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Daddy4UdderSlut -> RE: God, Darwin, and Kansas (8/9/2006 7:24:46 PM)
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Mastermind, I sincerely want to apologize for my last post. This absolutely was not meant for you or for any others for that matter who have sincerely participated in this discussion. It was really only meant for seeksfemslave, who was from the beginning neither an honest nor a respectful participant in the dialogue.
Your understanding of the common working definition of a species is correct. But, that was I believe an older definition, which, if you think about it, can only describe life that reproduces using sexual reproduction. Bacteria, for example, have no male or female, and do not mate.
As to the scope of allowed variation... well, effectively, it is only bound by what can be carried forward. Let me explain a bit more...
First of all, people are not a good model any longer, because we don't live according to the rather harsh rules of nature - only the strong survive. So let's just imagine any old animal... or people in the distant past.
Changes in the chromosomes occur randomly, with equal probability as to whether they are beneficial, detrimental, or neither. There are actually many forms of changes. If you like, I will list them out on the next post.
If a change leads to a greater likelihood of survival until, and then successful completion of reproduction, then it follows directly that more children carrying genes with the beneficial changes will be produced. The larger the reproductive advantage, the greater the intrinsic amplification of the new trait. So it should be easy to see that the mechanism exists for reinforcement and population domination of reproductive advantages. It really doesn't matter if the individual would live longer in old age. What counts is, will they produce more children with the same traits as they have - it's the act of passing on the genes that determines the nature of the future generations.
What is less obvious, is that detrimental changes can occur with equal likelihood, and still be tolerated....
First of all, a change may be detrimental, but not yet not debilitating in terms of survival or reproduction of the affected individual. That's a particularly important thing to realize, because it allows that chromosomal lineage to pass through suboptimal intermediate stages, and then arrive at something even better than the starting point. That is, each change doesn't need to be strictly for the better, one can go downhill for a little while and then back up.
Second of all, even if a change is detrimental, and simply a dead-end (not able to lead to better traits later), that's alright also. At worst, it simply means that the suboptimal individuals with those traits will die out, but remember, we're talking about a large population, so the population as a whole is unaffected by traits that are debilitating for a subpopulation. Because just as the frequency of superior genes are naturally amplified through reproductive successes, the frequency of inferior genes are naturally scaled back and eliminated through reproductive failures.
A particularly fascinating aspect of the genome, is that every so often, copies of genes are created and inserted back into the genome, due to what are called transposition, and unequal crossing over. Copies, in and of themselves, do little either way for fitness, serving at most to increase the concentration of the associated protein. Mutations in copies of genes will be well tolerated, because the original is still there as well. Most of the time, such copies succumb to deleterious mutations and become genetic junk, baggage in the genome. However, some of the time, these copies mutate to form a new functional gene that conveys an advantage, and then you have a new homologous gene, and a new homologous protein within the same organism. It's estimated that 50% of the human genome originated from such duplication and variation.
I suppose your proposal is indeed possible as an alternative explanation for our present diversity of life. However, to substantiate it, you must find evidence for it and expand the theory, always finding evidence to corroborate it, and if you cannot find such evidence, or find something that contradicts it, you must either modify the theory or discard it as needed and come up with a new theory. That is what scientists have been doing with their view of life on earth and it's history for centuries. The vision since Darwin's seminal work however, while it certainly has evolved and been fleshed out continually (Darwin didn't know about DNA, nor have even a detailed model for it's concepts for example)... there has been no major contradiction or revision. In that, Darwin has to go down in history with Isaac Newton as one of the true giants of science.
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