Last updated on 21 Jun 2018
Notes on Novelty series:
2. Historical considerations – before and after evolution
3: The meaning of evolutionary novelty
4: Examples – the beetle’s horns and the turtle’s shell
5: Evolutionary radiations and individuation
6: Levels of description
8: Conclusion – Post evo-devo
And having come to know that it is, we inquire what it is [Aristotle, Posterior Analytics, II.1.89b34–35, translated in Lennox 2006: 296]
Consider this diagram:
Stag beetle images from FCIT, royalty free.
Every description of the phenotype of the beetle has some grain of resolution, which is to say that some things are described while others are not. this may be because some grain of resolution is ignored due to it being irrelevant to the purpose of the description, or it may be because that grain is not yet known or understood. Traditionally, organisms are treated as what Sober once called the “benchmark entity” (Sober 1984: 280, 317), the standard grain of resolution. Sometimes, however, that grain is either too gross or too fine for the purposes of describing what is occurring. The notion of a “superorganism” (Hölldobler and Wilson 2009) is a case in point: the appropriate grain of description given what we know of insect colonies is the colony, not the organism.
However, sometimes (as is the case with Wilson and his colleagues), the need to describe at a certain grain is taken to imply some absolute “level” or “rank”; that is, to imply an ontological and metaphysical scale. This is a case of “Descartes before the horse”, taking semantic and conceptual properties to imply real world properties of the things being described. It is a common philosopher’s error, but equally a common biologist’s error, and in particular a common error of evolutionary systematists.
Let us generalise this a bit. Description of biological systems and facts is like this:
What counts as “observed phenomena” depends crucially on the instruments and assays used to observe. The naked eye when untrained has certain dispositions to observe, for example, organisms, but a trained eye can see traits, characters or even entire ecological objects; and having a grain of description at one level means the observer can decompose the observed phenomena into parts, or compose the parts (including organisms) into larger encompassing wholes, depending upon the needs of the describer.
If an explanation at a descriptor grain serves our purposes, then we can rest there. So, for example, if a representation of the spread of a gross trait can be cast in terms of organisms and their interactions with the rest of the world, then we do not need to go deeper (unless our purposes are reductive). Taking an organism grain resolution effectively makes the lifecycle of the organism type our focus, and so we have to decompose organisms into developmental parts and stages. But if we cannot explain what the causes of the parts are at that grain of resolution, we will then decompose the descriptions and accounts to finer grain descriptors (such as genes).
The mistake is to think there is a privileged grain or mode of description. If we understand that description is context, interest, and purpose relative, then a failure to explain something like an evolutionary sequence at one level of description is merely an invitation to change the grain, by composition or decomposition, until we find something promising as an avenue of explanation. In the next post I will discuss what make a grain satisfactory, and ask again: did Darwin give us the explanations of novelty?
Hölldobler, Bert, and Edward O. Wilson. 2009. The superorganism: the beauty, elegance, and strangeness of insect societies. New York, London: W.W. Norton.
Lennox, James G. 2006. Aristotle’s Biology and Aristotle’s Philosophy. In A Companion to Ancient Philosophy, edited by M. L. Gill and P. Pellegrin. Malden MA, Oxford UK, Carlton Australia: Wiley-Blackwell:292-314.
Sober, Elliott. 1984. The nature of selection: evolutionary theory in philosophical focus. Cambridge, Mass.: MIT Press.