1. Institute of Anthropology, Liaoning Medical University; Jinzhou 121001 China
2. Mel and Enid Zuckerman College of Public Health, University of Arizona; Tucson 85724-5211
3. Department of Basic Medicine; Nanyang Medical College; Nanyang 473061 China
4. Department of Stomatology, Liaoning Medical University; Jinzhou 121001 China