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From fossil evidence, it appears that life may have existed on Earth as early as 3.5 billion years ago. This suggests that life must have evolved sometime during Earth's tumultuous first billion years.
What were the first organisms to appear on Earth? A: It is believed that the first organisms to appear on Earth resembled singled-celled life forms known as Archaea, which are similar to bacteria but lack nuclei. Modern-day Archaea can live in extreme environments such as hot springs and deep-sea vents. These conditions replicate some of those on early Earth.