Re: Bacterial Evolution Question


Seanpit wrote:
Dave wrote:
Is the evolution of antibiotic bacteria micro- or macro-evolution?

I would think that it is macro- because the species has changed.

The terms "micro-" and "macro-evolution" are confusing because of this
very thing. The demarcation of genus and species is too subjective. It

Only to those who deny common descent.

is bit easier, though, to talk about different types of functional
systems. Can more and more functionally complex systems evolve? If so,

Yes.

how much time, on average, does it take for functional systems at a
particular level of complexity to evolve as compared to systems at a
higher or lower level of minimum size and specificity requirements?

As it turns out, antibiotic resistance, when it does evolve de novo, is
almost always the result of a block of a pre-established system of
function, such as the interaction of the antibiotic with a target
sequence.

Joshua Lederberg told me to tell you, "You are full of doo-doo".

Mutations that can give rise to interference between the
antibiotic-target interaction are relatively common and can be realized
in relatively short order. That is why bacterial resistance can evolve
to all kinds of antibiotics very quickly - because such evolution does
not require the formation of a novel function, only the breakdown of a
pre-established function/interaction. And, as even children
understand, it is much easier to break Humpty Dumpty than to put him
back together again - or even in the first place.

Well, in fact this is not the case at all. Bacterial resistance to
antibiotics, like all things of this nature, exhibits quite a bit of
variety. Some beasties seem to develop resistance more readily than
others, some don't seem to evolve resistance much at all, and almost
all of them develop resistance to different antibiotics at different
rates.

But why is this? Why is it easier to break something than to create it?
Because, there are so many different ways to break something or
interfere with a functional system relative to the very few ways there
are to put it together in such a way that it "works" properly.

Such forms of "higher-level" evolution are much harder to demonstrate.
Evolution that is not based on the disruption or loss of some other
pre-established function just doesn't happen as easily. In fact, as one
moves up the ladder of functional complexity, evolutionary powers of
creativity simply stall out in a rather dramatic manner - exponentially
in fact.

Exactly. Look, for example, at the total lack of functional jaws in
vertebrates, or the stunning dearth of middle ear bones in both birds
and mammals. Uhhhh...

Review the literature and you will find that there simply are
no observed laboratory examples of novel functions evolving that
require more than a few hundred fairly specified amino acid residues at
minimum.

You don't get out much, do you? Looked at the petals of a flower
lately?

[Typical bad statistical argument snipped]

Sean Pitman
www.DetectingDesign.com

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