Hobbits on a boat: early humans beyond the Wallace Line

 

Ground-breaking new research, through comparative study of rock art, genetics, artifacts and oral tradition, had definitely pushed back the arrival of humans to Australia to in or around 60,000 years ago, a migration involving long-distance ocean voyaging. Other lands and islands in the Australasian region were soon to be followed; the snakelike island of New Ireland was colonised as early as 40,000 BP, and New Britain either shortly after or immediately before.

However, our species wasn’t the first to take to the waves in this region, as the dwarf species Homo Floresiensis, which lived (or depending on who you ask, still lives) on the island of Flores from roughly 700,000 until around 5,000 BCE, demonstrates. Archaeological work over the last decade has revealed that before the earliest Homo Sapiens, another, possibly Erectus-related species made their mark on Sulawesi, where their choppers, flakes and prepared cores are known together as the Cabenge Industry. The site of Talepu, in southwest Sulawesi, features a bundle of limestone tools together with a scattering of ungulate bones – including bones from a giant four-horned warthog called Celebochoerus, and the teeth of a dwarf varieties of water buffalo and a forest elephant.

The stratigraphic placement of the lithics post-dates most of the animals, so they probably weren’t hunted, but it places their ages as between 118,000 and 194,000 years ago. They don’t belong to any known early human tool industry, such as the late Acheulean or the Aurignacian, and their relative simplicity links them with lithics known to have been made by Floresiensis and Erectus. The conclusion, then, is that an unknown hominid community found their way to Sulawesi, potentially 100,000 years before humans arrived.

Flakes, cores, and animal bones from Talepu in southwest Sulawesi, assigned to an unknown species of early human.

One species of archaic human is well documented to have crossed the Wallace Line, separating Asian from Oceanic species, and peopled Melanesia: the Denisovans. So far, their fossil record is limited to Denisova Cave in Russia, a jawbone from Tibet, some dubious fossils from northern China and a tooth in a cave in Thailand, but the recent genetic evidence seems solid, identifying modern Melanesian peoples as having the highest levels of Denisovan ancestry. Their genome has indicated that they looked and behaved similarly to Neandertals, apart from being more well adapted to tropical and humid climates. Looking at the routes of early human migration to the same area, key stop-over points seemed to have been western Java, Borneo and the southern Philippines, where indigenous communities today are closely related, in language, physiology and culture, to their pioneer forbears. 

The other possibility is a transitional population between Erectus and Denisovans, probably already undergoing some form of island dwarfism. The former species, which first emerged out of Africa about 1.2 million years ago, is known to have still been around in east-central Java in the same time range as these Sulawesi tools, and likely until just short of 100,000 years ago.

A useful parallel that can inform what the Homo Incognita of Sulawesi might have looked, behaved and walked like is the newly-identified hominin species of Homo Luzonesis, a bizarre hybrid of super-archaic Australopithecus and more modern features that stalked the forests of northern Luzon island about 67,000 BP. Their environment made this combination especially useful, with the ability to climb trees, scour canopies and chow down on forest-floor fauna. The same trends are seen, to a simultaneous less and more dramatic degree, with Floresiensis, which looked largely like Erectus save for being very tiny and hairy, suitable for its small rainforest world of dwarf elephants and flightless birds. These Luzon hominins were presumably only the last in a long line of archaic ancestors, although an incredible date of 709,000 BP, derived from magnetic-polarity dating of tools buried in a mudflow in Kalinga Province, seems to good to be true. A skull from eastern Java has, however, recently been dated much earlier to 1.45 million years ago, not long after Homo Erectus’s stay in Dmanisi Cave, Georgia, so I wouldn’t rule it out.

Some of the evidence has echoes of Pedra Furada, the site in eastern Brazil with simple stone tools that look, on first glance, to either be natural breakages or rocks smashed together by New World monkeys. A lot of controversy came from that site due to its advanced age of >22,000 BP, which is well before any other site in the Americas. What the Indonesian finds suggest is that early hominins progressively abandoned more ‘advanced’ technologies in areas where they weren’t needed, especially island environments where there were very few predators. They could have transferred the technology onto bone or wood, but humid conditions would have disintegrated anything left behind. Flores, Kalinga, Talepu and Pedra Furada make sense if the Lower Palaeolithic is seen as a time of adaptation and local variation, rather than a linear progression from stupid, fruit-guzzling, branch-swinging monkey to smart hunter-gatherer human.

All things considered, I would hazard a guess that the first hominins to reach Indonesia were Homo Erectus, and those that followed were descendants that had adapted back to archaic ways of living to suit their habitat.

References:

Détroit, F., Mijares, A. S et al (2019). A new species of Homo from the Late Pleistocene of the Philippines. Nature, 568(7751), 181-186.

Ingicco, T., van den Bergh, G. D et al (2018). Earliest known hominin activity in the Philippines by 709 thousand years ago. Nature, 557(7704), 233-237.

M.G. Leavesley, M.I. Bird et al (2002) Buang Merabak: Early Evidence For Human Occupation In The Bismarck Archipelago, Papua New Guinea, Australian Archaeology, 54:1, 55-57

Rizal, Y., Westaway, K. E et al (2020). Last appearance of Homo erectus at Ngandong, Java, 117,000–108,000 years ago. Nature, 577(7790), 381-385