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We present the first record of Holocene and Pleistocene environmental change derived from the chemical and stable-isotope composition of a tropical cave guano sequence from Makangit Cave in northern Palawan (Philippines). The 180 cm sequence of guano, derived predominantly from insectivorous bats and birds, consists of two distinct units. An upper section of reddish-brown oxidised guano to 110 cm was deposited since the mid-Holocene while a lower section of black, reduced guano was deposited through the Last Glacial Maximum (LGM) to >30 000 BP. Carbon-isotope (δ13C) values in guano deposited during the LGM are as high as −13·5‰ indicating that a C4-dominated grassland existed in the area around the cave at this time. Guano δ13C values of − 25‰ to − 28‰ suggest that this open vegetation was replaced by C3-dominated closed tropical forest, similar to that of the present, by the mid-Holocene. The results suggest that the climate of northern Palawan was substantially drier at the LGM than is currently the case.

The paper describes the initial results from renewed investigations at Niah Cave in Sarawak on the island of Borneo, famous for the discovery in 1958 of the c. 40,000-year old 'Deep Skull'. The archaeological sequences from the West Mouth and the other entrances of the cave complex investigated by Tom and Barbara Harrisson and other researchers have potential implications for three major debates regarding the prehistory of south-east Asia: the timing of initial settlement by anatomically modern humans; the means by which they subsisted in the late Pleistocene and early Holocene; and the timing, nature, and causation of the transition from foraging to farming. The new project is informing on all three debates. The critical importance of the Niah stratigraphies was commonly identified -including by Tom Harrisson himself -as because the site provided a continuous sequence of occupation over the past 40,000 years. The present project indicates that Niah was first used at least 45,000 years ago, and probably earlier; that the subsequent Pleistocene and Holocene occupations were highly variable in intensity and character; and that in some periods, perhaps of significant duration, the caves may have been more or less abandoned. The cultural sequence that is emerging from the new investigations may be more typical of cave use in tropical rainforests in south-east Asia than the Harrisson model.

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