Re: Micro and Macro Evolution ?

Daniel T. wrote:

> In article <nfmVe.371$Op3.326@xxxxxxxxxxxxxxxxxxxxxxxxxx>,
> John Harshman <jharshman.diespamdie@xxxxxxxxxxx> wrote:
>
>
>>Brett Aubrey wrote:
>>
>>
>>>"Tristan Miller" <psychonaut@xxxxxxxxxxxxxxxxx> wrote in message
>>>news:1301661.j3VuWU9u4J@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>>>
>>>
>>>>Greetings.
>>>>In article <S8kVe.39$7E5.16@xxxxxxxxxxxxxxxxxxxxxx>, boikat wrote:
>>>>
>>>>
>>>>>"Toadface" <mr_toadface@xxxxxxxxxxx> wrote in message
>>>>>news:1126549832.453409.87600@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>>>>>
>>>>>
>>>>>>The Theory of Evolution can be divided into two parts,
>>>>>>micro-evolution and macro-evolution. Micro-evolution
>>>>>>deals with small changes within a species which adapt
>>>>>>that species to be better suited to its environment.
>>>>>>This process is well supported with scientific
>>>>>>evidence and doesn't conflict with a Christian
>>>>>>understanding of reality.
>>>>>>
>>>>>>Macro-evolution claims that through major genetic
>>>>>>mutations
>>>>>
>>>>>That's one possible definition.
>>>>>
>>>>>
>>>>>
>>>>>>one species can evolve into another, so over
>>>>>>a long period of time fish could evolve into insects,
>>>>>
>>>>>No. Fish would not evolve into insects.
>>>>
>>>>Maybe not in the strict taxonomic sense of the word, but is it really
>>>>inconceivable that a species of fish, given enough time and the
>>>>appropriate environmental pressures, could evolve into something so
>>>>resembling an insect as to be indistinguishable from a real insect by a
>>>>layman? If it's tiny and has six legs and an exoskeleton,
>>>
>>>
>>>I think you've hit on a good specific example, but one that goes quite
>>>against your overall suggestion. Fish could more conceivably develop into
>>>small insect-like (i.e. somewhat visually similar) creatures with four legs
>>>and an endoskeleton than what you're suggesting. The extra limb pair and
>>>(especially, I think) the exoskeleton would be highly improbable.
>>
>>It could happen, though. There is nothing intrinsic in evolution that
>>prevents it from being fully reversible. So we could imagine a path from
>>any given species, backwards in time to a common ancestor, then forward
>>again to any other species. Or we could imagine something vaguely like
>>that, but not following exactly the same course, happening too. You
>>don't want to hold your breath, but it also clearly did happen once for
>>any such pair, provided you accept the idea of time-reversibility.
>
>
> We could *imagine* such a trek, but would it be possible? A particular
> feature is produce due to a particular evolutionary pressure, that
> doesn't automatically mean that there is a "counter pressure" that would
> force a reversal of the feature... I suspect that evolution is largely
> one-way.

Sure it is. But that's only because of probabilities. In the same way
that no physical law other than probability gives time a directional
arrow -- spilled water doesn't re-collect in the cup, but there is
nothing in physics that forbids such a thing happening -- any single
evolutionary event is reversible, but expecting the same sequence to
occur in reverse is absurdly improbable. Dollo's law, if you like.

But given the right sequence of selective environments and mutations, it
could happen.

.

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