Monomers may have been able to spontaneously form polymers under the conditions found on early Earth. For instance, in the 1950s, biochemist Sidney Fox and his colleagues found that if amino acids were heated in the absence of water, they could link together to form proteins^{10}
10
start superscript, 10, end superscript. Fox suggested that, on early Earth, ocean water carrying amino acids could have splashed onto a hot surface like a lava flow, boiling away the water and leaving behind a protein.