~ 1859 ~
Charles Darwin's "On the Origin of Species" is widely regarded as having laid the foundation for evolutionary biology. Published in 1859, Darwin's work presented the idea that populations evolve through natural selection. Despite controversy surrounding the notion of transmutation of species, Darwin's findings were taken seriously and scientific discussion ensued. Although scientists were slow to attribute the significance that Darwin felt was appropriate to natural selection, within two decades, widespread scientific agreement existed that evolution by means of a branching pattern of common descent had taken place. Darwin's theory of natural selection has become the unifying concept of the life sciences.