The Pleistocene Megafauna




There is something very important about nature that almost nobody knows about. It’s an astounding topic both for how intrinsically humanly interesting it is and also for how unusual it is that it’s not more widely discussed. In this article I’m going to talk about what are called the Pleistocene megafauna. I’ll present a series of ideas as quickly as I can, all of which can be looked up and verified, which have profound implications for the future. I’ll also try to address why I think this subject is only just starting to enter the public consciousness.

This subject is even more bizarre in that it has often been treated relatively unscientifically, even among scientists, until very recently.

But this is no scientific curio. If you’ve ever wondered why the dinosaurs were so huge and todays nature so small, scarce and hard to see, this might shed some light on things. If you’ve wondered why so many of the biggest and most iconic animals live in Africa and not the Americas or Europe, this will answer your question. It will also, I hope, present an awe-inspiring and dazzling vision for the future of conservation.

This topic, when understood, will likely seriously alter how you view nature.


Fragments of another world

In 1957 Trafalgar square in London was excavated. It came as a surprise to the public that the bones of giant elephants, hippos and several types of rhino were found in the excavations. But the bones of similar animals had been found there before during previous digs and paleontologists and zoologists expect such remains. These animals are known as Pleistocene Megafauna, literally giant animals of the Pleistocene (the epoch before ours).

The bones date from about 120,000 years ago. This is an interesting time on earth as it corresponds to the last time the climate was roughly similar to what it is now. It is fascinating to think of England as being covered in herds of enormous elephants (the English Straight tusked elephant is significantly larger than the living species) but it also begs the question of why no similar animals live there now. Englands largest animal is the red deer.

Around 115,000 years ago the climate began to change and once again the earth was covered in ice and remained so until about 12,000 years ago. The straight tusked elephants disappear from the fossil record of England as the ice comes, strongly suggesting they couldn’t adapt to the new climate. However, it is worth noting that during this ice age elephants [i] still lived in England in the form of the woolly mammoth.

The same pattern is seen elsewhere. Giant, and often otherworldly, animals lived almost everywhere until very recently. Most people are very familiar with the African animals. Elephants, rhinos, giraffes, lions, zebras, gorillas, chimpanzees etc are very often covered in nature documentaries and stories and are among the first animals that children learn about. But most people are unfamiliar with the South American animals. People don’t go driving in the grasslands of South America on Safaris like they do in Africa. This is despite the fact that it’s also a large, mostly tropical landmass.

This is partially because the largest animal in South America is a Tapir, about the size of a pig. There are no huge migrations of millions of hooved animals as there are in the Serengeti in Africa. Indeed the grasslands of South America are mostly empty. It seems odd that a fairly big, mostly tropical continent should have almost empty grasslands, especially when contrasted with Africa.

However, this was not always the case. When humans first arrived in South America it was utterly different.


Another world

In 2009 the remains of a 6000 year old Stegomastodon were discovered in Colombia. Stegomastodons are a type of elephant not closely related to those alive today[i]. Humans arrived on the continent about 13,000 years ago to find 3 species of elephant living there; two types of Stegomastodon – one which lived in the Amazon and the other on the grasslands – as well as a mountain elephant called Cuvieronius.

The Amazon also contained other, stranger, animals. Eremotherium and Mylodon were two types of giant sloths that roamed the primordial forest. The largest were over 3 tons in weight, 20 feet long and both occasionally walked on their back legs. It is tricky to imagine such creatures; they had enormous claws, walked on the sides of their feet and were covered in a kind of bony armour built into their skin. The predators were equally amazing. The Amazonian Smilodon, a cat twice the size of a lion, lived in pairs or small groups throughout the forest.

Moving South from the Amazon, the climate begins to dry and the landscape turns to grassland. The animals in turn become even more unusual. Macrauchenia, a 1 ton chimera possessing 3-toed feet like a rhinocerous, a body like a camel and a trunk lived in herds alongside car-sized relatives of armadillos called Glyptodonts. Toxodons – great, ponderous beasts that resembled something between a hippo and rhino – lived in huge numbers as one of the most common animals in this landscape.

