Jacob Suissa joins the Friedman Lab

After earning his undergraduate degree in plant biology from the University of Vermont, Jacob spent time studying the phylogenetics of lycophytes at the Smithsonian Institution’s National Museum of Natural History. As a PhD student in the department of Organismic and Evolutionary Biology, he plans to delve into research focusing on morphological development and diversification in a phylogenetic context.

Welcome Jacob!

Tracing the Evolution of Form and Function

The Arboretum’s 2017 plant anatomy summer short course kicks off at the Weld Hill research facility.

Read more.

Denis Diderot

Denis Diderot (1713-1784)

Coming soon.

Franz Unger

Franz Unger (1800-1870)

Franz Unger

Franz Unger was an Austrian botanist, biogeographer, and paleontologist who trained in law, medicine, and natural history before being appointed to the faculty of the University of Graz and director of its botanical garden. He was an early adherent of the “cell theory” (attributed to Schleiden and Schwann) that postulated that all cells in organisms are derived from preexisting cells and that such units are the fundamental building blocks of organisms.

Unger’s pre-Darwinian evolutionary views can be found in a series of books published in the 1850s, including Botanische Briefe (1852) which was translated into English Botanical Letters (1853), Versuch einer Geschichte der Pflanzenwelt (1852), and his popular illustrated treatment of the primeval world Die Urwelt in ihren verschiedenen Bildungsperioden (1851; see Rudwick, 1992 for reproductions of illustrations). Unger stressed that just as there was continuity of cells and cell lineage, that organisms gave birth to other organisms, the same is true of species, which must arise from previously existing species (as opposed to miraculous or spontaneous generation). In essence, Unger gave species the attributes of an ontogeny, with a birth, period of development, and finally extinction. Unger also viewed species and varieties as part of a continuum.  Ironically, after publication of On the Origin of Species, Unger rejected the mechanism of natural selection, as this would necessitate the evolution of the human mind. Unger was no materialist.

With respect to plants, Unger hypothesized that the origin of plant life could be traced to a single cell: “In short, the cell is not only the starting point of the individual life of the plant, but at the same time the starting point of the life of species and all higher unities; it is indeed likewise the starting point of the whole plant world.” Unger’s understanding of the fossil history of plants was used to argue that “the world of plants also, which is divided into seven great geological periods (including the present one), has gradually developed itself step by step.” Finally, Unger also noted that deviant forms of plants (sports) could give rise to new varieties and that such deviations were not the result of external (environmental) influences, but rather something more fundamental that can “transmute also one species into another.”

For an article on Unger and his evolutionism, see Gliboff (1998): Evolution, revolution, and reform in Vienna: Franz Unger’s ideas on descent and their post-1848 reception. Journal of the History of Biology 31: 179-209.

A Calamite Forest of the Coal Period

A Calamite Forest of the Coal Period

Charles Southwell

Charles Southwell (1814-1860)

Charles Southwell’s atheistical publication The Oracle of Reason, or Philosophy Vindicated is a primary example of the manner in which transformist ideas of the Victorian period could be co-opted and made to serve political, social, or philosophical aims. Southwell, the youngest of 33 children from a working-class English family, was a radical freethinker, social reformer, and an atheist. In 1841 he founded The Oracle of Reason along with William Chilton and John Field, and became the first editor of the periodical. In a 48-part series of short articles in the Oracle entitled Theory of Regular Gradation, Southwell drew on contemporary ideas of progressive evolution to further a materialistic and anti-religious worldview.

The series is heralded by a crude illustration of the French naturalist Pierre Boitard’s “L’Homme Fossile” and an accompanying quote from Boitard encapsulating the thesis of regular gradation: “…organic formation after organic formation has taken place, passing gradually from simple to compound bodies…”. Southwell then describes the clerical opposition to viewing man as having any relation to “the inferior animals”, denouncing those who “rest contented in most shameful ignorance, rather than their pride should be mortified by any discoveries in science, hostile to their cherished opinions” (I). Not a naturalist himself, Southwell attributed the scientific “facts” in his publication to an eclectic selection of naturalists-from the less reputable science of Boitard and Lord Monboddo to the more esteemed Buffon and Lamarck. (The Oracle’s co-founder, William Chilton, who would write the later articles in the Theory of Regular Gradation, drew more heavily upon Lamarck and Lyell.) Progressive evolution, Southwell claimed, proved that “there are no fixed modes (laws as they are styled) for each species and each part, there being nothing fixed in the parts of nature, which are in a continual state of flux or change (III).

