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What Killed the Megafauna?

Updated on November 5, 2013

A Land of Monsters

Today, East Africa is the last refuge for the megafauna that once inhabited the entire world except Antarctica.
Today, East Africa is the last refuge for the megafauna that once inhabited the entire world except Antarctica. | Source

Introduction

We live in a biologically impoverished world, a world where all of the hugest, fiercest and strangest creatures have disappeared. To get an idea of just how impoverished most of the world is today; imagine taking a trip to a place billed as one of the last great wildernesses, the northern Canadian pine forests. Nature documentaries often give the impression that moose and bears lurk behind every tree, but sadly it seems that this is not the case. I’ve watched documentaries where people have trekked through these very same forests of which I speak for days and weeks and found nothing except maybe some moose tracks and the odd black or brown bear at a distance. Yet, whenever I watch footage of the African Serengeti, I am constantly blown away by the sheer abundance and diversity of megafauna on show. In fact, I remember watching a documentary featuring survival expert Ray Mears, and he told of a funny story he’d heard from a safari lodge manager about how a tourist had decided to go for a jog during the early hours of dawn. Luckily this manager was already up and about patrolling the area, he spotted the naïve tourist and quickly bundled him into the jeep and said: ‘What do you think you’re doing? Going to feed the lions?’ This is a funny, yet sobering reminder that most of us have no idea what it’s like to live alongside dangerous large animals.

Of all the places in the world, Africa is the place that we associate with wildlife, because it still has its marvellous monsters. In the recent past, the rest of the world was not so different and the evidence for that lies right beneath our feet. Buried deep in the ground are the remains of some of the most bizarre and spectacular animals that ever walked the Earth. They thrived for millions of years, evolving and adapting to whatever environmental challenges they encountered. But during the latter stages of the Pleistocene epoch (1.8 million years ago-10,000 years ago) they suddenly and mysteriously disappeared. The scale of this vanishing is alarming: South America for example lost 80 per cent of its large animals, its northern neighbour lost 73 per cent, Eurasia 30 per cent, Australia 86 per cent and the oceanic islands which took the biggest hit of all lost a staggering 95 per cent. So what on earth happened to them?

Of course, extinction is a natural process, and all species disappear eventually, someday the same fate will befall us. Over millions of years, new species evolve, while old ones fade away, but there are times when the extinction process is accelerated dramatically; it’s an event where a large number of animals disappear en masse in a relatively short period of time. Whenever this happens, scientists call them mass extinctions. In Earth’s history, there have been five such mass extinctions, the last of which occurred 65 million years ago when the dinosaurs and other large reptiles disappeared. Mass extinctions are normally identified by their impact on small marine creatures, whose shells usually fossilise well, but the Pleistocene extinction was different, it failed to kill off enough species to truly qualify a true mass extinction. However, it remains the most devastating loss of large animals since the extinction of the dinosaurs.

Discovering the cause is very important, as the very same forces that wiped out the megafauna could perhaps one day overwhelm us. Many different hypotheses have been proposed to explain this phenomenon, but there are three particular hypotheses that tend to be favoured by experts. These are disease, climate change and human overkill - which one is correct?

Disease

We’ll start with a fairly obscure, but still credible theory that a highly infectious disease perhaps transmitted by humans or domestic dogs was responsible. The two main proponents of the theory are Ross MacPhee of the American Museum of Natural History and Preston Marx of Tulane University in Louisiana. They point out that long established diseases tend to evolve a benign relationship with their host, because destroying the host completely would prevent any future chance of transmission. In contrast, newly emerged diseases, which can form when viruses or bacteria jump the species barrier, tend to be lethal. A good example of this is the AIDS virus in humans, which emerged in the 1950s after the virus jumped from African monkeys to us through increased contact. Emerging diseases may be harmless to their ancient hosts but deadly to any new ones, and they are more likely to appear when two previously isolated species all of a sudden come into close contact. Is it possible that increased contact between man and megafauna triggered a lethal epidemic sufficient enough to wipe out all of the hugest, fiercest and strangest animals across the globe?

The main problem with this theory though is that the extinct megafauna not only included mammals, but also birds and reptiles. It’s unlikely that such a diverse range of animals would be all susceptible to the same microbe. Even so, scepticism from the wider scientific community hasn’t deterred MacPhee and Marx; they’ve already begun searching the tissue of frozen mammoths for bugs that could have caused a global Pleistocene epidemic, but thus far their hard work has met with little success, they still lack the concrete evidence that would validate their theory, so for now it remains conjecture.

