Charles Darwin's groundbreaking work of evolutionary biology, The Origin of Species introduces the scientific theory of evolution, which posits that species evolve over a period of many generations through a process of natural selection. Darwin's theories have been widely embraced by the scientific community as fact and have laid the foundation for subsequent major advances in the field of biology. It is arguably one of the most important scientific treatises ever written. This is the sixth edition of the formative text of evolutionary biology. Charles Robert Darwin was an English naturalist who realised and presented compelling evidence that all species of life have evolved over time from common ancestors, through the process he called natural selection. His 1859 book On the Origin of Species established evolutionary descent with modification as the dominant scientific explanation of diversification in nature. He examined human evolution and sexual selection in The Descent of Man, and Selection in Relation to Sex, followed by The Expression of the Emotions in Man and Animals. His research on plants was published in a series of books, and in his final book, he examined earthworms and their effect on soil.