Holocene Australia: Apocalypse?
LOSING THE FARM:India and the Prehistoric Settlement of Australia.
A question is sometimes asked of Australian prehistory: Why did pre-European Australian aboriginal societies not develop agriculture?
Recent genetic studies have revealed that Australia was colonised far more recently than is generally believed. The question must be re-phrased: Why did settlers from India, the ancestors of the present-day Australian Aboriginal people, not bring agriculture with them from their homeland?
Human occupation of mainland Australia can be traced back to around 45kya (O’Connell and Allen 2004). Rock art engravings in Outback Australia broadly concur with archaeological dates for human arrival in Pleistocene Sahul (Flood J 1997). However, the contention that the indigenous population at the time of European arrival were the direct, lineal descendants of those humans who colonised Sahul in Pleistocene times is an assumption, not a tested, established fact.
The Penultimate People of Sahul.
Mitochondrial studies by Redd and Stoneking (1999) indicate that Aboriginal Australians show close affinity with populations from the subcontinent of India. The closeness is best explained by a population influx into Australia at a mere 3,390 years ago. The authors estimate that the immigrants may have been few in number, perhaps as few as several hundred individuals. However, their genes then diffused rapidly throughout the continent. This would therefore be a 'founder population' who arrived in Australia at that time from India.
Because Redd & Stoneking's results are based upon mitochondrial DNA, the new arrivals must have included women. A founder population whose genes spread quickly across most of Australia was no casual visitation: by definition, it was a colonisation.
Riddles of the Past.
The fact of a rapid genetic 'takeover' of the entirety of Australia, from so small a start, presents us with three hugely confronting puzzles.
Firstly, it flies in the face of everything that is conventionally believed about the prehistory of Australia. To wit, that after the continent was colonised 450 centuries ago it developed more or less in isolation from events elsewhere and that the modern day aboriginal people are therefore the descendants, in unbroken succession, of those very first Pleistocene settlers. Clearly, this can not be true.
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Secondly, the speed of diffusion of the Indian genetic signature strongly suggests that a population expansion took place with little or no admixture from earlier populations. In other words, the immigrants found an empty, or near empty land, and simply moved in and multiplied. What happened to the earlier peoples who were here before them and disappeared? We do not know.
What we do know is that the date corresponds roughly to a climate event centered on 3200 ya. While Redd and Stonekings' estimated errors could put the Indian immigration at anytime between 1,700 years ago to 5,000 years ago it is tempting to associate the colonisation with the so-called Bronze Age Collapse at 3200 ybp that brought about the demise of civilisations throughout the Middle East, Anatolia, China and, notably, of the Indus Valley Civilisation on the Indian subcontinent (Robbins 2001).
This brings us to the third element of the riddle: the immigrants came from a land where farming had been practised for millennia. Why, then, did they not bring farming with them to Australia? Farmers maintain a veritable menagerie of domesticated animals and plants. Yet none of the domesticated plants and animals that Indus Valley farmers knew 3000 years ago were present in Australia in 1788.
The Long Road to the Farm.
Farming had been slowly developing in the mid-East since around 12,000 years ago (Zeder 2008), apparently as an adaptive response to increasingly dry conditions. By 6000 years ago it had spread to the Indian subcontinent. A few millennia later, it had brought to flower the high civilisation of the Indus Valley. The farmers of the Indus Valley Civilisation grew wheat, barley, peas, mustard, sesame, dates and cotton. They had domesticated dogs, cats, cattle, domestic fowl and, possibly, pigs, camels, buffalo and even the elephant (Britannica: Indus Civilisation).The immigrants to Australia some 3000 years ago brought none of these things with them. Why not?
Bronze Age 'Dust Bowl Refugees'?
A popular thought until the 1990s was that climate during the Holocene, the current interglacial, has been balmy, equable and above all stable. Research from many disciplines has revealed that past climates during the Holocene and in previous interglacials have been anything but "stable" (NOAA website).
I suggest that the people who arrived here from India were not the vanguard of a planned colonisation but came as refugees. I suggest they were set in flight by famine, and probably concomitant foreign invasion, brought about by one of the many abrupt environmental crises that have punctuated the Holocene. I suggest that they lost their farming 'know how' because their numbers were few and, having brought no farm-stock with them, they necessarily resorted to the hunter-gatherer lifestyle.
Wild animals are not farm animals. It is not feasible simply to capture wild animals, fence them in and farm them (Smith 2001). Farm animals have been selectively bred over thousands of years so as to become docile and amenable to the farmer's management. Picture a band of refugees fleeing the storm of death and anarchy that was the Bronze Age Collapse: picture them landing on Australian shores with but few possessions. Could they straight away, 'off the boat', begin farming kangaroos and emus? Surely not.
