J. B. S. Haldane, English-Indian geneticist and biologist (d. 1964)
John Burdon Sanderson Haldane (; 5 November 1892 – 1 December 1964), nicknamed "Jack" or "JBS", was a British scientist who worked in physiology, genetics, evolutionary biology, and mathematics. With innovative use of statistics in biology, he was one of the founders of neo-Darwinism. He served in the Great War, and obtained the rank of captain. Despite his lack of an academic degree in the field, he taught biology at the University of Cambridge, the Royal Institution, and University College London. Renouncing his British citizenship, he became an Indian citizen and worked at the Indian Statistical Institute for the rest of his life.

Haldane's article on abiogenesis in 1929 introduced the "primordial soup theory", which became the foundation for the concept of the chemical origin of life. He established human gene maps for haemophilia and colour blindness on the X chromosome, and codified Haldane's rule on sterility in the heterogametic sex of hybrids in species. He correctly proposed that sickle-cell disease confers some immunity to malaria. He was the first to suggest the central idea of in vitro fertilisation, as well as concepts such as hydrogen economy, cis and trans-acting regulation, coupling reaction, molecular repulsion, the darwin (as a unit of evolution) and organismal cloning.

In 1957 he articulated Haldane's dilemma, a limit on the speed of beneficial evolution which subsequently proved incorrect. He willed his body for medical studies, as he wanted to remain useful even in death. He is also remembered for coining the words "clone" and "cloning" in human biology, and "ectogenesis". With his sister, Naomi Mitchison, Haldane was the first to demonstrate genetic linkage in mammals. Subsequent works established a unification of Mendelian genetics and Darwinian evolution by natural selection whilst laying the groundwork for modern evolutionary synthesis and thus helped to create population genetics.

Haldane was a professed socialist, Marxist, atheist and humanist whose political dissent led him to leave England in 1956 and live in India, becoming a naturalised Indian citizen in 1961.

Arthur C. Clarke credited him as "perhaps the most brilliant science populariser of his generation". Nobel laureate Peter Medawar called Haldane "the cleverest man I ever knew". According to Theodosius Dobzhansky, "Haldane was always recognized as a singular case"; Ernst Mayr described him as a "polymath"; Michael J. D. White as "the most erudite biologist of his generation, and perhaps of the century"; and Sahotra Sarkar as "probably the most prescient biologist of this [20th] century." According to a Cambridge student, "he seemed to be the last man who might know all there was to be known."