MUNICH, GERMANY—The pattern of communicating in short turns in rapid alternation during conversations may have evolved before language, according to Stephen Levinson of the Max Planck Institute for Psycholinguistics. He has reviewed research on how modern humans listen and prepare a spoken response—it takes about 200 milliseconds on average to respond to one another, but it takes about 600 milliseconds to prepare a word for delivery, implying that people have to begin preparing a response while listening to the current speaker. Levinson notes that this is a pattern found across unrelated cultures and languages, and that infants begin taking turns in interactions at about six months of age, before they can speak. As language skills develop, however, infant turn-taking slows down as they struggle to master more complex language structures and speak rapidly. Levinson thinks that human ancestors may have taken turns gesturing to each other, as the great apes do, before they began communicating through the vocal channel some one million years ago. To read about how linguists reconstruct ancient languages, go to "Telling Tales in Proto-Indo-European."