Carry On, Jeeves

Evolution is like a really good butler or valet, who's already standing there with a favorite beverage for you just at the moment you realize you're thirsty. Whether you are a vertebrate that goes by land or by sea, in getting your food it helps a lot to have jaws and teeth. The most primitive fishes lacked jaws, so how did they get them? A report in Nature documents the curious brain structure of a jawless fish that swam in Chinese and Vietnamese seas 435-370 million years ago.

As...