Complexity of gene codes (Introduction)

by dhw, Monday, August 16, 2010, 12:51 (5022 days ago) @ David Turell

David has referred us to two websites, both of which as a non-scientist I find puzzling. I'll explain why, and then perhaps someone can shed some light on the issues.-http://www.physorg.com/news200842170.html-This deals with the discovery of a bacterium which researchers at Yale say is a remnant from the time before DNA. The cells use "ancient RNA technology to control modern gene expression", an ability "once believed to be possessed solely by proteins." Prof. Ron Breaker believes that early forms of life depended on such "RNA machines". So far so good. However, Breaker concludes with the statement that "a lot of sophisticated RNA gadgetry has gone extinct, but this study shows that RNA has the power needed to carry out complex biochemistry. [...] It makes the spontaneous emergence of life on earth much more palatable." -Without climbing aboard the ID bandwagon, I would just like to know how the newly discovered complexities of RNA make the case for "spontaneous emergence" more palatable. -The second article, available only in summary to non-subscribers, is on: -http://www.sciencemag.org/cgi/content/summary/329/5993/740-but David has kindly provided us with salient extracts. It illustrates "positive selection", e.g. Tibetans adapting to high altitudes in "just 4000 years". David says that this "is a much faster rate than the known rates of random mutation and natural selection can provide. Therefore, it is concluded there are subtle mechanisms that can push adaptive evolution."-Firstly, I don't understand the relevance of random mutations anyway. Why on earth would Tibetans have randomly acquired an ability to cope with high altitudes prior to being exposed to such an environment? Doesn't common sense tell us this is "adaptative evolution", not random mutation? If you can't cope with high altitude, you'll either die or you'll get back down to where you can breathe again. Presumably, Tibetans were gradually able to venture higher and higher, as each generation got more acclimatized, but even a single generation of animals can adapt to a changing environment. Otherwise the lions of Longleat (a safari park here in Britain) would hardly have survived our winters when the park first opened in 1966. Also I wonder how the researchers hit on the figure of 4000 years. If you take that as the equivalent of say 200 generations, it seems a mighty long time for the Tibetans to be huffing up and down. (I'm not disputing the arguments of the experts. I'm just explaining why I don't understand them, and I'm asking for help.)-Secondly, as we have said repeatedly on this forum, the mechanism allowing for potential adaptation must have been built into early forms of life ... otherwise there would have been no evolution ... and so I can't see what is so revelatory about "positive selection". Right from the start of evolution, natural selection has meant the survival of those features that are best adapted to the environment, and this has to be "positive". Negative selection ultimately means goodbye.-DAVID: Geneticists are now showing us that the genome is responding actively to environmental pressures, not passively as Darwin expected. [...] Chance mutation and natural selection are a totally passive mechanism.-Of course Darwin didn't know what we now know about genetics, but he certainly viewed adaptability as an integral feature of living things: "I am inclined to look at adaptation to any special climate as a quality readily grafted on an innate wide flexibility of constitution, which is common to most animals." (Origin, 'Laws of Variation', section on 'Acclimatisation'). I think David is right about the passiveness, since Darwin attributed acclimatisation to "mere habit" and/or natural selection working on "different innate constitutions", but again I don't see what this has to do with chance mutation, which seems to me to be a totally different subject from adaptation. I'd always thought of the former as a random, entirely internal change (which may or may not be useful), and the latter as an internal change arising from interaction with external conditions. Am I missing something here?