On the origin of species

Of the vast and varied productions of nature, from the hummingbird to the giant redwood, from the beetle's shell to the human hand-what is their origin? In this foundational work that forever altered humanity's understanding of its place in the natural world, Charles Darwin presents the theory that would become the bedrock of modern biology: evolution by natural selection. Based on decades of meticulous observation, from the famed voyage of the HMS Beagle to his studies of barnacles and pigeons, Darwin marshals an overwhelming array of evidence.
He demonstrates how species are not immutable, but are engaged in a constant struggle for existence. In this struggle, individuals with variations better suited to their environment tend to survive and reproduce, passing those advantageous traits to their offspring. Over immense spans of time, this gradual process of "descent with modification" gives rise to the breathtaking diversity of life, all branching from a common ancestor. On the Origin of Species is a masterpiece of lucid argumentation and humble reasoning: it connects the work of the earthworm to the geology of continents, and the instincts of the hive to the extinction of the mammoth.
Its revolutionary ideas challenged the scientific and religious orthodoxies of its day, and continue to provoke, inspire, and illuminate. This is the book that answered the question of questions, revealing the grand and simple mechanism that shapes all life on Earth.