From: lamoran@gpu.utcs.utoronto.ca (L.A. Moran)
Subject: Chris Colby's Evolution FAQ: What is hierarchy?
Organization: UTCS Public Access
Date: Mon, 12 Oct 1992 03:12:23 GMT


I believe that Chris is misusing the word "hierarchy" in his FAQ and that
he is conveying a false notion of "progress". In this posting I will attempt
to demonstrate that current classification schemes are hierarchical in 
the same sense that military ranks are hierarchical but that this is very
different from claims that "evolution is a hierarchical process" or that
"patterns of diversity are hierarchical". I have discussed these points with
Chris and he adheres to the opinion that he expresses in his FAQ.

First of all, let's be clear about the definition of the word "hierarchy".
If you look in your favorite dictionary you will see that hierarchy is
derived from the term for the chief priest in ancient times (Gr. hieros=
sacred; Gr. archein=to rule). A hierarchy is a collection successive officers
of different ranks as in the priesthood (prelate --> bishop --> cardinal -->
pope) or the military (private --> lieutenant --> colonel --> general).

The current classification scheme in biology is derived from that invented
by Carl von Linne (Linnaeus). He organized living organisms into successively
larger groups (species --> orders --> phyla --> kingdoms). "Kingdom" is the
highest level just as "pope" and "general" are the highest levels in the 
priestly and military hierarchies respectively. It is quite correct and
proper to state that biological classification schemes are hierarchical
in organization.

Now, let's see what Chris Colby says in his FAQ.

   "Further strong evidence for macroevolution comes from the fact 
    that suites of traits in biological entities fall into a hierarchical
    pattern...This pattern arises due to lineages splitting
    (speciation), retaining ancestral traits and deriving new traits."

   "This hierarchical pattern of diversity is what one expects to see 
    if species branch into new species and are modified with descent. 
    Here is a diagram to illustrate. Capital letters designate traits --
    these are shown both where they arise and how they are distributed
    in species.

    (diagram deleted)

    A hierarchical pattern can be produced even if the process
    responsible is not hierarchical. For example, microevolution
    leads to heirarchical patterns of genetic diversity even though
    it works at a single level. The question of hierarchical processes 
    in evolution is still being debated."

There is no "hierarchical pattern" in evolution. The fact that humans choose
to create a hierarchical classification system does not mean that one can
describe evolution as hierarchical. The classification scheme refers mostly 
to living species - it is independent of the mechanism that gave rise to the
species that we see today. I think that Chris should be using "branching" to 
describe the pattern of dendrograms. It is much clearer to say that the 
"branching" pattern is what one expects to see in evolution since living
species have evolved from common ancestors.

I also believe that Chris has his hierarchies reversed. He seems to be 
claiming that the species is the highest rank and that the process of
evolution produces a hierarchy over time. When he says that microevolution
leads to a hierarchical pattern of genetic diversity he is making a statement
that sounds very much like claiming "progress" in evolution. He also implies
that there are some scientists who believe in hierarchical processes in 
evolution; Chris, what are these hierarchical processes that you are referring
to?

Here is a partial answer from Chris Colby's FAQ.

     "Some paleontologists believe evolution is a hierarchical process. 
      The theory of punctuated equilibria attempts to infer the process
      of macroevolution from the pattern of species documented in the
      fossil record.

      (description of punctuated equilibrium deleted)

      Some PE proponents envision the theory as a hierarchical theory
      of evolution because they see speciation as analogous to mutation  
      and the replacement of one species by another (which they call
      species selection) as analogous to natural selection. Speciation
      adds new species to the species pool just as mutation adds new 
      alleles to the gene pool. Likewise, they argue that species
      selection favors one species over another just as natural selection
      can favor one allele over another. This is the most controversial
      part of the theory. Many biologists agree with the pattern of
      macroevolution these paleontologists posit, but many disagree with
      the mechanism -- species selection. Critics would argue that species
      selection is not analogous to natural selection and therefore
      evolution is not hierarchical."

I don't understand this description of the ideas of some "PE proponents"
and I don't understand what Chris means by a "hierarchical theory of
evolution". I hope that he will try to explain more claerly.


Laurence A. Moran (Larry)