Stanley L. Muller and Harold C. Ure used experiments to explain the origin of life on Earth. They believed that the early atmosphere of the Earth was capable of synthesizing amino acids from inorganic materials.
The two biologists used methane, water, hydrogen and ammonia, which they believe were found in Earth’s early atmosphere. The chemicals were placed inside sterile glass tubes and vials and circulated within the plant.
One of the wells is half full of water and the other has an electric couple. The water vapor was heated and the exhaust gas was added to the chemical mixture. Free air moved around the device, mimicking Earth’s atmosphere.
The water in the well represents the water above the earth and the water vapor is like water evaporated from the sea and the ocean. An extra was used to light a fire to simulate an electric current through the water vapor.
The mice got cold and the water turned to water. This distilled water flows back to the first water tank in a continuous cycle. Miller and Ure tested the cooling water a week later and noted that 10-15% of the carbon was in the form of organic matter.
Thirteen amino acids of 2% carbon were synthesized. However, Miller and Ure’s experiments were criticized by fellow scientists.
Criticism of the Miller Urey Experiment
These experiments failed to determine how proteins are responsible for amino acid synthesis. Some scientists protested that the gases used by Miller and Urey were not as abundant as shown in those experiments.
They thought that gases released from volcanic eruptions, such as oxygen, nitrogen and carbon dioxide, formed the atmosphere. Therefore the results are unreliable.
At the beginning of the 20th century, Oparin and Haldane suggested that if the Earth’s ancient atmosphere was reduced and if it had enough UV radiation, electricity and other energy, a variety of organic compounds could be produced.
Oparin believed that organic substances underwent a series of reactions to form complex molecules. He suggested that the molecules formed in the liquid state were coacervates.
Haldane proposed that the original ocean air was without oxygen, with ammonia, carbon dioxide, and UV light. This resulted in a group of organic compounds.
The lake contained many organic monopolymers, and the lake was called “hot exhausted soup”. He assumed that polymer monomers reach the lipid membrane. Molecules continued to grow, and the first organism was born. The term “prebiotic soup” was coined by Haldane.
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