Why study invertebrates? A philosophical argument from Aristotle

Guest post from Frédéric Ducarme of the Muséum National d’Histoire Naturelle (Paris)

Scientists who specialize on invertebrate biology often hear the same tune: “why are you studying sea cucumbers?! They are so disgusting, it is really not a thing worth wasting one’s time on!”. Indeed, for centuries the only subjects of European natural sciences have been the “useful” species: cattle, horses, vegetables and medicinal herbs – along with some pests[1]. Most natural history museums and botanical gardens around the world were initially set on in order to advance knowledge about “useful” species, and to acclimatize new ones. But both curiosity and potential usefulness of previously despised species progressively led to the study of more and more unexpected animals, always farther from Mankind and its direct interest, until they eventually got admitted altogether in Linnaeus’s ark, Systema Naturae (1735).

Before him (and even shortly after), invertebrate zoology was strikingly poor in Occident (countries of the West), and non-edible invertebrates were ignored, whereas they were hold in greater esteem in some remote countries like Japan (which had less big mammals though)[2].

Nevertheless, the very founder of biology, the Greek philosopher Aristotle (384~322 B.C.), had long before been advocating for the interest of studying every critter of nature, even the less remarkable-looking ones. In the introduction of the fifth book of his Parts of the Animals treatise, we can read the following words[3] :

“Having now treated of the celestial world, as far as our conjectures could reach, we must proceed to treat of animals, without omitting, to the best of our ability, any member of the kingdom, be it sublime or ignoble. Indeed, even for those things that have no graces to charm our sense, nature has organized the beings it offers to our sight so well that, when we look at them, we can feel an immense pleasure if we are able to analyze and understand them, and are inclined to philosophy. Indeed, it would be strange if we could enjoy only mere representations of wildlife, admiring the mimetic skill of the painter or sculptor, and not to get even more passionate for the natural things themselves, whereas we can experience them directly. 

We therefore must not be childishly repelled by the examination of the humbler animals. All things in nature are admirable. To illustrate this idea, we know this story about Heraclitus, when visitors who wanted to meet him stopped as they saw him warming himself by the furnace down in his kitchen; he invited them not to be afraid to enter, saying that there are deities in a kitchen too. So we must approach the inquiry about every kind of animal without aversion, since in all of them there is a part of nature’s power and marvel. […]

If any person finds the study of the rest of the animal kingdom an unworthy task, he must know that he is despising himself. For we cannot look at the framework of the human blood, flesh, bones, vessels, and other parts without much repugnance. Moreover, when studying any one of the body parts or organs, be it which it may, we must not only consider its material composition and think about it alone, but we must figure out its relation to the whole. Similarly, the true object of architecture is not bricks, mortar, or timber, but the house; and so the principal object of natural science is not the material elements, but their composition, and the totality of the system, independently of which they have no existence.”

These words come from a man who, two and a half thousand years before now, described and named hundreds of marine invertebrates such as holothurians (even if we now know that he probably used this word to describe some tunicates[4]), proved that sponges were animals and that dolphins were mammals, and gave his name to the sea urchins’ buccal system, because he quaintly compared it to a Greek lantern without its skin around. [Editor's note: see this interesting note about Aristotle's Lantern.]

Aristotle's Lantern, the jaws of a sea urchin, photo taken by Philippe Bourjon, via Wiki Commons. Used under Creative Commons license "by-sa 3.0".

Because some "crazy" people dared paying interest to uninteresting-looking creatures with no bones, now we know that a mantis shrimp have more powerful eyes than any camera, that some sea slugs can survive thanks to photosynthesis, that horseshoe crab blood contains a highly useful compound, that earthworms are good for agriculture, that one can extract a very useful fluorescent protein from a jellyfish, and that tardigrades can survive in outer space! Nature’s marvels are everywhere for those who know how to look, and want to study. 

 

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[1] See for example Buffon’s best seller, Histoire Naturelle (36 vol., 1749-1804).

[2] See for example this funny collection of Japanese traditional haikus about sea cukes: Robin D. Gill, Rise, Ye Sea Slugs!, Paraverse Press, 2003.

[3] Aristotle, Parts of the Animals (circa 343 B.C.), book 1 chap. 5. 

[4] Alexander M. Kerr, « A Philology of Òλοθóυριου : From Ancient Times to Linnaeus, including Middle and Far Eastern Sources », University of Guam Marine Laboratory Technical Report, n^o 151,‎ 2013

If you want to know more about the Heraclitus parabola:

Pavel Gregoric (2001), “The Heraclitus Anecdote: De Partibus Animalium i5.645a17-23”, Ancient Philosophy 21.

If you want to know more about taxonomic bias towards “beautiful” species in biology:

Ducarme, F., Luque, G. M., & Courchamp, F. (2013). What are “charismatic species” for conservation biologists? BioSciences Master Reviews, 1, 1–8.