Previous work has shown that the oral microbial community is relatively stable compared to communities at other body sites. However, these studies involved samples taken over a period of just 15 months and did not investigate the potential role of host genotype. Stahringer et al. recently used 454 pyrosequencing of 16S rRNA genes to study the variability in the microbiome of 264 saliva samples derived from 107 individuals sampled over a 10-year period. This study included samples from 27 monozygotic twin pairs and 18 dizygotic twin pairs. The authors found that in contrast to the gut or the skin — sites where individuals share a core microbiome at the phylum level — the saliva contains a core microbiome at the genus level, with eight genera present in >95% of samples. The oral communities of monozygotic twins were not statistically more similar than those of dizygotic twins, and both types of twins were more similar to each other at early time points than at later time points, as the twins aged and became less likely to cohabit.