2019-06-01_Discover

Absolute

Relative

INTERVISIBILITY

WAL

LAC

EA

SUNDA

(SOUTHEAST ASIA)

SAHUL

(AUSTRALIA &

NEW GUINEA)

precise methods, but her focus remains

on Wallacea.

“People were in the region at that time

[65,000 years ago],” she says. “There’s a

likelihood of them being in Australia by

that time, too.”

She’s now working with Australian

and Indonesian colleagues on a new,

three-year project to search for early

archaeological sites on islands along the

proposed northern route.

Meanwhile, on the Dampier Islands

off the northwestern coast of Australia,

Bailey and colleagues have begun the

first systematic exploration of Australia’s

submerged paleocoast.

Their plan, outlined in 2018 in the

journal Antiquity, is divided between

reconstructing submerged features, such

as rivers and lake basins, and reviewing

previously documented onshore sites.

“[We] look at onshore archaeology to

think about what sort of locations would

have been attractive to them,” says Bailey.

“There are often very specific features,

such as raw materials for stone tools,

fresh water, or a good place to ambush

animals.... You use that model to help

refine your understanding of targets to

home in on underwater.”

Two particularly promising targets:

carved rock art already found at multiple

onshore sites, and stone weirs, or fish

traps. Both could be spotted in new,

higher-resolution seafloor maps the team

is creating.

Early humans, traveling by boat, arrived in Australia by way of Wallacea, the

island zone between the Australia and Asia. In the 1970s, anthropologist

Joseph Birdsell proposed northern and southern routes these seafarers might

have taken, based on basic maps and other preliminary data. A new, more

precise model suggests the most likely course would have allowed travelers

to stay within sight of land at all times, a concept called intervisibility. When

calculating the new model, researcher Shimona Kealy considered two kinds

of intervisibility: absolute, when one island is visible from another, and relative,

which means individuals in a boat would be able to see the island ahead before

losing sight of the one behind them.

AUSTRALIA

Birdsell’s Northern Route

Birdsell’s Southern Route

Most likely routes from

Kealy’s research

NEW GUINEA

CHINA

BORNEO

Source: Shimona Kealy, Julien Louys and Sue O’Connor. “Least-cost pathway models indicate northern

human dispersal from Sunda to Sahul.” Journal of Human Evolution 125 ( 2018 ): 59 - 70

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JUNE 2019. DISCOVER 59