Archaeologists seeking evidence of the first modern humans in Indonesia have been looking in the wrong place, a new study claims. The topography and water resources would have pushed the first migration north to Sulawesi and New Guinea, rather than south to Java and Timor as has previously been thought. Searching the neglected northern islands could reveal a scientific treasure trove.
We have evidence of human presence in Australia dating back 65,000 years, but we don't know how people got there. The oldest signs of modern humans in South East Asia are 45,000 years old. Could people have passed through those islands without leaving a trace?
One possible explanation is that our searches have focused on Timor, Flores, and Java, which are thought to represent the path taken to reach Australia.
However, Australian National University PhD student Shimona Kealy tried to look at the paths from the perspective of those making the migration. Kealy noted that the era's low sea levels meant it was possible to walk between some modern islands. More innovatively, she included access to fresh water, tracing the routes of rivers through these long-drowned coastal plains. Kealy also took into account the steepness of the slopes travelers faced and whether they could see the next island from the shore of the one they were leaving.
In the Journal of Human Evolution, Kealy concludes the easiest (or as she puts it “lowest cost”) path would have been to travel east from Sumatra – across what is now sea, but was then the outskirts of Borneo – to Sulawesi. From there, the path would have run through many smaller islands to New Guinea, a course dubbed the “Northern Route”.
“This study … acknowledges the bravery, innovation and maritime technologies and skills of these early modern humans," Kealy said in a statement.
Most of the first part of this path is underwater, making the search for evidence hard. However, Kealy told IFLScience she and her supervisor are working on grant applications to seek caves on relevant islands that might have appealed to the first arrivals. These could then become the targets for excavation teams.
The oldest signs of humanity on this northern route date back 30,000 years, far less than on Timor, but this may be for lack of looking. “I was quite astonished at how little work has been done” investigating the Northern Route islands, Kealy said. “I knew there hadn't been much, but almost none of them have had any searched at all.” Northern Indonesia archeology has sought pottery at what might have been village sites in the last few thousand years, rather than caves that could have been used tens of thousands of years earlier.
This is likely to change soon, Kealy said. Indonesian universities are developing a new focus on archaeological science, and Australian researchers are keen to resolve the confusion on their continent's settlement.
If Kealy's work leads to sites humans inhabited 60-70,000 years ago, it could prove a scientific bonanza, telling us much about our ancestors at the time and their impact on the ecosystems of different-sized islands. If Homo erectus or relatives of Flores's Hobbits preceded modern humans at some of these locations, anything we learn about their interactions will be exceptionally precious.
Kealy told IFLScience the northern route has been neglected because sites are less accessible and parts of it have been dangerously unstable. Once discoveries were made on Timor and Flores, archaeologists kept returning to those places. Gradually, the idea Australia was reached by the Southern Route gained favor, and alternatives neglected.