The foundational work in evolutionary biology, Charles Darwin's On the Origin of Species introduced the scientific theory that animal populations evolve over the course of generations through a process of natural selection, and that diversity of life arose by common descent through evolutionary branching.

Written for readers without a specialized knowledge of science, it attracted much attention upon it's original publication, and the political and theological implications quickly became subject to intense debate as it challenged the natural theology views popular at the time. By the 20th century Darwin's concepts had become central to modern evolutionary theory and has become the unifying concept of life sciences.