Contents

22 November 2002
Vol 298, Issue 5598

About The Cover

Cover image expansion

COVER A Chinese native dog, showing one of many morphological types. Although extreme variation in morphology is seen among dog breeds worldwide, they may all have originated about 15,000 years ago from the single East Asia gene pool. 1610 [Photo: Y. Zhang, D. Pan, and L.-Y. Luo]