Forbidden Archeology_ The Full Unabridged Edition - Michael A. Cremo [346]
As we have seen (Section 7.1.5), eugene dubois originally attempted, on faunal grounds, to classify the trinil beds of the Kabuh formation as pliocene (Boule 1923, p. 98), but later researchers have characterized the Trinil fauna as post-villafranchian (Le Gros clark and campbell 1978, p. 91) or Middle pleistocene (Hooijer 1951, p. 273; 1956, p. 5).
the trinil beds of the Kabuh formation have also been dated by the potassium-argon method. potassium-argon dating relies on the fact that volcanic materials contain potassium 40, which decays into the gas argon 40. the argon gas remains trapped in crystals of volcanic material. By comparing the ratios of potassium 40 and argon 40 gas in a sample, one can date volcanic materials (for a fuller discussion of potassium-argon dating, see Section 11.6.5.1). Basalt at Mount Muria, from a layer above the Pithecanthropus erectus level of the trinil beds, yielded an age of 500,000 years, while tektites (pieces of glass produced by meteors) from the trinil beds yielded potassium-argon dates of 710,000 years (von Koenigswald 1968b, p. 201; Jacob 1973, p. 477). Further potassium-argon tests by G. H. curtis (Jacob 1973, p. 477) on pumice from trinil beds at tanjung and putjung, where the S10 and S12 fossils were found, gave similar ages. Jacob (1973, p. 477) said the average for the above four dates for the trinil beds is
830,000 years. this would put the trinil beds in the early Middle pleistocene.
As far as the Putjangan formation is concerned, it was originally classified as early pleistocene on faunal grounds by von Koenigswald. But d. A. Hooijer (1956) objected to this. He pointed out that both the trinil beds of the Kabuh formation and the djetis beds of the putjangan formation share fossil species characteristic of the Stegodon-Ailuropoda mammalian fauna of southern china, generally recognized as Middle Pleistocene (Hooijer 1956, p. 7).
According to Hooijer (1956, p. 8), von Koenigswald principally employed molluscan stratigraphy in assigning an early pleistocene age to the djetis beds. But Hooijer (1956, p. 9), after citing authorities on Javan molluscs, stated: “there is no reason to attach greater importance to the mollusks than to certain mammalian genera of long standing in establishing pleistocene correlations.” Hooijer (1956, p. 9) concluded that the trinil and djetis beds were of roughly the same Middle pleistocene age.
Attempts were later made to establish the geological age of the djetis beds using the potassium-argon dating method. the djetis beds of the putjangan formation near Modjokerto yielded an early pleistocene potassium-argon date of about 1.9 million years (Jacob 1973, p. 477; Jacob and curtis 1971; Jacob 1972).
The date of 1.9 million years is significant for the following reasons. As we have seen, many Homo erectus fossils (previously designated Pithecanthropus and Meganthropus) have been assigned to the djetis beds. if these fossils are given an age of 1.9 million years, this makes them older than the oldest African Homo erectus finds, which are about 1.6 million years old (Brown et al. 1985, p. 788). According to standard views, Homo erectus evolved in Africa and did not migrate out of Africa until about 1 million years ago.
Also, some researchers have suggested that von Koenigswald’s Meganthropus might be classified as Australopithecus (Jacob 1973, p. 475; Jacob and curtis 1971). if one accepts this opinion, this means that Javan representatives of Australopithecus arrived from Africa before 1.9 million years ago or that Australopithecus evolved separately in Java. Both hypotheses are