Ancient, Archaean Life Discovered in Loki's Castle May be Evolutionary Missing Link

Scientists may have discovered a missing link in the evolution of complex life. They've found a new microbe, nicknamed "Loki," that may reveal how billions of years ago complex cell types evolved from simple microbes.

Cells are the basic building blocks of all life. Yet whereas the cells of bacteria and other microbes are small and simple, all visible life is generally made up of large and complex cell types. The origins of these cells have long remained a mystery.

In this case, though, the researchers discovered a new group of Archaea, the Lokiarchaeota, or "Loki" for short. This group may actually be a missing link in the evolution of eukaryotes, which are more complex cell types.

"The puzzle of the origin of the eukaryotic cell is extremely complicated, as many pieces are still missing," said Thijs Ettema, one of the researchers, in a news release. "We hoped that Loki would reveal a few more pieces of the puzzle, but when we obtained the first results, we couldn't believe our eyes. The data simply looked spectacular. By studying its genome, we found that Loki represents an intermediate form in-between the simple cells of microbes, and the complex cell types of eukaryotes."

Loki actually formed a well-supported group with the eukaryotes in the scientists' analysis. In addition, Loki shares many genes with eukaryotes, suggesting that cellular complexity emerged in an early stage of evolution.

Loki was discovered in Loki's Castle, a hydrothermal vent system located on the Mid-Atlantic Ridge between Greenland and Norway at a depth of 2,352 meters.

"In a way, we are just getting started," said Ettema. "There is still a lot out there to discover, and I am convinced that we will be forced to revise our biology textbooks more often in the near future."

The findings are published in the journal Nature.

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