolution is invalid. Incidentally, these two meanings are the root cause of you and the person who responded to you misunderstanding each other. |