Evolution (Evolution)

by whitecraw, Wednesday, April 02, 2008, 17:19 (5874 days ago) @ David Turell

'My point is that all that Darwin has established is that species respond to challenges in nature.' - No they don't. That would have been something like Lamarck's position. All that Darwin established was a theory that explains in non-teleological terms how properties of populations of organisms that transcend the lifetime of a single individual change through time. According to Darwinian theory properly understood, such changes do not take place in response to the challenges of nature; they take place as a result of the competition between variant individuals for survival in a given environment, with those individuals whose physical variations disadvantage them in that competition being less successful reproductively than others who are not so disadvantaged, with the further consequence that those disadvantageous variations tend to die out of the population. What is 'disadvantageous' is of course relative to the environment in which the competition to survive and reproduce takes place; so that environmental changes, as well as random mutation in DNA sequences, impact on which variations are 'selected' over others and can indeed accelerate the process of change. But the point is that the process of change is driven by purely natural events, and there is no need (if the theory works) to postulate any non-natural agency in seeking an explanation of that process. - 'Some fail and some survive, but there is nothing in the fossil record to show that an earlier species changes into a later one. The gaps in the fossil record are huge. Yes there are transitional forms, but never the step by step approach Darwin calls for. Darwin does not explain the Cambrian Explosion, The Plant Bloom, or the earlier Avalon explosion of Ediacarans.' - There are indeed huge gaps in the fossil record. That's the nature of the evidence. But the job of Darwin's theory is to explain what evidence there is. What the fossil evidence shows is that the properties of populations of organisms change through time. Species appear and disappear. What Darwin's theory does is propose an explanation of how this change occurs. That explanation isn't falsified by whatever evidence there is, it is more economical than any alternative theory that has so far been proposed (all it needs for its explanation to work is variation, differential reproduction, and heredity), and it has great heuristic value in that it has generated a whole host of further problems that require ongoing investigation and research. All told, it's a damned good theory as scientific theories go. - 'AT THIS POINT IN RESEARCH NO ONE KNOWS HOW EVOLUTION WENT FROM SIMPLE FORMS TO VERY COMPLEX.' - It's a bit of an urban myth that 'evolution went from simple forms to very complex' forms. This myth even has a name in evolutionary science: it's called the 'ladder of progress' myth. Evolutionary scientists point out that evolution doesn't move in any direction. Certainly, random mutations in DNA sequences have resulted in the appearance over time of more and more complex physical structures, and these properties have survived within populations where they have not at any point in their growth been positively disadvantageous to their bearers. But there is no inexorable ascent or tendency to greater complexity. It is true that individuals that are unfit in a particular situation are 'weeded out' by natural selection; but 'good enough' is good enough. For example, many taxa have changed relatively little over great expanses of time; and the most successful life-forms, in terms of 'survivability', are the simplest. Life is not marching up a ladder of progress. Rather, if it is fit enough to survive and reproduce in whatever form it takes, complex or simple, that's all that's necessary to ensure it continues. Other taxa may have changed and diversified a great deal, and grown increasingly complex. But that doesn't mean they became 'better'. What works 'better' in one environmental context might not work so well in another. Survivability is linked to environment, not complexity.