Abstract: The Lajia site, located in Minhe County, Qinghai Province, is a large settlement site of Qijia Culture dated 3900-4300 BP. The study of the Lajia site is meaningful to understand the ancient civilization in the upper reaches of the Yellow River and its contribution to the local Qijia Culture. This paper analyzed elemental contents of human bones and tooth enamel samples from 42 samples (20 bone and 22 teeth; two contaminated bone samples of the original samples were removed) from 22 individuals ranging in age from child to adult. Eight pig tooth enamel samples were also collected. This research involved thermal ionization mass spectrometry for strontium isotope ratio (87Sr/86Sr). The eight pig samples were chosen to provide an independent gauge for the local ratio of strontium isotopes, because results of 87Sr/86Sr ratios in enamel samples from domestic animals revealed that the standard deviation for pigs was less than that for sheep or cattle at the Lajia site, which meant that pig enamel samples may provide better indicators of local biologically-available strontium isotope ratio signatures. The mean 87Sr/86Sr ratios of eight pig tooth enamel samples was 0.710930 based on which local strontium isotopes ratio range (±2σ) can be obtained as 0.711058-0.710802. Among the 22 individuals subject to our analysis, the strontium isotope ratios of tooth enamel samples of 17 individuals fell into this range, which might indicate local birth and life. Strontium isotope ratios of the tooth enamel samples of two individuals were very close to the upper and lower limits of this range, and are left for further study. Only the ratios of three individuals among the 22 fell outside the range showing that they might have been born in other regions and buried in the Lajia site after death. In addition, the similarities between bone and tooth enamel strontium isotope ratios suggest that native-born people at the Lajia site all had similar diets.

Key words: Lajia site; Qijia culture; Strontium isotopes; Human migration