A new study argues that life may have emerged twice on Earth. "Two of the main lineages of life -- bacteria and archaea -- may have independently figured out the secrets of metabolism that upgraded them from non-living to living," reports ScienceAlert, citing a new study that "focused on the most rudimentary set of chemical reactions thought to enable this transformation." From the report: "The surprise is that the enzymes that catalyze those reactions are not conserved across the evolutionary divide that separates bacteria and archaea," says William Martin, a biologist at Heinrich Heine University Dusseldorf in Germany. "The new data leave only one conclusion. The bacterial and archaeal lineages made the transition to the free-living state independently. Only free-living cells are alive. "Let's call it by name: we are looking at one origin of the genetic code, but two origins of life." That's a huge claim to make, especially when defining what life even is can be surprisingly tricky. The findings have been published in the journal Science Advances.

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