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it should be kept in mind, however, that the potassium-argon technique that gave the 1.9-million-year date is not any more reliable than the other dating techniques we discuss in Appendix 1. Jacob and curtis (1971), who attempted to date most of the hominid sites in Java, found “it has been difficult to obtain meaningful dates from most samples.” In other words, dates were obtained, but they deviated so greatly from what was expected that Jacob and curtis (1971) had to attribute the unsatisfactory results to “contaminants.”

Moveover, according to nilsson (1983, p. 329): “A much lower [potassiumargon] date for the djetis Beds, less than 1 million years, is indicated by later studies (Bartstra 1978).” this agrees with Hooijer’s conclusion that the djetis beds are, like the trinil beds, early Middle pleistocene. Finally, M. H. day and T. I. Molleson (1973, p. 147) reported that fluorine content “analyses of bones from both the djetis and the trinil faunas at Sangiran showed that it was not possible to distinguish, analytically, the two assemblages at this site.”

7.5.2 Chemical Dating of the Trinil Femurs

in Section 7.1.8, we learned that the trinil femurs are indistinguishable from those of modern humans and distinct from those of Homo erectus. this has led some to suggest that the trinil femurs do not belong with the Pithecanthropus skull and were perhaps mixed into the early Middle pleistocene trinil bone bed from higher levels (day and Molleson 1973, p. 152). Another possibility is that anatomically modern humans were living alongside ape-man-like creatures during the early Middle pleistocene in Java. in light of the evidence presented in this book, this would not be out of the question.

The fluorine content test has often been used to determine if bones from the same site are of the same age. Bones absorb fluorine from groundwaters, and thus if bones contain similar percentages of fluorine (relative to the bones’ phosphate content) this suggests such bones have been buried for the same amount of time.

M. H. Day and T. I. Molleson (1973) analyzed the Trinil skullcap and femurs and found they contained roughly the same ratio of fluorine to phosphate. Middle Pleistocene mammalian fossils at Trinil contained a fluorine-to-phosphate ratio similar to that of the skullcap and femurs. day and Molleson (1973, p. 146) stated that their results (table 7.1) “apparently indicated the contemporaneity of the calotte and femora with the trinil fauna.”

if the trinil femurs are distinct from those of Homo erectus and identical to those of Homo sapiens sapiens, as day and Molleson (1973, p. 128) reported, then the fluorine content of the femurs is consistent with the view that anatomically modern humans existed in Java during the early Middle pleistocene, about

800,000 years ago.

day and Molleson (1973, p. 147) suggested that Holocene bones from the Trinil site might, like the Java man fossils, also have fluorine-to-phosphate ratios similar to those of the Middle Pleistocene animal bones, making the fluorine test useless here. in discussing the La denise human bones (Appendix 2), Oakley pointed out that the rate of fluorine absorption in volcanic areas, such as Java, tends to be quite erratic, allowing bones of widely differing ages to have similar fluorine contents. This could not be directly demonstrated at the Trinil site, because there only the Middle pleistocene beds contain fossils.

day and Molleson (1973, p. 148) showed that Holocene and Late pleistocene beds at other sites in Java contained bones with fluorine-to-phosphate ratios similar to those of the trinil bones (table 7.1). But they admitted (day and Molleson 1973, p. 144) that the fluorine-to-phosphate ratios of bones from other sites “would not be directly comparable” with those of bones from the trinil site. This is because the fluorine absorption rate of bone depends upon factors that can vary from site to site. Such factors include the groundwater’s fluorine content, the groundwater’s rate of flow, the nature