history

I think many biologists have a pretty vague picture of why Linnaeus was important. To some, he probably seems banal -- how exciting could it be to make all those lists of species, just endless lists, over and over? "Yeah, sure, somebody had to come up with a classification system, but mainly, I'm sure glad it didn't have to be me!"

Other biologists may view Linnaeus through a lens clouded to some extent by the later development of evolutionary theory. Linnaeus is certainly the most familiar, and possibly the most apt, example of essentialist, typological thought prior to Darwin. His categorizations depended on typological features, and even today definitions of species based on morphological types are often called "Linnean species."

But several aspects of Linnaeus' writings belie this stereotype. For one thing, especially later in his career, Linnaeus became convinced that new species actually do appear over time, particularly through hybridization. I'll have more on that in a later post.

Another thing is that before Linnaeus and his contemporaries, people didn't approach biological diversity with an essentialist framework. An essentialist view of species required the assumption that species were fixed, not changing over time. A good source discussing the importance of Linnaeus in the formulation of species fixism is Ronald Amundson's book, The Changing Role of the Embryo in Evolutionary Thought.

I posted on Amundson's take on Weismann a couple of years ago. I think his take on Linnaeus and species fixism — although short — was the part of the book that struck me the most, mainly because of its heterodoxy in contrast to the historical work of Ernst Mayr and others.

To begin, he lays out the conventional story:

Modern narratives of the history of evolutionary biology take place against the background of species fixism. The story goes like this: The historical discovery of evolution was the overthrow of species fixism. From ancient days, Western intellectuals had conceived of a stable and unchanging world that had been created by God in pretty much the condition it now exists. Beginning in the early seventeenth century, traditional beliefs were shaken by a series of challenges to the world's constancy and stability ... [e.g., Copernican cosmology, geological process]. In this narrative, the fixity of species was the last vestige of the stable and unchanging world of the ancients.... Darwin's job was like that of Copernicus — the overthrow of an ancient belief in stability.

That's the story, but it's not true. The Western tradition was indeed centered on an unchanging world but the fixity of species was not a part of that world. It became widely accepted for the first time both among naturalists an theologians during the eighteenth century, only about a century before Darwin (Zirkle 1951:48-49; Zirkle 1959:642). Carl Linnaeus is widely known for his unequivocal statements of species fiexism and special creationism. It is less widely recognized that Linnaeus was one of the innovators of fixism. Prior to Linnaeus and his botanical colleagues, beliefs in transmutation and spontaneous generation were extremely widespread (Amundson 2005:34-35, emphasis in original).

For his story, it is important for Amundsen to spends some time describing belief in transmutation, and he devotes three pages to various illustrations of how widespread the belief was. I especially like the following passage on the "barnacle goose," which serves to set the background against which species fixism seems a starkly modern view:

Even more dramatic transmutations were commonly accepted. To the modern ear they strain the boundary between myth and honest empirical belief. The story of the phoenix was often treated skeptically, but it was no less extreme than the barnacle goose. The Oxford English Dictionary still contains the renaissance term anatiferous: "producing ducks or geese, that is producing barnacles, formerly supposed to grow on trees and dropping off into the water below, to turn into tree-geese" (Hacking 1983:70). Philosopher Ian Hacking uses the term anatiferous to illustrate incommensurability: Wht in the world could those people have been thinking of? But this was an honest factual belief. Raven quotes the sixteenth-century author Scaliger, who reports "as a thing he himself has seen" the stories "falsely told of the phoenix but veraciously of the Bernacle [sic] Goose" (Raven 1953:204).

Most people, sometime during the slow years of high school biology, learn about Francesco Redi and Lazzaro Spallanzani — Redi put rotting meat in a jar with gauze over the top, proving that maggots don't spontaneously generate; Spallanzani showed that microbes don't spontaneously generate but come from the air and may be killed by boiling. Both, and others such as van Leeuwenhoek, helped to roll back the idea that life was generated from nothing. Still, the problem with refuting spontaneous generation is that you have to be able to see all possible influences. Not until Pasteur was the idea of microbial spontaneous generation finally refuted once and for all.

Now, to bring the connection to Linnaeus -- Spallanzani's work on boiling and microbial transmission was in the 1760's. Spallanzani also demonstrated that sperm was necessary for reproduction (at least in mammals), performing the first known artificial inseminations (of dogs) -- all this in 1779, just after Linnaeus' death.

In other words, in Linnaeus' day, spontaneous generation and transmutation were still potent ideas. For animals in particular — not Linnaeus' strong point — they were quite difficult to disprove. Even the causes of reproduction were somewhat mysterious, and what radical transmutations were possible at birth were well-known.

