In my last post, I told the story of how certain changes in the intellectual climate of the 1700s created fertile soil for an evolutionary model of biology to emerge. The cheery, progressivist conception of human society, which arose from the scientific, industrial, and political revolutions of the age, was the model and inspiration for the evolutionary theories of Erasmus Darwin and other thinkers of that era; and in turn, the idea of evolution was used to preach the need for human progress. 

By the mid 1800s, however, the mental climate had shifted again, and the time was ripe for a new Darwin to craft a new Darwinism to match the spirit of the different age.  

Utopia vs Reality  

When Thomas Malthus wrote his influential “Essay on the Principles of Population” in 1798, the optimistic, progressive narrative of an ever-evolving Mankind was still dominant. This was the very same decade in which Erasmus Darwin, Lamarck, Goethe, and others were crafting theories of biological evolution in the image of a human society which seemed to be rising from the mud of savagery upwards, forever upwards, toward very godhood. But Malthus, looking around him, felt that something was a bit… off about this triumphant vision.  

You can see the contemporary dominance of the evolutionary worldview in the fact that Malthus chooses to address it at the outset. In the opening lines of his essay, he notes some of the social factors that made that worldview seem plausible to his contemporaries: the many discoveries of the scientific revolution, the increase in knowledge and education that came from the printing press, the French Revolution and the related upheaval in the way politics was understood. With great (rhetorical) humility, Malthus informs the reader that when such esteemed philosophers are so sure of the perfectibility of man, he, Malthus, ought to doubt his own reasoning rather than doubt their intellectual honesty or infer that they are willfully blind to unpleasant realities. 

Nevertheless, he goes on to say, these grand philosophical arguments have to pass the test of empirical observation, no matter how good they sound in theory. To make this point, he provides the humorous analogy of a theory that claims humans are in the process of evolving into ostriches:

A writer may tell me that he thinks man will ultimately become an ostrich. I cannot properly contradict him. But before he can expect to bring any reasonable person over to his opinion, he ought to shew that the necks of mankind have been gradually elongating, that the lips have grown harder and more prominent, that the legs and feet are daily altering their shape, and that the hair is beginning to change into stubs of feathers. And till the probability of so wonderful a conversion can be shewn, it is surely lost time and lost eloquence to expatiate on the happiness of man in such a state; to describe his powers, both of running and flying, to paint him in a condition where all narrow luxuries would be contemned, where he would be employed only in collecting the necessaries of life, and where, consequently, each man’s share of labour would be light, and his portion of leisure ample. 

Beyond the sheer lack of empirical evidence, Malthus argues that there is even an incontrovertible theoretical problem with these flighty utopian visions; the speculative philosophers of his day do not seem “to be aware of the tremendous obstacles that threaten, even in theory, to oppose the progress of man towards perfection.” The difficulty as he sees it stems from two relatively uncontroversial postulates: “First, That food is necessary to the existence of man. Secondly, That the passion between the sexes is necessary and will remain nearly in its present state.” The logical result of these two basic premises, Malthus says, is that population growth continuously outstrips food supply, and poverty and starvation are the inevitable result. And, since the amount of land in the world is fixed and since agricultural techniques do not seem to be improving as fast as humans can reproduce, he can see no easy way out of a permanent state of deprivation — utopian prophecies notwithstanding. 

A New Darwinism, for a New Darwin

In hindsight, it seems that Malthus underestimated the possible advances in agricultural technology. But I think he was correct in his most basic point: that achieving utopia or realizing “the perfectibility of man” is not as easy as it might seem at first glance, thanks to the basic constraints of the world we live in. 

In any event, his argument proved very influential. And just as Erasmus Darwin had created a model of biology in the image of the progressive vision of society in his day, Charles Darwin crafted his model in the darker, Malthusian mold. In the introduction to The Origin of Species, Darwin calls his theory simply “the doctrine of Malthus, applied to the whole animal and vegetable kingdoms.” And in his autobiography, he credits his Eureka! moment about evolution to reading Malthus’s essay: 

In October 1838, that is, fifteen months after I had begun my systematic enquiry [into the cause of evolution], I happened to read for amusement “Malthus on Population,” and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The result of this would be the formation of new species. Here then I had at last got a theory by which to work…

Neil Thomas has written a very enlightening essay at Evolution News about how Darwin found it useful to co-opt Malthus to support his evolutionary theory, which many of his peers found rather obvious and unoriginal. However, I don’t think we should go so far as to say that Darwin was merely appropriating Malthus for the authority of his name, and was lying about his inspiration. If you read Malthus’s essay, it’s not surprising that Darwin would have been inspired to connect his economic argument to a theory of biological evolution, since Malthus (in addition to joking about the evolution of man into ostrich) explicitly refers to biology to bolster his thesis. Malthus writes:

Through the animal and vegetable kingdoms, nature has scattered the seeds of life abroad with the most profuse and liberal hand. She has been comparatively sparing in the room and the nourishment necessary to rear them. The germs of existence contained in this spot of earth, with ample food, and ample room to expand in, would fill millions of worlds in the course of a few thousand years. Necessity, that imperious all-pervading law of nature, restrains them within the prescribed bounds. The race of plants and the race of animals shrink under this great restrictive law. And the race of man cannot, by any efforts of reason, escape from it.

