Japanese people have special tools that let them get more out of eating sushi than Americans can. They are probably raised with these utensils from an early age and each person wields millions of them. By now, you’ve probably worked out that I’m not talking about chopsticks.

The tools in question are genes that can break down some of the complex carbohydrate molecules in seaweed, one of the main ingredients in sushi. The genes are wielded by the hordes of bacteria lurking in the guts of every Japanese person, but not by those in American intestines. And most amazingly of all, this genetic cutlery set is a loan. Some gut bacteria have borrowed their seaweed-digesting genes from other microbes living in