English physician John Snow proves that cholera is spread by infected water (from a pump in London's Broad Street)

The first Neanderthal man to be discovered is unearthed by quarry workers in the Neander valley, near Düsseldorf

French chemist Louis Pasteur proves the existence of micro-organisms by showing that a liquid will only ferment if exposed to contamination from the air

Charles Darwin is alarmed to receive in his morning post a paper by Alfred Russell Wallace, outlining very much his own theory of evolution

Charles Darwin puts forward the theory of evolution in On the Origin of Species, the result of twenty years' research

Gregor Mendel reads a paper to the Natural History Society in Brno describing his discoveries in the field of genetics

English polymath Francis Galton publishes Inquiries in Human Faculty, developing the theme of eugenics and coining the term

In a paper to a congress in Madrid, on the 'psychology and psychopathology of animals', Ivan Pavlov announces his discovery of the conditioned reflex

German biologists Fritz Schaudinn and Erich Hoffmann discover the micro-organism Treponema pallidum which causes syphilis

English physiologists William Bayliss and Ernest Starling coin the word 'hormone' for glandular secretions into the bloodstream

English biologist William Bateson uses the word 'genetics' to describe the phenomenon of heredity and variation

Karl Landsteiner classifies the main human blood groups as A, B, AB and O

US geneticist Thomas Hunt Morgan establishes the chromosome theory of heredity through his study of the fruit fly Drosophila melanogaster

German scientist Alfred Wegener, impressed by the neat fit between the coasts of Africa and South America, proposes the theory of continental drift

English geologist Arthur Holmes publishes The Age of the Earth, offering evidence that the planet is at least 1.6 billion years old

Martha, 29 years old and the last passenger pigeon in the world, dies in the Cincinnati zoo in Ohio

Canadian physiologists Frederick Banting and Charles Best isolate insulin from the pancreas for the treatment of diabetes

Biology teacher John Scopes is prosecuted for breaking state law by teaching evolution to his class of children in Dayton, Tennessee

Austrian zoologist Karl von Frisch demonstrates that bees communicate the whereabouts of food by means of a dance

Scottish bacteriologist Alexander Fleming accidentally discovers a mould that selectively kills bacteria, and calls it penicillin

US seismologist Charles Richter devises a scale for measuring the magnitude of earthquakes

The Austrian zoologist Konrad Lorenz describes his experiments on young geese, with their capacity to imprint on human beings

German-born British scientist Hans Krebs discovers the biochemical cycle that becomes known by his name

US psychologist B.F. Skinner trains laboratory rats to use their brains in his 'Skinnner box'

Karl von Frisch demonstrates that bees make use of the polarized light of the sun to calculate direction