Some Comments on
M.T. Ghiselin, "Models in Phylogeny," Models
in Paleobiology, T.J.M. Schopf, editor (Freeman, Cooper & Co., San
Francisco, 1972), p. 131.
...it is true that many works on phylogeny do read like imaginative
literature rather than science. A disproportionate segment of the literature seeks to fill
gaps in the data with speculations and nothing more.
W.R. Thompson, Studia Entomologica, vol. 3,
Dec. 1960, p. 498.
...Though the remark may be regarded as provocative, I must say how far
superior the genetic, like the physico-chemical approach to the problems of organic form
and therefore of systematics, is, to the conventional speculative approach in terms of
evolutionary theory. Genetic analysis, like physico-chemical analysis, belongs to the
field of positive science. Evolutionary speculation as it is commonly developed in
relation to morphological and systematic problems is only too often at best merely a
dressing up of comparative anatomy in such a way as to foster the illusion that we know
things we do not know and are never likely to know.
Ledyard Stebbins, "Adaptive Shifts
and Evolutionary Novelty," Studies in the Philosophy of Biology, F.J. Ayala and Theodosius
Dobzhansky, editors (University of California Press, Berkeley, 1974), p. 298.
This postulated sequence of events [in supposed evolution of plants,
editor] is, I admit, highly speculative, and I doubt that firm evidence in favour of it
can ever be acquired. Nevertheless, it is plausible, and shows that the origin of a major
kingdom of organisms can be explained on the basis of adaptive shifts similar to those
that give rise to species and genera.
The problem of the origin of multicellular animals, or Metazoa, is even
more difficult and speculative than any of the other problems connected with the early
evolution of eucaryotes. This is because not only is there a complete lack of fossil
evidence but, in addition, living intermediate forms, which point towards analogous
sequences leading to the origin of multicellular algae and fungi, are completely lacking
with respect to all phyla of Metazoa, with the possible exception of sponges. Even the
question of mono vs polyphyletic origin of Metazoa is by no means settled.