The Origin of Species was written by Charles Darwin and published in 1859. This book brought order to the world of organisms. Darwin not only supported the notion of transformation of species, but also was able to suggest a mechanism by which such evolution could occur without recourse to other than purely natural causes. According to his theory of natural selection, minute variations in offspring are either favoured or eliminated in the competition for survival. This brought the idea of evolution to be perceived with great clarity. This book is a work of scientific literature that is considered to be the foundation of evolutionary biology. Darwin's book introduced the theory that populations evolve over the course of generations through a process of natural selection. Upon its publication, the book attracted widespread interest. Already regarded as a scientist, Darwin's findings were taken seriously and the evidence he presented generated scientific, philosophical, and religious discussion. His concept of evolutionary adaptation through natural selection became central to modern evolutionary theory, and it has now become the unifying concept of the life sciences.