Did a Virus Wipe out the Megafauna?

Although it has little support at present, Dr. Ross MacPhee is convinced that an epidemic virus wiped out the megafauna.
Although it has little support at present, Dr. Ross MacPhee is convinced that an epidemic virus wiped out the megafauna. | Source

Climate Change

Climate change certainly looks strong on paper, as there is plenty of evidence that it can exterminate animals. In fact, each of the previous big five mass extinctions is associated with drastic global climate change. But what exactly caused these wild temperature swings, and were these same forces responsible for ending the Pleistocene megafauna?

For most of the previous century, scientists argued over why the dinosaurs died out; while they all agreed that climate change was responsible, they quarrelled over exactly what had caused that changes. All of sorts of different factors were proposed including sunspot activity, changes in Earth’s orbit, continental drift, volcanoes and an asteroid impact. The debate rolled on for decades until a giant impact crater was found in Mexico, the size and timing of which corresponded with a global layer of ash and iridium (an element that’s rare on Earth but common in meteorites) in ancient rock strata. It’s unlikely that the megafauna suffered the same fate as the dinosaurs, because as of yet no big craters or iridium layers dating from the late Pleistocene have been found.

What about other climatic factors? Continental drift can be ruled out because there simply hasn’t been enough time for the continents to move substantially. Also, there is no evidence of any massive volcanism or lethal charges in solar radiation.

In North America, there have been at least six mini extinctions over the last 10 million years, with the end-Pleistocene disaster ranking only second in terms of the overall number of victims, but first by a large margin in terms of the number of large animals going into the dark. The earlier extinctions all coincided with a warming period at the end of previous ice ages, long before the arrival of humans. Some scientists have speculated whether it was changes in the distribution and availability of vegetation that ended the megafauna. This of course would have required drastic swings in temperature to occur. Or perhaps it was some sort of ecological ripple effect; maybe, as key species vanished ecosystems became disrupted forever, thus hastening the extinction. In modern times, we can still see iconic megafauna such as elephants influencing their landscapes. Just through their normal daily activities, they can turn forests into grasslands, and thus alter the fortunes of other species. These hypotheses attempt to distance themselves from climate change, citing habitat change as the biggest factor, but really any hypothesis that highlights habitat change is really a climate change hypothesis in disguise as climate is the biggest factor in governing a habitat.

While climate change can certainly exterminate life, attempting to apply it to the extinction of the Pleistocene megafauna exposes a number of flaws, which I will outline below. For me at least, the finger of blame points squarely in a very different direction.

Human Overkill

When the first Ice age animals were discovered and described in the nineteenth century, some palaeontologists proposed that hunting by humans was responsible for their disappearance. The most famous modern champion of this hypothesis, known as ‘overkill’ was the late Paul Martin of the University of Arizona. Paul spent his career arguing that human hunters inadvertently exterminated the megafauna as they spread across previously uninhabited lands. Below I shall highlight certain facts that about the Pleistocene extinctions that cannot be explained by any form of climate change.

