I will argue that chemiosmotic coupling constrained the evolution of life on earth to the complexity of bacteria and archaea for billions of years. A singular event, in which one bacterium somehow got inside another one, overcame these endless energetic constraints on bacteria. That endosymbiosis gave rise to eukaryotes with genomes that swelled over orders of magnitude, the raw material for morphological complexity. The intimate relationship between the host cell and its endosymbionts (which went on to become mitochondria) was, I shall argue, behind many strange properties shared by
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