Limited codiversification of the gut microbiota with humans

A recent study by Suzuki & Fitzstevens et al (1) argued that dozens of species of gut bacteria have codiversified with modern human populations. Further analysis of this data reveals that the correlations between human and microbial phylogenies are substantially weaker than unlinked human chromosomes, and that similar correlations can arise through geographic structure alone. This suggests that traditional codiversification has been a limited phenomenon within humans.