Botanists, including Linnaeus and his contemporaries, were in a much better position to establish the limits to variation. In this respect, Linnaeus' close focus on the sexual processes of plants and consequent classification were hugely important. Botanists' long experience in plant breeding experiments, and with the relative ease of exchanging seeds and cuttings across Europe, they developed an ability to assess the properties of hybrid strains and varieties -- even more than a hundred years before Mendel.

Spontaneous generation and transmutation are ultimately linked, since both predict very particular things about reproduction and the nature of parent-offspring resemblances: like from like, and nothing from nothing are joined principles.

Seen in the context of prefixist theories of spontaneous origins and transmutations, species fixism was a progressive scientific development. Beliefs in spontaneous generation persisted into the nineteenth century, but they were restricted to smaller and smaller organisms as time passed (Roe 1981). Fixism was established for nonmicroscopic plants and animals around 1750, primarily on the basis of plant breeding experiments. Plant variation had been an especially common area of transmutationist beliefs. The careful and controlled breeding programs of Linnaeus and others established fixism among most naturalists (Amundsen 2005:37).

Amundsen argues for Linnaeus' dual importance -- not only as the innovator of his system of taxonomic descriptions and classification, but also as an experimenter and gatherer of information about botanical forms:

Linnaeus's fixism, like that of his contemporaries, was based on evidence that had been painstakingly gathered from a vast network of horticultural gardens across Europe. The old transmutationist beliefs in the influences of climate on plant forms had been tested by returning the modified forms to their original locations. The plants then reverted to their original forms. Experiments had been done in the production of hybrids ("bastards"), and the limitations on viability and fertility had made it seem exceedingly unlikely that this was a cause of new species (Amundsen 2005:40).

This "painstaking" work underlay the basic scientific description of variability under human domestication between Linnaeus and Darwin. Plants might be changed in new environments, and they might be bred or hybridized by humans, but they would revert to their wild, "natural" state. Stamos (2005:91) discusses Linnaeus' view of this reversion:

Linnaeus, for example, exhibited a belief in the law of reversion in his Critica Botanica (1737) when he wrote that "every day new and different florists' species arise from the true species so-called by botanists, and when they have arisen they finally revert to the original forms. Accordingly to the former have been assigned by Nature fixed limits, beyond which they cannot go: while the latter display without end the infinite sport of Nature" (Ramsbottom 1938: 200n).

And Stamos (ibid.) quotes further from Jussieu, in many ways Linnaeus' taxonomic successor:

Jussieu too, in his Genera Plantarum (1789), expresses a belief in the law of reversion. Although a species, he says, "is occasionally subverted for a while by chance or human industry; that is to say, some individuals may vary one from another on account of location or climate or disease or cultivation . . . But these varieties, obeying the law of nature, . . . return to the primordial species, their character restored, if other factors do not interfere" (Stevens 1994: 340-341).

Hence, reversion served as evidence that species are fixed, and that their variation is transient. Botanical experimentation supported the essentialist view of species, against the tranmutationist view.

The belief in fixism was important to the classification -- if organisms could readily transmute to radically different forms, then a "natural" classification of them would likely be impossible. Linnaeus' classification was not itself a "natural system", but his hierarchical use of characteristics -- and recognition that reproductive features were the basis of large-scale similarities in plants -- put the outline of such a system in view.

References:

Amundson R. 2005. The changing role of the embryo in evolutionary thought: roots of evo-devo. Cambridge University Press, Cambridge UK.

Stamos DN. 2005. Pre-Darwinian taxonomy and essentialism -- a reply to Mary Winsor. Biol Phil 20:79-96. doi:10.1007/s10539-005-0401-9

I found this passage in the discussion following T. Dale Stewart's paper, "The problem of the earliest claimed representatives of Homo sapiens," from the 1950 Cold Spring Harbor Symposium on Early Man.

DOBZHANSKY: The great variability of the Neanderthaloids, so ably described by Drs. McCown and Stewart [McCown's paper immediately preceded the one under discussion], bears upon one of the basic problems of human descent. It is now clear that the Neanderthaloids and the so-called sapiens type were at no time two reproductively isolated species, but rather component races of a single species. Some modern populations may carry genes that were present in the Neanderthaloids, and other moderns may not carry such genes. But this does not mean, of course, that mankind consists of races descended from Neanderthaloids and other races which came from the sapiens type contemporaneous with the Nenderthaoids. In general, the old anthropological alternative of monogenic versus polygenic descent of man ceased to exist when considered from the vantage point of the present evolution theory. Different populations (races) of a polytypic species may be descended largely from different races of the ancestral species and may differ in some genes in which these ancestral races differed. And yet, a polytypic species may still evolve as a single genetic system. Favorable mutants or gene combinations arrived at in one part (race) of such a species may, under the influence of natural selection, eventually spread to all other parts and thus become a common property of the entire species. Thus, local autonomy of the gene pools of racial populations does not preclude retention of a basic unity of the species as a whole. I would like to point out that this view agrees quite well with the conclusions reached by the late Weidenreich on basis of purely morphological analysis of pre-human populations. This is worth while [sic] stressing because Dr. Weidenreich has sometimes used expressions which seemed to put him close to the old-fashioned polygenist camp, which he actually rejected absolutely (Dobzhansky, following Stewart 1950:106-107).

