Yet Flores lies to the south of Sulawesi – and strong ocean currents in the area flow predominantly from north to south. “It would be very difficult, if not impossible, to cross [from Flores to Sulawesi] without any means of boat or raft technology,” says van den Bergh – the kind of technology the hobbit is not thought to have mastered.
The tools could also indicate that other species made the crossing, perhaps Java Man (Homo erectus): who lived on Java, just a few hundred kilometres west of the line until some 500,000 years ago.
Enigmatic Denisovans
Or they could have been made by an enigmatic group called the Denisovans.
The Denisovans have at some point interbred with our species. Curiously, Denisovan DNA is only common in people today who live to the south-east of the Wallace line – which suggests that our species met and interbred with Denisovans only after crossing the line.
More clues to the toolmaker’s identity might come from even further north, given the way the currents flow through the region. “We think that the ancestors of the Talepu toolmakers came from either Borneo or the Philippines,” says van den Bergh.
There have been very few archaeological searches of Borneo, so at the moment we know practically nothing about its fossil record.
Philippine secrets
But the Philippines is beginning to reveal its riches. In 2007, researchers found a 67,000-year-old human foot bone on the island of Luzon. It was provisionally suggested that it belonged to an unusually early Homo sapiens to the east of the Wallace line.
But there are also unpublished reports that more human fossils were found on Luzon in 2014 – and that these additional finds suggest that the Luzon hominin may have been a more primitive species.
The ancient human colonisation of the islands to the south-east of the Wallace line is certainly a complex story, says archaeologist Roy Larick.
But he says we can look forward to finding out more in the next few months to few years. “In totality, the coming papers should indicate that tool-using early hominins occupied a number of Wallacean islands,” he says.
Journal reference: Nature, DOI: 10.1038/nature16448