Life on Earth is said to have formed somehow from the ‘primordial soup’ that existed on the early planet.
Life on Earth is said to have formed somehow from the ‘primordial soup’ that existed on the early planet.
In 1953, the same year scientists discovered the structure of DNA, a student and his professor simulated those conditions – and made the building blocks of life in a flask full of chemicals.
Charles Darwin’s theory of evolution showed that all living things are related by common ancestors. Look back far enough, and you reach the beginning of that long process.
The oldest fossils show that early life forms were extremely primitive. It seems reasonable to suggest they arose somehow from lifeless matter – a kind of ‘chemical evolution’.
In the 1920s, Russian biochemist Aleksandr Oparin (1894–1980) and British biologist J.B.S. Haldane (1892–1964) independently proposed that the complex organic chemicals necessary for life were manufactured in the atmosphere and that rain washed them into the seas, where they formed a ‘soup’ from which life developed.
The experiment conducted by Stanley Miller (1930-2007) and Harold Urey (1893–1981) at Chicago University involved a loop of glass tubes containing the gases that Oparin and Haldane supposed were in the early Earth’s atmosphere.
They were connected to a flask full of water and a reaction vessel. Two metal electrodes poked into the reaction vessel and sparks jumped across the gap between them to simulate lightning.
The water was heated, so that it evaporated – that way it ‘rained’.
After a week, the two scientists found good quantities of compounds called amino acids inside their apparatus.
Amino acids join together to make proteins, complex compounds important to all life on Earth.
Miller and Urey’s experiment made 13 of the 21 amino acids ‘essential’ to life as we know it.
It was a long way from creating living things or even a complete set of the ‘building blocks’ of life, but the experiment did show how it is possible to produce a cocktail of complex organic compounds from simple inorganic ingredients.
Since the 1950s, several other scientists have carried out similar experiments with similar results.
Other researchers have taken different directions.
For example, using radio telescopes, astronomers have discovered complex organic molecules on comets in our solar system and even in huge clouds of gas and dust between the stars.
Many of these interstellar gas clouds contain rich mixtures of chemical elements and receive energy as ultraviolet radiation from nearby stars.
They could be ‘breeding grounds’ for chemical evolution to take place.
Our solar system formed from an interstellar cloud; so the ingredients that kicked off evolution on Earth may have formed even before the planet did.
Another promising theory to explain the origin of life on Earth involves a kind of hot spring on the ocean floor, called a hydrothermal vent.
Tiny enclosures of rock about the size of large cells provide ideal environments for ‘breeding’ complex organic chemicals.