I love these discussions, which often included exactly the people whose opinions you would like to see, and sometimes some surprising ones. For instance, after Dobzhansky in this particular discussion, Joseph Birdsell and Stewart had an exchange about the implications of the fluorine dating of Piltdown for interpreting variability within modern humans (Birdsell's point being that such an apelike jaw must extend the variability of Homo sapiens even further if it is actually recent! Ha!)

And they often jumped off on tangents, like the Piltdown tangent, which remind you of the other things that people cared about besides the immediate topic. I think it's the closest thing to science blogging that the 1940's and 1950's had to offer!

References:

Stewart TD. 1950. The problem of the earliest claimed representatives of Homo sapiens. Cold Spring Harbor Symp Quant Biol 15:97-107, comments following.

Afarensis reviews the book The First Fossil Hunters: Paleontology in Greek and Roman Times, by Adrienne Mayor:

In Chapter Three, Mayor discusses discovery of bones in the Greek Pre-classic and Classic. Classical scholars should be familiar with these in a different context. For example, the Spartan discovery of the bones of Orestes or the shoulder of Pelops kept at the sanctuary of Olympia. The bones of Theseus were discovered by the Athenians (who also swiped the bones of Oedipus from Thebes). As Mayor points out there was a veritable bone rush at that time with skeletons of heroes popping up all over the place. One of the traits that united these finds was the large size of the bones. The ancient Greeks felt that their heroes were larger in stature than they were. An idea that traces back to Hesiod's Works and Days (where he discusses the five ages of Man) and probably earlier. Over time, according to the ancient Greeks, humans have grown shorter. So when giant bones were discovered - especially those that looked vaguely human - they were interpreted as the bones of Greek heroes. The Roman emperors Augustus and Tiberius also collected bones. What unites a lot of these discoveries is that they come from areas with a lot of fossils - mainly from the Miocene to the present and composed of large megafauna such as mammoths, mastodon, giraffe and rhinoceros to name a few.

According to the review, the book includes a number of archaeological instances where fossils were found in classical or preclassical contexts. I like Afarensis' point that despite the possibility that such finds guided mythological formulations of ancient giants and the like, classical philosophers "made little mention of such discoveries."

It makes you wonder what might have been done with the same evidence and the right person. As I was reading the review, I was reminded of Thomas Jefferson and the mastodon, and I went looking up some details:

In 1784, Jefferson had bravely argued against Buffon's statement that the "mammoth" bones of North America represented the same species as those of the modern elephant. Lacking professional confidence, Jefferson successfully enlisted the support of Ezra Stiles, president of Yale College, but Buffon never wavered in his identification. Ultimately, Jefferson's position was sustained by Georges Cuvier (1769-1832), the brilliant French anatomist, who recognized the bones as those of the mastodon (Coonen and Porter 1976:747).

In the eighteenth century, those knowledgeable about fossils and anatomy to a sufficient degree to argue such facts were rare. In classical times, such people simply did not exist. Considering the spacing of natural historians in the late eighteenth century (a handful per nation-state), it is probable that no conversation could have been sustained among them without technologies, particularly printing. This is particularly true because the comparative study of such remains requires visual representations -- diagrams at a minimum; ideally casts or original specimens -- which could hardly have been distributed to a critical number of people very much earlier in time.

It's no surprise that there was some change in mindset between classical times and the Enlightenment. Still, one wonders which innovations were essential to the growth of science. As indicated by the review, classical peoples were evidently interested in ancient remains and even collected them. This acquisitiveness had increased by the eighteenth century -- with a substantial number of avocational antiquarians -- but was hardly different in character.

The interpretation that ancient mastodons and other such fossils were the remains of an ancient race of "giants" was perfectly straightforward. Although clear evidence is rare, it seems probable that every culture with exposure to such ancient bones arrived at similar mythology-inspired conclusions. In Europe and America, such explanations persisted in Jefferson's day. Even post-Renaissance antiquarians arrived at semi-mythological explanations for ancient artifacts -- for instance, ancient stone tools as "thunderstones." Most straddled the boundary between mythology and naturalism.

