“There is reason to believe that vaccination has preserved thousands” — Charles Darwin
An argument that impacted how I think about vaccination happened not in a clinic or a hospital, but on a boat near the Galápagos Islands, where a naturalist guide told me that humans shouldn't try to modify their lives in ways that interfere with natural selection.
He meant it as wisdom. He was wrong, and Darwin himself would have told him so.
Darwin's most important sentence could be one you don’t know
Everyone knows Darwin for On the Origin of Species, published in 1859. But the book that reveals what he actually thought about human beings is The Descent of Man, published in 1871, where he turned his lens from finches and tortoises onto humans.
A sentence that should be far more famous than it is comes from Chapter III: "Of all the faculties of the human mind, it will, I presume, be admitted that Reason stands at the summit."
That sentence isn’t just a philosophical aside. He wrote it as an evolutionary statement. By The Descent of Man, Darwin had worked out what distinguished humans from every other species: not our size, not our strength, not our speed, not even our immune systems — but our capacity to reason. To form abstractions. To look at a pattern and induce a principle. To look at a virus and build a countermeasure. Darwin’s view of reason is that it is the means of survival for humans.
For Darwin, reason is not separate from natural selection but is natural selection's crowning project.
The Galápagos, of all places, is where this argument gets tested
I was standing in the place where Darwin assembled the observations that led him to his theory. Marine iguana, blue-footed Boobies, and the famous finches with their divergent beaks. And a guide — a naturalist, someone who had devoted his life to understanding this place — was telling me that when infectious disease shapes our species, we should let it.
I disagreed then, and I disagree now, on Darwin's own authority.
The guide's mistake was treating natural selection as something that happens to humans from the outside. But Darwin's argument was that reason itself is what natural selection built in us. When a virologist reads the genome of a novel coronavirus in January 2020 and a vaccine is in arms eleven months later, that isn't interference with Darwinian evolution. It's Darwinian evolution doing what it has been doing for millions of years: favoring the traits that help our species survive. Our trait is reason. Reasoning our way to vaccines. (Not by accident, Darwin’s view of reason was a topic I wrote a paper on in a favorite course I took in the 1990s as a post-baccalaureate student because I was so excited about the material: Jim Lennox’s Darwinism and its Critics at the University of Pittsburgh).
The anti-vaccine movement gets Darwin backwards
The "natural immunity is better" argument is an attempt at constructing a respectable-sounding voice of vaccine hesitancy. It has scientific adjacent clothing — it invokes evolution, selection pressure, immune memory and draws on real phenomenon. It sounds like Darwin.
It isn't. In fact, Darwin wrote: “There is reason to believe that vaccination has preserved thousands, who from a weak constitution would formerly have succumbed to small-pox.” Darwin recognized vaccination as a triumph of reason. Jenner looked at milkmaids and cowpox lesions and induced a principle from scattered observations. He saw a pattern in nature and converted it into a technology that liberated humanity from smallpox.
The people who make this argument are, implicitly, asking you to treat nature as a norm-setter, something Darwin’s quote about vaccines stands in opposition to. As if what nature does to us without our intervention is what should happen — those with “a weak constitution” succumbing to smallpox. This is the naturalistic fallacy dressed in evolutionary costume: the idea that because something is natural, it is good, or at least better than the alternative.
But Darwin didn't believe nature was a norm-setter. He described a blind, indifferent mechanism that favors whatever survives. He recognized that vaccination, a product of human reason, is a countervailing force that emanated from Edward Jenner’s faculty of reason. Nature’s mechanism, devoid of human intervention, produces outcomes that no sane person would call a design goal: the Black Death killing a third of Europe; the 1918 influenza killing 50 to 100 million people; malaria, operating as a Darwinian selection pressure on the human genome for so long that it left permanent marks.
Which brings me to the honest face of natural immunity: it is a real phenomenon that comes at a cost.
Natural selection’s solution to malaria is a blood disorder
Of all the things I've written about infectious disease, the malaria-sickle cell story is the one that most concretely illustrates what natural selection, left to its own devices, actually produces.
It is often said that malaria has killed roughly half of all humans who ever lived. The Plasmodium parasites that cause it have been killing humans for so long, and in such numbers, that they became a selection pressure — they began to shape our genome.
