Sir Julian Sorell Huxley was a British evolutionary biologist, eugenicist, and internationalist. He was a proponent of natural selection, and a leading figure in the mid-twentieth century modern synthesis. He was secretary of the Zoological Society of London (1935–1942), the first Director of UNESCO, a founding member of the World Wildlife Fund, the president of the British Eugenics Society (1959–1962), and the first president of the British Humanist Association.

Evolutionary biology is the subfield of biology that studies the evolutionary processes that produced the diversity of life on Earth. It is also defined as the study of the history of life forms on Earth. Evolution holds that all species are related and gradually change over generations. In a population, the genetic variations affect the phenotypes of an organism. These changes in the phenotypes will be an advantage to some organisms, which will then be passed on to their offspring. Some examples of evolution in species over many generations are the peppered moth and flightless birds. In the 1930s, the discipline of evolutionary biology emerged through what Julian Huxley called the modern synthesis of understanding, from previously unrelated fields of biological research, such as genetics and ecology, systematics, and paleontology.