In contrast to the HMP, the Global Gut project [28] set out to characterize microbial diversity at spatial and temporal scales. To do this, the researchers collected samples from three distinct populations (US citizens, Malawians, and Venezuelan Amerindians), the latter two of which are culturally distinct from western populations. Within each population, samples were collected cross-sectionally over an age gradient. Notably, the two non-western populations appear to be completely distinct from the western individuals, suggesting the limited population size and emphasis of the HMP grossly underestimate the variation in community structure across the human race. However, the populations do intersect on samples collected from infants, suggesting that it is potentially lifestyle, diet, or environmental choices that shape our microbiomes as we age (including interaction with our genetic predisposition [25]). Although the sequence data are readily available for reuse, the distribution of many of the study variables is not approved, limiting the long-term usefulness of the samples. (It should be noted that the Global Gut did not intend to be a reference for microbiome research, but the populations represented in the
