In 2021 a team led by Axel Meyer finished reading the genome of the Australian lungfish, a slow, olive-coloured fish that has hardly changed its shape in a hundred million years. It came to about 43 billion letters, roughly fourteen times the length of ours, and for a while it was the largest animal genome anyone had sequenced. (A South American cousin has since been reported larger still.) The surprise isn’t the size; it’s that the extra length doesn’t buy anything you can point to. The lungfish has about as many genes as other vertebrates. Most of the rest is repeats, copies of copies that got in a long time ago and were never thrown out. It’s the instruction manual as a family keeps it, with every old receipt still folded inside, and the fish goes on working perfectly well. Length was never the measure of what a thing knows how to do.