Charles Darwin

In 1859 Charles Darwin proposed the theory of natural selection.

At his important magnum opus On the Origin of Species, the main arguments are:

1. Species are not fixed or static existence but are in constant change.
2. Life appears as a constant struggle for existence and survival.
3. The struggle for survival lead to the best adapted to reproduce, this process is called "natural selection"
4. Natural selection and evolution process requires an enormous amount of time so long that a briefly of the human life span.

Reference: http://darwincharlesrobert.wordpress.com/11/