On the Origin of Species by Charles Darwin — Summary, Key Ideas & Quotes

Darwin’s central idea is that species evolve over generations through a process called natural selection. Individuals with traits better suited to their environment are more likely to survive and reproduce, passing those advantageous traits to their offspring. Over long periods, this leads to gradual changes in populations and the emergence of new species. This concept challenged the prevailing belief in fixed, unchanging species and provided a naturalistic explanation for the diversity of life.

Darwin observed that individuals within a species are not identical; there is always some variation. These differences, though often subtle, are crucial for natural selection to operate. Without variation, there would be no traits for selection to favor or reject. Darwin’s emphasis on variation laid the groundwork for later developments in genetics and population biology.