Xref: utzoo sci.bio:1977 talk.origins:4873 Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!shadooby!accuvax.nwu.edu!tank!mimsy!cvl!haven!aplcen!aplcomm!stdc.jhuapl.edu!jwm From: jwm@stdc.jhuapl.edu (Jim Meritt) Newsgroups: sci.bio,talk.origins Subject: Re: The birds and the beaks Keywords: evolution, birds, beaks Message-ID: <3576@aplcomm.jhuapl.edu> Date: 6 Apr 89 12:36:00 GMT References: <28330@apple.Apple.COM> <3561@aplcomm.jhuapl.edu> <28379@apple.Apple.COM> <3566@aplcomm.jhuapl.edu> <28434@apple.Apple.COM> Sender: news@aplcomm.jhuapl.edu Reply-To: jwm@aplvax.UUCP (Jim Meritt) Organization: JHU-Applied Physics Laboratory Lines: 65 In article <28434@apple.Apple.COM> sabol@Apple.COM (Bryan Sabol) writes: }In article <3566@aplcomm.jhuapl.edu> jwm@aplvax.jhuapl.edu.UUCP (Jim Meritt) writes: }>I don't thinkI am mincing words. I am using words in a manner that matches }>the process. The original mutations are not selective. At least _I_ don't }>think that the organism mutates itself towards a goal. (Mary? I read that }>some bacteria do this?) The filter that does the selection removes things. }>Therefore, the filter selects "why not". A trait that is not selected against }>continues. example: Do you have blue, brown, green,, or other eyes? } } I'm not sure what you mean by this. Mutations are much more }commonly deleterious than advantageous. If a mutation is deleterious, }then an organism will have a lesser chance of survival than a 'normal' }organism, and one could gather that the same mutated organism would have }a much less chance of survival than one who had an advantageous }mutation. } It is true that "a trait that is not selected against }continues", but neither does it change. Without the advantageous }mutations, the population/species would never change, and therefore no }new species would develop at all (such as modern birds from _archeoptyrx_). }So, if you really wanted to be specific about how you phrase the process, it }would be more accurate to say that the filter that "does the selection" }removes the deleterious mutations, but the manner (at least for this }arguement) in which new species develop would be from advantageous }mutations. Therefore, one should say "why does ___ have ___", and not }"why doesn't ___ have ___". Precisely. The "Why is this here?" initially is random mutation. For the first occurrance it would be a spontaneous event without particular reason. The "Why is this here?" for a trait which is passed down is because it has not been removed. If the trait is of minimal impact, it will remain (even though its origins were totally random) so "why is it here?" is not especially informative. As per the example of eye color. A trait which is of negative impact will probably disappear. (note: probably does not mean will eventually, or even will at all) IF the distribution of "adaptiveness" is random (due to the variance from those random mutations being stirred around) and the tail of the distribution is continuously being chopped off (by natural selection) the mean will slowly creap up to the max. If the variance is continuously being forced upon the system (by the spontaneous mutations) at a rate such that the new "tail" is smaller than the old "tail" (deliterious mutations do not exceed the number selected against) the distribution will shift upward. There are two processes: one random (mutation) that really doesn't have a reasonable "why?" aside from luck, and selection that has a "Why?" that is really a "Why not?" that selectively removes the tail. _TWO_ processes are required. One can be (appears to be) random, and the other a selection process on the distribution. "Why?" should not have the answer "luck?" unless that is the answer, and it is not (strictly) Doc Terry - if you are still doing your attempts at ecosystem modelling, try generating a random selection of numbers. Calculate the mean. Remove the lowest 5%. Add a random value to each number (-/+ small value). Calculate the mean. Remove the lowest 5%.... What is the trend of the mean over generations? Try with varying elemination percentages and magnitude of change. The above was test data, and not the responsibility of any organization.