Nature 252, 378 - 379 (29 November 1974); doi:10.1038/252378a0

Reliability of amino acid racemisation dating and palaeotemperature analysis on bones

MICHAEL L. BENDER

Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island 02881

THE general inability of isotope geologists to work out techniques for dating continental Pleistocene deposits has led to the conception of nonisotopic chemical methods. Hare and Mitterer¹ noted that fossils could possibly be dated by determining the extent to which the l optical isomer of a given amino acid had racemised to form the d isomer which is initially absent in skeletal material. Obviously, the rate constant for the reaction must be known accurately if age is to be calculated, but its value is difficult to assess: it is highly temperature dependent² (about 20%° C^-1); it depends on the state of the amino acids (free amino acids racemise about an order of magnitude more rapidly than those bound as peptites)³⁻⁵; and it is highly dependent on environment⁶. Furthermore, free amino acids may back react to produce the bound forms, and there could be open system conditions during diagenesis².

References

1.	Hare, P. E., and Mitterer, E., Yb. Carnegie Instn. Wash., 67, 205 (1969).
2.	Bada, J. L., Kvenvolden, K., and Peterson, E., Nature, 245, 308 (1973).
3.	Wehmiller, J. F., and Hare, P. E., Science, 173, 907 (1971).
4.	Wehmiller, J. F., thesis, Columbia Univ. (1971).
5.	Bada, J. L., and Schroeder, R. A., Earth planet. Sci. Lett., 15, 1 (1972).
6.	Kvenvolden, K., and Peterson, E., Annual Meeting of the Geological Society of America Abstracts with Programs, 704 (1973).
7.	Turekian, K. K., and Bada, J. L., in Calibration of Hominoid Evolution (edit. by Bishop, W. W., and Miller, J. A.), 171 (Scottish Academic Press, Edinburgh, 1972).
8.	Thurber, D. L., ibid, 1.
9.	Bada, J. L., Earth planet. Sci. Lett., 15, 223 (1972).
10.	Schroeder, R., and Bada, J. L., Science, 182, 479 (1972).