Fugu—the poisonous puffer fish sought after by brave suchi-eaters—has the smallest known vertebrate genome. When researchers unraveled its genetic structure in 2002, they found that 75 percent of its genes have direct human counterparts, even though the fish and humans diverged from their common ancestor over 400 million years ago. By comparing human and fugu genomes, researchers found almost 1,000 previously unidentified human genes.