The oldest evidence of life is seen in rock samples with organic carbon compounds that have less carbon-13, as biological processes tend to use more carbon-12. Rocks from around 3400-3500 million years ago also show signs of biological carbon and sulfur cycles.

Question

The oldest evidence of life is seen in rock samples with organic carbon compounds that have less carbon-13, as biological processes tend to use more carbon-12. Rocks from around 3400-3500 million years ago also show signs of biological carbon and sulfur cycles.
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GPT 3.5 · Answer

Signs of early life can be found in rocks containing organic carbon compounds with a higher ratio of carbon-12 to carbon-13, indicating biological processes. These rocks dating back over 3 billion years also exhibit evidence of biological carbon and sulfur cycles.