Systematics and Evolution 149Gordian knots have been cut. The phylogeny of the placental mammals was an unsolved
mystery that was already two centuries old when scientists at the American Museum, such
as Malcolm McKenna, Mike Novacek, Earl Manning, and I, tackled the problem. By the late
1980s, we had solved many aspects of the problem using cladistic analysis (see the papers in
the volumes edited by Benton [1988a, 1988b] and Szalay et al. [1993]), and most studies pub-
lished since then have corroborated our original topology (although there are some slightly
different answers from the molecular world, and the differences are still to be resolved).
Likewise, the deciphering of the phylogeny of life (fig. 5.6) and of the major groups of ani-
mals (fig. 5.7) are great achievements that have resolved over a century of controversy. Today,
hundreds of systematists are at work solving these important problems, trying to test older
hypotheses with new data, and working to resolve the issues even more definitively.
From the vaguely formulated hypotheses of ancestry published only a generation ago,
we are now in a new age of understanding of life’s history (see Dawkins 2004). Where we
once knew very little about its true pattern, we now have multiple lines of evidence that
converge on a common answer and give a robust solution corroborated and tested many dif-
ferent ways that is almost certainly “the truth” (as much as we can use that term in science).
In the chapters that follow, we may find that we are missing evidence from fossils at a certain
interval or from anatomy at another. Contrary to creationists’ claims, there are always addi-
tional lines of evidence that allow us to decipher that phylogenetic problem. We are always
continuing to move forward and find new answers, but we have already learned more in
the past two decades than we did in all previous centuries. We no longer have to use the
guesswork that creationists criticize because the tree of life is now as well known as almost
any other fact of nature.
The great molecular biologist Emile Zuckerkandl and the Nobel-Prize-winning chemist
Linus Pauling said it best over 50 years ago:
It will be determined to what extent the phylogenetic tree, as derived from molecular
data in complete independence from the results of organismal biology, coincides with
the phylogenetic tree constructed on the basis of organismal biology. If the two phylo-
genetic trees are mostly in agreement with respect to the topology of branching, the best
available single proof of the reality of macro-evolution would be furnished. Indeed,
only the theory of evolution, combined with the realization that events at any supra-
molecular level are consistent with molecular events, could reasonably account for such
a congruence between lines of evidence obtained independently, namely amino acid
sequences of homologous polypeptide chains on the one hand, and the finds of organ-
ismal taxonomy and paleontology on the other hand. Besides offering an intellectual
satisfaction to some, the advertising of such evidence would of course amount to beat-
ing a dead horse. Some beating of dead horses may be ethical, when here and there they
display unexpected twitches that look like life. (Zuckerkandl and Pauling 1965:101)For Further Reading
Adoutte, A., G. Balavoine, N. Lartillot, O. Lespinet, B. Prudhomme, and R. de Rosa. 2000. The new
animal phylogeny: Reliability and implications. Proceedings of the National Academy of Sciences
USA 97:4453–4456.