How did life on Earth begin?

How early did life appear?

Start with the clock. The U.S. Geological Survey puts Earth’s age at 4.54 billion years, with an uncertainty of less than 1 percent. The question is how soon life followed.

Some of the earliest convincing evidence comes from the 3.48-billion-year-old Dresser Formation in Western Australia. A 2017 study in Nature Communications describes stromatolites there, along with other signs of microbes, preserved in ancient hot-spring deposits on land.

Older claims exist, and each is argued over. In 2016, a team reported 3.7-billion-year-old stromatolites in Greenland. In 2018, another team looked again in 3D and concluded the shapes were more plausibly made by the rocks being squeezed and bent, not by microbes. Other studies point to tube-like structures at least 3.77 billion years old in Quebec, and to carbon trapped in a 4.1-billion-year-old crystal from Australia that may have come from life. These are possible signs, not settled facts.

Genes offer a separate clue. By comparing genes across living things, a 2024 study in Nature Ecology & Evolution estimated that the last universal common ancestor, the shared ancestor of all life today, lived about 4.2 billion years ago. That ancestor was already a fairly complex cell, so life itself must have begun even earlier. So the fair summary is this: life was here by about 3.5 billion years ago, and perhaps much earlier.

Can nature make life’s building blocks?

Yes, some of them. In the 1950s, Stanley Miller ran electric sparks through a mix of hydrogen, water, methane and ammonia, then thought to match Earth’s early air. Amino acids formed. Many geoscientists now think the early air was different, as a 2011 study in PNAS notes. But a 2008 reanalysis of Miller’s saved samples found that a version of his setup imitating a steamy volcanic eruption made a wider variety of amino acids than the classic one. Volcanic eruptions, with their lightning, may have released the right gases in some places.

Space delivers ingredients too. Together, some meteorites that fell to Earth contain all five nucleobases used in DNA and RNA. The Hayabusa2 spacecraft brought back samples from asteroid Ryugu that contain uracil, one of RNA’s four letters. In January 2025, NASA reported that samples from asteroid Bennu, delivered by the OSIRIS-REx spacecraft in 2023, hold 14 of the 20 amino acids that life uses to build proteins and all five nucleobases. Because the samples were collected in space and handled under strict contamination controls, they avoid most of the Earth contamination that clouds studies of meteorites. NASA was careful to add that the findings do not show evidence for life itself.

Bennu also raised a puzzle. Many molecules come in left-handed and right-handed forms, like a pair of gloves. Life on Earth uses almost only left-handed amino acids, but Bennu’s were an even mix. Why life “turned left” is, in NASA’s words, still a mystery.

What were the first living systems like, and where did they start?

In today’s cells, DNA stores the instructions and proteins do the work. Each needs the other, which makes it hard to see how either came first. Sidney Altman and Thomas Cech discovered that RNA can also do chemical work, like a protein enzyme. Their 1989 Nobel Prize announcement called the discovery a complete surprise. This points to an early stage when RNA did both jobs. It became known as the “RNA world,” the title of a short 1986 paper by Walter Gilbert in Nature. The Nobel committee called it very likely that RNA molecules came first. Still, not everyone agrees: some researchers, such as Bruce Damer and David Deamer, argue that life’s start cannot be reduced to one kind of molecule working alone. So the idea is well supported, but still debated.

Could the first arrangement to appear have locked in?

Some readers ask whether a “first to arrive wins” logic could apply before life. A version of this idea is famous in biology. In 1968, Francis Crick proposed the “frozen accident”: the genetic code, the rule book that turns genes into proteins, is shared by modern life because, once it was in use, any change would have been badly harmful. As Eugene Koonin explains, this is a default view, but later studies found the code is also highly resistant to errors, and no one has a compelling explanation of how it was set up. So early “winners” may have locked in, but how much was chance and how much was chemistry is an Open question.

Sea-floor vents or ponds on land?

One camp favors hot vents on the sea floor. A 2008 review notes striking parallels between the hydrogen and carbon dioxide chemistry at these vents and the energy reactions of some simple microbes today. Another camp favors hot-spring pools on volcanic land. In a 2020 paper, Bruce Damer and David Deamer argue that pools that dry out and refill could concentrate ingredients and link them into longer chains, where the open ocean would dilute them. Charles Darwin guessed at something similar in 1871, in a letter imagining a “warm little pond.” Both camps propose tests. Neither has won.

What is the strongest objection?

The strongest objection comes from inside the field. Making building blocks is one thing. Getting them to organize into a system that feeds itself, copies itself and evolves is far harder. Damer and Deamer open their own paper with a warning from the researcher Leslie Orgel: to assume a whole suite of lucky chemical steps “is to appeal to magic.” They agree that self-sustaining cycles of reactions remain a key unsolved problem. This is why the page says “Nobody knows yet” and means it.

What do people often get wrong?

“Miller made life in a jar.” He made amino acids, which are parts of proteins. That is a long way from a cell.

“Life’s ingredients on an asteroid means life on an asteroid.” NASA said plainly that Bennu shows no evidence of life itself.

Is a virus alive?

It depends on the definition, and that is the point. NASA’s working definition calls life “a self-sustaining chemical system capable of Darwinian evolution.” Viruses evolve, but according to the National Human Genome Research Institute, a virus cannot copy itself alone; it must use a host cell. Koonin and a colleague argue that the question has no single answer, because any definition of life draws the line somewhere. Viruses sit near that line, which makes them a useful reminder that the jump from chemistry to biology may not have had one sharp edge.

Where people of faith and skeptics can agree

Both can agree on the evidence above: the ages, the experiments, the samples. The U.S. National Academies say science studies nature and cannot investigate the supernatural. They also warn that pinning each unsolved question on God, a “god of the gaps,” weakens both science and faith. So a gap in the science is not proof of God, and a natural explanation would not disprove God. Whether life carries an ultimate meaning is a question for philosophy and belief.

Check it yourself

• When you see “oldest life ever found,” look for replies from other teams. The Greenland case shows that early dates can be overturned.
• When you read “ingredients of life found in space,” check whether the article says what NASA said: ingredients, not life.
• Read the short summaries (abstracts) of the papers linked on this page. They are free and often plainer than you expect.
• For the bigger story, read our feature How Did Life on Earth Begin? and our explainer on how evolution works, which picks up once life exists.