Numeracy

A group of illiterate knights arrive for dinner at a round table and rush to sit down. The head waiter, Merlin, discovers, on reading their name-cards, that none has occupied the correct seat. When they all refuse to move he says: "Never mind, I'm sure we'll be able to rotate the table so that at least two of you will be seated correctly." How could he be so sure?

Yesterday's answer: Both populations have equal male and female. Half the babies are boys and half girls whenever they decide to stop.