How Was Australia Populated?

It's one of anthropology's most enduring and controversial mysteries "“ no one is quite certain just how or when the indigenous peoples of Australia (also known as "aboriginals") arrived. As recently as the turn of the last century, it was believed that they had been on the continent no longer than 400 years or so. That eventually gave way to the notion that Aboriginals had been in Australia since about 8,000 years ago. Then in the 60s, a geologist named Jim Bowler uncovered the skeleton of a woman on the banks of a long-dried lake bed, who had died some 23,000 years ago. Nowadays, experts put the date of arrival from anywhere between 45,000 and
60,000 years ago.

That's where the trouble begins. Australia, as you probably already know, is an island; considered by some to be the world's largest, to be precise. It is surrounded by a not inconsiderable amount of water, the narrowest bits of which "“ like the Torres Strait in the north, between the top of Queensland and the bottom of Papua New Guinea "“ are dangerously rough and notoriously difficult to navigate. In general, human beings were not an oceangoing people prior to about 10-15,000 years ago, so the idea of people from what is now Indonesia crossing the Timor Sea in fishing rafts to populate the Northwestern coast of Australia is, needless to say, a problematic one. In his wonderful travel memoir In A Sunburned Country, Bill Bryson expresses this problem best:

"In order to put Homo sapiens in Australia you must accept that at a point in time so remote that it precedes the known rise of behaviorally modern humans there lived in southern Asia a people sufficiently advanced that they were fishing inshore waters from boats of some sort, rafts presumably. Never mind that the archaeological record shows no one else on earth doing this for another thirty thousand years. Next we have to explain what led them to cross at least sixty miles of open sea to reach a land they could not know was there. The scenario that is invariably invoked is of a simple fishing raft "“ probably little more than a floating platform "“ accidentally carried out to sea, probably in one of the sudden squalls that are characteristic of this part of the world. The craft then drifted helplessly for some days before washing up on a beach in northern Australia. So far so good. The question that naturally arises "“ but is seldom asked "“ is how you get a breeding stock out of this. If it's a lone fisherman who is carried off to Australia, then clearly he must find his way back to his homeland to report his discovery and to persuade enough people to come with him to start a colony. This suggests, of course, the possession of nautical skills sufficient to shuttle back and forth between invisible landmasses "“ a prowess few prehistorians are willing to grant. "¦ No one can possibly say. All that is certain is that Australia's indigenous peoples are there because their distant ancestors crossed at least sixty miles of fairly formidable sea tens of thousands of years before anyone else of earth dreamed of such an endeavor, and did it in sufficient numbers of begin to start the colonization of a continent. By any measure this is a staggeringly momentous accomplishment."

There is one other possible explanation, which the humorous and always-elegant Bryson fails to mention. Tasmania, Australia, Papua New Guinea and the patch of islands between the latter two all make up a single ancient continent, called Sahul, and as global sea levels rose and fell throughout the ice ages of the past 100,000 years, the forbidding straits of ocean between them occasionally disappeared, replaced by lush, tropical landbridges. In fact, it's thought that the now-underwater lowlands beneath the Torres Strait, between New Guinea and northern Australia, were a very popular place to live prior to about 10,000 years ago, when rising sea levels submerged them. (This is a very cool interactive site that allows you to check out the changing sea levels over time.)

Which is to say, at one time it was a bit simpler to get to Australia than Bryson lets on "“ though still not a cakewalk. It would have involved sailing (on planklike pseudo-rafts) from now-submerged islands on the eastern tip of Indonesia to now-submerged bits of what was western New Guinea "“ a distance certainly less than 60 miles.

Either way, the population of the Australian continent by humans remains a fascinating mystery.