The Enlightenment was the first point at which the tide of science was capable of formulating and testing a coherent alternative. The fossil record provided clear evidence directly on the origins of the earth and its history, and the logical options were clear enough once some connection between rock layers and time was made. As an example, Jefferson already knew enough to predict overkill as a cause for the disappearance of ancient megafauna:

Jefferson argued that an animal as large as the "great-claw" [the giant sloth] must always have been rare because, he reasoned, the "ordinary economy of nature" would provide "sufficient barriers" to large populations:

If lions and tygers multiplied as rabbits do, or eagles as pigeons, all other animal nature would have been long ago destroyed, and themselves would have ultimately extinguished after eating out their pasture (Jefferson 1799, p. 256)

Referring to Africa, Jefferson also claimed that a "new population" -- namely, man -- tended to drive off large animals to the continental interior. He suggested that in North America the pressure of Indian hunters had accomplished the same shift. This analogy was the rationale behind his seemingly whimsical instruction that Lewis and Clark look for signs of the living mammoth west of the Mississippi. Furthermore, Jefferson hinted that, by preferential hunting of these giant animals for an obviously great store of meat and hides, the Indians had probably exterminated them (Coonen and Porter 1976:747).

Two assumptions had crystallized by the eighteenth century: exponential (or "Malthusian") growth of populations, and the progressive decay of ancient things. Both assumptions are products of everyday observations that may have gotten more ordinary over time.

Old cities decay and are replaced; old things are buried and unburied. Sometimes the cities themselves get higher as a result -- a fact increasingly known as excavations into the subterranean layers of cities (for foundations and sewers) increased. The classics surely knew these things, but the recognition of old things must have grown as human history piled itself up into deeper and deeper layers.

The fleeting nature of life and youth was a standard of classical authors, but the disappearance and decay of entire civilizations was particularly part of the Enlightenment zeitgeist. Perhaps it was no accident that the beginnings of paleontology coincided with Edward Gibbon's Decline and Fall of the Roman Empire. Lost signs of ancient things became a staple of early Romanticism, and several scenes in Wordsworth's work wear on the implications of hidden histories. Better-known is Shelley's "Ozymandias," written in 1817:

I met a traveller from an antique land
Who said:—Two vast and trunkless legs of stone
Stand in the desert. Near them on the sand,
Half sunk, a shatter'd visage lies, whose frown
And wrinkled lip and sneer of cold command
Tell that its sculptor well those passions read
Which yet survive, stamp'd on these lifeless things,
The hand that mock'd them and the heart that fed.
And on the pedestal these words appear:
"My name is Ozymandias, king of kings:
Look on my works, ye mighty, and despair!"
Nothing beside remains: round the decay
Of that colossal wreck, boundless and bare,
The lone and level sands stretch far away.

A paleontologist reading the poem may find that it evokes a great fossil eroding from a desert badlands; replace "Ozymandias" with "Tyrannosaurus", and the verse sums up the present-day attitude toward the dinosaurs, far more than that toward ancient Egypt.

Imperial Rome, at over a million souls, was the apotheosis of classical population growth, but a clear reflection on the implications of such growth may have needed post-medieval mathematical insights or monetary and economic insights. London reached its first million shortly before 1800 -- the first city to do so since classical Rome. By that time, economics and mathematics were ready to infer the consequences of rapid population growth.

We now know that both insights were necessary for evolutionary theory to emerge, and the strands of evolutionary thought emerged before Darwin in the Enlightenment. This short-term history of thinking in the eighteenth and nineteenth century certainly benefits from considering just how much had changed in human existence since classical Greece and Rome.

References:

Coonen LP, Porter CM. 1976. Thomas Jefferson and American biology. BioScience 26:745-750.

I really like this Neurophilosophy post on Dostoyevsky's epilepsy. It's a nice piece touching on history, literature, and psychology. Autobiographical details in his novels detail his symptoms, and contemporary accounts from relatives and friends add to the story

According to biographical accounts, Dostoyevsky suffered no more than 10 attacks of epilepsy in the 20 years following his first seizure, whenever that may have been. Dostoyesky himself stated that his seizures began one Easter night during his exile in Siberia. He had been arrested on April 23rd, 1849, for his involvement with the Petrashevsky circle, a group of liberal intellectuals. After his arrest, Dostoyevsky was subjected to a mock execution, as a form of psychological torture, before being taken to Semipalatinsk prison in Omsk; some researchers have suggested that the trauma of the mock execution is what triggered his epilepsy.

From 1860, Dostoyevsky recorded the dates of his seizures in a notebook; from that time, up to his death some 20 years later, he documented 102 seizures. This provides the researcher with precise information about the frequency of his attacks, and shows that it was not until 1857, soon after Dostoyevsky's first marriage, that his condition was unequivocally diagnosed as epilepsy.

I think it is a story very relevant to the nineteenth-century context, which increasingly moved toward acceptance of mysticism on the one hand, and psychological science on the other. And strange blends of the two, manifested by Freud (who makes an appearance in the post) and others.