How did we come to think of ourselves as human? What exactly does it mean to be human? What are the implications of defining what human means for the nonhuman others?

Two billion years ago, an archaeon gobbled up a bacterium. Instead of providing a meal, this ingestion sparked a mutually beneficial relationship, a phenomenon known as endosymbiosis. The bacterium evolved into mitochondria, the ‘powerhouse’ organelles of the cell that helped to fuel eukaryotes’ rise, that is, ourselves.