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Chapter 9
The great megafaunal extinction debate

‘It seems to me that the conditions of life can have very little changed [in western NSW], as the same shells live still in similar waterholes. The want of food can scarcely be the cause of their [Diprotodon] disappearing; as flocks of sheep and cattle depasture over their fossil remains. But as such a herbivore must have required a large body of water for his sustenance, the drainage of these plains or the failing of these springs … has been, probably, the cause of their retiring to more favourable localities.’ (Leichardt)
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‘to a race of man depending like the blackfellows for subsistence on the chase, the largest and most conspicuous kinds of wild beasts first fall prey’ (Owen)
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‘This is known as the Pleistocene overkill. Sentimentalists among us still try to insist that it was a changing climate, not mankind, that did the damage, or that we only delivered the coup de grâce to species that were already in decline. It is remarkable how strong remains the wishful thinking for finding an excuse to believe in climatic change.’ (Ridley)
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‘And the dead tree gives no shelter, the cricket no relief,
and the dry stone no sound of water. Only
There is shadow under this red rock’
(Eliot
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It’s an old debate, and like many old debates, a good debate . What caused the extinction of the Australian megafauna in the late Pleistocene — human action or climatic change? It is reminiscent of the old debate in physics about whether light was a wave or a particle, and I remember the imaginary dialogue which answered this. ‘Is light a wave?’ ‘Yes’. Is light a particle?’ ‘Yes’. Some people have tried to create the same dialogue for megafauna extinction. ‘Did human action cause the extinctions?’ ‘Yes’. ‘Did climatic change cause the extinctions?’ ‘Yes’.

But this is a cop-out, and no answer at all. The real way to frame the question, as is the case with so many other questions about Aboriginal impact on the Australian environment, was spelled out brilliantly by Rhys Jones . ‘If man had not managed to cross the last water channel of Wallacea those distant tens of millennia ago’ asked Rhys, ‘would our knowledge of the late Pleistocene “giant marsupial” fauna only have come to us from the bone breccia of a Wellington Cave — or would at least some large beasts, lumbering down to the water’s edge, have graced the sketch books of a Joseph Banks or a Charles Lesueur?’ In short, would the megafauna have become extinct had humans not been on the continent? People who have addressed this question have probably been roughly equally divided in their answer, although fashion swings the proportions one way or another over time.

In the early days of Australia the landscape must have seemed as alien to the British and European colonists as the landscapes of Mars and Venus do to us today. Such harshness of view, such strange and rough plants and animals, such monstrous swings in climate. This view of Australia coloured the Australian psyche generally, but had, in the context that concerns us here, a particular effect on the scientists who were investigating the past. Not only did this environment make archaeology a very difficult endeavour, but it also left little doubt in the scientific mind that environmental change was the most logical explanation for the extinction of the giant marsupials.

Something else which set the tone for theories was the extinction of the giant mammals of Europe. There was a pretty clear picture of a quite different world in Europe, where glaciers covered the continent, people lived in caves for warmth, and woolly mammoth and rhinoceros roamed a snow-covered landscape. That environment had clearly gone, and with it the animals, and that was a fairly clear cut link. William Anderson made the link between mechanisms in Europe and in Australia explicit — ‘there can be little doubt that [glacial conditions] were among the most potent causes of the extinction of these large Pleistocene vertebrates, just as has been proved to have been the case in other parts of the world where the large Pleistocene forms of life died off on the advent of glacial conditions of climate’. In Australia, although there was some evidence for glacial action, it soon became clear that drought and aridity was considerably more to the point than snow and ice.

From Ludwig Leichardt onwards, himself soon facing his own extinction (either because of climate or by human action), observers lined up to link climatic change to various mechanisms of extinction. One author for example, in a grand sweep in 1879, spoke of an early wet climatic period when ‘large mammals roved over the land … conditions were favourable to the growth of succulent herbage capable of sustaining a large and varied mammalian fauna … This period was brought to a close by the lowering of the land … the fertile tracts of the lowlands were submerged, and the productive powers of other areas would be diminished by the gradual desiccation going on … a struggle for existence would ensue, in which the less adapted and less easily modifiable would succumb.’

