>>> "Mr P.A. Van Heusden" <pvanheus at hgmp.mrc.ac.uk> 10/06/99 10:26AM >>>
On Wed, 6 Oct 1999, Charles Brown wrote:
> Isn't it true that biologists have no direct proof of any specific trait
> of any animals being developed by natural selection ? Is Darwinism
> falsifiable as formulated ?
>
Depends on what you mean by proof. The classic 'proof' - the differently coloured moths that got selected because of the effects of the industrial revolution - has been shown to have been an experimental error. The problem was that the original scientist had put the moths in clearly visible spots, where their colouring - light or dark - blended in / did not blend in with the surroundings. That is not their natural habitat, apparently.
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Charles: I mean empirical proof. Yes, I recall this experiment, but , you know, Darwinism claims to explain the origin of every or many, many species of any type going back to the beginnings of life. There is no way to prove empirically that such a delicate and precise "instrument" as the eye of many species( to give one of Darwin's examples) actually developed by the mechanism of natural selection because critical elements of the empirical evidence are gone.
The other problem is that for many traits and species the experiment would have to go on for millions of years.
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I'm not certain what other work has been done in 'natural selection observable in the time we have been looking for it' - for complex organisms, which evolve comparatively slowly, it isn't surprising that not much has been spotted.
On smaller scales, however, natural selection is clearly demonstrable. In one example, Manfred Eigen took a group of RNA viruses, and put them in a certain solution which is hostile to a particular component of their make-up. After forced evolution (exposure, selecting a sample, more exposure, selecting another sample, etc) the population was composed of a mutation of the virus which responded to the hostility by a modification of its RNA. (Eigen, M in Gene 135 (1993) pp. 37-47).
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Charles: OK , that's good one. Yes, there is untreatable tubercal bacilli developing in Russian prisons and elsewhere today, as you say next..
CB
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Peter: Also, of course, antibiotic resistance in bacteria is clearly a demonstration of natural selection at work (and this trait is used by geneticists for various purposes - leading to interesting interactions of the 'biological' and the 'social').
None of this means that the existence of a trait means that that trait is a 'response' to natural selection.
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Charles: And ,of course, Darwin said he did not hold that natural selection was the only mechanism by which new traits arise.
CB