Claim CB821:
Modern versions of the phylogenetic "tree of life" are based on DNA and
other molecular analyses. Inconsistent and bizarre results based on
different molecular analyses "have now plunged molecular phylogeny into a
crisis" (Wells 2000, 51).
Source:
Wells, Jonathan, 2000. Icons of Evolution, Washington DC: Regnery
Publishing Inc., pp. 49-54.
Response:
- A few inconsistencies are to be expected, because biology is messy.
Genes need not always evolve at the same rate in different lineages.
Some molecules may converge as a result of selection or chance.
Horizontal gene transfer occasionally occurs. Such exceptions will be
rare, but there will be a few of them among the vast body of consistent
results. Most inconsistencies can be resolved by basing an analysis on
multiple genes (Rokas et al. 2003).
Other inconsistencies will occur as a result of methodological and
interpretive mistakes (Sanderson and Shaffer 2002). Phylogenetic
analysis is a very complex subject; people who do not understand it
well cannot be expected to get it right all the time. Publishing one's
methods and results allows others to catch mistakes.
Creationists looking for inconsistencies can dishonestly pick out the
few there are while disregarding the vast body of consistent results
and the reasons for the inconsistencies.
- Some claimed inconsistencies are really consistent. Wells, for
example, cited a study which "placed sea urchins among the chordates"
(Wells 2000, 51), but sea urchins (and echinoderms in general) do group
with chordates as a sister group. Wells (2000, 51) also cited another
study that "put cows closer to whales than to horses," which is also
entirely consistent with genetic, morphological, and fossil evidence.
Links:
Tamzek, Nic, 2002. Icon of obfuscation.
http://www.talkorigins.org/faqs/wells/iconob.html#Treeoflife
References:
- Rokas, A., B. L. Williams, N. King and S. B. Carroll, 2003. Genome-scale
approaches to resolving incongruence in molecular phylogenies.
Nature 425: 798-804.
- Sanderson, Michael J. and H. Bradley Shaffer, 2002. Troubleshooting
molecular phylogenetic analyses. Annual Review of Ecology and
Systematics 33: 49-72.
- Wells, 2000. (see above)
created 2003-8-7, modified 2003-10-22
