Homology and Relatedness

Harry Erwin (herwin@gmu.edu)
Wed, 28 Jun 1995 06:57:23 -0400

The following disappeared into the /dev/net/null.

In "Summary" (in Primates and their Relatives in Phylogenetic Perspective,
Ross D. E. MacPhee, ed., Plenum Press, New York, 1993), Ross MacPhee
quotes M. Cartmill: "biological theory warrants no deductive inferences
from the relationships of organisms to the distribution of various
attributes among those organisms; and therefore _distributions_of_
(Cartmill, 1981, "Hypothesis testing and phylogenetic reconstruction,"
Zeitschr. Zool. Syst. Evolut.-forsch. 21:21-36). MacPhee continues by
noting that there are no evolutionary laws from which the distribution of
characters can be deduced.

I'm afraid I must differ. The phenomenon of 'premature convergence,'
discovered independently by a number of genetic algorithm researchers
around 1987-1992 provides an evolutionary law that can be used to predict
the distribution of characters. Premature convergence is a phenomenon seen
when a new, selectively advantageous characteristic emerges in a
population. As it converges exponentially to fixation, it will carry along
with it those characteristics that happen to be accidentally associated
with it at the time and place of emergence. This implies that unless a
population has been well-adapted to its environment for a long time
(>>relaxation time for the genome), the population will possess
_selectively neutral_ monomorphic characters that distinguish it from
other populations. These characters will have been inherited from the
ancestral population, will be shared (homologous) with other
closely-related populations, and can be used to falsify hypotheses of
relationship. The key point is that these characteristics have to have
been selectively neutral since before the evolutionary event that brought
them accidently to fixation.


Harry Erwin
Internet: herwin@gmu.edu
Home Page: http://osf1.gmu.edu/~herwin (try again if necessary)
PhD student in comp neurosci: "Glitches happen" & "Meaning is emotional"