 Finally, the evolution of biological individuality continues to be a lively topic (Okasha 2011; Calcott &amp; Sterelny 2011; Bourrat 2015; Clarke 2016b; O’Malley &amp; Powell 2016; Queller &amp; Strassmann 2016; Herron 2017; Sterner 2017). The starting point here is the idea that the history of life is the history of the construction of more complicated biological individuals from simpler individuals, with natural selection (operating at one or more levels) facilitating the transitions between these individuals. Underlying these ideas is the assumption that many or all biological individuals are hierarchically organized: earlier individuals provide the material basis for later individuals. For example, prokaryotes, which are single-celled organisms without a nucleus, form the material basis for single-celled eukaryotes, which do have a nucleus; in turn, single-celled eukaryotes serve as the material basis for multicellular eukaryotes.