Older histories of biology are often full of useful and interesting facts. One of my all-time favourites is Eric Nordenskiöld's history, but I came across an earlier one by Louis Compton Miall in which I found this text:
Bonnet in 1745 traced the scale of nature in fuller detail than had been attempted before. He made Hydra a link between plants and animals, the snails and slugs a link between mollusca and serpents, flying fishes a link between ordinary fishes and land vertebrates, the ostrich, bat, and flying fox links between birds and mammals. Man, endowed with reason, occupies the highest rank; then we descend to the half-reasoning elephant, to birds, fishes, and insects (supposed to be guided only by instinct), and so to the shell-fish, which shade through the zoophytes into plants. The plants again descend into figured stones (fossils) and crystals. Then come the metals and demi-metals, which are specialised forms of the elemental earth. Water, air, and fire, with perhaps the aether of Leibnitz, are placed at the bottom of the scale.
In Bonnet's hands the scale of nature became an absurdity, by being traced so far and in so much detail. It was not long before a reaction set in. The great German naturalist, Pallas, in his Elenchus Zoophytorum (1766) showed that no linear scale can represent the mutual relations of organised beings; the branching tree, he said, is the appropriate metaphor. Cuvier taught that the animal kingdom consists of four great divisions which are not derived one from another, and his authority overpowered that of Lamarck, who still maintained that all animals form a single graduated scale. A complete reversal of opinion ensued, so complete that at length the theologians, who had once seen in the scale of nature a proof of the wisdom of Providence, were found fighting with all their might against the insensible gradations which, according to Darwin's Origin of Species must have formerly connected what are now perfectly distinct forms of life. [p46]
Naturally, I was intrigued. According to the received history, tree diagrams were either entirely new with Darwin or go back to Aristotle, depending on how you define things. So I did a little digging, with some help from my friends.
Thanks to the largesse of the Internet Archive, Pallas' book was easily accessible. But it's in Latin, and I just learned enough Latin to fail it at university. So I tried to look for sections that might be what Miall is talking about, and came across the phrase arbore quasi vitali on page 8. Success! "Tree of life" - couldn't be clearer. Only, there were a few hints that I was wrong; as the section (page 8f) is talking about the circulatory system. My net friend Reed Cartwright - another of those overeducated scientists who put us humanists to shame - reads Latin and he informed me of my error. So I was starting to give up, thinking that yet another myth had found its way into the history of biology, when I had an idea. I tasked (well, begged) Reed to look through it, and yes, he found the passage on pages 23 and following, just as Miall had said.
There's something to be said for the exhaustive and careful sort of scholarship of the late nineteenth and early twentieth century; generally if a good scholar like Nordenskiöld or Miall says X, then you had best believe that X is right until you have further evidence to the contrary. So here are a couple of passages that Reed has roughly translated, with my editorialising interventions. Pallas is discussing the great chain of being idea that species can be arranged in a single series from minerals to man. Dismissing it he says:
But on the contrary, let the System of all organic Bodies be well represented by a the likeness of a Tree, which at once from the base, out of the simplest plants and animals, twofold, it brings forth diversely a contiguous trunk, Animal and Vegetable.
With this figure, let organic Bodies be also shown to be neither successive nor adjacent with beasts but to stand like a great tree on the ground. According to (this) principle, the trunk, full of series of adjacent genera, puts out little branches, having been brought together by those lateral affinities not able to be set between.
It could hardly be more direct. There is no diagram, but it is clearly a taxonomic tree that he is talking about.
This arises in the context of a debate that spans two centuries, from around 1840 to now, on what counts as a "natural" arrangement of species. While Linnaeus had arranged his as "group within group", his presentation was simply as a hierarchical scheme useful for diagnosis. He himself had said that it was a conventional scheme, although he held that genera and species were natural:
Naturae opus semper est Species et Genus; Culturae sapius Varietas; Naturae et Artis Class et Ordo.
The work of nature is always Species and Genus. Cultivation understands varieties; of nature and skill [are] Class and Order.
So what Pallas is asserting is that the best analogy for a natural arrangement of genera (i.e., natural groupings) is a tree, not a ladder. This sets up the problem for which Darwin's notion of descent with modification is a solution.
- Log in to post comments
There are several uses of the phrase "tree of life" in the Bible, other than references to the tree in the Garden of Eden. I'm not sure what it means, but it undoubtedly does not reference a taxonomy of any kind.
There are all kinds of "trees of life" from the Sephirot to the Yggdrasil, but none of them have any taxonomic import.
