Friday, 22 June 2018

Positive and negative feedback in evolution

Evolutionary theory has its own historical tradition and has developed its own terminology. However I sometime wonder what it would look like if it was (re)discovered by 21st century engineers. This post consists of some musings on that theme.

If evolution was (re)discovered by modern engineers, one concept that would probably be more extensively employed is "feedback". Feedback is the name for systems whose outputs are "fed back" into their inputs. Of course, this happens all the time in biological systems in various ways. The term "homeostasis" is often used in biology, and this is just a type of negative feedback. In particular, gene pools typically have their outputs fed back into them. From this perspective, favorable selection is a type of positive feedback acting on trait frequences (or gene frequencies), while unfavorable selection is a generally similar type of negative feedback.

Framing natural selection in terms of positive and negative feedback seems useful to me. The "feedback" terminology seems more general, and that is often a virtue in science.

Another piece of biological terminology that might be framed differently by engineers is "fitness". "Fitness" is an overloaded term, but "inclusive fitness" could plausibly be replaced by "utility" - the more general term from economics which refers to "that which is optimized". The common term "expected fitness" would become "expected utility" - another standard concept. One slight difference is that "fitness" is usually though of as being "relative", while "utility" is usually thought of as being absolute. It's a minor issue because there are usually many players and so the distinction doesn't make much difference. Anyway, IMO, the way to resolve this is to say that economics has got this wrong.

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