Oswald Heer

Oswald Heer: The Invalid Who Warmed the Arctic

Through the 1870s, crates of rock arrived in Zurich from Greenland and Spitsbergen, sent back by polar expeditions that had no idea what to do with them. They were opened by a tubercular Swiss professor who by then could barely leave his rooms. Oswald Heer read the leaf impressions inside and concluded that the high Arctic had once carried a vegetation nothing like the tundra sitting on top of it — that the far north had been, in deep time, a warm and crowded place. He was working from flattened leaves, and he was broadly right.

A Minister's Son at Halle

Heer was born in 1809 at Niederuzwil, in the canton of St Gallen, into a Protestant minister's household. He was sent to Halle to train for the clergy and took doctorates in philosophy and medicine along the way, but from about 1828 the natural sciences had him. Clerical training would leave a permanent mark on his thinking, and not only in the obvious way: it gave him the philological habit of treating a difficult text as something to be read closely and reconstructed, which is more or less what he would spend fifty years doing to slabs of Tertiary limestone.

Beetles First

His first reputation was entomological. From 1834 he published steadily on Alpine beetles, and his *Fauna Coleopterorum Helvetica* (1838–41) became the standard work — the book that made his name before anyone associated it with fossils. He was appointed to a chair at the University of Zurich in 1851 (some sources say 1852), teaching botany and entomology and running the botanical garden, and he held the post for the rest of his working life, close to half a century of teaching in the same institution.

The beetle years matter more than they look. They gave Heer the one skill his later work absolutely required: the ability to identify an organism from fragmentary, distorted, badly preserved evidence, and to know exactly how far such an identification can be pushed before it becomes a guess.

The Turn to Fossil Plants

The pivot came with a discovery of fossil plant remains near Lausanne. From there Heer moved into palaeobotany and effectively rebuilt the field. His *Flora Tertiaria Helvetiae* — the Tertiary flora of Switzerland, published from 1855 — established him internationally, and it was followed by what a contemporary called a nearly uninterrupted series of works. He also wrote *Die Urwelt der Schweiz*, "The Primeval World of Switzerland," a synthesis for a wider readership, and studied the plant remains recovered from Switzerland's prehistoric lake-dwellings, which put him at the origins of archaeobotany as well.

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The scale of the output is difficult to overstate. Across his career Heer described roughly 2,632 plant species, of which some 1,627 were new to science. From the single fossil deposit at Oeningen he described 826 insect species. He was not merely cataloguing: at Oeningen he reconstructed an ecosystem, reading plants and insects together as a functioning prehistoric community, which was not how most of his contemporaries worked.

Reading the Arctic

His best-known work is the *Flora Fossilis Arctica*, published in volumes from 1868 until the year of his death in 1883. The material came from the great Arctic expeditions of the period, and Heer became the man everyone sent their plant fossils to. He also worked on European material — the Bovey Tracey deposits in Devonshire, examined with W. Pengelly — but the Arctic collections were the ones that broke open a general question.

What the Greenland and Spitsbergen fossils showed was a Tertiary flora of a richness and character the modern Arctic cannot support. The obvious implication, and the one Heer drew, was that climate at high latitudes had changed enormously. This is now unremarkable. In the 1870s it was a substantial claim about the history of the whole planet, built on leaves.

The Arcto-Tertiary Hypothesis

Heer went further, and this is his most interesting idea. He proposed what became known as the arcto-Tertiary theory: that the Arctic had functioned as a centre from which plant groups spread southward, and that this migration explained one of the standing puzzles of botany — the striking resemblance between the floras of eastern Asia and eastern North America, two regions separated by an ocean and a continent. A shared northern origin, followed by southward retreat as the climate cooled, accounts for the pattern without requiring anything miraculous.

He got things wrong too. Several of his stratigraphic age assignments — what he called Miocene, in particular — were revised by later workers, and his species counts include a good deal of over-splitting of the kind that afflicted all nineteenth-century descriptive science.

The Argument He Would Not Have with Darwin

Heer corresponded with Darwin, who valued his judgement on fossil plants, and the two remained on cordial terms while disagreeing fundamentally. Heer rejected natural selection on religious grounds. In its place he proposed periods of creation, during which species could give rise to related descendants — a model of relatively sudden transformation rather than continuous gradual change. It is a position that reads today as a rearguard action, and it was; it is also worth noticing that the man supplying much of the fossil evidence that would be used to argue for evolutionary continuity did not himself accept the argument.

Why Oswald Is Called a Genius

The faculty is inferential reach from impoverished evidence. A fossil leaf is a smear of carbon with a vein pattern. Heer could name it, place it in a climate, put it in a community with the insects that fed on it, and then use its distribution across two hemispheres to propose a global history of plant migration. That chain — from a single flattened frond to a hypothesis about how the world's forests came to be arranged — is the mark of a genuinely powerful scientific imagination, disciplined by a taxonomist's exactness about what the specimen does and does not show.

He did it, moreover, under conditions that would have ended most careers. Tuberculosis caught in his forties confined him progressively indoors; he was bedridden at the end; and the 1911 *Britannica* summarises his working life as one of "slender means and ill-health." He never married, and the Arctic he reconstructed in such detail he never once saw.

The counter-case: Heer was a describer more than a theorist, and even his central hypothesis is an inference from distribution rather than a mechanism. His datings were substantially revised. His refusal of Darwin was not scientific caution but doctrinal, and it left him arguing for a creation model that went nowhere. Much of his international standing in Britain owed to Charles Lyell's advocacy rather than to his own reach. What holds up is the arcto-Tertiary idea and the sheer bulk of accurate, usable description he left behind — which is the foundation later people built theory on.

Legacy

Heer died at Lausanne on 27 September 1883, aged seventy-four, the final volume of his Arctic flora barely behind him. *Nature*, marking his death, observed that the real difficulty would be finding anyone competent to work through the polar expeditions' material at his pace — an unusually practical form of tribute. The Geological Society of London had given him its Wollaston Medal in 1874 (some sources say 1873), and Cape Heerodden on Spitsbergen carries his name on ground he studied at second hand. Palaeobotany as a discipline capable of saying something about climate, migration and deep time largely starts with him.