Zeroing in on the last common ancestor of all complex cells

(credit: David Mulder)

A nucleus is one of many membrane-bound compartments that distinguishes our eukaryotic cells from the prokaryotic cells of microorganisms like bacteria. Eukaryotic cells also possess energy-producing compartments we call mitochondria.

Because mitochondria look like prokaryotes, it's long been assumed that eukaryotic cells came into existence when one prokaryote swallowed another prokaryote. The subsumed prokaryote then set up shop inside the host prokaryote and evolved into a mitochondrion. A problem with this idea is that prokaryotic cells lack the ability to phagocytose—to swallow other cells. Eukaryotic cells can, but every eukaryote we know about has mitochondria. It's not clear which came first: the ability to swallow other cells, or the mitochondria.

But over time, researchers have made the case that the ancestor of all eukaryotes belonged to a group of organisms called archaea. And now, one team says it can point the finger at a specific organism.

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