Dating human bone: is racemization dating species-specific?

Area of Science:

• Biogeochemistry
• Paleochronology
• Analytical Chemistry

Background:

• Amino acid racemization dating relies on the natural conversion of L-amino acids to D-amino acids over time.
• Aspartic acid racemization has shown promise for dating organic materials, but its application across different species requires validation.

Purpose of the Study:

• To develop and validate an aspartic acid racemization dating technique for human and mammal bones.
• To assess the species-specific accuracy of aspartic acid racemization dating.

Main Methods:

• Utilized capillary electrophoresis mass spectrometry (CE-MS) to measure the D/L ratio of aspartic acid in bone samples.
• Developed calibration curves using well-dated human bones (150 to 10,000 years) and compared them with curves generated from various mammal bones.

Main Results:

• Achieved a strong linear correlation (R² > 0.99) for human bone dating up to 10,000 years.
• Observed lower correlations (R² = 0.88 to 0.58) when applying the human calibration curve to mammal bones, indicating species-specific differences in racemization rates.
• Demonstrated that species-specific calibration curves are crucial for accurate amino acid racemization dating.

Conclusions:

• Aspartic acid racemization dating is a reliable method for human bones up to 10,000 years old.
• Amino acid racemization rates vary significantly between species, necessitating species-specific calibration curves for accurate paleochronological studies.
• The findings underscore the importance of species specificity in developing robust dating techniques.