 Interestingly, however, much of the recent progress in understanding the origin of metazoans depends on findings about close unicellular relatives of animals, particularly choanoflagellates as well as slightly more distant protists called filastereans and ichthyosporeans. Genomic and experimental analyses of these organisms have allowed evolutionary inferences about genes and features once thought to be exclusively metazoan. It turns out that the genetic bases of many characteristics once thought of as unique to metazoan evolution are also found in closely related unicellular organisms. Adhesion capacities, developmental signalling pathways, and “metazoan-specific” gene regulatory factors—all features not normally thought of as properties of unicellular organisms—long pre-existed metazoan origins (King et al. 2008; Sebé-Pedrós et al. 2017). Moreover, many of these extant unicellular relatives of metazoans turn into different cell types as they transition to different stages in their life cycles. Some stages form sophisticated multicellular arrangements, which may sometimes be driven by interactions with bacteria (Alegado et al. 2012; Woznica et al. 2016). The moral of this story is thus becoming familiar: even the evolutionary divergence of the organisms considered the most complex (because of giving rise to ourselves) needs a microbial perspective.