Another take on volvocine individuality

Dinah Davison & Erik Hanschen

Dinah Davison and Erik Hanschen.

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.

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Cells, colonies, and clones: individuality in the volvocine algae

Biological Individuality

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.

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Look what came in the mail yesterday!

Biological Individuality

A project started five years ago has finally borne fruit. In May, 2012 I joined a group of philosophers, historians, and biologists in Philadelphia for the Cain ConferenceE pluribus unum: Bringing biological parts and wholes into historical and philosophical perspective.” The meeting was organized by Lynn Nyhart and Scott Lidgard, with the goal

…to pursue the question: How can historians, philosophers, and biologists help each other to understand part-whole relationships in biology, both today and in the past?

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What kind of individual do you mean?

One of the discussions I find most interesting in the philosophy of science is about what exactly constitutes a biological individual (or organism). The discussion would be a lot less interesting if everything were a vertebrate. Vertebrates (nearly always) develop from a single fertilized egg, so the (mostly) genetically homogeneous and (usually) genetically unique unit is the same as the spatially bounded, contiguous and physiologically integrated unit (this doesn’t even cover all the proposed criteria; see Clarke 2010 for a fairly comprehensive list with citations). But when we look outside of the vertebrates, what we often find is that some biological units have some of these properties and either groups or parts of those units have others.

Aphid on dandelion by Amoceann. Public domain image from Wikimedia Commons.

Aphid on dandelion by Amoceann. Public domain image from Wikimedia Commons.

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Problems with major transitions: Maureen O’Malley & Russell Powell respond

The Great Oxidation Event by Adelle Schemm.

The Great Oxidation Event by Adelle Schemm.

In a recent series of posts, I reviewed Maureen O’Malley and Russell Powell’s paper in Biology and Philosophy, “Major Problems in Evolutionary Transitions: How a Metabolic Perspective Can Enrich our Understanding of Macroevolution.” Although they made several good points, I thought that some of their criticisms were off the mark and that their proposed solution to the real and perceived problems with the major transitions framework was unsatisfying.

Drs. O’Malley and Powell are both heavy hitters in the philosophy of biology, and as I usually do when I dig deeply into someone else’s paper, I invited them to respond to my criticisms. They kindly provided a thoughtful rebuttal and permitted me to post it here. I’ll have more to say later, but for now I’ll just say that they make some good points and (most importantly) fairly represent my arguments. As usual for guest posts, I have made no edits to the content of their response, only formatted and added links:

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Time for a revision? Maureen O’Malley and Russell Powell on Major Transitions, part 3

Maureen O’Malley and Russell Powell say that the major transitions framework is in need of repair. They have a point, or rather several good points. I have looked at their criticisms of three different versions (the original framework as laid out in the book by John Maynard Smith and Eörs Szathmáry, Rick Michod’s ‘evolutionary transitions in individuality‘ framework, and Szathmáry’s revised ‘Major Transitions 2.0‘). But what is their proposed fix, and will it have the intended effect?

Figure 4 from O'Malley and Powell 2016. Two major aeons of evolution (modified from Falkowski 2006). ‘Gya’ stands for ‘billion years ago’; the date for the origin of photosynthesis may need to be pushed back (see Crowe et al. 2013).

Figure 4 from O’Malley and Powell 2016. Two major aeons of evolution (modified from Falkowski 2006). ‘Gya’ stands for ‘billion years ago’; the date for the origin of photosynthesis may need to be pushed back (see Crowe et al. 2013).

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Time for a revision? Maureen O’Malley and Russell Powell on Major Transitions, part 2

One of the cool things about studying the so-called major transitions is that they are as interesting to philosophers of science as to biologists. So you really can’t help being exposed to the philosophy of science literature, and many (maybe most) biologists in the field cross the lines at least occasionally. I’ve been to both, and I’m here to tell you that philosophy conferences are more fun than biology conferences.

Last time, I briefly summarized the various forms of the major transitions framework and addressed one of O’Malley and Powell‘s criticisms, that the framework is progressivist. Now I’d like to look at their other two problems: lack of unity and missing events. By and large, I agree with these points, although there are some caveats I’d like to point out. Next time, I’ll consider their proposed solution, which I’m afraid I don’t find helpful.

Disunity is actually O’Malley and Powell’s first criticism, but it will be a bit more complicated than progressivism to address, and I was short on time on part 1. Essentially, they are arguing that the major transitions are not a natural kind, philosophese for groupings that belong together because of some fundamental commonality, as opposed to more arbitrary groupings whose members are only superficially similar. So what are the transitions? Here’s the list from the book:

Table 1.2 from Maynard Smith J, Szathmáry E (1995) The Major Transitions in Evolution. Oxford University Press, Oxford.

Table 1.2 from Maynard Smith J, Szathmáry E (1995) The Major Transitions in Evolution. Oxford University Press, Oxford.

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Levels of selection in biofilms: Ellen Clarke on individuality

Pseudomonas biofilm. From Spiers et al. 2013.

Pseudomonas biofilm. From Spiers et al. 2013.

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.

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Karen Kovaka on biological individuality

psa-home

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.

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Pathways to pluralism: Beckett Sterner on biological individuality, part 2

Aphids on dandelion

Aphids on dandelion. Public domain image from Wikimedia Commons.

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.

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