Pierrick Bourrat has reviewed Scott Lidgard and Lynn Nyhart’s book Biological Individuality: Integrating Scientific, Philosophical, and Historical Perspectives for Notre Dame Philosophical Reviews.
Derek Skillings from University of Bordeaux/CNRS has a new article at Aeon about biological individuality:
For millennia, naturalists and philosophers have struggled to define the most fundamental units of living systems and to delimit the precise boundaries of the organisms that inhabit our planet. This difficulty is partly a product of the search for a singular theory that can be used to carve up all of the living world at its joints.
Skillings reviews the deep historical roots of the question, touching on the views of Charles Darwin and his grandfather, both Huxleys (T. H. and Julian), Herbert Spencer, and other 19th and early 20th century thinkers, as well as some more recent authors, including Daniel Janzen and Peter Godfrey Smith.
A couple of weeks ago, I indulged in a little shameless self-promotion, writing about my new chapter on volvocine individuality in Biological Individuality, Integrating Scientific, Philosophical, and Historical Perspectives. Now two graduate students in the Michod lab at the University of Arizona, Erik Hanschen and Dinah Davison, have published their own take on volvocine individuality in Philosophy, Theory, and Practice in Biology (“Evolution of individuality: a case study in the volvocine green algae“). The article is open-access, and Hanschen and Davison are listed as equal contributors.
As I mentioned previously, I have a chapter in the newly published book Biological Individuality, Integrating Scientific, Philosophical, and Historical Perspectives. The chapter was actually written nearly five years ago, but things move more slowly in the philosophy world than that of biology. Finally, though, both the print and electronic versions are now available; here is the electronic version of my chapter. The book currently has no reviews on Amazon, so if you want to give it a read, yours could be the first. If you’re interested in current and historical views on individuality, there is a lot of good stuff in here, including contributions by Scott Lidgard & Lynn Nyhart, Beckett Sterner, Andrew Reynolds, Snait Gissis, Olivier Rieppel, Michael Osborne, Hannah Landecker, Ingo Brigandt, James Elwick, Scott Gilbert, and Alan Love & Ingo Brigandt.
In the Major Transitions class, the students keep pointing out that the transitions on Maynard Smith and Szathmáry’s list come in two flavors with very different properties. Sure, there are some important similarities between multicellular organisms and social insects, but they are quite different from cellular slime molds and the conspiracy of prokaryotes that make up eukaryotes.
The question of what constitutes a biological individual is intimately entangled with questions about levels of selection. Many authors implicitly or explicitly treat individuals as units of evolution or some variation on this theme. A recent appreciation for the complexity of bacterial biofilms has led to comparisons with multicellular organisms. A recent paper by Ellen Clarke bucks this trend by claiming that multispecies biofilms are not evolutionary individuals.
At the Philosophy of Science Association meeting in Chicago, I attended an interesting talk by Karen Kovaka, “Biological Individuality and Scientific Practice” (the abstract of her talk is here). Now the paper arising from that talk is out in the journal Philosophy of Science. It argues that biologists do not need to resolve the question of what constitutes an individual in order to do good empirical work, with which I agree. She contrasts two views of the relationship between individuality and scientific practice, the “quality dependence” account and the “content sensitivity” account:
Quality dependence: the quality of empirical work in biology depends in part on the resolution of the debate about biological individuality…
Content sensitivity: Biologists’ understanding of biological processes is sensitive to the individuals they take to be participants in those processes.
Previously, I introduced Beckett Sterner’s new paper comparing and critically evaluating the views of Ellen Clarke and Peter Godfrey-Smith on biological individuality. For Clarke, individuality is recognized by the presence of ‘individuating mechanisms’: traits that increase the capacity for among-unit selection or decrease the capacity for within-unit selection. Godfrey-Smith recognizes different kinds of individuals, but at a minimum, populations of individuals must have Lewontin’s criteria of phenotypic variation, differential fitness, and heritability of fitness, i.e. be capable of adaptive change.
In grad school I wound up hanging around with John Pepper (yeah, Dr. Pepper) a good bit. I think I disagreed with him more than I agreed with him, sometimes to the point of exasperation, but conversations with him were never boring.
One of John’s most annoying refrains was “is it an organism?” I was studying (and still study) a group of algae for which this question can be genuinely confusing. Most people would say a Chlamydomonas cell is a single-celled organism, and most would agree that Volvox is a multicellular organism, but what about the four-celled species Tetrabaena? A four-celled organism or a collection of four single-celled organisms? What about an undifferentiated colony of 32 cells, such as Eudorina? Or Pleodorina, which is around the same size but with two cell types? Somewhere between a unicellular ancestor and Volvox, a new kind of individual emerged. Among the extant species*, where do we draw the line between organisms and groups of organisms, or can we (or should we) draw a line at all?
Hisayoshi Nozaki and colleagues have described another new species of volvocine algae, a member of the genus Eudorina from Lake Victoria in Tanzania. Unlike most species in this genus, the cells of Eudorina compacta are tightly packed around the surface of the colony, which is ellipsoidal. They coexist in Lake Victoria with Colemanosphaera charkowiensis, another species that Dr. Nozaki and colleagues described in 2014.