The enormous Megatherium, a sloth even larger than those in the Amazon, lived in a vast range the entire way down to Patagonia. At 4-5 tons in weight it would have matched the grass eating Stegomastodon elephants as the largest animals in its ecosystem. The short-faced bear Arctotherium, related to the modern spectacled bear but more than twice the size of a polar bear, was the top predator of these grasslands. Recent evidence suggests that Smilodon probably lived here too.

Living alongside these were relatives of animals that are still found elsewhere – camels, horses were all common. This list is by no means exhaustive (for example it mentions nothing about birds nor the smaller animals) but serves to give some idea of just how spectacular and almost otherworldly the continent was when man first landed there.

Were South America to still have it’s whole ecosystem intact people would undoubtedly take safaris to see the giant sloths, elephants and huge herds of Macrauchenia and Toxodon.

The same pattern is found around the world. North America used to have a similar collection of amazing animals as did Europe and Northern Asia. Madagascar and New Zealand had huge birds, some 14 feet tall. Australia had huge birds too, along with giant kangaroos, 20 feet long lizards, and strange marsupials bigger than rhinoceros.

There are several strange things about this information. The giant sloths survived for at least 30 million years before dying less than 5000 years ago. 5000 years is nothing in terms of evolution. The most obvious question is what happened to them.

So, what did?


The grasslands of South America as they would have looked about 13,000 years ago. Machrauchenia is visible in the front, with the cat Smilodon drinking. In the middle is a ground sloth while in the background are a group of elephants (Stegomastodons) [viii]

Eden Vanishes

The answer to that question is closely tied to the reason that most people haven’t heard about these animals. The answer is that human beings hunted these animals to extinction. The reason Africa has still got such a dazzling array of creatures is that humans evolved there. The African animals learned to avoid humans as hunters, but this was not so everywhere else.

When people arrived in the Americas they were already skilled hunters armed with throwing weapons. The animals of the continent had never seen a predator that looked like us and didn’t fear us. The same is true in Australia, New Zealand, Madagascar, Europe and Northern Asia. Southern Asia was the first place early man arrived to after leaving Africa and it retains part of its megafauna. It has lost hippos and giant apes for example, but still has a (relatively) small elephant species, rhinos and tigers.

Until the 1960’s it was assumed that climate change killed the megafauna, however since then the evidence has been mounting that something more was at play. For example there had been nearly 30 previous ice ages/inter-glacial cycles and no similar mass extinction occurred at their junctions. Furthermore the megafauna of Australia and New Zealand died at different times than those in the Americas (50,000 years ago and 500 years ago respectively compared to 11,000 years ago for the Americas). They died at time when the climate wasn’t really changing. However, humans arrived on Australia 55,000 years ago and on New Zealand about 700 years ago.


Elephant Car
People are fascinated by megafauna and will pay and travel to see and interact with them. A world with more megafuana would help generate a greater interest in nature and with it, conservation and the environment. This princple is sometimes used in conservation already – protect the “charismatic megafauna” and the rest of the forest and smaller creatures get saved too. But it’s value lies far beyond this. A world with more megafauna would simply be a more interesting world.


As a final argument against the idea that climate change was to blame, consider the following:

The North American animals died as the climate was warming. Given that North America contained 3 groups of elephants – the tropical Gomphotheres, the temperate Colombian Mammoths and the cold-adapted Woolly mammoths (in addition to mastodons) – it would seem that some of the elephants would do better as others would do worse for any change in temperature. If it would get warmer we would expect a greater range for the tropical elephant or colder a greater range for the cold elephant. Instead, at the end of the last ice-age – when man arrived – all 3 groups go extinct.

Already we’ve established that the world until recently was inhabited by giant animals, that man ate them all and that basically nobody knows about this. This is unusual in itself. But the story gets stranger still.

