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A new finding announced today provides some clues as to how life went from being simple to complex billions of years ago. NPR's Nell Greenfieldboyce reports that scientists made their discovery in some blackish muck from the bottom of the sea.
NELL GREENFIELDBOYCE, BYLINE: Scientists think life appeared soon after our planet formed some four and a half billion years ago.
THIJS ETTEMA: The microbes that lived back then had to cope with completely different conditions.
GREENFIELDBOYCE: Thijs Ettema is a biologist at Uppsala University in Sweden. He says in our planet's early days, there was no oxygen, lots of volcanoes. It was intense. The life forms that eked out a living back then were bacteria and another group of microbes called the archaea.
ETTEMA: These are typically very small cells that look very simple.
GREENFIELDBOYCE: Then, starting about 2 billion years ago, much more fancy cells appeared, the kind of cells in your body and in all plants and animals. These cells are larger. Their genetic material is wrapped inside a nucleus. They've got all kinds of little organs, like energy-producing mitochondria. Ettema says in these cells there's just a whole lot of business going on.
ETTEMA: And this transition from these simple cells to the complex cells, this is a big question in biology.
GREENFIELDBOYCE: His team went looking for answers in an extreme place - the bottom of the Atlantic Ocean a mile and a half down. A colleague collected some muddy sediments not too far from a hydrothermal vent that was spewing out hot water. In the lab, the team extracted DNA, sequenced it and used computers to reconstruct the genetic codes of microbes. What they found was surprising - a group of archaea that have a whole bunch of genes normally only found in more complex cells. Ettema says this looks like an intermediate form of life - a kind of missing link.
ETTEMA: Suddenly, we find something that no one has ever seen before or, some people even said that, well, maybe this organism existed, but we'd never know for sure. And now, we find it.
GREENFIELDBOYCE: A report on the finding appears in the journal Nature, and it thrills Martin Embley, a biologist at Newcastle University in the United Kingdom.
MARTIN EMBLEY: This is a great paper. It's a real, real breakthrough.
GREENFIELDBOYCE: He says this shows complex life emerged from within the archaea. And finding more microbial cousins like this one could let researchers trace the evolution of cells that eventually became us. Nell Greenfieldboyce, NPR News.