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RNA world
named 1986; scenario c. 4 billion years ago· Theory or idea· Microbes & cells
HypothesisA serious idea with limited direct evidence so far.
The idea that early life ran on RNA, a molecule that can both store genes and speed up chemical reactions.
See it on the Life map →What happened
In cells today, DNA holds the recipes and proteins do the work, but each is needed to make the other. RNA, DNA's single-stranded cousin, can do both: carry information and act as an enzyme, called a ribozyme. Thomas Cech and Sidney Altman discovered ribozymes in the early 1980s (Nobel 1989), and Walter Gilbert named the 'RNA world' in 1986. DNA and proteins would have taken over later as sturdier storage and better workers.
Why it matters
It is the leading answer to the chicken-and-egg problem of genes and proteins, and explains why RNA still sits at the heart of every cell's protein factory.
Think of it like
Like a founder who is both architect and builder until the firm can afford separate staff.
The evidence (fossils, genes, rocks)
The ribosome's working core is RNA (structure solved in 2000); lab-evolved ribozymes copy short RNA strands; John Sutherland's lab made RNA building blocks under plausible early-Earth conditions in 2009.
Still debated
No fully self-copying RNA has been made, and RNA is fragile; many researchers now favor RNA and short proteins evolving together.
Connections (2)
▸RNA world proposes a first step in Origin of lifeHypothesis
The connection
Today DNA stores genes and proteins do the work, but each is needed to make the other, a chicken-and-egg problem. RNA can do both jobs. So the first living systems may have been self-copying RNA molecules, with DNA and proteins added later.
When and how
Suggested by Carl Woese, Francis Crick and Leslie Orgel in the 1960s; RNA enzymes found by Thomas Cech and Sidney Altman in the early 1980s; named by Walter Gilbert in 1986.
How sure are we?
RNA enzymes exist; the core of the ribosome, every cell's protein factory, is RNA; lab-made RNA enzymes can copy short RNA strands.
Debates and open questions
Whether RNA was truly the first genetic molecule or replaced a simpler, now-vanished one, and where on early Earth its fragile building blocks could have gathered.
▸RNA world may explain the origin of The universal genetic codeHypothesis
The connection
If RNA came first, the genetic code may have arisen as RNA molecules began helping string amino acids into short proteins. Some three-letter RNA 'words' may have stuck to particular amino acids chemically, or the pairings may have been fixed by chance and kept because changing them would break everything.
When and how
Francis Crick proposed the 'frozen accident' idea in 1968; Michael Yarus and others ran chemical-attraction experiments from the late 1980s.
How sure are we?
Weak: some RNA pieces bind their matching amino acids in lab tests, and the ribosome's RNA core does the protein-building. No step-by-step record exists.
Debates and open questions
Whether the code is a frozen accident, chemically driven, or tuned by selection to limit damage from copying errors; probably some mix.