This month in Australian Archaeology

Join us each month, as Dr Amy Way discusses new research in Australian Archaeology.

The Initial Peopling of Australia

One of the big questions in Australian archaeology is when did people first arrive and how big was the founding group? New research by Allen and O’Connell (2020) re-writes our understanding of the arrival of the first people in Australia, who were the ancestors of modern day First Nations people.

Previously, archaeologists thought that Australia could have been founded by a very small group of people, possibly as few as 10, but this paper uses genetic evidence to show that the founding group was much larger, with hundreds or perhaps even thousands of people in the first wave of migration.

When we thought the founding group was very small, it meant that this crossing could have happened almost accidentally, with a couple of small rafts possibly blown off course. However, moving hundreds or thousands of people across a four to seven-day open sea voyage is a very different story, and one that requires a lot of planning. On these figures, it now means that we have good evidence that the initial colonisation of Australia must have been a deliberate act (Bird et al. 2018). Indeed, we can now view this as ‘the first great maritime migration’ ever conducted by modern humans (Norman et al. 2018).

When did this big group of people first arrive?

In Australia, the oldest date for human occupation is 65,000 years ago, which comes from a rock shelter in northern Australia called Madjedbebe (Clarkson et al. 2017). However, the problem with this very early date is that it is much older than the earliest dates in Wallacea, which are the islands that people had to cross on their way from Malaysia and Indonesia to Australia and Papua New Guinea (PNG), which only see evidence of occupation from around 45,000 years ago (Roberts et al. 2020). This leaves a gap of approximately 20,000 years for which there is no evidence of modern human occupation in this region.

What this means is that if people did arrive as early as 65,000 years ago it must have involved so few people that they didn’t leave any trace of their movement through these islands. Adherents to this minimalist theory argue that this absence of evidence is evidence in itself for a tiny founding population. These theorists also like the early date of 65,000 years at Madjedbebe because at this time the sea level was at its lowest (De Deckker et al. 2019), approximately 100m lower than it is today, which exposed up to 100 extra islands and meant that island hopping over to Australia happened when the water crossings were shortest (Kealy et al. 2017, 2018; Kealy et al. 2016; Norman et al. 2018). Which again provides support for the minimal effort, smallest group and accidental crossing theory.

This new paper disputes this early date and instead favours an initial arrival time of around 50,000 years ago. Allen and O’Connell dispute the Madjedbebe 65,000 date as flawed (their argument points out that the sand body in which the tools were located is disturbed, which means that younger artefacts might have moved downwards into older sand - and the dates come from the sand as well as several other problems which you can read about in Allen (2017). Instead they say there is good evidence for an earliest date of around 50,000 years and there are multiple sites in north-western Australia which support this timing.

What might motivate hundreds of people to build and board a raft and head off into the open ocean without any control over an eventual landfall?

Especially if we accept the later date of around 50,000 years, because at this point, the sea level has risen, so the ocean crossings were then even longer to reach Australia. But contrary to what you would think, this could have been a better time to cross for modern humans than when sea levels were lower and ocean crossings shorter. This is because coastlines contain shellfish, and humans love to eat shellfish, and when the ocean level was higher there was more coastline, and hence more coastal food. I know it seems counter intuitive that there was more coastline when the sea levels were higher, but this is because the landmass that these first people were travelling through, Sunda (which today includes the many islands of Indonesia, was previously a single peninsular with one coastline). When the ocean rose, this created a series of islands each with their own coastline. So this paper sees these first people moving through Sunda and Wallacea and into unoccupied and un-depleted areas in search of new coastlines and shellfish beds. And it was this that propelled people through Wallacea and ultimately on to the Australian and PNG landmass (Sahul).

Were there any other hominins in Wallacea when these first modern humans arrived?

