For over half a century the presence of crude stone tools on several SE Asian islands, such as Flores and Sulawesi in Indonesia and Luzon in the Philippines, have hinted at their colonisation by Asian Homo erectus. Hominin fossils have yet to be exhumed, outside of Flores (Homo floresiensis) and dating the earlier finds has been imprecise, but evidence continues to accumulate. As regards the Philippines, the earliest hominin fossil is a modern human toe bone dated at 66.7 ka. Another curious feature of these isolated parts of what might be termed ’Wallacea’, on broader floral and faunal grounds, is the presence in the Pleistocene fossil record of large mammals, or at least dwarfed species of megafauna found in mainland Asia. These include elephants, rhinos and deer.
A large team, with members from France, Philippines, Australia, Spain, Germany, Holland, Spain and Greece, has been excavating a tool- and fossil-rich site in thick alluvium at Kalinga in northern Luzon since 2014 (Ingicco, T. and 22 others 2018. Earliest known hominin activity in the Philippines by 709 thousand years ago. Nature, published online). It occurs in an erosional channel filled with mud. Stone artefacts comprise 56 flakes, hammer stone and cores, the tools being crude – a common feature of the Asian H. erectus lithic culture, unlike that in Africa and Europe. As well as fragments of other animals, the site is notable for a 75% complete, but disarticulated, skeleton of a rhinoceros scattered over a small area. That in itself suggests that the beast may have been butchered, and is confirmed by cut marks and signs of smashing on several of the bones. Uranium-thorium dating of one of the animal’s teeth (709±68 ka) and sediment grains from above and below the fossiliferous unit by electron-spin resonance (701±70 and 727±30 ka respectively) confirms the great antiquity of the site. Dating of volcanic plagioclase crystals from sediments by the 40Ar/39Ar method yields even older dates around 1 Ma, but the crystals may have been washed for older volcanic ash deposits.
It seems beyond doubt that early hominins, possibly H. erectus, colonised Luzon some 700 ka ago, yet, according to the authors, ‘it still seems too farfetched to suggest that H. erectus, or another unknown Pleistocene ancestral candidate … were able to construct some sort of simple watercraft and deliberately cross sea barriers’. That seems to be pushing caution a little too far. Do the authors not believe their own – to me compelling – evidence and analyses? But the paper spent a year in review, so maybe they came up against a singularly pernickety referee (three are named but one remains anonymous). Presumably, if a hominin fossil turns up during on-going excavations, that would change everything apart from the question, ‘Did they walk, swim or navigate?’ Luzon and the Philippines archipelago as a whole are surrounded by sea shallow enough for them to have been a single landmass during a glacial maximum when sea level was around 100 m lower than at present. At such a juncture a less than 20 km sea journey would have separated the Philippines from Borneo, then part of a vast area of lowland to the SW (Sundaland) that was connected to the Asian mainland.