Neandertal development and the phylotypic stage

There were some interesting articles published this week. PNAS has a paper from Smith et al. on Neandertal development. Seems they matured faster than modern Homo sapiens. Yet more evidence that we're not the same species.

Smith et al. 2010. Dental evidence for ontogenetic differences between modern humans and Neanderthals. PNAS 107:20923-20928.

Over in Nature, there are two papers relevant to the old "phylotypic stage" argument. Though creationists generally conflate anything related to embryology and evolution as simply "recapitulation," historically there have been a number of distinct arguments that were used to relate evolution and embryology. A good number of them pre-date Origin. One such argument (or observation, if you will) was based on von Baer's observation that vertebrates at a particular stage of development were very similar. This stage was dubbed the "phylotypic stage" by German evolutionist (and lover of neologisms) Ernst Haeckel. More recently, the phylotypic stage has been observed in other phyla than just the chordates.

The two new articles by Kalinka et al. and Domazet-Lošo & Tautz look at phylogenetically conserved gene expression during development of Drosophila and zebra fish respectively. They found that genes expressed in early and late development tend to be more divergent than those expressed at the "phylotypic stage." In other words, the most conserved genes seem to be preferentially expressed at the development stage when the embryos are most similar. That's a remarkable correlation.

Kalinka et al. 2010. Gene expression divergence recapitulates the developmental hourglass model. Nature 468:811-814.

Domazet-Lošo & Tautz. 2010. A phylogenetically based transcriptome age index mirrors ontogenetic divergence patterns. Nature 468:815-818.

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