The theory of evolution explains how life on Earth has changed over time and how all living things are related through common ancestry. Here are its key principles:

## Core Concepts

**Natural Selection**: Organisms with traits better suited to their environment are more likely to survive and reproduce, passing those beneficial traits to their offspring. Over many generations, this leads to changes in populations.

**Common Descent**: All living organisms share common ancestors if you go back far enough in time. This explains why different species share similar features and DNA.

**Gradual Change**: Species change slowly over long periods through the accumulation of small genetic variations across many generations.

## Key Mechanisms

- **Mutation**: Random changes in DNA create new genetic variations
- **Gene flow**: Movement of genes between populations through migration
- **Genetic drift**: Random changes in gene frequencies, especially in small populations
- **Selection pressures**: Environmental factors that favor certain traits (climate, predators, food sources, etc.)

## Supporting Evidence

The theory is supported by evidence from:
- Fossil records showing changes over time
- DNA and molecular similarities between species
- Observable evolution in laboratories and nature
- Geographical distribution of species
- Developmental similarities among embryos

## Important Notes

Evolution doesn't explain the origin of life itself (that's abiogenesis), but rather how life diversified after it began. It's also not about "progress" toward a goal—it's simply about adaptation to changing environments.
