What We Talk About When We Talk About Life.

1. What We Talk About When We Talk About Life. Trento, October 6, 2008 John Dupré Egenis, University of Exeter

2. The General Problem of Biological Individuality • How does one divide massively integrated and interconnected systems into discrete components? • Is there a unique way of doing this? • Genes • Species • Organisms

3. Hierarchies, cooperation and self-interest • Biological nature generally seen as a hierarchy: • Molecules, cells, organisms, social groups (etc.) • Are higher level individuals consortia of lower level individuals temporarily cooperating because it serves their immediate (‘selfish’) purposes, or are they fused into wholes uniformly committed to the good of the collective? • This line of thought often driven by anthropocentric considerations

4. Above the Human Individual: “There is No Such Thing as Society” • Contemporary assumption is that human individuals are essentially selfish, with various partial exceptions: • Genetic connectedness creates qualified commitment to other members of a family • Self-interest encourages certain kinds of contractually bound associations (reciprocity) • Appropriate upbringing can make some kinds of altruism automatic, though probably unstable when faced with serious individual costs • Generally, “altruism” requires explanation. Why? Natural selection? What does selection select?

5. Challenges to this model • Empirical: is human behaviour in fact typically self-interested (ethnocentric assumption?) • Conceptual: is the concept of individual involved intuitively self-evident, or does it beg the question at issue? (I.e. the question of what is selected.)

6. Overview of the General Biological Argument • Cells as fundamental units of life (questionable working hypothesis) • Kinds of cellular aggregation • Promiscuous realism about individuals • Further implications: new units of selection

7. Cells • All organisms composed of cells, many exist (sometimes) as independent cells • Cells generally have clear boundaries and integrated internal functioning • Whether viruses, plasmids, etc., are alive ‘merely semantic’—at any rate a crucial feature of the environment in which cells live

8. Macrobes and Microbes Traditional differentiation of organism types: unicellular, multicellular • Microbes: prokaryotes, yeasts, protists • Macrobes: plants, animals, some fungi But: this is a very simplistic classification Most life is, and always has been microbial: ‘Our planet has always been in the “Age of Bacteria”’, Stephen Jay Gould

9. Simple Views of Biological Diversity

10. Eukaryotes and the Tree of Life

11. Kinds of Cellular Aggregations • Colonies of similar cells with varying levels of structure (various bacteria; mycelial mats; monospecies biofilms) • Homogeneous colonies with occasionally differentiated cell-types (myxobacteria; some slime moulds; mushrooms) • Genomically homogeneous colonies with strongly functionally differentiated cell types (traditional view of macrobes) • Genomically distinct cell types with cooperative division of labour (multispecies biofilms; lichens) • As 4, but in obligate symbiosis with cell lineage as in 3 (macrobes, alternative conception; corals) • Associations of numerous similar or diverse macrobes (ant colonies; human social groups)

12. Clonal Colonies with More or Less Structure more or less Structure Armillaria: Mycelial mat Colony of Paenibacillus Red clover rhizobacterial biofilm

13. Clonal Colonies with Occasionally Differentiated Cell-Types Myxobacteria Slime mould Fruiting bodies Amanita Muscaria

14. Dental plaque Genomically Diverse Microbial Colonies Biofilms in Yellowstone Ponds

15. Macrobes

17. c.90% of cells are microbial symbionts c.99% of genes are in microbial symbionts Essential for development, digestion, immunity, etc. Evolutionary human vs. functional human Humans

18. Is there a fact of the matter as to which of these assemblies constitute distinct higher level individuals?

19. (Fairly) familiar case: ramets and genets Less familiar (but much more important) case: holobiont* (synbiotic community) and distinguishable components of holobiont (including monogenomic macrobes). The synbiotic community is a (perhaps typically the) unit of selection *Rosenberg et al., Nature Reviews Microbiology, 2007, 5: 355-362. Promiscuous Individualism

20. Synbiotic Communities as Units of Selection • Symbiotic wholes are typically what interact with the environment. Provided they are able to reassemble themselves reliably no reason not to model them as fundamental units of selection. (However, if component cell types are involved in different symbiotic wholes, tracking cell type dynamics may require also treating constituents as individuals.) • Evolutionary integrity (as unit selected by evolution) is at the base of many arguments for the individuality of monogenomic macrobes. Hence the above point is vital for questioning this assumption.

21. Some Larger Philosophical Themes • If casual powers define individuals, promiscuity is inescapable • Biological individuals are always abstractions from processes • Capacities of individuals are determined both by capacities of constituents and membership in larger wholes

22. Human Groups • Humans are ontologically much like other abstractions from the hierarchy of biological processes • They are typically members of many groups from which their most distinctively human characteristics arise (e.g. language) • The group and the individual appropriate foci for different questions • Margaret Thatcher was wrong: there is such a thing as society

23. Biology and Society: Historical Coda • Much of the explanation for the naturalness of the individual perspective is historically contingent • Notoriously, general ideas from social theory and biology have been mutually informing, e.g.: • Malthus to Darwin; (Smith?) • Darwin to Social Darwinism (post-Spenserians), but also Darwinian socialists (Marx and Engels; Kropotkin) • Mill’s convention, Nietszche’s herd, totalitarianism: individualism as a political move against perceived group determination • No unequivocal grounds for taking the individual as fundamental rather than mutually constituting and constituted by groups as in, e.g., Mill, Kropotkin, Darwin (?) • Abstract individualism a Whig history constructed in the C19, linking Hobbes, Smith, Mill and Darwin as precursors of neoclassical economics, rational choice theory, etc.

24. Some Further Philosophical Questions • What is the difference between being ecologically interdependent and being part of an individual (system?)? • What is a system? • Individuals (things) vs. processes • What are the political implications of recognising traditional human individuality as an optional theoretical perspective

25. The support of the Economic and Social Research Council (ESRC) is gratefully acknowledged. The work presented forms part of the programme of the ESRC Genomics Network at Egenis. Thanks to many colleagues at Egenis, and especially Maureen O’Malley, Regenia Gagnier, Barry Barnes and Steve Hughes