Transmutation was helpful to the reformer and the atheist agenda not only because it debunked the theory of special creation, but also because it seemed to indicate a sort of fluidity in nature – a lack of any true distinction among natural kinds – which aided Southwell and his peers in portraying the existing hierarchical religious and social structure as having been arbitrarily imposed on the natural world by an aristocratic elite anxious to maintain the status quo. In the Theory of Regular Gradation, Southwell was particularly devoted to teaching his readers about Boitard’s “oscillatoires de murailles” – ambiguous simple-celled forms of life which were difficult to classify as belonging to either the plant or animal kingdom. His writing makes evident that he saw in this ambiguity in nature, support for a materialist, reductionist view of the world which made it possible to denounce both the existing social structure and traditional Christian teaching.

In fact, whereas other reformers of the period accepted at least a nominal association with Protestant Christianity for the sake of achieving their goals of social reform, Southwell had a particular virulence toward the Church of England and for this reason had broken from the socialist missionary group founded by Robert Owen before founding The Oracle. Ultimately, his denunciation of religion in The Oracle (he used particularly racist and offensive terms in his descriptions of the Bible) led to his arrest and imprisonment for blasphemy. As a result, William Chilton assumed authorship of the Theory of Regular Gradation series, picking up where Southwell left off after the sixth article. Eventually, The Oracle shut down in 1843 due to financial difficulties.

For a more in-depth treatment of Southwell’s use of evolutionary biology in the sociopolitical context of Victorian England, please see Adrian Desmond’s Artisan Resistance and Evolution in Britain, 1819-1848 and Beyond the ‘Common Context’: The Production and Reading of the Bridgewater Treatises by Jonathan Topham.

Constantine Rafinesque (1738-1840)

Constantine Rafinesque (1783-1840)

The truth is that Species and perhaps Genera also, are forming in organized beings by gradual deviations of shapes, forms and organs, taking place in the lapse of time. There is a tendency to deviations and mutations through plants and animals by gradual steps at remote irregular periods. This is a part of the great universal law of PERPETUAL MUTABILITY in everything. Thus it is needless to dispute and differ about new G. [genera] Sp. [species] and varieties. Every variety is a deviation which becomes a Sp. As soon as it is permanent by reproduction. Deviations in essential organs may thus gradually become new G.” (Rafinesque, “Principle of the Philosophy of New Genera and New Species of Plants and Animals”, 1833).

In 1841, the American botanist Asa Gray authored a “Notice of the Botanical Writings of the Late C.S. Rafinesque.” Regrettably for Rafinesque, Gray was no fan of his voluminous additions to the number of plant taxa that were previously recognized as species by botanists.  In his lifetime, Rafinesque would go on to name more plant species than even Linnaeus.  Gray wrote,  “According to his principles, this business of establishing new genera and species will be endless; for he insists… that both new species and new genera are continually produced by the deviation of existing forms, which at length give rise to new species… He assumes thirty to one hundred years as the average time required for the production of a new species, and five hundred to one thousand years for a new genus… (238, American Journal of Science and the Arts, 1841).

Rafinesque’s ideas on the variation of botanical form were inseparable from both his evolutionary theory and his botanical methods. In 1833, he published, “Principle of the Philosophy of New Genera and New Species of Plants and Animals”, containing excerpts of a letter he had written to the botanist John Torrey, in his own Atlantic Journal, and Friend of Knowledge to advance his opinions that recognition of the “great universal law of Perpetual mutability” implied a change in classificatory practice among professional botanists. He proposed that the “tendency to deviations and mutations through plants and animals by gradual steps at remote irregular periods” would allow observers of the natural world to trace each species or variety back to its primitive original, therefore creating a new “natural” genealogical method of classification and condensing and simplifying extant classificatory systems (1833, 1836).

