Extraterrestrial Extrapolations of Earthly Organismality

It has long been known that the microbial component of terrestrial ecosystems provides the capacity for nutrient and elemental cycling and other key ecosystem services. Advances in DNA sequencing technology and analytical capacity continue to reveal novel insights into the structure and dynamics of these microbial ecosystems. These insights have led to an increasing appreciation of the importance of the microbial species that associate with multicellular organisms, including plants. The relationship between the multicellular host and its microbiota is sufficiently interdependent that the plant has come to be understood as a “holobiont” that encompasses a multitude of prokaryotic and eukaryotic species. This expands the traditional view of what constitutes an independent organism to include a collectivity of species that coexist for mutual benefit. The concept of organismality presented by Queller and Strassman goes even further than that, arguing that organisms can be defined as collectivities of cells or species that share a common purpose, regardless of genetic identity. As applied to plants, the ideas elaborated by Simard and others that plant communities and their associated mycorrhizal networks form an interconnected collectivity with cognitive functions also fits into this theme. Stephen Jay Gould discussed ideas of what constitutes an organism in the 1990s. But the ideas themselves are even older than that, dating all the way back to Charles Darwin himself. Incredibly, the connections among these philosophical concepts were anticipated in a science fiction story written by Isaac Asimov over 70 years ago.