Most life on Earth exists as single cells. But the ones comprised of many cells, from the tiniest ant to the tallest tree, have had an undeniable impact on our planet. These ‘multicellular’ creatures evolved from single-celled ancestors at least 25 times throughout Earth’s history. These transitions are arguably some of the most significant in evolution, but we only have a vague understanding of how they happened.

It probably went a bit like this. A single cell split into two and rather than going their separate ways, they stayed together. This happened again and again. Eventually, the groups of individual cells became individuals of grouped cells, evolving as a unit. It’s the story of how I became we, and how we