There is considerable controversy within zoology/paleontology about what happened to the megafauna. Recently this controversy had finally shifted in favour of accepting humans as the culprit, but only just. Even now there is a considerable holdout among scientists who favour alternative explanations. This is despite the overwhelming evidence that humans, and humans alone, killed them.

Alternative proposals have included climate change, which I’ve shown above has basically nothing going for it, a hypothesis that suggests a very dangerous disease was spread and a bizarre theory about another meteorite hitting the earth. But there are gaping holes in these theories – why would a disease kill nearly all unrelated species of big animal but almost no small animal? Diseases also don’t jump species that quickly anyway. Why would it leave almost all of Africa intact when close relatives of those animals on other continents died? How could a meteor be responsible for killing animals in various continents that went extinct tens of thousands of years apart?

What I want to impress upon you is that such childish and easily debunked theories are not found in the rest of science.

The debates about climate change and intelligent design are not born of scientists but rather of outside influences trying to change and distort public perception of scientific understanding.

But the silly ideas and scientific infighting surrounding the megafauna are unique in science and have contributed to the lack of public understanding of the topic. If they are simply just extinct animals, then they, along with Dinosaurs, are something of a curio, an academic topic of interest. But they take on a whole new importance if it was man that killed them. Especially if they died extremely recently and their destruction has wrecked havoc on the environment.

Everywhere, until very recently, used to look like the Serengeti, with a huge assemblage of exotic and often giant animals moving by the million. At some point we should accept the unusual truth that much of the damage that mankind has done to the environment was done by caveman.

It would seem that we as a species don’t like accepting the enormously destructive influence of early man and the truth that what we see nowadays is in no way unspoiled, natural, untamed nature. We like to fantasize that National Parks such as Yellowstone are in a natural state, when it would be more correct to view them as reeling from the effects of a mass murder that occurred just yesterday.

I’m trying to put this in emotive language as I believe it is emotion, and not reason, that has scientists create such baffling and below-par theories to try and explain away what happened.

There is an extra element too. We typically do not identify ourselves with early man/caveman. In school we mostly learn about mankind after agriculture and largely after the advent of cities and civilization, starting about 6000 years ago. However modern humans have existed for 200,000 years and very similar humans (some with larger brains) have existed for at least 500,000 years. The humans from 200,000 years ago were just as intelligent as us, had complicated language, made fire, hunted and would be indistinguishable from us were they to be raised in the modern world.

They would have been comparable to modern day Amazonian tribes with complex languages and sophisticated hunting techniques. They were just like us and would have been capable of hunting large animals and ultimately, just like us, unintentionally wrecking the environment and causing mass extinction.


The consequences

As you can probably imagine, the removal of almost all large animals from an ecosystem has enormous consequences. The vegetation changes with many species of plant going extinct and the remaining animals being affected in a variety of ways. Perhaps the biggest consequence is the relative lack of animals even in areas that are left alone by man.

For example, it is not uncommon to go to forests in North America and not see many animals. Even open grasslands don’t seem to contain much. Green alpine meadows in the summer, in areas with no hunting, don’t contain many large or visible species. You might see some squirrels in a forest, or ground squirrels in a meadow but, aside from the occasional deer, it is not common to find a large groups of bigger and visible animals.

Canadas excellent Jasper National Park contains about 1300 Elk and 150 Moose. The park is approximately 11,000km^2 and is well preserved with no hunting allowed. By contrast the similarly sized Chobe national park in Botswana contains more than 50,000 elephants.

Even more incredible is the Serengeti, perhaps the worlds most intact ecosystem[ii]. It is just 3 times the size of Jasper but contains 1.7 million wildebeest, 250,000 zebra and 500,000 gazelles. This is to say nothing of it’s elephants, hippos, giraffes etc.

In terms of predators Jasper contains about 110 Grizzly bears, 90 black bears and just 45 wolves. The Serengeti has over 3000 lions, 8000 hyenas and 1000 leopards. These statistics are even more incredible when one considers the poaching pressure on the African wildlife. The buffalo population in the Serengeti was 65,000 in 1969 but has been reduced to “just” 16,000 now.