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The new arrivals must have resorted to hunting to stay alive. If hunting were successful, what incentive or means would the next generation have to rediscover agriculture?
It may well be feasible to domesticate kangaroos and emus and to cultivate native grains. I suggest, however, that it would have taken many thousands of years of selective breeding to so. Just as it did elsewhere. The immigrants were not allowed the time.
Bronze Age Terra Nullius?
A question thrown at us by Redd & Stoneking is this: if the settlers from India found an empty, or near empty land in mid-Holocene Australia, how did it become so? A curiosity of the genetic results is that the population of the central highlands of Papua-New Guinea (PNG) and West Papua do in fact trace back to 40,000 years ago, whereas surrounding populations in the former Sahul do not (Redd and Stoneking 1999). Why did PNG highlanders not move down from their mountains and take possession? We do not know.
There are indicators that Australia was repeatedly depopulated by extreme aridification throughout the late Pleistocene and early to mid-Holocene (Smith et. al. 2008, Gould et. al. 2002), and that the continent was repopulated in successive waves of immigration (Redd and Stoneking 1999).
I suggest that the original human populations in Pleistocene Sahul perished along with the megafauna, probably in staggered pulses of extinctions that lasted up until the mid-Holocene.
The Thylacine (Thylacinus cynocephalus) and Tasmanian Devil (Sarcophilus harrisii) appear to have vanished from the mainland somewhat before the Dingo (Canis familiaris dingo) arrived in Australia (Johnson 2006) and may have been killed off by mega-drought (Brown 2006).
Likewise, the Diprotodon (Diprotodon optatum) may possibly have survived in eastern Australia up until about 6500 years ago (Kohen 1995, Wright 1986), although the single C14 date for the specimen finds little mainstream acceptance (Johnson 2006). Interestingly, however, in South America Megatheria not only survived into the Holocene but they too disappeared around 6500 years ago (Politis and Messineo 2008). It seems reasonable to suppose that roughly coincident extinction periods of at least hemispheric extent must reflect a common cause. The apparent coincidence of extinction events therefore forces us to ask: did the mega-drought events of the mid-Holocene also kill the former human population of Australia, the people who were here before the Indians arrived?
Savolainen et al (2004) estimate the Dingo was introduced into Australia around 3500 to 5000 years ago. It seems likely the Dingo was brought here by those self-same refugees from India. I surmise that the Dingo was able to disperse successfully because it found an ecological niche left vacant by the (then recent) extinction of the Thylacine.
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Polynesia and Australia: Traces of Repeated Depopulations?
The late anthropologist Thor Heyerdahl's theories about the colonisation of the Pacific by peoples from South America never found favour with mainstream anthropology. Recent genetic results are held to rebut Heyerdahl's thesis: genetic history shows that modern Polynesians do in fact emanate from Asia. (Friedlaender et al 2008). Yet Heyerdahl's theory asserted that two races colonised the Pacific: that there was an early wave of settlers who came from the so-called "lost civilisation" of Tiahuanaco, that once was extant in Peru and Bolivia, and a later wave, the Polynesians, who came to the central Pacific from Asia by way of the coast of northwest America (Heyerdahl 1952).
Heyerdahl's archaeological and botanical evidence is compendious and persuasive: can his arguments be dismissed as simply wrong? Can his theory be reconciled with genetics? And does it have anything to do with the Australian-Indian riddle?
For if Heyerdahl's thesis is broadly correct, that if the early monolith builders in the Pacific were replaced by later Polynesians at around 1400CE, then we have a situation analogous to Australia at 3000BCE. Here, an early population also was apparently replaced by latter day immigrants.
We now know that the megalithic period in the South Pacific ceased with the onset of the Little Ice Age (Bickler and Ivuyo 2002). We must therefore ask: are we looking at archaeological and genetic signatures of repeated human population crashes? Can Holocene climate crises decimate populations in disparate parts of the globe, thus opening the door to waves of refugee-immigrants from lands less afflicted? How else can we account for the apparent lack of genetic interchange between early and later settlers?
Conclusion: A Clear and Present Danger?
Obviously, the scenario brought to light by modern genomics flatly contradicts the conventional narrative of Australian prehistory. My thesis, too briefly outlined here, will be controversial.
Equally obviously, if the past lights the way to the future then Australia may be uniquely vulnerable to the regular cycle (Singer and Avery, 2008) of abrupt-onset climate crises that characterise the Holocene. If that is a warning from the relatively recent past, we might be well advised to take heed: we are the megafauna now.
Thoughts on the above?
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Copyright © 2009 to D. Hynes. All rights reserved.