  • The spread of the extinction dates: If global climate change did indeed kill off the megafauna then all of the extinctions should have taken place simultaneously. But an examination of the dates for each continent reveals something significant. North America, for example lost its megafauna around 12,000 years ago, while Australia lost theirs over a broader period, but mostly around the 40,000 years ago mark, and finally the islands did not experience any extinctions until around 4000 years ago. These dates are rather erratic in terms of attempting to apply a climate change theory, but they do show a suspicious correspondence with the arrival of humans.
  • Size and lifestyle: Climate and disease theories struggle to explain why large animals and flightless birds were more likely victims. This rather odd pattern is absent from all other mass extinctions. In many areas of the world, the survivors tended to be small, fast poisonous, tree dwelling or nocturnal, while the victims were rather slow, terrestrial and diurnal. Climate change does not discriminate in this way, but hunters do.
  • Naïve animals: Many of the New World victims were native species, without any experience of modern humans whatsoever. In contrast, when you take a look at the surviving American megafauna (moose, elk, bison, caribou and musk-ox) they are all in fact recent Eurasian colonists just like humans. The truly native animals had little instinctive fear of humans and thus would have been easy targets for hunters. Climate change cannot explain why the African and Eurasian megafauna fared so much better than their American and Australasian brethren; but overkill can because the animals that were accustomed to us had evolved ways of defending themselves.
  • Delayed extinction on islands: Long after the megafauna disappeared from the continents, some did survive on islands for up to several thousand years longer. For example, Woolly mammoths survived on Wrangel Island in the Arctic until 4000 years ago, but disappeared from both North America and Eurasia more than 10,000 years ago. Ground sloths survived in Cuba more than 4000 years longer than in North America. The climate of these islands was virtually identical to that of associated mainlands.
  • Reintroduced megafauna thrive: If climate induced habitat change destroyed the megafauna, then reintroduced relatives should have difficulty surviving in the new habitat. Yet, horses reintroduced to the New World by the Spanish have spread right across the American West so successfully that they are now a pest. Similarly, European wild boar, llamas and capybara also thrive in modern America; they are all related to extinct Pleistocene fauna. Another example is the musk-ox which has been successfully reintroduced to their former ranges in Siberia, Scandinavia and Alaska.

Connie Barlow Talks About the Megafauna Extinction

A Megafaunal Graveyard

This cave contains a bone deposit all belonging to the moas' which once roamed widely across New Zealand.
This cave contains a bone deposit all belonging to the moas' which once roamed widely across New Zealand. | Source

Where's the Evidence?

A criticism of the overkill theory that surfaces every so often is the fact there is little archaeological evidence to prove humans hunted the megafauna to extinction. But evidence does exist. In New Zealand for example, vast piles of moa bones fill ancient Maori refuse dumps, while kitchen middens throughout Pacific islands contain the remains of numerous extinct species. In the Americas, mammoth bones bear telltale marks of human butchery and weapon damage. Also, the blood of an extinct horses has been identified on the end of Clovis spear-points. In Eurasia, evidence exists that shows that our ancestors did hunt aurochs and woolly mammoths regularly.

Of all the continents, Australia seems to be the one lacking evidence, with the exception of the Cuddie Springs site which has yielded evidence of human butchery marks on megafauna bones. It does seem rather puzzling that evidence for human hunting in Australia is scarce at best; did humans and the megafauna actually co-exist over a long period of time? Is Australia the anomaly? Did climate play a bigger role here than elsewhere? Peter Murray of the Central Australian Museum thinks not. He suspects that another form of human interference played a much bigger role than hunting- burning. There is mounting evidence that the ancient settlers of both Australia and Madagascar used fire to change the landscape. Though Australia experiences frequent wildfires in the dry season, humans altered the natural cycle by setting fire to the landscape at other times of the year. Such a change would have had a profound impact on plant life, which of course would have had severe consequences for animals.

Conclusion

Scientists often attempt to try to make peace among the warring academic camps by arguing that the megafauna succumbed to a combination of factors, often suggesting that climate change and human hunting combined to push them over the edge. But while scientists struggle to unravel the full story, the evidence so far points to one culprit- Homo sapiens. As we spread throughout the world, armed with fire, weapons and intelligence we met monsters, creatures scarcely within the realms of human imagination and yet, in our wake we left a trail of death. Where once huge, fierce and strange monsters roamed, now stands vast swaths of silent forests and empty grasslands. Ours is a world of boring uniformity, its megafauna annihilated. Are we instead the real monsters?

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    • watergeek profile image

      watergeek 4 years ago

      I absolutely believe this. My eyes were first opened when I was a Peace Corps volunteer in Botswana - a country that has the widest diversity of wildlife in the world. The herds are smaller than the Serengeti, but there's greater variety. The area is swampland, grassland, dry lakes that fill when it rains. For over two years I was located in the midst of it.

      Back in the States I got a job with the US Forest Service on a remote district in the Cascade Mountains. I was excited to see what kind of wildlife was there and my ranger was excited to show me. We drove and drove, seeing little squirrels, birds, a very few black-tailed deer running away. No giant herds like what I was used to. Then we came to a small herd of 12 elk. My ranger was ecstatic. I kept my mouth shut (beyond a minor ooh and aah).

