The book’s biological argument depends on a current of evolutionary theory that spent decades at the margins of mainstream biology. Lynn Margulis published “On the Origin of Mitosing Cells” in the Journal of Theoretical Biology in 1967, after the paper had been rejected by roughly 15 previous journals. Her thesis was that the mitochondria and chloroplasts inside eukaryotic cells (cells with nuclei, the kind that compose plants, animals, and fungi) descend from once-free-living bacteria absorbed by larger cells through symbiotic merger rather than gradual mutation. The hypothesis met sustained resistance from neo-Darwinian orthodoxy through the 1970s, gained acceptance for organelle origins in the 1980s as molecular evidence accumulated, and underwrote Margulis’s broader argument in Symbiotic Planet (1999) that “the intimacy of strangers” drives major evolutionary development (60). From this perspective, biological change is driven through the inherent connections between all things rather than through singular, isolated strings of evolution.

Two later developments made Haraway’s use of this lineage possible. The term “holobiont” (host plus its symbiotic microorganisms) entered the literature in David Mindell’s 1992 paper on phylogenetic consequences of symbioses; was extended to coral-associated bacteria by marine biologist Forest Rohwer in 2002; and was consolidated as a framework by developmental biologist Scott F. Gilbert, biologist-historian Jan Sapp, and immunologist Alfred I. Tauber in their 2012 Quarterly Review of Biology paper “A Symbiotic View of Life: We Have Never Been Individuals.” Sympoiesis was coined separately by Canadian environmental studies graduate student M. Beth Dempster in her 1998 University of Waterloo master’s thesis, where she distinguished collectively producing systems lacking self-defined boundaries from autopoietic (self-producing, boundaried) systems. Haraway’s Chapter 3 draws all these threads together with developmental work by Margaret McFall-Ngai and Nicole King on symbiosis and animal multicellularity. The biology contributes to one of the book’s conclusions that if individuals never were autopoietic units, then the political fiction of the individualistic human becomes harder to defend.