Count Alexander von Keyserling was among the first of Darwin’s “foreign scientist” acquaintances to receive a complimentary presentation copy of On the Origin of Species directly following its publication in 1859 (DCP-LETT-2505). A Baltic German geologist, known for his geologic expeditions in Russia, Keyserling had previously proposed a unique explanation for the transmutation of species in a brief article “Note sur la succession des êtres organisés,” [Note on the succession of organized beings] in 1853. Keyserling argued that all species possess a unique chemical composition, or signature, which can be modified by the interaction of “foreign molecules” – such as those believed to cause disease – with the “germinating elements.” Or, as Darwin summarized in his Historical Sketch, “as new diseases, supposed to have been caused by some miasma, have arisen and spread over the world, so at certain periods the germs of existing species may have been chemically affected by circumambient molecules of a particular nature, and thus have given rise to new forms.”

Keyserling’s hypothesis about the origin of new species is essentially unique among early evolutionists in arguing that the nature of each species can be tied to a basic set of chemical elements. “For, once we consider organized species as products of the chemical action of different particles or substances on some primitive types, the possible combinations become more and more numerous and complicated; four types, for example, under the influence of twenty-four substances, already produce, by simple combination, 96 species, which, in turn, influenced by 24 bodies, compose a yardstick of 2304 species…” While it is difficult to view this insight as a precursor to knowledge of a genetic code, it nonetheless speaks to an essential relationship between the environment and a chemical blueprint that is determinative of each species on Earth. For Keyserling, a “change in this intimate constitution of the chemical formula of the species, so to speak, would produce a transformed species.”

At the time of Keyserling’s paper, the causes of disease were often attributed to the idea of miasma, or sickness-inducing particles which traveled suspended in the air (this was thought to be the case in the cholera epidemics in 1850s London and Paris). The evidentially real havoc that these particles (miasmas) wreaked on the constitutions of once-healthy individuals suggested to Keyserling the existence of similar chemical packages able to induce a chemical change in the early development of an organism. Keyserling’s theory met with mixed reviews. The hypothesized transformations would be saltational, affecting species around the globe.  Keyserling wrote that his theory could explain the destruction and subsequent succession of large swaths of flora and fauna in Earth’s history (major extinction events) through analogy with the episodic nature of various diseases which had arisen and desisted in times past. In addition to accounting for the destruction and replacement of species and the general trend toward increasing complexity, Keyserling argued that his theory solved one of the difficulties which most troubled Darwin – the lack of intermediate forms in the fossil record (which was certainly the case in the mid-1800s).

“[O]ur hypothesis… alone accounts for depletion as well as the replacement of species, without resorting to the fiction of transitory forms; it explains the general extent of the modifications of terrestrial fauna and flora in a similar order of succession in every place; it makes us understand why each of the phases of the organized world of the earth joins, as to the resemblance of the forms, to the preceding and the following more than to all the others; finally, it accords with the increase in the variety and complication of organized beings, through geological epochs, as our research has established.”

 Although Keyserling seems to have received Darwin’s gift of On the Origin of Species cordially, he did not do so without critique. As Darwin wrote to Charles Lyell in May of 1860, “I have had a brief note from Keyserling, but not worth sending you: he believes in change of species, – grants that natural selection explains well adaptation of forms, but thinks species change too regularly, as if by some chemical law, for natural selection to be sole cause of change.” With time, however, Keyserling came to appreciate Darwin’s work, and, in 1886 (after Darwin’s death), he wrote that he had come to accept natural selection as the best possible explanation for the origin of new species.