Not only the past but the present gave evidence for those who would see. Another in 1885, observing one of the many severe droughts of the nineteenth and other centuries, said — ‘striking evidence has been afforded by the dryness of the last few seasons, of how quickly, through want of rain, and overstocking, savannahs of waving grass may be converted into desert-like plains; and the immediate influence of these climatal changes on the fauna is fully attested by the numbers of kangaroos and emus, which died last year through want of sustenance on the western plains’. Having seen what drought could do in the 1880s, he applied the lessons to the marvellous Cuddie Springs site, which would continue to be investigated for over a century. There had been water, as the remains of crocodiles showed, ‘in abundance’ and then it had gone. Bones of megafauna were there in abundance too and ‘nothing but want of water could have brought together such a heterogeneous assemblage of animals to the same drinking place; and what must have been their last terrible struggle for existence, as the supply of water failed, must be beyond description. This one instance may be taken as typical of the general cause of the disappearance of these animals since Pleistocene times … diminished rainfall … probably led to the gradual dying out of the once rich Pleistocene fauna.

Modern observation and ancient fossil site also combined to good effect at another classic site, Lake Calabonna in South Australia. Thousands of giant marsupials and birds were there, bones not jumbled up together like Cuddie Springs, but in the form of complete whole skeletons. They had therefore died where they were found, and ‘met their death by being entombed in the effort to reach food or water, just as even now happens in dry seasons, to hundreds of cattle which, exhausted by thirst and starvation, are unable to extricate themselves from the boggy places that they have entered in pursuit either of water or of the little green herbage due to its presence. The accumulation of so many bodies in one locality points to the fact of their assemblage around one of the last remaining oases in the region of desiccation which succeeded an antecedent condition of plenteous rains and abundant waters.’

There was no evidence of human presence at either Lake Calabonna or Cuddie Springs (though evidence would be found over a century later in a different part of the Cuddie Springs site, using the more advanced arcaeological techniques available), and if you were a gambler you’d have had your money very firmly on climate change as the cause of megafaunal extinction. But if it was a simple as that the debate wouldn’t have raged for 150 years, and running alongside these environmental explanations was a very strong true believer in human causation. And a very powerful figure he was too, Richard Owen, Curator at the British Museum, and a towering figure in the scientific establishment of Victorian England. What was his problem? Well, it lay in the potent phrase ‘struggle for existence’ used above and elsewhere. Where did a struggle for existence lead you from 1859 onwards? Well it led you to the theory of evolution, and Owen wasn’t having a bar of it. As in the late twentieth century, megafaunal extinctions were a powerful piece of evidence in relation to religious or quasi-religious beliefs.

Why was Owen so opposed to the Theory of Evolution? Well, it may have been religious beliefs, but it was more likely to be jealousy — someone who Richard Owen probably saw as extremely junior had created this work which had shaken the world, and it had to be stopped by the most senior biologist. It is not an uncommon reaction to great works someone else has created.

But the religious climate was also important of course, and the mid-nineteenth century was a great battleground between science and religion, in Australia as elsewhere . Darwin’s theories generally received a hostile reaction in conservative Australia, with a massive assault on Darwinism from pulpit and lectern, with people flocking forward to be counted on the side of the angels. They included people who Darwin might have confidently expected to be on his side, but many intellectuals and scientists were shocked by the implications of The Origin of Species.

A classic example is the great Australian scientist William Macleay. In 1842 the young man could scoff in a very advanced way at religious belief — ‘I cannot consider the bible as a scientific book according to the vulgar meaning of the word ‘scientific’, and although I do not conceive that Moses wrote anything inconsistent with the truth, I confess I have as much confidence in his opinion of the binomial theories as I have in his dictum on Geology.’ But in 1860 he received a copy of that book, and you wouldn’t think it was the same man speaking — ‘I see God in everything; but then I believe in his special Providence, and that he is the constant and active sole creator and all-wise administrator of the Universe … It is far easier for me to believe in the direct and constant government of the Creation of God, than that he should have created the world and then left it to manage itself, which is Darwin’s theory in a few words.’ Darwinism represented a yawning pit of materialism and atheism and the conservative colonials stepped back from the brink with a shudder. Darwin’s theory, said Macleay, ‘is almost a materialistic one — nay, even so far atheistic that, if it allows of a deity at all, he has been ever since the institution of the primordial type of life fast asleep .’

Macleay’s reactions were paralleled by Richard Owen in England. Owen had himself toyed with evolutionary ideas before 1859, but as the wave broke and he found himself left behind by the new biology, he became Darwin’s most implacable opponent. If he hadn’t produced evolutionary theory then no one else was going to, again, not an uncommon academic attitude. Of particular interest to us here, is how Owen’s attitude to evolution coloured his attitude to the question of the extinction of the Australian megafauna. In 1843, just four years after the Australian megafauna had first been discovered when Thomas Mitchell’s party descended into the Wellington Caves, Owen’s fertile and intelligent brain was at work on the implications. And what did he come up with? Why, climatic change of course — ‘time was when Australia’s arid plains were trodden by the hoofs of [Diprotodon]; but could the land then have been, as now, parched by long continued droughts, with dry river courses containing here and there a pond of water? … May not a change from a more humid climate to the present peculiarly dry one have been the cause, or chief cause, of the extinction’.