In Northumbria the pie- annet (barnacle goose) birth involved falling out of a dragon tree.
May be related to old norse myths as Odin in one text is described falling from a tree to become a fish then a bird. A creature of air land and sea; which represents a common medieval classification of the creatures of the earth into those of air, land or sea. Their is one other widespread story with the same themes, seems to develop from the 12th cen. onward. Texts show often early intrest in the new developments in science stemming from the Arab world.
It certainly seems to be playing with common medevial concepts concerning the natural world and it's classification.
I assume you know about the 1837 example by Martin Barry in an attempt to illustrate von Baer's theory of embryology cited by Ruse in Monad to Man.
There is a very interesting book on this subjetc by Giulio Barsanti, called "La scala, la mappa, lâalbero: immagini e classificazioni della natura fra sei e ottocento" : "The scale, the map and the tree : images and classifications of nature from 16th to 18th centuries."
I have no idea whether it exists in English, though...
I think I've seen a diagram of what Pallas' tree would have looked like (can't remember where), but it was made by someone else, probably in the 20th century.
Thje oldest actual tree diagram of classification is probably that of Augusin Augier, in his "Essai d'une nouvelle classification des vÃ©gÃ©taux" (1801), depicting the whole plant kingdom. I haven't seen the book, and it doesn't seem to be online anywhere, but there's a paper on it by Peter F. Stevens:
Stevens, P.F. 1983. Augustin Augierâs âArbre Botaniqueâ (1801), A Remarkable Early Botanical Representation of the Natural System. Taxon 32: 203â211.
It appears that very little is known about the author, but he probably didn't believe in evolution, but he did have a concept of homologous vs. analogous similarity. The classification itself was not very good, as many of his families contain plants that have little to do with each other.
This paper also seems interesting:
Augier's tree is on page 4 of the pdf.
So before there were phylogenetic trees, there were taxonomic trees...
If I don't forget, I can tell more on this topic next week, based on a fascinating book by Philippe Taquet that probably only exists in French...
The branched model of natural affinities (Aristotle?) seems well known in Linnaeusâ time, although Linnaeus preferred a more practical system. See Philosophia Botanica, aphorism 153 and following (from botanicallatin.org):
153. Dispositio Vegetabilium vel Synoptice vel Systematice absolvitur, & vulgo Methodus audit.
Synoptica divisio seculo XVI & XVII. maxime in usu fuit.
Systematica vero seculo XVIII. praecipue exculta fuit, incepta a Tournefortio & Rivino.
Methodici summi methodo mathematica, in scientia naturali, a simplicioribus ad composita adscendunt, adeoque incepere ab Algis, Muscis, Fungis, uti Rajus, Boerhaavius, &c.
Naturalis instinctus docet nosse primum proxima & ultimo minutissima, e. gr. Homines, Quadrupedia, Aves, Pisces, Insecta, Acaros, vel primum majores plantas, ultimo minimos Muscos.
Natura ipsa sociat & conjungit Lapides & Plantas, Plantas & Animalia: hoc faciendo non connectit perfectissimas Plantas cum Animalibus maxime imperfectis dictis, sed imperfecta Animalia & imperfectas Plantas combinat, e. gr.
Lernaeam Animalculum & Confervam Algam.
Spongiam Algam & Corallia Animalia:
Toeniam, Conferuam, articulatam, Corallinam.
Lythoceratophyton B. intra Vegetabile, extra Lapideum, ex Animali.
I did not adventure to translate the text, but the meaning is plain.
The Cobweb of Life
Although "tree" is firmly enshrined as a taxonomic term of art, a naive observer might still question its appropriateness as a characterization of taxonomic diagrams, because virtually none of them has anything like a leaf.
The analogical exactness of every metaphor must end somewhere, but a metaphor which ignores the most salient characteristic of its target is undeniably faulty, and since the branches of most trees are obscured by leaves for most of the year, there isn't much more of a resemblance between real and taxonomic trees than between a man and a skeleton.
Even if we confine our attention to bare trees in a wintry metaphor, a second and significantly more serious objection arises, especially in evolutionary taxonomy, because there's nothing in evolution even remotely analogous to a trunk, and if all the many "branches" of life actually emanate from anything, it's more like a speck than a central supporting pillar.
The evolutionary connection of all living things is shaped more like a cobweb than a tree, and however inelegant such a metaphorical substitution may appear to be, it nevertheless has the merit of suggesting the extreme fragility of all life, in a world which is rapidly becoming unfit for the survival of anything.
Jacob makes a good point, cobweb is a much better description than tree.