Dienekes, the pseudonym of an unknown anthropology blog author, publishes today PCA plots of human populations against Denisovans, Neanderthals and Chimpanzees. (link)
In the first plot, humans cluster tightly, reflecting their remarkable homogeneity.
In Dienekes' second plot, he claims to "zoom in" on the little blob of humans on the first plot. I have good eyesight and cannot quite see how the "zoomin" of the second plot is taken directly from the "blob" at the center of the first plot.
It's true that the little cluster of humans in the first plot is somewhat multimodal. Those who have been following developments in genetic anthropology won't be surprised that Africans and Non-Africans cluster closely, but separately. Clearly, there are many early humans who didn't make it through events of the last 100,000 years. Additionally, there is evidence of separate low level (<4%) admixture events for Africans and Non-Africans that may account for some of the multimodality. The wiki page on archaic human admixture touches on the relevant references.
Still, I can't quite make out how the two graphs match. The first graph shows that the human cluster is skewed right toward Chimpanzees. In the "zoomed in" plot, Africans seem to be skewed downward and away from Chimpanzees, Denisovans and Neandertals. Yet, the optical illusion is enough for some commentators to think they are observing a "shift toward chimps" of some populations. It would be easy to laugh off Dienekes' amateurish analysis as harmless. However, his blog is widely read. Many of his readers are curious, but not equipped with the analytical skills to see the mistakes in his experiments. Sadly, experts in the field of genetics rarely speak out about Dienekes' biased publications.
While we're on the topic of bias, there's another area of genetic anthropology where I can see a less deliberate form of bias. That's in the area of sampling. More than one sixth of the world's population are African or of recent African origin (within the last five hundred years). However, in the world of genetic anthropology, you would never know it. Study after study show a diverse choice of Non-African samples invariably referenced against a tiny group of African samples. Perhaps this is because the African samples are not widely available. However, it is hard to see how we are going to be able to understand our Out-of-Africa origins when so little effort has been expended to obtain a diverse set of African samples. We will also not learn about migrations within Africa. Additionally, if Africans are going to benefit from genetic research, more attention needs to be paid to Africans as a diverse people, not a tiny reference blob of "Yorubans".
I'm sure that as more African DNA becomes available, genetic anthropology studies will make an effort to include a wider array of African samples. Hopefully, some of those genetic research dollars will make their way toward treating the diseases that Africans suffer from.
As to Dienekes, a more ethically based genetics blogosphere would have more researchers and the curious realize that the message he is presenting is often distorted and potentially clouded with an uninformed view of many Sub-Saharan African groups.