Lesson 1 — What Is This All About?

Understanding the Complex: What Is Evolution Really?

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In 1988, a microbiologist at Michigan State University placed 12 flasks of E. coli bacteria in a warm room and began feeding them every single day. His name was Richard Lenski, and he had no way of knowing that this experiment — which he called the Long-Term Evolution Experiment, or LTEE — would still be running nearly four decades later, watched by scientists around the world as one of the most remarkable demonstrations of evolution ever conducted.

For the first twenty years, the bacteria behaved predictably. They adapted to their sugar-water environment, becoming better at consuming glucose, growing faster, fitter by the only measure evolution cares about: survival and reproduction. Then, in 2008, Lenski's team noticed something strange in one of the twelve flasks. The bacterial culture had turned cloudy — much cloudier than the others. When they analyzed what was happening, they found the impossible: the bacteria in that flask had evolved the ability to digest citrate.

This mattered enormously. E. coli cannot normally metabolize citrate in the presence of oxygen. It's a defining characteristic of the species — something used to identify it in clinical labs. And yet here it was, a population of E. coli doing exactly that. Lenski's team had the frozen samples to trace it back: the ability had emerged through a sequence of mutations, each building on the last, over tens of thousands of generations.

No one designed that outcome. No one planned it. Blind variation, filtered by selection, had produced genuine novelty.

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That experiment sits at the heart of what this course is about.

Evolution is the most consequential idea in the history of biology. It explains why every living thing on Earth — every bacterium, every oak tree, every blue whale, every human — is related. It explains why we get sick, why antibiotics stop working, why dog breeds look so different from each other, and why our DNA is 98.7% identical to a chimpanzee's. It is the framework that makes modern medicine, agriculture, and biotechnology possible.

It is also, in the public conversation, the most misunderstood idea in science.

People say evolution is "just a theory" — as if that diminishes it, when in science a theory is the highest form of explanation. People say evolution means humans came from monkeys — a misreading so fundamental it would make Darwin wince. People say evolution implies there is no purpose to life, or that it endorses a brutal survival-of-the-fittest worldview — neither of which follows from the biology.

This course is about what evolution actually is.

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Over eleven lessons, we'll move from the basic mechanisms — selection, mutation, drift — to the extraordinary lines of evidence that support the theory, to the cutting-edge research that is rewriting parts of what Darwin first proposed. We'll look at the scientists doing this work, the genuine disputes within the field (there are several), and the questions that sit at the edge of what science can answer and where personal worldviews legitimately differ.

We won't pretend those edges don't exist. The question of whether evolution says anything about the existence of God, or whether it strips life of meaning, is not a scientific question — it's a philosophical one, and people hold very different views. This course won't tell you what to conclude there. But it will make sure you understand the biology well enough to engage with those questions honestly.

The central thread running through everything: Why do living things look and behave the way they do — and how did they get that way?

Lenski's bacteria in that cloudy flask were not trying to evolve. They were not aiming at citrate. They were just reproducing, mutating, dying, reproducing again — and over 33,000 generations, something new emerged from the noise. That's the process. Once you understand it, you'll see it everywhere.

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Next lesson: Why should you care? — Antibiotic resistance, COVID variants, and what evolution reveals about the human body.

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Reading time: approx. 8–9 minutes