These figures should be taken as a rough comparison only. Jasper has a shorter growing season, with less intense sunlight while the Serengeti suffers poaching and a seasonal drought [iii]. However there is an *enormous* discrepancy in the quantity of animals living in both parks[iv]. A major reason for the difference is the recent extinction of megafauna in North America.

To illustrate why, consider the following:

Imagine there is a simple ecosystem with just 2 types of plant and 2 types of herbivore. Herbivore A eats plant A and herbivore B eats plant B. Imagine what happens if we remove herbivore A from the ecosystem. Over time plant A, no longer being eaten, becomes much more common than plant B. Eventually the ecosystem is mostly plant A. However the only herbivore is B, which cannot eat it, so it becomes rare.

Ecosystem changes


In reality ecosystems are very complicated and there are a wide range of factors affecting animal populations. Elephants knock down trees creating open habitat for other animals and they eat vegetation from high branches and bring it to the forest floor, increasing the amount of nutriment within the reach of smaller animals. Predators change the places that prey species congregate, preventing them from eating plants that haven’t adapted to being eaten. These types of changes are called trophic cascades.

Despite it’s relative drought the Serengeti is home to literally millions of large animals




Brazil Cerrado
The vast tropical savannah of Brazils Cerrado region is almost entirely devoid of large animals. The lack of wildlife is striking when compared with the Serengeti. This is despite it having a more favourable climate with higher temperatures, more rainfall and a shorter and far less intense dry season. When man first arrived here it was home to millions of elephants, giant sloths, macrauchenia, toxodon and other animals.


The astonishing case of the reintroduction of wolves to Yellowstone provides a dramatic example of this. When wolves were reintroduced to Yellowstone they prevented Elk from eating young willow and aspen trees, by making it dangerous for them to congregate in areas where they grow. Beavers and songbirds use these plants, so the result was a great increase in the numbers of songbirds (such as common yellowthroat and the song sparrow) and an even greater increase in the number of beavers (just 1 beaver group lived in park previously, there are now 12). The massively increased beaver population has led to increases in fish and duck population by way of the beaver ponds it creates.

While it’s hard to estimate the quantity of animals that would be present if Jasper were an intact ecosystem, Dr. Sergey Zimov provides some figures for the Northern Siberian grasslands [v] . Based on analysis of the fossil record he suggests about 1 mammoth per square kilometre in one of the coldest environments on earth. He also provides figures for some other species.

Zimovs figures suggest that Jasper should have about 11,000 mammoths, 66,000 horses, and 165,000 deer/reindeer. In Jasper, the figure for mammoths would more likely be split between mammoths and another huge elephant like animal known as a mastodon. The area should also contain camels, giant sloths, giant beavers, lions, jaguars, saber toothed cats, saiga antelope, dire wolves, giant bears, American cheetahs, giant bison, several species of musk-ox and pronghorn.

Mastodons are forest dwelling elephants, with mammoths preferring open grasslands (though there is considerable overlap). Lodgepole pine, a very common type of tree in Western Canada, grows in large stands in Jasper. However not much eats it. Bears do sometimes eat its bark and sheep can eat very young trees, but the leaves of mature trees are largely uneaten by existing animals.  This helps in keeping it widespread. It is the equivalent of plant A in the above diagram.

When the megafauna collapsed fires became much more common. Without large animals eating the vegetation it falls to the ground and dries out creating much more fuel for bigger, hotter and more frequent blazes[vi]. Lodgepole pine is fire adapted and has benefited from this. In the end we find that Lodgepole pine is so common precisely because nothing alive can eat it, in turn helping cause fire which suppresses other plants. The large stands of it are devoid of animals and represent an unnatural situation.

Mastodon teeth have been found repeatedly with pine needles in them. They would have eaten the lodgepole pines in addition to knocking them down (something all elephants do today). This would have created more varied habitat for the other animals in the ecosystem and prevented forest fires. The end result would have been herds of a sort of forest elephant, increased populations of many other species, far less fires and greater diversity of plantlife.