But then came 1859, and Darwin observed that Owen’s review of The Origin of Species was ‘extremely malignant’ and ‘full of spite’. Owen in fact was trying to have it both ways, attacking Darwin’s theory while simultaneously claiming to have thought of it first (and he had indeed dabbled in the idea). That is also a familiar strategy in the academic world, but it must have rapidly become clear to Owen that Evolution was Darwin’s baby and that the only way to reassert his own primacy was to discredit the theory. Certainly there was no way he was going to advance the cause of natural selection, and continuing to present megafaunal extinctions as being caused by climatic change would have done just that (remember the ‘struggle for existence’ at drying water holes).

In a paper published in 1870 Owen had two bob each way, speaking of the extinctions as ‘exemplification of the fruitful and instructive principle which under the phrases “contest for existence”. and “battle of life”, embodies the several circumstances, such as seasonal extremes, generative power, introduction of enemies etc, under the influence of which a large and conspicuous quadruped is starved out, or falls a prey, while the smaller ones migrate, multiply, conceal themselves and escape’. But he went on to speculate about the ‘introduction of the Human kind’ and ‘the final extinction’. In 1877 he was using ethnography — ‘as the elephant succumbs to the spears and pitfalls of the negro hunters, the minor bulk of the Diprotodon is not likely to have availed it against the combined assaults of the tribe of Australoid wielders of club and throwing sticks’. By 1879 he had a mechanism for the selective extinction of the large animals — ‘to a race of man depending like the blackfellows for subsistence on the chase, the largest and most conspicuous kinds of wild beasts first fall prey’ .

So, no way was Richard Owen going to give comfort to his enemies in Darwin’s camp. Megafauna had been killed by humans, and there were no evolutionary implications in that. But he would have been whistling in the wind about this as much as he was in trying to stop the acceptance of Darwinism (just think, it could have been ‘Owenism’) except for one thing. The proponents of a climatic mechanism had failed to come up with a mechanism by which climatic change would cause the extinction of some species and not others. In fact the current examples they used, of cattle and kangaroos dying in drought, referred to animals smaller than the megafauna, and in the case of kangaroos, to species which had survived the extinction period quite happily and continued to do so. Owen on the other hand did have a mechanism — hunters preferred bigger animals and had hunted them to extinction first.

There was another reason for the continuation of the debate, and it too had psychological overtones. Archaeological investigation into Australia’s past, and the attempt to find out whether humans had been here a long time, eventually came to rest, in the absence of radiocarbon dating, on finding evidence of association between humans and megafauna. The only really convincing association, in a land of shifting sand dunes and deep cracks in the earth, was going to be evidence of human modification of megafaunal bone. It was the only proof about which there could be no argument of association. A scientific community searching for cut marks on bones did not want to be told that climate change had caused extinctions. If that was the case, then there may be no ‘kill sites’ with Diprotodon bones chopped with stone axes, which would have proved ancient human occupation.

In spite of Richard Owen, the scientific community in Britain fairly quickly came to accept the obvious (once pointed out!) truth of evolutionary theory. Australia was a much harder nut to crack, where some scientists (in an eery parallel to the views of conservatives today about the world as a whole) had — ‘never cause to entertain any doubt, that we are surrounded by species, clearly defined in nature, all perfect in their organisation, all destined to fill by unalterable laws those designs for which the power of our creating God called them into existence’. Even as late as 1876, Macleay, then President of the Linnean Society of NSW and therefore a leading member of the scientific establishment, had to ‘admit’ that the ‘testimony of the rocks, so far from giving ground for a theory of continuous modification of form, seems rather to afford proof that there may have been many successions of distinct creations at long intervening periods’ . It was really not until after 1900 that opinion turned in favour of Darwin, by then safely dead.

So, like two opposing armies in the trenches of the first world war, the debate ground to a halt. You could document climatic change all you liked, but without a mechanism that selectively removed large species you were wasting your time. You could postulate club wielding ‘Australoids’, sweeping across Australia like a horde of Vandals, but without the kill sites the evidence was only circumstantial.

It was in fact, very difficult to put people at the scene of the crime. Nobody had much doubt that human occupation was very old, and that humans had seen megafauna alive and well, but demonstrating this proved devilish hard. Strangely, radiocarbon dating, shining a light into every other nook and cranny of Australian prehistory, failed to shed much light on this question.

