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sea levels fell, typically meant global shifts to a drier climate that
could have made inland areas less habitable.
“During periods of lower sea levels, those coastal regions would
have been particularly attractive because they generally coincide
with periods of greater aridity in the hinterlands,” Bailey says.
PARADIGM SHIFT
Naturalists and other curious proto-scientists recorded archaeo-
logical sites at or near the shoreline as early as the 18th century. A
handful of researchers in the mid- to late 20th century employed
seabed survey methods developed for offshore oil and gas explo-
ration, but results were modest.
For a long time, Bailey says, few people bothered with underwater
exploration of submerged coastal areas because “it would have
been too difficult with a very low prospect of finding anything.”
It’s only recently that systematic, high-resolution study of
Aquaterra has become possible, thanks to newer technology
such as lidar bathymetry, which uses laser pulses fired overhead
from drones or planes to create high resolution maps of seafloors
in shallow waters.
Research into paleocoastlines was also long hampered by cost,
but more projects are partnering with offshore gas and mining
exploration companies, piggybacking on their survey expeditions.
“There’s been a huge explosion of people exploring the seabed,
mainly for commercial reasons. It opened up possibilities,” says
Bailey, adding that more and more, governments require offshore
archaeological assessments when signing off on development
projects.
Paleocoastline research logistics have improved, but the mind-
set of some in the field hasn’t evolved. A bias remains against
the idea that early humans were advanced enough to use coastal
resources, including traveling by boat.
“There is still a deep-rooted belief, even today, that there is a
ladder of progress in human evolution, and that seafaring and
use of marine resources is a very high, very late rung on that
ladder,” Bailey says.
Many younger researchers, however, are more open-minded
about early seafaring. While still a graduate student, Shimona
Kealy, an archaeologist and paleontologist at Australian National
University, found new evidence for a possible route for early
humans to have reached Australia by about 65,000 years ago.
Much of their travel would have been by sea, both island-hopping
and crossing significant distances with strong currents.
“I think resistance to the degree of maritime technology
early humans may have had comes from sitting in your office
in Europe, thinking Captain Cook didn’t find Australia until
the 1700s, so it must take a tremendous amount of courage and
bravery to head out to sea,” quips Kealy.
“You have to step back,” she says, drawing on her own experi-
ence working in Indonesia to imagine early human explorers.
“These people are growing up, and their culture is developing, on
an island archipelago where, most of the time, you can see across
to at least one island. Being there and doing fieldwork there makes
you realize how interconnected this area is.”
➲
Aquaterra, even at its largest, would
not have let the First Australians keep
their feet dry. The extended landmasses of
Sunda (modern Southeast Asia) and Sahul
(today’s Australia and New Guinea) have
never been connected. Reaching Australia
required seafaring skills, navigating boats
through strong currents and Wallacea, a
transitional zone of islands.
Named for British naturalist Alfred Russel
Wallace, who described it in the mid-19th
century, the islands of Wallacea were never
connected to either Sunda or Sahul. Animals
found in Sunda, to the west, may have made
it to Wallacea, but most never expanded
beyond it to Sahul in the east. Among
mammals, there are just two exceptions:
rodents and humans.
More than 40 years ago, anthropologist
Joseph Birdsell attempted to find the
most likely path of human migration
across Wallacea and into Australia.
He came up with two routes, northern and
southern, using basic paleoenvironmental
reconstructions. For decades afterward,
researchers focused on the route that
skirted the southern edge of the region,
believing it was the more plausible of
the two.
But Shimona Kealy, a researcher at
Australian National University, used
more precise, modern map technology
and improved Pleistocene sea level
records to look at the potential routes.
She also incorporated updated models
of intervisibility: where early seafarers
were able to see from one island to the
next. Published in 2018 in the Journal of
Human Evolution, her research found that
the northern route would have been more
likely, and that, amid fluctuating sea levels,
it would have been easiest to travel by boat
about 65,000 years ago.
The timing of the possible northern route
is crucial because, in 2017, other researchers
dating thousands of artifacts at the northern
Australian site of Madjedbebe reported
in Nature that the materials were up to
65,000 years old.
The Madjedbebe dates are controversial
because many researchers believe that
humans did not arrive in Australia until
45,000 to 50,000 years ago. Kealy thinks
the consensus will change as more sites on
the continent are dated using newer, moreDispersals
Down Under
65,000 years ago