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Index of Subjects --Apple-Mail-1-525265478 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; format=flowed On 20-Oct-06, at 1:35 PM, Paul MacDonald wrote: > ... Hi Dave and All > In-breeding or line-breeding will produce the > modifications that you suggest. Hi Paul, you seem to be thinking of within-species variation -- my point was about the emergence of new species (of mimetic flies) during evolution. The definition of what's a species is difficult these days, but a common theme is that different species are those 'varieties' that can't interbreed and are therefore reproductively isolated (not a cast-iron definition, though, many exceptions) . The species concept these days is tricky, need to get expert advice on what the best idea is (I don't think that there's full agreement on this, and maybe it doesn't matter scientifically). > One of the general > rules of nature is the more closely related the > parents - the more variation in the offspring. Some > good some not so good. > I don't know where this idea comes from, but if it were true, it > wouldn't be possible to isolate different strains of cattle, dogs, > pigeons, geese, etc by selective breeding -- the opposite would be > true. Darwin became an expert on this, and used the example of > short-term selective animal breeding (to produce extreme true-breeding > 'varieties') as a model argument for what he proposed had happened > during long-term natural evolution. The examples from in-breeding > are not usually new species, as the various dogs etc can still often > interbreed successfully. > The great majority of the food > consumed daily in the world has been produced by > taking this rule into account. > I suspose you could make the point that the pairing > with insects is chance! Maybe this last idea is correct, and it would also be for some birds -- those with males that sing and otherwise advertise themselves and their territories to prospective females. Other birds apparently pair for life, however, so it is not always a rule. I flinch at straying into this birdy territory myself -- you'd need to get Ian McLaren or someone on this, on the extent of lifetime pair-bonding in birds and whether this actually runs as a trait in bird families, or not. Steve Have a nice fall > Paul > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com > --Apple-Mail-1-525265478 Content-Transfer-Encoding: 7bit Content-Type: text/enriched; charset=US-ASCII On 20-Oct-06, at 1:35 PM, Paul MacDonald wrote: <excerpt>... Hi Dave and All In-breeding or line-breeding will produce the modifications that you suggest. </excerpt> Hi Paul, you seem to be thinking of within-species variation -- my point was about the emergence of new species (of mimetic flies) during evolution. The definition of what's a species is difficult these days, but a common theme is that different species are those 'varieties' that can't interbreed and are therefore reproductively isolated (not a cast-iron definition, though, many exceptions) . The species concept these days is tricky, need to get expert advice on what the best idea is (I don't think that there's full agreement on this, and maybe it doesn't matter scientifically). <excerpt>One of the general rules of nature is the more closely related the parents - the more variation in the offspring. Some good some not so good. </excerpt> <excerpt><color><param>000A,0000,0128</param> I don't know where this idea comes from, but if it were true, it wouldn't be possible to isolate different strains of cattle, dogs, pigeons, geese, etc by selective breeding -- the opposite would be true. Darwin became an expert on this, and used the example of short-term selective animal breeding (to produce extreme true-breeding 'varieties') as a model argument for what he proposed had happened during long-term natural evolution. The examples from in-breeding are not usually new species, as the various dogs etc can still often interbreed successfully. </color></excerpt> <excerpt>The great majority of the food consumed daily in the world has been produced by taking this rule into account. </excerpt> <excerpt>I suspose you could make the point that the pairing with insects is chance! </excerpt>Maybe this last idea is correct, and it would also be for some birds -- those with males that sing and otherwise advertise themselves and their territories to prospective females. Other birds apparently pair for life, however, so it is not always a rule. I flinch at straying into this birdy territory myself -- you'd need to get Ian McLaren or someone on this, on the extent of lifetime pair-bonding in birds and whether this actually runs as a trait in bird families, or not. Steve Have a nice fall <excerpt>Paul __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com </excerpt> --Apple-Mail-1-525265478--
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