Cobra Effect · Big open questions
How did life begin?
What is known about how life began, and which parts are still guesses.
7 cards, read aloud in 2:58, with a test and sources.
Earth is about four and a half billion years old, and life appeared early in its history.
The most widely accepted traces of life are about three and a half billion years old, in rocks from Western Australia. Some scientists argue for much older signs, but those claims are disputed. Nobody knows exactly how, where or when life began.
In 1871, Charles Darwin imagined life starting in a warm little pond.
In a letter to a friend, he pictured a pond with ammonia and phosphorus salts, and light, heat and electricity. He framed it as a big if. Experiments in the next century showed that some of life’s building blocks can form from simple chemicals and energy.
One of the hardest puzzles is which came first, the instructions or the machinery.
In living cells, DNA stores the instructions and proteins do most of the work, but each is needed to make the other. RNA can do a little of both. It carries information, and some RNA molecules can speed up chemical reactions. In 1986, the biologist Walter Gilbert named the idea that life passed through an early RNA world.
The RNA world is a favourite idea, but it is not proven.
The part of the cell that joins the building blocks of proteins together is made of RNA, which fits the idea. But making RNA’s own building blocks under early Earth conditions is hard, and RNA breaks down easily. Nobody has yet made RNA that copies itself, starting from simple chemicals.
Scientists also disagree about where life began.
Some favour deep sea vents, where warm mineral rich water meets the cold ocean and offers chemical energy. Others favour pools on land, where drying out and wetting again can join small molecules into longer chains. Each setting solves some problems and raises others.
Clues also come from working backwards through the tree of life.
All living things today share a last common ancestor, nicknamed LUCA. One 2024 study estimated that LUCA lived about four point two billion years ago, and was already fairly complex. LUCA was not the first life. It was the most recent ancestor that everything alive today shares.
So when you hear that science has explained how life began, ask which parts are still guesses.
We know life began early, and that some of its building blocks can form naturally. Nobody has yet turned non living chemistry into life. The steps in between are still an open question.
Sources
- Life’s last universal common ancestor, University of Bristol. A plain summary of the 2024 study dating LUCA.
- The nature of the last universal common ancestor, Nature Ecology and Evolution, 2024. The full open access study, with its uncertainty ranges.
- Abiogenesis, Wikipedia. The RNA world, vents and ponds, and Darwin’s warm little pond.
Nearby ideas
- Lightning in a flask. How sparks in a glass loop made some of the building blocks of life.
- The flasks with necks like swans. How a bent glass neck showed that microbes come from other microbes.
- The third branch of life. How comparing one molecule revealed a whole domain of life hiding in plain sight.
- What is dark matter?. What the evidence says about dark matter, and why nobody knows what it is.
- What is speeding up the universe?. Why the universe's expansion is speeding up, and the rival ideas about why.
- Why is there more matter than antimatter?. Why the universe is made of matter, when the Big Bang should have made equal antimatter.
- Why do we have experiences at all?. Why brain science can track experience, but not yet explain why it exists.
- Are we alone in the universe?. Why no sign of life beyond Earth has been confirmed, despite planets everywhere.