The broadest outlines of life's emergence on Earth are fairly simple,

from organic molecules to single-celled organisms to more complex ones that eventually led to us and every other living thing on the planet.

But here is a mind-blowing idea.

Maybe multicellular life forms arose far earlier than anybody thought and died out completely,

only to have more complex life emerge again hundreds of millions of years later.

From KERA in Dallas, this is Think.

I'm Chris Boyd.

A geochemist studying some uniquely preserved sediments in Gabon believes he's found the remains

of species that thrived in conditions that would pretty much kill anything that lives

on Earth today.

That hypothesis could radically change the

way we understand biological history. But as my guest has learned, skeptics aren't even convinced

the specimens are definitely fossils. Osher Elbein is a science and culture journalist. His article

for Scientific American is titled Life's Big Bangs. Asher, welcome back to think.

Thank you so much for having me.

Will you start, I don't want to take the whole hour with this, but will you walk us through

the kind of standard story of how complex life is believed to have emerged on Earth?

Of course.

So the basic story, as it has evolved over time, is that we believe that when we talk

about complex life, we're talking about generally eukaryotic life, which is organisms with the

kinds of cells that everything from seaweed to us has. And it was generally thought that that

originated probably around once, around 1.6 billion years ago,

...