Nice commentary on a study of the evolution of language from John Wilkins at Evolving Thoughts..
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And Kallio is right: there are no fixed decay rates, or molecular clocks. In fact there aren’t such things in biology either. Molecular rates of change are not universal or constant, and inferences based upon them are at best hypotheses based hypotheses. Phylogeny is a tool, but what does it show?
In my last post I noted that phylogenetic reconstructions show only relatedness. What they do not show, without some extensive ancillary assumptions, is how that relatedness arose. The increasing awareness of lateral transfer and hybridisation between taxonomic lineages indicates that there can be some complex histories even if the taxonomic relationships are treelike. NB: to head off the most common error about this, lateral transfer does not undercut the treelike structure either of evolution or phylogenetic diagrams. It makes them harder to detect, but a certain admixture can be accommodated in a standard tree classification. Of course, if the rate of lateral transfer approaches equality, then you no longer have separate taxa, and so that would count as a single lineage that temporarily separated like populations either side of a geographic barrier that are brought back into contact.
In the case of sociocultural evolution, such lateral transfer is often assumed to be rife. This is thought by some to undercut the importance of phylogenetic method in cultural contexts. I want to argue that it doesn’t, but that the inferences from phylogeny are not so obviously historical as some seem to think.
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phylogenetics can apply nicely in contexts where traditions (or species) are well behaved. If they are relatively stable (i.e., not so transitory that they cannot be tracked), and distinct (i.e., the rate of lateral transfer is not so high they aren’t recognisable traditions any more), then you can do a phylogenetic analysis of them. It’s not so surprising really. Willi Hennig, whose Phylogenetic Systematics (1966) set up modern phylogenetics, took some of his ideas out of the discipline of stemmatics, or tracking manuscripts by differences in transcription (Platnick and Cameron 1977, Atkinson and Gray 2005)
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