Upcoming talk
Robert
Skipper
Institute of Advanced Study, University of Durham,
and Dept. of Philosophy, University of Cincinnati
"What's Fundamental about Fisher's
Fundamental Theorem of Natural Selection?"
14 May Monday
5pm in room G3,
22 Gordon Square
Abstract
The locus classicus on the origins of theoretical
population genetics is R. A. Fisher's 1930, The Genetical Theory of Natural
Selection. The center piece of Fisher's natural selection theory developed there
is his Fundamental Theorem of Natural Selection. Fisher's 1930 statement of the
theorem is that "the rate of increase in fitness of any organism at any time is
equal to its genetic variance in fitness at that time." Fisher's theorem is
notoriously abstruse as stated. And so the immediate questions to ask are "What
does the theorem say?" and "What's fundamental about it?"
Warren Ewens'
1989 rediscovery of George Price's 1972 derivation and interpretation of the
theorem resolved to the satisfaction of most everyone the first question. The
theorem states, "the rate of increase in the mean fitness of any population at
any time ascribable to natural selection acting through changes in gene
frequencies is exactly equal to its genic variance in fitness at that time"
(following A. W. F. Edwards).
There are a number of alternative
assessments of the "fundamentality" of Fisher's theorem. Probably, the
Price-Ewens assessment of theorem is the most well known: According to Price and
Ewens, Fisher's theorem is broad in scope, but it's otherwise not so fundamental
because it is, as they say, incomplete, capturing only a partial change in mean
fitness. This is an assessment of what one might call the "biological depth" of
the theorem. But others have argued that Fisher's theorem is fundamental in its
influences (Edwards) and its role in Fisher's argument for neo-Darwinism (Anya
Plutynski). The aim of this talk is to sort out the alternative assessments of
the theorem with the aim of arriving at the correct one. My view is that the
right assessment is to be made on the basis of the theorem's biological depth. I
argue, in the company of Edwards and Alan Grafen and contra Price and Ewens that
Fisher's statement about the partial change is indeed the biologically deep
statement Fisher thought it was.