Theoretical origin of life: age of LUCA (Introduction)

by David Turell , Wednesday, November 22, 2023, 19:25 (157 days ago) @ David Turell

Latest estimates:

https://www.sciencedaily.com/releases/2023/11/231121175308.htm

LUCA, the 'last universal common ancestor' of all living organisms, lived 4.32 to at most 4.52 billion years ago. This is indicated by a study from NIOZ biologists Tara Mahendrarajah and senior author Anja Spang, with collaborating partners from Universities in Bristol, Hungary and Tokyo, that was published today in Nature Communications. What LUCA looked like is unknown, but it must have been a cell with among others ribosomal proteins and an ATP synthase. "These proteins are shared by all bacteria, archaea, and eukaryotes such as plants and animals," Spang said. Using a new molecular dating approach, the researchers were able to more accurately estimate the moment when LUCA split into bacteria and archaea, as well as when eukaryotes emerged.

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"Archaea are often called ancient bacteria," says Spang. "That would suggest that they stem from an ancestor that is older than the one of today's bacteria. But with this improved dating approach, we see that the ancestor of all current archaea lived between 3.37 and 3.95 billion years ago . This makes the last common ancestor of known archaea younger than the one of all bacteria, which lived between 4.05 and 4.49 billion years back. This suggests that earlier archaea either died out, or they live somewhere hidden on Earth where we have not found them yet," Spang hypothesizes.

The eukaryotes, meaning cells with a nucleus, such as all plants and animals, had their last common ancestor between 1.84 to 1.93 billion years back.

Tara Mahendrarajah explains: "If you imagine all life on earth as a family tree, LUCA is at the base and at some point, the trunk splits into a bacterial and an archaeal branch. But eukaryotes are not a separate branch on this tree of life, but rather a fusion of two branches that came out of the bacterial and the archaeal branches. We have a bit of both in us."

Comment: this is consistent with previous estimates, which means life appeared within 300-400 million years after the Earth formed.