![]() Minerals precipitate inside the layers, creating durable structures even as the microbes die off. Stromatolites are created as sticky mats of microbes trap and bind sediments into layers. The signals consisted of a type of carbon molecule that is produced by living things.Įvidence of microbes was also preserved in the hard structures (“stromatolites”) they made, which date to 3.5 billion years ago. The earliest life forms we know of were microscopic organisms (microbes) that left signals of their presence in rocks about 3.7 billion years old. With an environment devoid of oxygen and high in methane, for much of its history Earth would not have been a welcoming place for animals. ![]() But that’s not how life on Earth used to be. These and other animals require oxygen to extract energy from their food. Our ecosystems are structured by feeding relationships like killer whales eating seals, which eat squid, which feed on krill. Today we take for granted that we live among diverse communities of animals that feed on each other.
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