# The Theory of Evolution

Evolution is the scientific explanation for how life on Earth has changed and diversified over time. Here are its core ideas:

## Main Principles

**Common Descent**
- All living organisms share common ancestors
- Life branched and diversified from earlier forms over billions of years

**Natural Selection**
- Organisms with traits better suited to their environment are more likely to survive and reproduce
- These advantageous traits become more common in populations over time
- Less advantageous traits become less common

**Genetic Variation**
- Individuals within a species vary in their traits
- This variation is heritable (passed to offspring through genes)
- Mutations and genetic recombination create new variations

## Key Points

- Evolution works on **populations** over **long time periods**, not individual organisms
- It explains both the unity of life (shared biology) and diversity (different species)
- Evidence comes from fossils, genetics, comparative anatomy, and direct observation
- Evolution is not purposeful or directed toward a goal

## What It's Not

- It doesn't explain the origin of life itself (that's abiogenesis)
- It doesn't address purpose or meaning
- It's not random—natural selection is a non-random process

Evolution is the foundation of modern biology and is supported by evidence from multiple scientific fields.
