Baboons inform on human gut microbiota Commensal bacteria are found throughout an organism, but it is not known whether associations between gut bacteria and their host are heritable. Grieneisen et al. examined changes in the microbiomes of 585 wild baboons from fecal samples collected over 14 years (see the Perspective by Cortes-Ortiz and Amato). Almost all microbiome traits tested demonstrated some level of statistically significant heritability. Most heritability values were low but varied over time correlating with the age of the host. Baboons live in an environment similar to that postulated for early humans and have a microbiome similar to that of humans. Thus, this heritability of the microbiome may reflect similar genetic determinants in humans, for which similar datasets are not available. Science , aba5483, this issue p. 181 ; see also abj5287, p. 159