Abstract: Linear enamel hypoplasia (LEH) is a developmental defect of enamel appearing as one or more horizontal lines or grooves on the surface of a tooth crown. The defect forms when physiological stress, such as disease or poor nutrition, and disturbs enamel matrix formation, resulting in a deficiency of enamel thickness. The expression of LEH is a sensitive dental indicator of physiological stress. This paper focused on linear enamel hypoplasia of late Miocene Lufengpithecus lufengensis from Shihuiba site, Lufeng county of Yunnan of China.Specimens including 246 permanent teeth of 26 mandibles were examined with a 10X hand lens for the presence of surface disturbances of enamel formation. To diversity degrees, almost 100 % individuals of 26 mandibles of Lufengpithecus lufengensis showed LEH. 85. 0 % of permannent teeth (209 of 246) were affected by LEH. Most of the teeth, especially canines showed repetitive LEH (rLEH), and the spacing between episodes of rLEH was almost uniform. Based on perikymata counts between episodes of rLEH, the periodicity of rLEH of Lufengpithecus lufengensis showed a semi-annual pattern. The apparent ubiquity of twice yearly stress was attributed to regular seasonal cycles which could lead to both disease and nutritional stress.
Although linear enamel hypoplasia was ubiquitous among the permanent teeth of Lufengpithecus lufengensis, the LEH incidence of the first permanent molars, which were the earliest forming permanent teeth, was so much low as only 5.7 % among 35 first permanent moalrs. The decidous teeth almost had no incidence of LEH.The fact indicates Lufengpithecus lufengensis was not easily affected by LEH at the very early age, or before the age of 2-3 years old.
Based on the analysis on the paleoclimate, habitat and diet of Lufengpithecus lufengpithecus, the author suggested that higher LEH incidence of Lufengpithecus lufengpithecus might be caused by nutri-tional stress which depended on the intensified seasonal habitat of Lufengpithecus lufengensis.

Key words: Lufengpithecus lufengensis; Linear enamel hypoplasia