If you look at the world around you now - at the plants, animals, and the people around you, it's easy to take for granted our multicellular existence. Life didn't always look like this. In fact, way before multicellular organisms took over, life was much less complicated as a single cell.
Scientists believe the Earth is about 4.5 billion years old. And in that span, single-celled organisms have been around for about 3.5 billion years. These include bacteria, protozoa, and unicellular algae and fungi. By contrast, multicellular organisms have only existed just a fraction of the time, appearing at about 600 million years ago.
Because unicellular life has been around for at least an additional 2 billion years, we know that this existence is successful. But why did organisms evolve to become multicellular only to never look back? Watch the video to find out!