If it is inescapably true that in every small variant of nature, Rafinesque saw the potential makings of a new species, it is also true that this world view represented the antithesis of the dominant views of most classifiers and taxonomists, who insisted – at least for purposes of their science – that species were eternally unchanging. “Nature only acknowledges individuals, and varies them constantly; so as to produce new species now and then…” (The World, 1836) Rafinesque had a keen awareness of variation within species, and understood that such variation was the raw material of evolution.

“The process is by the seedlings being somewhat different from the parents, and thus evincing a deviation of typical mould, that may be, or may not be; propagated again. If it is, this soon assumes a permanence, becoming a permanent variety if the deviation is slight, such as mere color of flowers, size of stem, leaves, &c.; but becoming a New Species! if at last several deviations are permanently combined. A tendency to such deviations is sometimes met even in the various annual shoots of the perennial plants, or shrubs and trees, that are not always alike to those of the preceding years.” (16, New Flora and Botany of North America, 1836)

What is clear in Rafinesque’s transmutationist writings is that he did not view all of life as descended from a single common ancestor. “All species may have been varieties once, except the original types or ancestors of the genus…”; a failing that was noted in Darwin’s Historical Sketch. Thus, in a manner reminiscent of the eminent plant hybridizer William Herbert, Rafinesque could envision the evolution of new species but could not imagine scaling this common process to all of life.

“We know not how many living forms existed at first, or were created on earth at the earliest period; but by the fossil relics of many, we ascertain that they were fewer and often different. Whatever was their original number and types; it is probable that these primitive individuals have produced all the actual various species, of which we have already ascertained nearly eighty thousand of animals, with a hundred and twenty thousand of plants. The proofs of this fact are found in the varieties and monstruosities, still proceeding under our eyes, or that have for ages past. Every species was once a variety, and every variety is the embryo of a new species.” (The World, 1836)

Also like Herbert, Rafinesque wrote a lengthy poem that included the topic of mutability in the natural world. In The World, or Instability (1836), his ideas on evolution in nature are placed in the context of his philosophical view of a Hericlitean world. This poem also strongly echoes Erasmus Darwin’s posthumously published Temple of Nature (1803).  Advocating for an eternal law of constant change which causes deviations in the form of living beings, including plants, he writes:

“…CHANGE extends also to vary forms,

…Not even two leaves or blooms

In vain you’ll seek to match upon a tree.

…This is the Law, the positive decree…” (14-15, Worlds, 1836).

Complicating Rafinesque’s supposedly simpler method of classification was the fact that he believed each new form should be given a new name. This propensity for “multiply[ing] names” upset many of his botanical contemporaries who, like Gray, disregarded much of Rafinesque’s work during his lifetime. Nevertheless, Rafinesque’s existing publications show him to have been a polyglot who published on a multitude of topics including botany, zoology, and linguistics. Despite being denied a position on the Lewis and Clark expedition of 1806, Rafinesque individually surveyed much of the southern and central North American flora. He was appointed a professorship at Transylvanian University in Kentucky in 1819, but left over disagreements with the administration.

Jean Louis Marie Poiret

Jean Louis Marie Poiret (1755-1834)

Not only do we conceive the possibility of the creation of new species, but we frequently have the proof before us.

When circumstances are favorable, new species of plants are formed on the surface of the globe, either by change of locality or by means of other congeners.

Can one, in fact, fail to recognize, in a large number of genera, such relationships between species, that they are often very difficult to distinguish, and lead one to believe that they owe their origin to a common strain, I mean to a primitive species.

We believe we must admit, as I have shown the possibility, that varieties can perpetuate themselves as species over time.

Portrait of Jean Louis Marie PoiretJean Louis Marie Poiret 1755 – 1834) was an important French botanist (and clergyman) whose work on the flora of Barbary was followed by major contributions to Encyclopédie Méthodique: Botanique (1816) and Tableau encyclopedique et methodique des trois regnes de la nature: botanique (1819-1823); both in collaboration with Jean Baptiste Lamarck. Poiret would go on to serve as a professor of natural history at the École Centrale in Aisne. However, it is his Leçons de Flore published in 1819-1820, that Poiret fully reveals his evolutionist views.

