In this ground-breaking book, Johanna Nichols proposes means of describing, comparing, and interpreting linguistic diversity, both genetic and structural, providing the foundations for a theory of diversity based upon population science. This book will interest linguists, archaeologists, and population specialists.

"An awe-inspiring book, unequalled in scope, originality, and the range of language data considered."—Anna Siewierska, Linguistics

"Fascinating. . . . A brilliant pioneering study."—Journal of Indo-European Studies

"A superbly reasoned book."—John A. C. Greppin, Times Literary Supplement