The result: a mutation that, in carriers who inherit one copy, confers resistance to malaria. Natural selection preserved it because carriers survived long enough to reproduce. But inherit two copies of the mutation, and you have sickle cell anemia — a painful, debilitating, life-shortening blood disorder.
That is what natural immunity looks like when it's working as designed. Nature's answer to one of history's most lethal pathogens was to introduce blood diseases into the human population as a consolation prize. You can see the geographic overlap precisely: superimpose a map of where malaria has historically been endemic with a map of where sickle cell anemia (and the other malaria-influenced blood diseases G6PD deficiency, thalassemia, and hereditary spherocytosis) is prevalent, and the lines match almost perfectly. Natural selection did this. Over thousands of years of uncountable death.
Contrast this with what reason did to malaria: DDT eliminated it from most of the industrialized world within decades. Artemisinin-based therapies transformed treatment. Insecticide-treated bed nets keep sleeping humans safe. Vaccines decrease deaths. Modified mosquitoes will add even more. The tools built by conscious minds are doing in years what blind selection couldn't accomplish in millennia — and without the blood disorder as a byproduct. Human reason is also addressing sickle cell anemia, natural selection’s deadly byproduct, with bone marrow transplants and gene therapies.
The mRNA vaccine is what reason built
The mRNA vaccine platform is one of the clearest contemporary illustrations of this I know. For decades, scientists worked on the basic science of messenger RNA — how to stabilize it, how to deliver it, how to get cells to read it as an instruction and produce a protein. The key breakthrough on the delivery mechanism came in the 1990s. The key breakthrough on mRNA stability — a modification to the nucleoside that makes up the molecule — came from Katalin Karikó and Drew Weissman, a discovery that eventually earned the 2023 Nobel Prize in Medicine (and a Time Magazine cover that adorns my wall). None of this was done in anticipation of a specific pandemic. It was basic science, driven by curiosity and the slow accumulation of knowledge.
When SARS-CoV-2 arrived, its genome was sequenced and published in January 2020, and within 11 months, a vaccine built on that entire accumulated foundation was authorized and in arms. The speed looked miraculous. It wasn't. It was what happens when reason suddenly has a problem needing a solution at maximum urgency.
I have been calling vaccines "liberation technology" for years. When humans refuse to accept hostile nature's terms, they create the means to master these problems, winning freedom for themselves from being helpless against nature’s machinations.
The deeper point is Darwinian: we aren't refusing nature's terms. We are executing nature's terms.
Nature built a species capable of this: us. When we use that capability, we aren't defying the process that made us. We are the process that made us.
What my Galápagos guide got wrong
The guide on that boat had a philosophy that sounds like reverence for nature but is actually a form of self-abnegation. He was asking members of the most cognitively sophisticated species in the history of the planet to suppress the faculty that makes them what they are, out of deference to a blind mechanism that, left to itself, produces sickle cell anemia and the Black Death.
Darwin would have found this baffling. The man who spent his life documenting the adaptive genius of natural selection understood that what it had built in us — above all else — was reason.
The anti-vaccine movement, in all its varieties, makes the same error as my guide. It mistakes nature for a moral authority. It treats "natural" as a synonym for "correct." It advocates letting disease do what it would have done before we had the capacity to stop it, on the theory that this is somehow more authentic to who we are.
But nothing is more authentic to who we are than thinking our way to a solution.
The real Darwinists vaccinate
There is a false version of Darwinism that concludes vaccines are interference.
Darwin's version —reason standing at the summit — concludes something quite different. It concludes that the species capable of reasoning its way out of the jaws of infectious disease is doing exactly what natural selection shaped it to do. That is the mRNA vaccine, developed from a genome sequence in under a year. It stands as one of evolution's most recent and most impressive outputs.
We have had 10,000 generations of humans. Only the last four have lived in a world where we can reliably master some infectious diseases. The tools that made that possible — vaccines, antimicrobials, diagnostics, sanitation — are the products of the one trait Darwin identified as the summit of what natural selection can build.
If you want to honor Darwin, don't retreat to nature's indifference. Use your mind. That's what Darwin said it was for.
Vaccinate.