Zoonomia, by Erasmus Darwin

“Zoonomia,” published in 1794, was written by Erasmus Darwin, Charles’ grandfather. I found it very accessible, though as a sign of the times some passages in Latin were not translated.

Erasmus was a deist. Because causes are superior in power to effects, he says, so as we trace the operations of nature from cause to cause, climbing up the links in these chains of being, so our idea of the power of the Almighty Creator becomes more elevated and sublime, till we ascend to the Great Source of all things. But his Creator is not the God of the Gospels. He speaks of living creatures existing for millions of generations; he quotes David Hume: …the greatest part of the Earth having been formed out of organic “recrements”; as the immense beds of limestone, chalk, marble, from the shells of fish; and the extensive provinces of clay, sandstone, ironstone, coals from decomposed vegetables… the world itself might have been generated, rather than created.” Erasmus appreciates natural laws since it would seem to require a greater infinity of power to cause the causes of effects, than to cause the effects themselves.

I’ve introduced him by the closing pages of Part One of his work [Part Two is a summary of all medical knowledge of the time, divided up into classes and orders as Linneaus divided living species]. The meat of his thinking on living creatures lies  in his accounts of how they develop and evolve. Here I found all the ideas we usually attribute to later evolutionists. But Erasmus in turn attributes some of them to his predecessors.

Here’s a quick review:

Development of the embryo
. He rejects “preformationism,” the idea that during development from an embryo a miniature version of a creature simply expands into an adult. As a good atomist he sees the atomic nature of matter precludes the original embryo having come with a cascade of ever-smaller embryos stored within it—this would involve “a greater tenuity to organized matter, than we can readily admit,” Also, if creatures simply enlarged that would preclude them from being able to regrow parts they lost, as a crab can regrow a lost claw. And, that mechanism couldn’t create hybrids.

Instead: “Mr. Buffon has with great ingenuity imagined the existence of certain organic particles, which are supposed to be partly alive, and partly mechanic springs.” What a great prefiguring of the genome! Erasmus borrows that idea and applies it to the spermatozoa, that he then refers to as “living filaments.” He then supposes that all living creatures originate in such filaments.

Erasmus believes all the information needed for building an adult creature comes in the spermatazoa, the female supplying primarily the supplies the male filament needs to go about its work. In our terms this would be as if the male genome alone directed the growth of the new adult, the female influencing it through cytoplasmic features, rather as the embryo acquires mitochondria.

Development: The male sperm acts on the female “egg” as a fiber through a process of irritability and sensitivity, to create “glands,” by which Erasmus seems to mean organs and tissues in general. Each “gland” then develops a fiber that induces the development of the next “gland.” The embryo is “supposed to consist of a living filament, which acquires or makes new parts with new irritabilities, as it advances in its growth.”

Origin of species: The differences in the forms and qualities of embryos arises “only from the different irritabilities and sensitivities, or voluntarities, or associabilities, of this original filament; and perhaps in some degree from the different forms of the particles of the fluid [female tissues] by which it has been at first stimulated into activity. And, from hence, as Linnaeus has conjectured in respect to the vegetable world, it is not impossible, but that a very great variety of species of animal, which now tenant the earth, may have their origin from the mixture of a few natural orders. And that those animal and vegetable mules [hybrids], which could continue their species, have done so, and constitute the numerous families of animals and vegetable which now exist…” Clearly Linnaeus and Erasmus do not regard species as fixed.

Physicality of the process of development: “All animals, therefore, I contend, have a similar cause of their organization, originating from a single living filament, endued indeed with different kinds of irritabilities and sensibilities, or of animal appetencies; which exist in every gland, and in every moving organ of the body, and are as essential to living organizations as chemical affinities are to certain combinations of inanimate matter….the animal appetencies are not only perhaps less numerous originally than the chemical affinities; but like these latter, they change with every new combination; thus vital air and azote, when combined, produce nitric acid; which now acquires the property of dissolving silver; so with every new additional part of the embryon, as of the throat or lungs, I suppose a new animal appetency to be produced.”

Inheritance of acquired characteristics. “The ingenious Dr. Hartley in his work on man, and some other philosophers, have been of opinion, that our immortal part acquires during this life certain habits of action or of sentiment, which become for ever dissoluble, continuing after death in a future state of existence… I would apply this ingenious idea to the generation of production of the embryon, or new animal, which partakes so much of the form and propensities of the parent…. In its more advanced state, the fetus evidently possesses volition, as it frequently changes its attitude… and afterwards the power of volition contributes to change or alter parts of the body during its growth to manhood… From their first rudiment, or primordium, to the termination of their lives, all animals undergo perpetual transformations; which are in part produced by their own exertions in consequence of their desires and aversions, of their pleasures and their pains, or of irritations, or of associations; and many of these acquired forms of propensities are transmitted to their posterity.” ".... and thus possessing the faculty of continuing to improve by its own inherent activity, and of delivering down those improvements by generation to its posterity, world without end?

Influence of parental thought on development of an embryo: “I conclude, that the imagination of the male at the time of copulation, or at the time of the secretion of the semen, may so affect this secretion by irritative or sensitive associations… as to cause the production of similarity of form and features… as the motions of the chisel of the turner imitate or correspond with those of the ideas of the artist.” The female may have less influence: “the world has long been mistaken in ascribing great powers to the imagination of the female, whereas from this account of it, the real power of imagination, in the act of generation, belongs solely to the male.”

Laying the ground for "Vestigies..." mechanism, creation by the Christian God: "... would it be too bold to imagine that in the great length of time, since the earth began to exist, perhaps millions of years... that all warm bloodied animals have arisen from one living filament [Vestigies' "original embryo"], which THE GREAT FIRST CAUSE endued with animality." "shall we conjecture that one and the same kind of living filament is and has been the cause of organic life?"

Laying the ground for natural selection: “Every individual tree produces innumerable seeds, and every individual fish innumerable spawn, in such inconceivable abundance as would in a short space of time crowds the earth and ocean with inhabitants…. This arguments only shews, that the productions of nature are governed by general laws…”

The second part of "Zoonomia" is a catalog of medical conditions by order, class, down to species, inspired no doubt by Linnaeus’ cataloguing of living species, each having symptoms detailed, then a remedy. Almost no science. It’s a sobering reflection of how little was known just 200 years ago. I assume the comprehensiveness and the novel classification of diseases made this book very popular throughout Europe, carrying the first part, with its speculations about evo-devo along with it. As I said, there’s little in Lamarck that isn’t here. New ideas seem to begin with “Vestiges…” That's where the division of development from evolution seems to start, a process to be completed by Erasmus’ grandson, Charles.

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