In the nineteenth century, belief in the causal agent in the extinctions depended on where you stood in relation to religious beliefs, the evolution debate, and your vested interest in finding an old archaeological site. The absence of a mechanism on one side, and a site full of butchered Diprotodons on the other, meant that faith and belief were enough.

In a sense not much has changed as we wearily reach the end of another century, but the current scorecard would probably see something of a majority in favour of human causation. Why is this so? Well there are a range of vested interests with bets on the outcome of this debate. Some are on the side of the angels, arguing for the proposition that Aboriginal people do have a right to the country because they did modify the environment massively. Others are less angelic, arguing that if Aborigines modified the environment massively so could or should we. Others want to argue against any notion of Aborigines as conservationists, acting in the interest of the society, because they want to promote the idea that greed is good, and that the natural state of humanity is all for one and all for one. Good government is no government, and we should only conserve things, by private ownership or commercial development, that are of value to humans, put on earth to hold dominion over the birds of the air and the beasts of the field.

Furthermore if climate change caused such massive extinctions then we really should get our act together on greenhouse gases pretty quickly or there will be tears before bedtime. As evidenced later, that is not a message that big business and its allies wants promoted. (And this is a bit curious. It is reminiscent of the same coalition of interests arguing against decent wages, social security, public housing, public transport and so on. They have no interest in the urban ghettos and savagery and misery that such policies create, because they can move out to the country, or build high security walls, or fly to the Barrier Reef. Perhaps they think space travel will be advanced sufficiently for them to fly to another planet when their policies make the earth uninhabitable).

Australia is a critical country for the debate for a range of reasons we will go into later. But how has this conglomeration of interests managed to tip the weight of the debate to their side? Has new evidence been found? Well, no, not really, but it hasn’t seemed to matter. Paul Martin , from Arizona, in a very influential book in 1967 argued the case for human causation. ‘Pleistocene Overkill’ was the evocative term. It was little different to anything which had come before except for one absolutely crucial and magnificently simple proposition. The lack of kill sites had always been a problem. No problem said Paul, the essence of overkill is that it happens very fast, so fast in fact that there are very few kill sites and your chances of finding them are correspondingly low. In fact the faster the extinction the fewer the sites, so it could be argued, and was, that the more you looked and failed to find kill sites the better the evidence for overkill. Finding sites with evidence would have been contrary to the interests of the model. It was marvellously religious in its overtones, requiring great faith, and the greater the faith the better you were. Or, as Joseph Heller suggested in a slightly different context — Catch-22, that’s the best catch there is.

In America the game was easy. Humans hadn’t been there very long, only around 12,000 years, and the American megafauna had become extinct sometime around then. Not much time to play with anyway, and there was no rule about how fast fast had to be when it came to overkill. Australia wasn’t so easy. Radiocarbon in the hands of people enthusiastically looking for older and older sites had pushed Australia’s occupation at least back to 40,000 years (subsequent work with newer techniques would hit what is probably about 50,000). Conversely sites with megafauna which looked to be a lot younger than this kept popping up everywhere like mushrooms after rain. The problem was that there were an awful lot of years to play with, and even if you only had megafauna surviving to, say, 26,000 years (as at Lancefield) it meant humans had coexisted happily for at least 14,000 years, and it would be a bit odd if they had suddenly turned around and started massively butchering them after that length of time. Similarly it would be odd if the megafauna had suddenly decided to make themselves available to be butchered after 14,000 years of watching humans in action. Paul Martin’s big idea needed naive animals and inexperienced people in a short, sharp, explosive mixture, like a shootout in a saloon where bullets fly for a few minutes and then the smoke clears to reveal bodies all over the floor and the lone sheriff still standing. It had to happen fast or it wouldn’t happen. If people had time to think about it they would all shuffle their feet and look at the floor and then put their guns back in the holsters and order another round of drinks.

What to do to save the theory? Well Rhys Jones rode in with the solution in the manner of a circuit judge declaring all the prisoners innocent. None of the dates for megafauna younger than the time of human arrival were valid he said, therefore extinction had happened quickly. Hang on a minute your worship you feel like saying, aren’t you assuming what you are meant to prove? No says Rhys, like the Queen of Hearts in Alice in Wonderland, sentence first, trial later. It is a technique which continues to be used successfully by Tim Flannery. But what if there were a plausible mechanism for climate change acting to select only the megafauna, wouldn’t that tip the balance back again? Yes it would, and we will come to that next.