Scientists think they've found the origin of all earthly life

Where did life come from? — (Image credit: iStock)

Four billion years ago, sometime around Earth's 560 millionth birthday, Luca was born.

Luca is your great-to-an-infinite-degree grandmother and grandfather, as it is your dog's and your goldfish's and your ficus'. Every living thing on Earth owes its existence to Luca, whose very name stands for "Last Universal Common Ancestor." It is the origin of life on Earth, from which the rest of us evolved. And now scientists believe they have mapped a genetic picture of the qualities that would have belonged to Luca, giving us a startling look at how life on Earth might have begun:

...By comparing their sequence of DNA letters, genes can be arranged in evolutionary family trees, a property that enabled [Dr. William F.] Martin and his colleagues to assign the six million genes to a much smaller number of gene families. Of these, only 355 met their criteria for having probably originated in Luca, the joint ancestor of bacteria and archaea.Genes are adapted to an organism's environment. So Dr. Martin hoped that by pinpointing the genes likely to have been present in Luca, he would also get a glimpse of where and how Luca lived. "I was flabbergasted at the result, I couldn't believe it," he said.The 355 genes pointed quite precisely to an organism that lived in the conditions found in deep sea vents, the gassy, metal-laden, intensely hot plumes caused by seawater interacting with magma erupting through the ocean floor. [The New York Times]

Chemist John Sutherland, of the University of Cambridge, has a rival theory that life formed in shallow pools, not the ocean. Others say that Dr. Martin's version of Luca is actually the sophisticated descendent of some other original Luca.

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But regardless of which theory you believe, as James O. McInerney wrote in a commentary about Dr. Martin's research, Luca is "a very intriguing insight into life four billion years ago." Read all about it at The New York Times.

Jeva Lange was the executive editor at TheWeek.com. She formerly served as The Week's deputy editor and culture critic. She is also a contributor to Screen Slate, and her writing has appeared in The New York Daily News, The Awl, Vice, and Gothamist, among other publications. Jeva lives in New York City. Follow her on Twitter.