Mastodons, shown here with horses and a tapir, are native to forests all across North America. They are the largest and most important species in their ecosystem. They were the guardians of the forest, the most intelligent entities in it and helped greatly to maintain other animal populations. With their loss came a collapse and simplification of the ecosystem. The forest is wounded without them and their presence is sorely missed.


Some plants are still alive that depend on megafauna for their seed dispersal and without them are slowly going extinct. The most striking example is the Osage orange tree. The plant produces a large fruit that nothing eats. It’s a huge waste of energy. Fruit is typically used to distribute seeds. No modern animal eats it, so it falls to the ground and the plants range contracts, not being spread as intended. When Europeans first recorded the Osage orange it was confined to a limited area in central/northern Texas. However on the fossil record it occurred all over the continent. In fact we now know there used to be 7 species, the other 6 dwindled to extinction without the megafauna. It (and many other species) still hangs on, producing fruit, waiting for a mammoth or a ground sloth to eat it and distribute it. Such large and exotic fruit trees should be far more common.




Osage Orange tree left, with fruit right. Note the fruit beneath the trees, uneaten





So what’s to be done about all this?


Pleistocene Rewilding

“We live in a zoologically impoverished world, from which all the hughest, and fiercest and strangest forms have recently disappeared”

-Alfred Russell Wallace, co-discoverer of evolution, 1876


Starting in the 1960’s a number of scientists, led by Paul S. Martin, began advocating for a radical rethink of ideas around conservation. By their logic, keeping national parks (such as Jasper, Yellowstone etc) in their current condition, is akin to keeping them in a state of severe depletion. If the preceding sections of this article were perhaps twinged with sadness then their stated solution, and its present day extension, offer a wondrous vision of what the future of nature might look like.

The original idea was to take (often very endangered) animals and introduce them into ecosystems where a similar animal went extinct. For example, elephants are being hunted for ivory intensely in Africa. But if herds of them were to be transported to the USA and let free their diet, social behaviour and impact on the environment would mimic closely that of the Columbian mammoth, an animal the ecosystem sorely misses.

The Bactrian camel is another candidate. Wild Bactrian camels are extremely endangered with less than 1000 remaining. However North America naturally has camels (in fact camels originated in America). North American plants are already adapted to being eaten by camels. If camels were brought back they would help to distribute nutriment and water to dry and inhospitable locations.

Cheetahs, Saiga antelope, horses, donkeys, zebras and tapirs could all be introduced into the former range of closely related (and in some cases identical) species. This would hugely impact the ecosystem and help restore it to something closer to what the animals and plants living there are adapted to. The idea of Paul S. Martin can be summarised as this: why take the world of a few hundred years ago to be the point we consider natural. The ecosystems around the world were already enormously damaged by then. If we are looking to bring back bison and wolves to areas where they have been wiped out, there is no reason not to consider other native species too, even if they were not seen in modern times. 10,000 years is nothing in terms of evolution.

Modern African forest elephants, being hunted at an alarming rate, could be introduced into the Amazon. The Amazon contained what is likely millions of elephants at the point of human contact and they were greatly needed to transfer nutriment throughout the forest. It has been estimated than 98% of nutriment transfer has been lost since the megafauna extinction in the Amazon [vii]. This is an extraordinary statistic. As amazing as the amazon is large sections of it (particularly in the east) have limits on how many animals the region can contain (with sodium as a shortage) and how fast plants can grow (by shortage of phosphorus). The reintroduction of elephants would save the species as well greatly increase the quantity of both plants and animals in the Amazon.

These ideas (and very similar ones) have been proposed since the 1960s with, at first, limited support among zoologists. However by 2005 the thinking had changed and a paper was published, authored by many of the worlds top biologists and zoologists, suggesting that megafauna needed to return to areas outside of Africa (the article focused on North America). Gradually the bizarre and silly theories for why there are no mammoths have fallen by the wayside. But by 2005 something else was apparent. There might be, in some cases, an even better solution.

