For most of human history, the diversity of life was explained by one simple idea: species are fixed, created once, unchanging.
A rabbit begets a rabbit. An oak begets an oak. World without end.
Even naturalists who classified thousands of species rarely asked: where did all this variety come from?
In 1859, Charles Darwin proposed something radical: species are not fixed.
They change, slowly, over generations — new species arise from old ones through an entirely natural, unplanned process.
He called it natural selection.
No designer. No goal. Just a mechanism.
Replication + Variation + Selection = Evolution
Darwin never used these three words this way — but this is the abstract engine hiding inside his argument.
Three ingredients. Run them together, over and over, and something astonishing happens: design without a designer.
Something must be copied from one generation to the next.
Offspring resemble parents — not perfectly, but closely enough that traits persist.
Darwin did not know about DNA. He only needed: like tends to produce like.
No copy is perfect.
Within any population, individuals differ — in size, colour, behaviour, shape.
Some of this variation is heritable: it gets passed on, imperfections and all.
Without variation, there is nothing for selection to act upon.
Not every variant survives. Not every survivor reproduces equally.
Resources are limited; environments are demanding.
Whatever traits make an individual slightly better at surviving and reproducing become, on average, more common in the next generation.
Nobody chooses. The environment simply… filters.
In 1835, Darwin collected small birds across the Galápagos Islands — a few hundred kilometres off the coast of Ecuador.
Back in London, ornithologist John Gould identified them: not varieties of one species, but more than a dozen distinct species of finch — found nowhere else on Earth.
Each island's finches had a differently shaped beak: thick and crushing, thin and probing, long and curved.
The beaks matched the food available on each island: hard seeds, soft fruit, insects, nectar.
Darwin's explanation: all the finches descended from a single ancestral species that reached the islands long ago.
On each island: beak-shape variation + a different food source + generations of selection → a different finch.
One ancestor. One mechanism. Many birds.
The finches are not proof of evolution by themselves — but they are an unusually clean illustration of the engine in action, isolated on real islands, at a scale a visitor could actually observe.
Replication (finches breed finches), variation (beak shapes differ), selection (local food decides who thrives) — nothing more was needed.
So here is a strange question. Does this engine only run on carbon?
Darwin described biological evolution. But notice: nothing in the three-step engine mentions DNA, cells, or carbon chemistry.
It only requires: entities that are copied, imperfectly, and then differentially filtered.
Richard Dawkins called this generalized claim Universal Darwinism: wherever you find replication + variation + selection, you will find evolution — in biology or anywhere else.
The pattern shows up again and again, once you know to look for it:
your immune system selects among antibody variants for the ones that bind an intruder;
computer scientists breed populations of candidate solutions in “genetic algorithms”;
markets select among competing products and firms.
Could the same be true of ideas themselves?
In 1976, Richard Dawkins published The Selfish Gene — and reframed the whole story.
It is not organisms that are the true unit of selection, he argued. It is the gene.
“We are survival machines — robot vehicles blindly programmed to preserve the selfish molecules known as genes.”
Two roles, easy to confuse:
Replicator — the thing that gets copied. The gene.
Vehicle — the thing that is built, survives, and reproduces, carrying replicators inside it. The organism's body.
Selection acts on vehicles — but its lasting effect is on which replicators get copied into the next generation.
If the gene is just one possible kind of replicator…
…could there be others? Things that are copied, vary, and are selected — but are made of neither DNA nor protein?
Dawkins proposed there could. He needed just one more word.
“I think that a new kind of replicator has recently emerged on this very planet… I shall call it a meme.”
— Richard Dawkins, The Selfish Gene, 1976
Tunes, catch-phrases, fashions, ways of making pots or building arches — copied from mind to mind, by imitation.
Gene — replicated via reproduction; vehicle: the body; variation: mutation; selection: survival & reproduction.
Meme — replicated via imitation; vehicle: brains, books, screens; variation: mis-copying, reinterpretation; selection: attention, memorability, usefulness.
Same three-step engine. A completely different substrate.
We began with finches on volcanic islands and ended with an idea that may be living, right now, inside each of you.
If memes are real replicators, then minds are their islands — and culture is the ongoing experiment.
In the sessions ahead, we will look much closer at how exactly this second replicator moves: through imitation, through everyday life, through law, politics, and the machines we now build.