Life, once it arises, does not stay the same. It changes. The mechanism — natural selection acting on heritable variation — was described by Darwin in 1859 and has been confirmed and extended by every branch of biology since. Evolution is not a theory in the colloquial sense of “a guess.” It is the organizing framework of all modern biology, as well-supported as the germ theory of disease or atomic theory of matter.
This is the evolution layer: the science of how life changes over time through mechanisms that are now well understood at the molecular level. It spans from the statistical mechanics of allele frequencies in small populations to the five mass extinctions in Earth’s fossil record to the specific trajectory of human evolution over the last six million years. It connects the origin-of-life chemistry of the layer above it to the emergence of mind and consciousness in the layer below.
The core questions at this scale
- How does natural selection produce apparent design without a designer?
- What role does randomness play in evolution, beyond selection?
- What does the interbreeding between Homo sapiens, Neanderthals, and Denisovans tell us about what “species” means?
- How have mass extinctions repeatedly reshuffled the trajectory of complex life?
- Why did the Cambrian explosion produce so many body plans so quickly?
Mechanisms of change
- Natural Selection — how differential reproduction drives adaptation
- Genetic Drift Explained — how random sampling shapes small populations
- The Cambrian Explosion — the most dramatic diversification event in animal history
- Evolution of the Eye — how a complex organ evolved incrementally
- Unlocking Non-Coding DNA — what the non-protein-coding genome does
Human lineage
- Neanderthals and Denisovans — what ancient DNA reveals about our archaic relatives
- African Origins of Homo Sapiens — the fossil and genetic evidence
- Homo Erectus: The Legacy — the first human to leave Africa
- Peopling of the Americas — how and when humans reached the New World
- Where Did Humankind Originate? — a synthesis of the current evidence
Extinctions and disruptions
- The K-Pg Extinction — the asteroid impact that ended the dinosaurs and launched the age of mammals
← Layer above: Life — the origin and distribution of living things → Layer below: Mind — the emergence of consciousness and cognition