Re: If you believe any of your theories, you've turned science into a religion.
- From: pausch@xxxxxxx (Paul Schlyter)
- Date: Sat, 03 Dec 2005 10:13:02 GMT
In article <dmrhl1$5lo$1@xxxxxxxxxxxxxxxx>, Brian Tung <brian@xxxxxxx> wrote:
>us2 wrote:
>
>> If heredity breeds true, then forget Macro-evolution (no accidental
>> mutations)
>
>You misunderstand macro-evolution. But you've probably been given an
>improper explanation, by people who are trying to further the ID agenda.
>
>All mutations are accidental. They might be caused by cosmic rays, or
>by a copying error by an enzyme, or *something*. But what is not
>accidental is how those errors affect the population in the succeeding
>generations. Most errors make the descendants less likely to survive to
>reproduce, but a few make it more likely. Those organisms eventually
>leave more descendants, and if the modification is sufficiently
>advantageous, they eventually dominate the population.
It's worth pointing out here that random mutations aren't the only triggers
of evolution. Another mechanism, which is more important particularly
among more complex organisations, is sexual reproduction, where the offspring
has a set of genes different from either of its parents. This is quite
different from asexual reproduction, where the offspring is a genetic clone
of its parent - it might even be impossible to say which is the "offspring"
and which is the "parent", in cases like an amoeba splitting in two.
Relying on sexual reproduction rather than random mutations to change the
set of genes has one big advantage: the success rate is way much larger.
That's why most organism propagate sexually rather than asexually. Of
course natural selection then works in either case.
Some species can even switch between sexual and asexual reproduction:
the dandelion is one such species. When the environment remains fairly
constant, it reproduces mostly asexually, but if there's a change in
the environment, it switches to sexual reproduction.
In artificial evolution (i.e. when humans purposely breed some animal
species) the breeded relies only on controlled sexual reproduction to
change the set of genes to what's considered reliable. The farmer who
would expose his cattle to farily large doses of radioactivity hoping
that it would produce some successful mutation is extremely likely
to become disappointed. Otoh the farmer wants results within a generation
or a few - he can't wait a million years or so. Nevertheless, controlled
breeding is also a kind of evolution -- and there we can actually start
to talk about "intelligent design", where we humans are the designers.
--
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e-mail: pausch at stockholm dot bostream dot se
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