Stanley Miller experiment
You may have heard of the Stanley Miller experiment at school. In the 1950s, Stanley Miller and Harold Urey performed a famous experiment when they attempted to simulate what they thought might be the conditions present at the beginning of the Universe. They took some simple materials – some methane, ammonia, and water vapour, then zapped them with an electric spark to simulate lightning. In just a week, they produced amino acids, the building blocks of protein, which is fundamental to life. Had they re-created the Primordial Soup?

Understandably, the results attracted a lot of attention and found their way into many textbooks. However, a subsequent review highlighted several major flaws in the design and outcome of the experiment,
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Stanley Miller in his Lab (Credit: University of Chicago)
Wrong starting materials,
  • They used Hydrogen, water vapour, methane and ammonia, but no oxygen.
  • However, there is no evidence to suggest that the Earth ever had a 'reducing' atmosphere (scientific term for a lack of oxygen), as oxygen is present in all rock layers.
  • Their experimental reactions wouldn't have occurred with oxygen present - life couldn't have evolved with oxygen.
  • But if there was no oxygen at the point where life began, then there was no ozone, and this means UV light from the Sun would have destroyed the ammonia.
Wrong conditions,
  • An electric spark was used to provide energy, but not allowed to destroy the products, as they were filtered off.
Wrong conclusion,
  • The main product was tar (85%), with carboxylic acid (13%) - both of these are toxic to life. The amino acids were a trace product (2%), although it was claimed that the product was rich in amino acids. Both left and right handed amino acids were formed and yet life is based purely on left-handed molecules. In fact, the presence of one right handed amino acid molecule prevents the production of protein.

Click here for a full description of the experiment.
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