I figured this out a while ago (with charts and graph paper - I'm quite the nerd) , but it's come up in two seperate conversations recently, so I'd better share: Chinese food has rice and noodles, but no cheese. Mexican food has rice and cheese, but no noodles. Italian food has noodles and cheese, but no rice. Government conspiracy? Collusion between restaurants? Undisputable proof that our cultures were put here by aliens? Draw your own conclusions.