Re: [asa] Guided evolution mechanism?

>Christine Smith wrote:
>>Can someone provide some more background on "control theory"?
>>
>Christine:
>
>Look at
>http://en.wikipedia.org/wiki/Control_theory
>for a good description of Control theory is.
>
>From wiki, a typical control application looks like:
><http://en.wikipedia.org/wiki/Image:Feedback_loop_with_descriptions.svg>
><http://en.wikipedia.org/wiki/Image:Feedback_loop_with_descriptions.svg>
>The concept of the feedback loop to control the dynamic behaviour of
>the system: this is negative feedback, because the sensed value is
>subtracted from the desired value to create the error signal which
>is amplified by the controller.
>...
>
>
>Take the case of a car cruise control. The Reference is the desired
>speed. The controller interacts with the car system by changing the
>position of the throtle. The speedometer (logically) is the sensor
>and feeds the actual speed back to the Measured error point where it
>is subtracted from the desired speed and feed into the controller.
>Of course the actual system is likely to be more complex than I have
>described in that the difference between the reference speed and the
>actual speed is likely allowed to reach some small difference prior
>to actually increasing/decreasing the throttle. Otherwise one would
>likely get surging where the fuel going to the engine was constantly
>being changed.
>The study of the behaviors of such systems is called control theory
>and is quite complex in many cases as instabilities can tend towards
>oscillations or vary large values.
>
>Feedback is a very powerful mechanism and I tend to think of the
>Variation/Natural Selection mechanism in those terms. Dave W

Positive and negative feedback are well established and central
concepts in regulation of metabolism and gene expression. They were
of course imported to biochemistry from engineering. My scientific
"grandfather," (my dissertation advisor's dissertation advisor)
Daniel Atkinson, was an engineer who became an enzymologist and
participated in the early development of these concepts in
biochemistry.

Of course there is no implication of consciousness by these
mechanisms - the cruise control on your car is not conscious.

The new work described seems to be an application of these ideas not
in physiology but directly in evolution itself, and I couldn't tell
from the news article exactly what is being proposed. Since the
research is being published in a physics journal, I'm not sure I will
be able to comprehend it even if I look at it, but there will
certainly be informative treatments in Science and Nature in a week
or two.

Preston G.

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Received on Wed Nov 12 14:24:18 2008