The origin of an idea
The coordinates point to the Downing Site, a major scientific campus of the University of Cambridge. In 1929, John Burdon Sanderson Haldane worked here as the Sir William Dunn Reader in Biochemistry. That year, he published an eight-page essay in The Rationalist Annual titled "The Origin of Life". In it, he laid out a purely chemical hypothesis for how life on Earth may have begun.
Haldane proposed that the primitive Earth's atmosphere contained little to no free oxygen. It was instead a "reducing" atmosphere, full of compounds like carbon dioxide, ammonia, and water vapor. With no protective ozone layer, the planet's surface was bombarded by intense ultraviolet radiation from the sun. This radiation, Haldane argued, provided the energy to break apart these simple molecules and reassemble them into more complex organic compounds. Over millions of years, these compounds would accumulate in the early oceans, creating what he famously described as a "hot dilute soup". Within this chemical broth, molecules could react further, eventually forming self-replicating structures inside an "oily film"—precursors to the first living cells.
From hypothesis to experiment
Haldane was not entirely alone in this line of thinking. The Soviet biochemist Aleksandr Oparin had independently published a similar theory in 1924, though Haldane was unaware of Oparin's work when he wrote his essay. Together, their ideas form the Oparin-Haldane hypothesis, which transformed the origin of life from a philosophical puzzle into a testable scientific problem.
The first major experimental test of the hypothesis came in 1953. Chemists Stanley Miller and Harold Urey at the University of Chicago created a closed system containing a heated pool of water and a mixture of gases thought to be on early Earth: methane, ammonia, and hydrogen. They introduced electrical sparks to simulate lightning. After a week, they found that several complex organic molecules, including amino acids, the building blocks of proteins, had formed spontaneously. While scientific understanding of the early Earth's atmosphere has evolved, the core concept of abiogenesis, the gradual chemical evolution from non-living matter to life, remains the foundation of modern origin-of-life research.