Yes, for more than a million years before modern humans arrived, archaic humans lived on these islands. We know that modern humans came in contact with at least three archaic humans living there – Denisovans and two less well-known species called Extinct Hominins 1 and 2 (Teixeira and Cooper 2019). These first modern humans may also have come in contact with Homo floresiensis commonly known as ‘the hobbit’, who also survived on the island of Flores until around 50,000 years ago (Teixeira and Cooper 2019). When modern humans arrived in the Wallacea islands, they would have found these archaic humans, who were smaller in statue, had simpler tool kits and more restricted diets. And this is where our love of shellfish really kicks in – these other archaic humans appear not to have eaten shellfish, which was eaten in great quantities by modern humans (O’Connor et al. 2017). This evidence comes from a recent review of Pleistocene dietary remains in sites from Sunda to Sahul which noted an unusual distinction between the deposits left by archaic human and modern humans across Wallacea, where archaic human sites reflect no dependence on littoral/marine resources (ie they did not eat shellfish) while modern human sites are full of shellfish remains (O’Connor et al. 2017).

Indeed, this is part of our bigger human story – it seems our willingness to eat just about anything has contributed enormously to our success on this planet, propelling us into new regions (Roberts et al. 2020).

In Wallacea, the incoming modern humans rapidly displaced these archaic hominins, however just as we see in Europe where incoming modern humans displaced already resident Neanderthal populations, this didn’t happen until after some inter-breeding had taken place. Just as modern humans with European heritage carry around 3% Neanderthal DNA, modern First Nations groups in Australia and New Guinea carry DNA from Denisovan and two extinct Hominins that they came in contact with in the Wallacea islands (Teixeira and Cooper 2019). As Allen and O’Connell note, the parallel in modern human behaviour throughout the world is striking.

Did the archaic humans also make it to Sahul?

The Wallacea islands have never been connected to the Indonesian/Malaysian peninsula so this means the archaic humans living in Wallacea must have been able to make water crossings. However, there is no evidence that these archaic humans ever made it to Australia and PNG.

How did the first people get to Australia?

This is a difficult question to answer because the evidence doesn’t survive. The watercraft would have been made of organic material, which normally perishes over time. In addition, the first landing sites are also under water now as the sea level is higher today than it was back then. The best theory is that the rafts or boats were made of large diameter bamboo, which would have been readily available, floats well and is easy to work with. A large bamboo raft could keep 50-100 people seaborne almost indefinitely and would have been able to carry people for 4-7 days

Did one group arrive or many?

Did the first people arrive in a short period of time, perhaps even at the same time or over thousands of years? Unfortunately, the archaeological record cannot answer this question. However demographic modelling suggests that small, isolated groups are at a much greater risk of extinction than larger, interconnected groups which can exchange mates and rapidly expand. On this basis, nearly simultaneous arrivals of multiple groups landing close to each other is the most likely scenario.

What data did the authors use?

Allen and O’Connell (2020) reviewed recent genetic studies which looked at hundreds of living First Nations people across Australia, and also studies which used old hair samples collected last century. These genetic studies identified up to 9-10 pre-Sahul common mtDNA macrohaplogroups (Tobler et al. 2017). The easiest way to think of these macrohaplogroups is as a lineage. And assuming that each haplogroup was represented by an effective population of 20 or so people (enough to ensure the post-arrival persistence of the haplogroup), the number of people in this first founding population might have been in the low thousands (O'Connell and Allen 2012). And as we discussed earlier, this would require significant transport capacity – a fleet of watercraft capable of holding hundreds or even thousands of passengers would have required considerable planning and effort.

What could be wrong with this theory?

One of the things this theory rests on is the assumption that these haplogroups or lineages already existed before the founding group(s) arrived in Sahul. If however, they evolved after arrival, then this reduces the number of haplogroups in the founding population, and therefore means the founding population could have been smaller (e.g. see (Bergström et al. 2016; Nagle et al. 2017a; Nagle et al. 2017b)).

On the other hand, the founding population could also have been BIGGER than predicted by this study as it may have included lineages which have disappeared over time.

Conclusion

Allen and O’Connell (2020) make a strong case for a large founding population for Sahul, of a least hundreds and possibly thousands of people, who arrived in a relatively short time span. This means that the initial peopling of Australia must have been much more complex than previously considered. It would have required extensive planning and large-scale sea-craft construction. First occupation would have involved deliberate and concerted effort to build the watercraft needed to transport this many people and to motivate this many people to set off on a long-distance open-sea voyage. We can no longer think of this as a minimalist event. Rather, this is ‘the first great maritime migration’ by modern humans (Norman et al. 2018).

Dr Amy Mosig Way, Archaeologist, Australian Museum Research Institute