Origin of Life; LUCA (Introduction)

by dhw, Sunday, November 27, 2011, 15:51 (4723 days ago) @ David Turell

DAVID: Folly, foolishness, futility mixed with a taint of scientific research, or does study of 'conserved' genes paint a real and proper picture of the first organism?

http://www.newscientist.com/article/mg21228404.300-life-began-with-a-planetary-megaorga...

Quote: “Once upon a time, 3 billion years ago, there lived a single organism called LUCA. It was enormous: a mega-organism like none seen since, it filled the planet's oceans before splitting into three and giving birth to the ancestors of all living things on Earth today. This strange picture is emerging from efforts to pin down the last universal common ancestor - not the first life that emerged on Earth but the life form that gave rise to all others.”

As usual, I need help on the science, although I’m reassured by David’s scepticism. Here are some statements I don’t understand – so please put me right.

First, though, a complaint. The headline tells us: LIFE BEGAN WITH A PLANETARY MEGA-ORGANISM, but now we learn that LUCA wasn’t the first life that emerged, so life didn’t begin with the mega-organism. Misleading headline.

“It was around 2.9 billion years ago that LUCA split into the three domains of life: the single-celled bacteria and archaea, and the more complex eukaryotes that gave rise to animals and plants (see timeline). It's hard to know what happened before the split.”

And it must be equally hard to know what the first forms of life actually were, what happened to them, why they didn’t survive, or why they didn’t merge with this extraordinary mega-organism, or even merge to form it (in which case, they would all be LUCAs). What evidence have the researchers provided that bacteria, archaea and eukaryotes didn’t already exist before the birth of the ocean-filling organism? And what evidence have they provided that there ever was such a thing?

“The latest results suggest LUCA was the result of early life's fight to survive, attempts at which turned the ocean into a global genetic swap shop for hundreds of millions of years. Cells struggling to survive on their own exchanged useful parts with each other without competition - effectively creating a global mega-organism.”

What sort of cells were these, if they weren’t the first forms of life? Where did they come from? Life’s early fight….without competition….Then the happy monster splits up and there is competition again. Why would that happen? A big, accidental oops? And why would a “single organism” split into three separate, readymade forms?

Perhaps my questions are stupid, because I’m way out of my depth, but I’m willing to learn!