      Later I began to see the extent of the clearcutting that had devastated a good part of the forest, separating habitats, and all the timber roads and trails built, with vehicles driving through the forest constantly. It's no wonder there was no wildlife to speak of . . . and that doesn't even take into account the noise and devastation of guns. We destroy wildlife and habitat all the time, without even thinking twice.

    • JKenny profile image
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      James Kenny 4 years ago from Birmingham, England

      Hi watergeek, wow! Sounds like you had a whale of a time in Botswana. I've never been to Africa, but already whenever I'm told about supposedly great wildlife spectacles in Britain- I just nod my head without getting excited. The problem is that most of us are ignorant of the predicament the world is in. Most of us have no idea just how biologically impoverished the world is.

    • aviannovice profile image

      Deb Hirt 4 years ago from Stillwater, OK

      Yes, James, wherever humanity rears its ugly head, there is vast devastation. Hopefully, we can keep it at bay in the future, so we won't lose animals at a faster pace than they can arrive in our midst.

    • mandarmk9 profile image

      Mandar Karandikar 4 years ago from Ratlam, India

      A very interesting hub indeed. It is quite obvious that we have lost a greater number of species than we have at present. About fierce beasts, I think it must be left for further detailed explorations and researches. We must seize each opportunity we get to conserve wildlife. It's a necessity.

      :) Mandar

    • JKenny profile image
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      James Kenny 4 years ago from Birmingham, England

      I hope you're right Deb, I really hope you are. Thanks for stopping by.

    • JKenny profile image
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      James Kenny 4 years ago from Birmingham, England

      Thanks very much Mandar, hopefully in the future, the tragedy of the megafauna will be just as widely known as the dinosaur extinction. I think that by knowing about the loss of the megafauna, reveals a great deal about our very nature.

    • christopheranton profile image

      Christopher Antony Meade 4 years ago from Gillingham Kent. United Kingdom

      In one sense, it is quite sad that all these animals are extinct. In another sense, I'm glad. I wouldn't like a "megafauna" jumping over the wall when I was relaxing in my garden.

      Thanks for another fascinating and really well written article James.

    • JKenny profile image
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      James Kenny 4 years ago from Birmingham, England

      Thanks Chris, yes whenever you think about the loss of the megafauna- one part of you wants them back- but then the logical part of you thinks 'Well, we can't have elephants and lions running amok in our cities,' But still, for me there's a part of me that mourns their loss. Thanks for stopping by, always appreciated.

    • profile image

      whowas 4 years ago

      That is a superb overview and discussion of the history and demise of the great megafauna.

      I concur with your idea that the impact of human expansion and activity played a major, if not unique, role in their demise. Many of the megafauna were undoubtedly finally hunted to extinction within a historical time period, never mind prehistoric.

      Equally, in a wider perspective, much extinction by our predation may also prove to have been a valuable ecological development, making room for a different kind of perfectly natural flourishing of other species. But that is a vague conjecture, I confess.

      However, I am not entirely convinced of your assessment that we live in a world of 'boring uniformity.' With the range of ever-changing ecosytems and habitats that we have - surely richer and more complex than in most of the Earth's 5 billion year history - and current estimates of total species diversity landing around the 9 million mark, I hardly think that we can claim that the planet yet suffers from 'boring uniformity.'

      In any case, long before human intervention was even a twinkle in nature's eye, she had amply demonstrated that getting very big is ultimately to run a course down an evolutionary dead end. You can only challenge the laws of physics so far before your great size starts to play against you.

      That much said - I am in complete agreement that the human project is currently having a very negative impact on the stability of natural systems. We really need to focus on the necessary research and interventions to get things back in a greater state of functionality and sustainability (even if the concept of sustainability per se is somewhat contrary to the forces of nature as we have so far known them).

      A fascinating and beautifully written piece and always thought-provoking as well as informative. Thank you.

    • JKenny profile image
      Author

      James Kenny 4 years ago from Birmingham, England

      HI whowas, yes I might have gone a bit far stating that the world is boring and uniform; I meant it in the context of there being no great herds of large mammals anywhere except Africa. I am thankful that there is still some natural wonder and complexity in the world, but as our presence becomes ever greater, so the world continues to become more homogenised and mono-cultured, if its not boring and uniform now, its certainly heading that way. Thanks very much for popping by and for your very detailed comment. I love reading feedback that makes me think. Thanks whowas.

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