Life Began With a Planetary Mega-Organism

Life Began With a Planetary Mega-Organism

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.