Last month, a group of scientists from around the world announced that they had successfully determined the DNA sequence of the tomato genome. One of the most surprising results of this work was that the lowly tomato, like rice and the common Arabidopsis before it, has more genes than we do – about 25% more.

How could this seemingly passive plant that we know and love, that key ingredient in ketchup and in our summer salads, be genetically more complex than we are?

This...