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According to the clay hypothesis of A. G. Cairns-Smith , silicate minerals in water played a crucial role in abiogenesis : they replicated their crystal structures , interacted with carbon compounds , and were the precursors of carbon-based life .
 A. G. Cairns-Smith
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 A. G. Cairns-Smith