Mass extinction; on Darwin, Adam Smith, Newton (and Parfit)
Every so often the significance of extinction to Darwinian natural selection is rediscovered. (The present post is triggered by Mary Pickard Winsor's (2023) "Darwin’s dark matter: utter extinction" Annals of Science which landed in my mailbox because I try to keep informed on trends in scholarship in the history of science.) During the mid 1990s, when I was in graduate school, and Bill Wimsatt and I were talking a lot about the mechanisms of cultural or memetic evolution (including in a reading group with Betty Van Meer) he remarked that we had not really considered cultural extinction. One of Bill's great methodological themes is consilience (although he prefers 'robustness'), and he was enchanted at the time with the ways in with the Alvarez hypothesis was being confirmed through many lines of inter-disciplinary research not the least the growing awareness of the significance of the Chicxulub crater.
As an aside, it's pretty clear that 'mass extinction' was in the air in the 1970s and 80s due to growing awareness of the unfolding impact of humans on the environment and concern over atom bombs. And that, of course, this included the possibility of human extinction. Parfit's Reasons and Persons, with its famous last two pages (recall), appeared in 1984. So, if you want you can read what follows as another contribution to the archeology of the pre-history of population ethics (recall this post on Cantillon and Sidgwick) in what I call its ‘popular sense.’
In fact, at Chicago David Raup (who was part of a group of very charismatic paleontologists at the time) was a well known figure on campus pushing the argument that mass extinction events were cyclical and caused by astrophysical events. The opening sentence of his paper, "The role of extinction in evolution," always stuck with me: "The extinction of species is not normally considered an important element of neodarwinian theory, in contrast to the opposite phenomenon, speciation." I return to Darwin and extinction below.
Interestingly enough, Newton, in the closing page of the Principia, also hints at a doctrine of mass extinction. There Newton's emphasis is on how interstellar vapors "derived from the sun, the fixed stars, and the tails of comets" are the source of "terrestrial substances." And so it's natural to read Newton as offering a story of cosmic hope in which our life is seeded by the stars (perhaps overseen by the Deity). But somewhat slyly, Newton had just noted that these very fixed stars are not themselves eternal, but "appear and disappear by turn". (I am using the old Motte translation.)
Newton is, thus, echoing Stoic and Epicurean doctrines of eternal return by way of cosmic conflagrations. And before you think this is all based on terribly slender evidence, his classically trained readers (Bentley and Halley, in particular) would have discerned the echo of Seneca's treatment of comets (recall here despite my caution; and here). Halley knew his Seneca on comets (recall). To what degree this connects to Newton's millenarianism I leave to readers better informed on such topics.
This is to say the possibility of mass extinction was put back on the agenda in the most admired book of the eighteenth century. And its significance would have been known to readers informed of Robert Hooke's conjecture in his posthumously published work on earthquakes (1705): “There have been many other Species of Creatures in former Ages, of which we can find none at present; and that ’tis not unlikely also but that there may be divers new kinds now, which have not been from the beginning.” In fact, the difference between Hooke and Newton here foreshadows the debate between volcanos vs and asteroids as the source of mass extinction in our time. Either way, the age of the Earth and species extinction and its causes were simmering issues throughout the eighteenth century.
For example, as I have noted in my own scholarship, there are plenty of hints in the writings of Adam Smith (who was a very good friend of Hutton) that he was aware of such debates especially in his posthumous Essays on Philosophical Subjects. In particular, as Spencer Pack has emphasized, Smith took an interest in species extinction in the Wealth of Nations (WN 4.7.a.11, 560), where he treats Buffon’s Natural History as a source on the extinction of a number of species (note the plural):
Smith, who was himself a passionate botanist, clearly recognizes that when new predators enter an environment local animals may be vulnerable to extinction.
Now, there is a small cottage industry devoted to the relationship between Darwin and Adam Smith (to which I have contributed; I argue that Smith was a kind of group selectionist.) This relationship is not without interest to Marxists, environmentalists, and Social Darwinians (etc.) and scholars thereof. The consensus view seems to be that Darwin's account of the emotions and ethics owes something (although less than one might think) to The Theory of Moral Sentiments, but, despite many people assuming otherwise, almost nothing to the Wealth of Nations which he probably did not read. (See, for example, this piece by Greg Priest.) However, as Priest notes, we do know that Darwin almost certainly read Dugald Stewart's intellectual biography of Smith printed in Smith's Essays of Philosophical Subjects. Oddly, nobody has figured out whether he also read Smith's essays in EPS. (In part, I suspect, because people don't seem to realize that these essays are relevant to the question of Smith's possible impact on Darwin.)
As an aside, Malthus, whose importance to Darwin I need not emphasize, and who is very influenced by Smith in lots of ways, is definitely alert to the possibility of extinctions of populations, but I am unfamiliar with a place where he worries about mass extinction of the human population. (I'd love to learn otherwise.)
I was going to end here. But there is, in fact, an incredibly long and much debated footnote (!) passage in The Theory of Moral Sentiments that bears on this pre-history:
Thus self-preservation, and the propagation of the species, are the great ends which Nature seems to have proposed in the formation of all animals. Mankind are endowed with a desire of those ends, and an aversion to the contrary; with a love of life, and a dread of dissolution; with a desire of the continuance and perpetuity of the species, and with an aversion to the thoughts of its entire extinction. But though we are in this manner endowed with a very strong desire of those ends, it has not been entrusted to the slow and uncertain determinations of our reason, to find out the proper means of bringing them about. Nature has directed us to the greater part of these by original and immediate instincts. Hunger, thirst, the passion which unites the two sexes, the love of pleasure, and the dread of pain, prompt us to apply those means for their own sakes, and without any consideration of their tendency to those beneficent ends which the great Director of nature intended to produce by them. (TMS 2.1.5.10, p. 77 in Glasgow edition--emphasis added.)
Let's leave aside to what degree Smith wants us to think of Nature and its director as distinct entities. And to what degree his invocation of natural teleology must itself be explained through efficient causes (compare Kleer and Lisa Hill with younger and older versions of Pack & Schliesser). All I want to call attention to here is Smith’s insistence that we don't just have an innate desire for the continuance and perpetuity of the species but also have an innate aversion to mass extinction of the human population. Now, that aversion to mass extinction wouldn't be in us for no reason at all; the presence of the desire suggests it's a live possibility. To what degree the desire reflects our species’ history I leave for another time. But if Darwin read Smith’s TMS with selection-ist eyes, as seems agreed, this passage would have been quite noticeable.