3.5 Combining Different Approaches to Biological Individuality
Immunology is clearly not alone in shedding light on biological individuality,
an issue to which many biologicalfields can contribute (Clarke 2011; Pradeu
2016a; Lidgard and Nyhart 2017). First, the contribution of immunology, as we
saw, concerns primarily the biological individual understood from
aphysiologicalpoint of view, and moreover it is not the onlyfield contributing
to that question (developmental biology, neuroscience, and many others also
contribute). Second, beyond physiologicalfields, other biological domains,
most prominently evolutionary biology, can shed light on the problem of
biological individuality. In the last four decades or so, especially after the
founding work of David Hull, most of the debates about biological individuality
among philosophers of biology and biologists have focused on evolutionary
individuality. This includes discussions over units of selection, the replicator/
interactor distinction (Hull 1980), Darwinian individuals (Godfrey-Smith
2009), the possibility of defining species as individuals (Hull 1978; Haber
2016), the question of how groups of entities can aggregate and form new
individuals (Buss 1987; Maynard Smith and Szathmáry 1995; Michod 1999), as
well as multilevel selection and the constitution of an organism from an evolu-
tionary viewpoint (Okasha 2006; Queller and Strassmann 2009). Otherfields
also have much to say about the concept of a biological individual, including,
for instance, ecology (Huneman 2014).
Recently there have been many calls in favor of pluralistic and practice-
oriented approaches to biological individuality (Kovaka 2015). As useful as
these calls have been in undermining the idea that accounts of biological indivi-
duality based solely on a single scientificfield (typically evolution, but the same
wouldapplytoanyother“monistic”approach) and on a purely theoretical
viewpoint would be sufficient, it is now important to take a step further. The
existence of a plurality of approaches to biological individuality, many of which
are rooted in certain scientific practices, is not disputable. The major challenge at
present is to determine whether it could be useful tocombinedifferent approaches
to biological individuality and, if so, how (Pradeu 2016b; Lidgard and Nyhart
2017 ). Some entities in the living world display a high degree of physiological
and/or metabolic individuality without displaying a high degree of evolutionary
individuality, or the other way around (Dupré and O’Malley 2009; Pradeu 2010).
Other entities, in contrast, may express a high degree of individuality on both
grounds. Perhaps determining which entities express a high degree of individual-
ity along several criteria tells us something important about their roles in the
living world. An equally important issue is to establish to what extent different
criteria of biological individuality are compatible or mutually exclusive. Indeed,
28 Elements in the Philosophy of Biology