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The Philosophy of Species

Massimo Pigliucci writes about the species problem in the latest issue of Philosophy Now (via the Uneasy Chair):

...a recent count by R.L. Mayden lists a whopping 21 different concepts of species proposed in the literature! Part of the problem is that biologists (and some, but not all, philosophers) keep adopting an essentialist concept of species: there has to be one right way to think of the problem, and hence one unique solution, which we would surely find if only we had more data (say biologists) or thought a bit harder (say some philosophers).

Dave Roberts at the Gristmill argues that though our methods of categorization are many, they are not essentialist, since they don’t correspond to “bright, unambiguous […] lines of separation” built into the natural world. From a philosophical perspective I believe he's correct, but unfortunately his insight doesn’t move us toward a solution of the problem of species; it actually further confuses classification.

Humans create artificial categories where natural (essential) categories do not exist – we draw bold lines through the shades of gray that lie between black and white. We do this to better understand the world around us. The concept of ‘species’ is of itself artificial; Linnaean taxonomy relies on seven levels of classification for organisms, and yet we still need to attach ‘sub-’ and ‘super-’ to many of these in order to better understand the evolutionary relationships between organisms. Modern cladistics improves slightly on this model by relying less heavily on a set number of taxonomic levels, but still divides groups of organisms into artificial categories called “clades.”

In the original article Pigliucci cites Ludwig Wittgenstein in an attempt to provide a more flexible (and thus more realistic) alternative to the way we approach taxonomy. I’m not an evolutionary biologist, but to me his proposed system of classification sounds prohibitively complex at best. As I said above, we simplify in order to understand; it’s like lowering the resolution of an image in order to fit it on your computer screen – incredibly high resolution sounds nice, but what use is it if the picture is too big for you to even tell what you’re looking at?

This is all exactly right --

By Dave Roberts (not verified) at March 31, 2005 - 7:53pm |

This is all exactly right -- nothing I said should be taken as contrary to what you wrote.

The pragmatists say precisely this: we divide in order to understand -- and by "understand" they mean "be able to navigate, to do work." I certainly wouldn't advocate *not* drawing lines through the gray, as you say. Nor would I advocate a taxonomy that's unweildy in its complexity. It's usefulness that should guide us, not some attempt to "mirror reality." That's all I was getting at.

Re-reading my post, I have to

By chris at March 31, 2005 - 10:15pm |

Re-reading my post, I have to say that the last sentence of the paragraph in which I addressed what you wrote now sounds unfairly critical. I agree with what you said and simply intended to take it a step further than what I read in your Gristmill post. There is, of course, nothing in your original post that is contradictory to any of the conclusions that I drew here. My apologies if it came off any other way.

Classification Confusion

By Hungry Hyaena (not verified) at March 31, 2005 - 8:27pm |

Chris,

I particularly appreciate the poignant analogy you close with. If you don't mind, I will steal it for future use. ;)

Taxonomy is one of my favorite messes. I spend too much time memorizing scientific names and studying the proposed relationships. Learning the taxonomic system is a little like learning a vanishing language. Unless your goal is preservation, it's a bit silly.

I received an email yesterday directing me to the paper below:

Hillis, D.M. and T.P. Wilcox. 2005. Phylogeny of the New World true frogs(Rana). Molec. Phylogen. Evol. 34:299-314.

The author of the email, one Dr. James Stuart, writes "To my knowledge (and I may be wrong), the...article is the first to employ the Phylocode in a taxonomic revision of a genus in herpetology."

The "phylocode" is the clade based system you mention, and upon reading the paper, I have to laugh. I was already distressed when the black rat snake (Obsoleta obsoleta) became Patherophis obsoletus. Now, we're quickly headed for a reclassification of the animal and plant kingdoms, with many, but not all, scientific names changing in the process! Such confusion seems unhelpful, especially because the transition, guaranteed to be long and odious, will make it even more difficult to stimulate future interest on the part of amatuer biologists or the curious cats.

Whew...it will be an interesting ride. For my part, I continue to enjoy it. The coordinated effort of the world biology community to create an accepted, universal classification system is as absurd as it is marvelous. I'm grinning as I write this. The prospects alone make me giddy.

-HH

Same here

By chris at March 31, 2005 - 10:32pm |

This issue attracted me for the same reason; I don't pretend to be interested in knowing the exact taxonomy of every species I stumble across, but I do have a soft spot for vascular plants, specifically big trees.

As far as reclassification, I grant that it's important for scientists to have a system that is accurate, and invariably revisions will have to be made when errors are found. At the same time, I always found it frustrating when I ran across categories for which there were multiple names.

This is especially true for the ones that I'm most familiar with, since they are mainly the plant families that have two names*. Some of these are more commonly referred to by their old names, and others are more commonly referred to by their new names.

For a thorough display of my total plant geekdom, check out this online field guide I worked on in college. And because no one should be exempt from embarrassment, here's Pete's.

*The plant families in question are:

  • Palms - Palmae and Arecaceae

  • Grasses - Gramineae and Poaceae
  • Legumes - Leguminosae and Fabaceae
  • Mustards - Cruciferae and Brassicaceae
  • Mangosteens - Guttiferae and Clusiaceae
  • Carrots - Umbelliferae and Apiaceae
  • Mints - Labiatae and Lamiaceae
  • Asters - Compositae and Asteraceae

Mistake

By Hungry Hyaena (not verified) at April 1, 2005 - 6:31am |

I just logged on and realized that, in my haste, I screwed up the scientific name of my favorite colubrid. The black rat snake was never named Obsoleta obsoleta, but Elaphe obsoleta. After years of celebrating this snake, I somehow bastardized the name. My bad...

Chris, I just visited your college tree field guide (and Peter's). Good stuff. Interestingly, you are both younger than I had imagined. Funny how things change in cyberspace. Keep up the good work.