When did the fascination with phylogenetic trees begin?

James Francis Lyons-Weiler weiler at ERS.UNR.EDU
Tue Feb 25 08:05:09 CST 1997

On Tue, 25 Feb 1997, warren frank lamboy wrote:

> To Taxacomers:  I am trying to determine how and when the great emphasis on
> constructing (implicitly or explicitly) evolutionary or phylogenetic trees
> of (plant) taxa came about.  One might expect that it would have begun soon
> after Darwin's publication of "On the Origin of Species . . . " in

In fact, Darwin's work included tree-thinking.  It is clear for example,
from his diagrams (e.g., p 167 in Origins) that his thinking included
tree-thinking.  Moreover, his thoughts apparently allowed for

Haeckel (1866) proposed a phylogeny and classification of life, including

(_Monophyletischer Stammbaum der Organismen_)

The idea, so far as I can tell, that some trees might provide better
estimates than others was more than an after-birth; consider, for example,
a passage from Clements (the same F. Clements of succession infamy) on
"Phylogenetic Charts":

        "Since one of the main objects of the present monograph
        is to present a classification based upon phylogeny, it
        has been thought desirable to give a graphic presentation
        of the relationships between the numerous forms.  A number
        of charts have been prepared to accompany the discussions
        of phylogeny.  _There is no thought to finality in the
        diagrams as here presented.  There purpose is to express
        the results of evolution as now understood, and it is
        fully appreciated that the evidence of certain phyletic
        lines is still far from conclusive."

Following this, the dicussion includes more caveats regarding certainty, a
consideration of phylogenetic charts as expressions of degrees of
relationship, and the difficulties of accurately defining the direction
(polarity) of evolution.  The thinking at the time clearly allowed for
primitive and advanced forms (lower, higher).

Then a paragraph that seems to predict current phylogenetic systematics,
including phylogenetic taxonomy, the general value of phylogenetic trees
(charts), and mapping character state changes on the charts.

        "Even though the exact lines of evolution can not alwayys be
        indicated with certainty, the bringing together of related forms
        into increasingly larger and larger natural groups should be
        undertaken whenever possible, for this is the basis of taxonomy.
        The graphic reprsentation of such relationships, if carried to
        all groups of plants, would doubtless be of much value to
        geneticists, breeders, and others who need to know the related
        forms of plants with which they are working.  Furthermore,
        if properly prepared, phylogenetic charts may replace, to some
        extent at least, the analytical keys now in vogue.  Largely
        with this use in mind, the differentiating characters as will as
        the names of the groups themselves have been inserted on the
        charts here presented".

It is easy to argue that this pair had the concept of synapomorphy in
mind; i.e., if the direction of evolution could be known, it requires no
gigantic leap of inference to suppose the the "differentiating
characters" they refer to are equivalent to Hennig's synapomorphy...


 The phylogenetic method in taxonomy; the North American
species of Artemisia, Chrysothamnus, and Atriplex, by Harvey M. Hall and
Frederic E. Clements. 1923. Washington, The Carnegie institution of
Washington, 1923. Carnegie Institution of Washington publication; 326.

Bessey's chart from 1915 was predated by Haeckel; The Hall and
Clements passage indicates that even by 1923 the gospel of
tree-thinking was about, but was perhaps not generally appreciated.
> So when did the current fascination with evolutionary trees and phylogenies
> arise?  I am baffled by this.  My sense is that it has crept up on us
> little by little over the years, and that it did not really 'begin' at any
> particular point in time.  Did the "New Systematics" of J. Huxley, ed.,
> (1940) and/or the "Evolutionary Synthesis" of the 1940's have any effect?
> Did the tree construction boom really get rolling with Numerical Taxonomy
> of the 1960's, and then, and with the advent of cheap computing time, gain
> additional momentum with the development of cladistic methods and all the
> different types of data that can be "input" into those procedures?  Have
> there been any review articles published on the history of the use of
> evolutionary
> trees and phylogenies?  Thanks for any light you

Mark Ridley's book The reformation of cladism has a decent historical
accounting.  Numerical taxonomy and cladism emerged somewhat in tandem
(see Sneath (1995) Syst Biol 44:281-298) for one accounting).

It is fascinating to me that the main problems that persist in present-day
phylogenetic systematics (accuracy, justified polarity assessment, and
application (i.e., comparative method; character mapping) were recognized
in 1923, by Clements of all people.  I also find it fascinating
that Hall and Clements referred to phylogeny as a process (see
above), and did not conflate the lines on the page  (an
evolutionary tree) with a phylogeny (the truth which is sought).

James Lyons-Weiler
University of Nevada, Reno

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