**Thomas Barfield *is professor of anthropology at Boston University. His books include The Perilous Frontier: Nomadic Empires and China, 221 BC to AD 1757 *; The Central Asian Arabs of Afghanistan; and Afghanistan: An Atlas of Indigenous Domestic Architecture.

**Thomas Barfield *is professor of anthropology at Boston University. His books include The Perilous Frontier: Nomadic Empires and China, 221 BC to AD 1757 *; The Central Asian Arabs of Afghanistan; and Afghanistan: An Atlas of Indigenous Domestic Architecture.