History of life

The history of life traces how living organisms originated, evolved, diversified, and became extinct across geological time, reconstructed from fossils and other evidence.

Fossil: A preserved remain, trace, or impression of an organism from the geological past. Fossils preserve direct evidence of organisms and their activities across geological time.
Natural selection: A process in which heritable traits affecting survival or reproduction become more or less common in a population. It can adapt populations to changing conditions and contribute to evolutionary divergence.
Origin of life: The emergence of the first living systems from nonliving chemistry on the early Earth. It marks the beginning of the biological history reconstructed by this field.
Georges Cuvier: A French naturalist who established comparative anatomy and argued that successive faunas had vanished through catastrophic events. His fossil studies made extinction a central fact in reconstructing life’s past.
Abiogenesis: The natural emergence of living systems from nonliving chemical precursors. Evidence has not yet established the detailed pathway from early chemistry to the first life.
Stratigraphy: The study of rock layers and their order, distribution, and correlation. Rock-layer sequences place fossils in relative chronological order.
Speciation: The formation of distinct species through the evolution of reproductive isolation. It generates new branches in the history of life.
Great Oxidation Event: A major rise in atmospheric oxygen around 2.4 billion years ago, driven largely by microbial photosynthesis. It shows how microbial activity transformed Earth’s atmosphere and later possibilities for life.
Charles Lyell: A British geologist who argued that geological processes operating today also shaped Earth in the past. His geological reasoning helped establish deep time as a setting for biological change.
Cambrian explosion causes: The competing explanations for the rapid diversification and fossil visibility of animals during the Cambrian period. The timing and drivers of this major diversification remain debated.

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