Although Poiret is now a relatively obscure figure in the history of early evolutionary thought, a recent publication has claimed that Poiret was in fact not a transmutationist. This view is based on a series of historical errors that have been compounded by an erroneous citation dating back to the mid-nineteenth century. As Frederic Gerard, a formidable French evolutionist and botanist in his own right, wrote in his entry on Species in Dictionnaire universel d’Histoire naturelle (1844), “I am therefore convinced, like Lamarck, Poiret, and Geoffroy, that varieties become species, and that this is how new species are formed…” It is clear that Poiret’s contemporaries viewed him as a leading force in advocating evolutionary views.

In the second volume of Leçons de Flore, Poiret devotes an entire chapter (“Des espèces”) to the concept of species and how species might be formed. This is not surprising, given the rise of the natural system of classification and its corollary that species are fixed and immutable for all of time. Beginning in 1810s, the Swiss botanist Auguste-Pyramus de Candolle had been a leading advocate of natural systems of classification. As he wrote in Essai elementaire de geographie botanique (1820): “The whole theory of botanical geography is based on the idea we have of the origin of organized beings and the permanence of species.”

In Leçons de Flore, Poiret begins his arguments by noting that domesticated plants offer evidence of considerable variation and plentiful evidence of the creation of novel varieties. He advances what was then a commonly accepted (but incorrect) view that the notable variation in domesticated cultivars exceeds what might be found in nature, because species brought into gardens are exposed to environmental conditions that exceed what natural species experiences in nature. With a standard Lamarckian perspective on the induction of evolutionary change in organisms by altered environmental conditions, Poiret extends this logic to the wild (and even proposes transplant experiments to confirm the heritable nature of such evolutionary changes):

There are however special circumstances where plants end up naturalizing in climates or soils which are foreign to them: then it results in varieties which in the long run lose their original type, and reproduce, after many generations, endowed with these new attributes which they do not lose, and which lead to the formation of new species. It would then be desirable to be able to transfer these plants to the homeland of their ancestors, to follow successive generations, and to ascertain whether they would resume their primitive character over time.

Poiret demonstrates the power of domestication history to advance an evolutionist perspective  – much as Charles Darwin would do in the first chapter (“Variation under domestication”) in On the Origin of Species. “Although it seems a little reckless, according to the most generally adopted opinion, to suggest that new species are formed in nature, it is very difficult to deny this assertion when we carefully observe what is happening every day in our gardens, where it is not uncommon to see varieties end up constantly reproducing the same by their seeds. Why wouldn’t the same thing happen in nature?” Poiret also invokes hybridism between congeneric species as possible source of new species, noting how common hybridization in gardens is, and extending this process to nature.

Poiret notes “the great revolutions that the terrestrial globe has experienced” and assumes that the Earth was originally covered by water, which over time receded and created the mountains and the plains:

With the lowering or retreat of the waters, the plains have become mountain peaks; the temperature, the exposure, the quality of the terrain have ceased to be the same; the nature of the plants must also have experienced great changes. They have imperceptibly taken on the character of the new localities: the trees have disappeared on great heights; those which could resist, such as birches, willows, etc., have become deformed, shortened, converted into small creeping shrubs, the stems of herbaceous plants, shortened or hardened into almost woody stumps, have lost their ramifications, or else they sprawled on the rocks in grassy tufts; the leaves, struck by the cold, have shrunk and hardened…

Poiret, departing from the dominant catastrophist theories of the day, is clearly a gradualist, noting that “these changes have most probably only come gradually: it was on the first side only varieties which, by supporting themselves, by reproducing constantly, had to take place among those that we have called species. I am even inclined enough to believe that there was first for each of our present genera, only one primitive species, that the others were formed in the long run by the change of localities…”

Poiret ends this extraordinary chapter on the nature of species by forecasting future evolutionary changes, as climates alter over time: “Today our Alps, the face of the vegetation, as well as the forms of the plants, would also change by the influence of a new temperature. Many, no doubt, would perish; but the species which could resist would experience in the long run, in the texture of their organs, modifications which, by making them lose their original character, would convert them for us into species.” Although there no scholarship on Poiret to date (with the exception of a recent erroneous claim that he was not an evolutionist), he deserves to be viewed as an important figure, one who was certainly recognized in France by Gerard in the 1840s, and from an historical perspective, as one of the first three individuals (along with von Buch in 1819 and Herbert in 1821) to draw heavily on plants to posit an evolutionary worldview.

Lorenz Oken

Lorenz Oken (1779-1851)

Coming soon.