I present for you an example of inferring a bit too much from inappropriate data. This isn’t quite the same as making claims about demography based on 100 nucleotides from 6 individuals. But it’s not much better given that this example is from a study of extant organisms. Abstracts to clarify what the hell I’m talking about are below the fold.
Exhibit A comes from a paper on human demography and mitochondrial DNA. Here is the abstract:
Human mitochondrial DNA (mtDNA) studies have entered a new phase since the blossoming of complete genome analyses. Sequencing complete mtDNAs is more expensive and more labour intensive than restriction analysis or simply sequencing the control region of the molecule. But the efforts are paying off, as the phylogenetic resolution of the mtDNA tree has been greatly improved, and, in turn, phylogeographic interpretations can be given correspondingly greater precision in terms of the timing and direction of human dispersals. Therefore, despite mtDNA being only a fraction of our total genome, the deciphering of its evolution is profoundly changing our perception about how modern humans spread across our planet. Here we illustrate the phylogeographic approach with two case studies: the initial dispersal out of Africa, and the colonization of Europe.
Cool stuff, eh? That mtDNA is really neat. Or not, as Exhibit B points out:
Within-species genetic diversity is thought to reflect population size, history, ecology, and ability to adapt. Using a comprehensive collection of polymorphism data sets covering ~3000 animal species, we show that the widely used mitochondrial DNA (mtDNA) marker does not reflect species abundance or ecology: mtDNA diversity is not higher in invertebrates than in vertebrates, in marine than in terrestrial species, or in small than in large organisms. Nuclear loci, in contrast, fit these intuitive expectations. The unexpected mitochondrial diversity distribution is explained by recurrent adaptive evolution, challenging the neutral theory of molecular evolution and questioning the relevance of mtDNA in biodiversity and conservation studies.
So much for the power of mtDNA.