Why do doughnuts have holes?

Question: We're all familiar with the ring doughnut as an American confection. One thing I've always been curious about is why they have holes in them (or are toroidal in shape). What advantages, if any, does this shape have in the preparation process, and are there any other historical reasons for this shape?

Answer: Legend has it that the inventor of the ring shaped donut with a hole came up with the idea because he was dissatisfied with the raw centre of regular donuts.

Hanson Gregory, an American, claimed to have invented the ring-shaped doughnut in 1847 aboard a lime-trading ship when he was 16 years old. Gregory was dissatisfied with the greasiness of doughnuts twisted into various shapes and with the raw center of regular doughnuts. He claimed to have punched a hole in the center of dough with the ship's tin pepper box, and to have later taught the technique to his mother. Smithsonian Magazine states that his mother, Elizabeth Gregory, "made a wicked deep-fried dough that cleverly used her son's spice cargo of nutmeg and cinnamon, along with lemon rind," and "put hazelnuts or walnuts in the center, where the dough might not cook through", and called the food ‘doughnuts’.

Having done quite a few doughnut experiments recently, it's true that having shapes where the distance from the centre to the surface is smaller increases your chances of properly cooked doughnuts. So toroids make sense, but then so would thin cylinders.

You can however, fry up donuts with no hole, that are cooked all the way through. Look at Berliners or jam-filled doughnuts.

But however doughnuts came about, they are loved by everyone!