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+--- Thread: Research Two origins of life found by tracing early chemical reactions in one-celled organisms (/thread-21041.html)
Two origins of life found by tracing early chemical reactions in one-celled organisms - C C - Aug 7, 2026
https://www.smithsonianmag.com/science-nature/a-new-study-points-to-two-origins-of-life-on-earth-by-tracing-early-chemical-reactions-in-single-celled-organisms-180989260/
EXCERPTS: All organisms alive today descend from the last universal common ancestor (LUCA) that likely dwelled in the early oceans. This mysterious ancestor, the new study suggests, was still reliant on its environment to conduct metabolism.
This mysterious ancestor, the new study suggests, was still reliant on its environment to conduct metabolism. Rather than fueling its energy-producing reactions on its own with enzymes, LUCA depended on small organic molecules and metals in the environment to conduct about half of the core metabolic reactions, the researchers found. Then, over time, some of these metals were replaced with more specific and efficient enzymes as the proteins evolved to do the same jobs.
[...] Archaea and bacteria are two of the three domains of life, and these microbes arose early in Earth’s history. The third domain, eukaryotes—the one that animals, plants and all organisms with nucleus-containing cells belong to—evolved later, from a hybrid of the first two groups.
For many years, scientists contemplated three possible scenarios for the origin of life: Either bacteria evolved from archaea, archaea evolved from bacteria, or both independently evolved from LUCA. The new study makes the argument that the last possibility is the most likely one.
[...] The team then found that bacteria and archaea shared some enzymes with LUCA—but each lineage also had some that were not present in the ancestor. Essentially, bacteria and archaea independently evolved different enzymes to replace the same metal-catalyzed reactions. “This shows the reaction is older than the enzymes that catalyze it,” says University of Ottawa chemist Joseph Moran, a co-author of the study.
These distinct solutions to the same metabolic problems are evidence to Martin that bacteria could not have been derived from archaea, or the reverse. “The simplest interpretation,” he says, “is that there were two independent transitions” from LUCA to free-living cells.
[...] Based on its metabolism, too, Martin argues that LUCA was a simpler ancestor—something not completely alive. “There can be no question that free-living cells are alive,” says Martin, referring to cells that are capable of growing, dividing and surviving on their own. “We can all agree on that.” But LUCA was still reliant on small organic molecules and metals in the Earth’s crust to carry out metabolism. When it comes to being classified as truly alive, “that’s not going to cut the mustard,” he says.
Martin has long argued that metals were the original catalysts for metabolic reactions, and that over time, those metals were replaced by enzymes. “There’s strong support for the idea that geochemistry would have led to life’s biochemistry,” says Donato Giovannelli, a microbiologist at the University of Naples Federico II in Italy who studies the origin of life... (MORE - missing details)