With this kind of language, it’s no surprise that Darwin might latch onto Malthusian population theory as the key he had been looking for. If anything, it’s surprising no one had thought of it earlier.

The Second Social Darwinism

The main point is that Darwinism was a product of so-called “social Darwinism” just as much as “social Darwinism” was a product of Darwinism. It was Malthus who inspired Darwin, not the other way around. Although Darwin denied (again, in his autobiography) “that the subject [of evolution] was in the air,” or that “men’s minds were prepared for it,” as some people were saying at the time, we can see in retrospect that this was true — Darwin’s competitive model of evolution seemed intuitive because of the common assumptions of his age, just as his grandfather’s more optimistic model had seemed intuitive in his age.

This leads to a question: What was the root cause of this mental shift? If the industrial and scientific revolutions made a “stairway to perfection” seem like a plausible model of nature in the 18th century, what made “nature red in tooth and claw” dawn on everybody’s minds at the beginning of the next century? 

I don’t know whether the world was genuinely worse or more competitive in that era than in any other (though of course it’s tempting to refer to the rise of capitalism and the dark culmination of the industrial revolution), but there was a key new factor in play that made the grim reality of scarcity more apparent: the observable effects of lack of scarcity. 

In his essay, Malthus notes the remarkable fact that the population of the United States of America had doubled in the last 25 years. This occurred simply because farmland was abundant in America. Meanwhile in Britain and Europe, farmland was limited, and therefore people were forced to wait longer to get married (and sometimes never got married at all) simply because they couldn’t afford to support a family. 

A few decades later, Alexis de Tocqueville would be foretelling (accurately) that America and Russia were destined to become the two great powers of the world, due to the rapid population growth made possible by available land and untapped natural resources. 

These developments were enlightening to people back in Britain and Europe. Sometimes, you don’t know what you’ve lost until you have it. The sudden availability of a whole new world without the economic constraints of the old one had made the basic problem with the old world clearer.

Yet Malthus perceived that, ultimately, land was limited even in America, while childbearing was not — and so he inferred that scarcity and competition for limited resources would always be dominating forces in the world. The situation in the New World seemed to be only a temporary reprieve from the rule of scarcity. 

The Rise of a Zeitgeist 

Once Darwin provided the scientific model to fit the Malthusian spirit of his age, a self-reinforcing system was created. Darwin’s ideas influenced social Darwinists from Rockefeller to Hitler; and the actions of social Darwinists from Rockefeller to Hitler made Darwin’s model seem all the more self-evident. 

That’s not to say the cultural victory of Darwinism was a smooth and unbroken process. During the late 19th century (which is typically portrayed as an era of prosperity and decadence), “survival of the fittest” was rejected as the main driver of evolution by most evolutionary biologists in favor of various other explanations.¹ Darwinism didn’t achieve true victory until the 1930s and early 1940s, with the creation of the Modern Synthesis of Darwin’s theory and Mendelian genetics. During that era, the Darwin-inspired science of eugenics was all the rage, with supporters ranging from Margaret Sanger to Winston Churchill. By coincidence, perhaps, it was in an era of world war and global economic depression that “survival of the fittest” finally achieved uncontested dominance as the most prominent explanatory mechanism for evolution. 

C. S. Lewis was right: the intellectual climate of an era influences the scientific model of the universe in that era, just as much as the scientific model influences the intellectual climate. 

The End of the Second Social Darwinism 

Who could have predicted that in a few years, the “climate of opinion” would have once again shifted? But Hitler ruined social Darwinism by moving too fast, going just a few steps further than society at large was yet ready for. When what the Nazis had done in the name of eugenics was brought to light, society turned away from eugenics in disgust. The age was over. 

I imagine that’s often how it goes with zeitgeists. Much like the boom and bust of out-of-control population growth, sometimes the spirit of the age needs to get out of hand before it can be made to retreat. Social Darwinism had to reach its dark but logical conclusion in Nazi Germany for it to expend its zeitgeist energy and die away. But die away it did. 

The zeitgeist is dead.

Long live the zeitgeist. 

A different spirit has emerged from the ashes of World War II. And in this new mental climate, the old neo-Darwinian model just doesn’t quite fit anymore. So it should come as no surprise that, in 2025, evolutionary biologists are proposing new models of evolution, crafted in the image of a new and very different mental climate. 

I’ll examine the still-in-process development of this third “social Darwinism” in a further article. 

Notes

1. This era has been called “the eclipse of Darwinism.” But historian of science Mark Largent suggests that the concept of an “eclipse of Darwinism” from 1880 to the 1930s was invented by mid-20th century neo-Darwinists partly as an attempt to extricate Darwinism from some ideas, such as eugenics, that had become unsavory — when, in reality, there were Darwinists (and Darwinists teaching and working on eugenics) in the earlier period as well. He also points out that natural selection was not widely accepted as the main driving force behind evolution in the decades before the “eclipse” either, contrary to what the term would seem to imply. If his assessment is correct, the modified picture is one of Darwinism as an influential idea throughout the late 19th and early 20th century, which nevertheless did not become completely dominant among specialists in the field until the Modern Synthesis was developed in the 1930s and 1940s.