Bone strontium levels and hydroxyapatite crystal sizes increased with time in two exposed wildebeest skeletons. The strontium increases could not be removed by sequential washing according to the method of Sillen, A. (1986). Biogenic and diagenetic Sr/Ca in Plio-Pleistocene fossils of the Omo Shungura Formation. Paleobiology 12, 311-323. Human subfossil bone recovered archaeologically also showed evidence of extensive diagenetic reworking that resulted in crystal growth and elevated strontium levels. The increase in bone strontium content was independent of non-apatitic contaminating crystal phases.