What it is
Evolution by natural selection explains the diversity of life: individuals vary, some variations survive and reproduce better, and over many generations populations change. Darwin set out the argument in 1859; genetics later revealed the mechanism of inheritance.
Deep time is hard to feel. Earth is about 4.54 billion years old, the oldest evidence of life is about 3.7 billion years old, and our own species appears only in the last few hundred thousand years.
Life on a timeline of deep time
Places key moments in the history of life on a scale where each step back is ten times older.
- ≈ 4.54 billion years ago Earth forms · US Geological Survey
- ≈ 3.7 billion years ago Earliest evidence of life. Microbial structures in Greenland rocks · Nature
- ≈ 538.8 million years ago Cambrian period begins. Animal life diversifies rapidly · International Commission on Stratigraphy
- ≈ 66 million years ago End of the dinosaurs. The Cretaceous–Paleogene boundary · International Commission on Stratigraphy
- ≈ 300,000 years ago First Homo sapiens · Smithsonian Human Origins Program
Sources: US Geological Survey · Nature · International Commission on Stratigraphy · Smithsonian Human Origins Program
Ideas to carry
- 1
Variation plus selection
No designer is needed: small differences, filtered by survival, add up over time.
- 2
Deep time
If Earth’s history were one day, humans would arrive in the last few seconds.
- 3
Search without a goal
Evolution explores possibilities blindly, which is why it inspired search algorithms in computing.
Established What we know
- Earth is about 4.54 billion years old, based on radiometric dating of meteorites and the oldest minerals.[1]
- Stromatolite-like structures in Greenland rocks suggest microbial life existed about 3.7 billion years ago.[2]
- Charles Darwin published On the Origin of Species in 1859.[3]
- The earliest fossils of Homo sapiens are about 300,000 years old.[4]
Interpretation The older lens · Comparative myth
Many creation stories, from Genesis to the Popol Vuh, tell of life made in stages. Evolution tells a stage-by-stage story too, measured in rock.
Reading
- 1859On the Origin of SpeciesCharles Darwin
- 1976The Selfish GeneRichard Dawkins
- 2008Your Inner FishNeil Shubin
One cell, 3.7 billion years ago
Its descendant, now: opening a website about the universe
Connected subjects, projects and writing
- AI and neural networksSubject · Intelligence
Established Artificial neural networks were loosely inspired by neurons, and evolutionary search inspired optimisation methods.
- Living systemsSubject · Life
Cells, genes, proteins and ecosystems: life as systems of feedback, from molecules to forests.
- Body and healthSubject · Life
Health, movement, sleep and the biology of energy: the physical ground every plan stands on.
Sources
- Geologic Time: Age of the Earth US Geological Survey. Checked 5 Nov 2026.
- Rapid emergence of life shown by discovery of 3,700-million-year-old microbial structures Nature, 2016. Checked 5 Nov 2026.
- On the Origin of Species, by Charles Darwin Project Gutenberg, 1859. Checked 5 Nov 2026.
- Homo sapiens Smithsonian Human Origins Program. Checked 5 Nov 2026.