The ultimate solution would be to bring the megafauna back to life.

If the megafauna could be brought back from the dead they might be released into their former native ranges. Following from what we’ve discussed earlier this would have a profound impact on the environment.




If I might be poetic for a moment….

When Prometheus stole fire from the Gods his brother Epimetheus was given Pandoras box, which contained the evils of the world. The development of fire made possible the destruction of most of the worlds large animals and with it much of the natural world. But at the bottom of Pandoras box was hope. The forbidden fruit of knowledge, when followed to its end, would seem to come full circle and endow us with the power to resurrect Eden. //end poet



In 2015 the full DNA of woolly mammoths was sequenced. DNA has been acquired from several other extinct species (including ground sloths). While there are several techniques that might be used to resurrect them, perhaps the most likely is CRISPR, in which (for the case of a mammoth) Asian elephant DNA would be modified at several points and used to create an embryo which would be carried to term in a modern elephant.

There are several groups trying to resurrect mammoths right now – with groups in Japan, Korea, America and Russia (with considerable government funding and backing) all making the attempt. The Korean group is also trying to clone cave lions (the native lion to Northern Asia). In March of 2015 CRISPR was used to change several sections of Asian elephant DNA to mammoth DNA (including the genes for hair, ears and subcutaneous fat). The effort was successful and woolly mammoth genes were therefore active/alive for the first time in thousands of years. It’s just a matter of time before we can bring it back to life (probably the most difficult challenge is actually being able to clone regular elephants).

What’s needed more than technology at this point is for people to understand what has happened to nature. Understanding what to do depends on several ideas, none of which are widely known, even among educated people. It seems strange that sloths a thousand times the size of modern ones roamed the Americas when people first arrived. But in many ways it’s stranger yet that people don’t know this. Perhaps the most important idea to impress is that the effect of reintroducing the megafauna would be extremely beneficial.

The cloning of extinct animals is going to be possible and probably sooner than later and current megafauna reintroduction would be cheap to implement now and have a range of immediate benefits with almost no downsides at all. We could save endangered species, protect the environment, help halt climate change while creating wonder and inspiring kids with new and dramatic science. What’s needed now is education. From that will come a demand to act upon this huge gap of information and make a wilder, richer and more natural world.


The future of conservation lies with rewilding. Through a combination of changing attitudes towards nature and massive technological advancement lies a far more interesting, alive and natural world.


Ciaran McNamee


[i] In this essay I use the term “elephant” loosely to refer to any member of the proboscideans. The term itself is slightly unusual as it can be used to refer to both Asian and African elephants, but not mammoths typically. This is despite mammoths being closer related to Asian elephants than African elephants are. Furthermore, modern elephants are about 7 million years diverged. Given that Lions and Tigers are about 4 million years diverged from each other, and we would never call them the same animal, it seems we call Asian/African elephants both “elephants” simply because they look like one another. For the sake of brevity I occasionally call similar looking and related extinct species “elephants”.


[ii]The Serengeti allows for the full north/south migration of great herds of animals without fences. It is probably the most intact (land) ecosystem on earth.  Thus I am keen to use it as a reference for comparison. It has suffered huge poaching of elephants however, so I use the Chobe park in Botswana for elephant numbers. The soil in Botswana is relatively depleted of calcium so elephants there have naturally smaller tusks there. Thus poaching was never intense in the area and the elephant population is much higher.


[iii] Jasper is also mountainous, which has some effect on the composition of fauna. However its by no means cherry picked – the more famous Banff park has just 350 Elk and 80 moose. Unfortunately there is no intact temperate/arctic ecosystem with which to compare it.  The important point to impress here is that there is a vast difference in animal densities, which cannot be explained simply by a hotter climate. Moreover, as Zimovs work has shown, animal densities even in the far north of Siberia were once much, much higher.

The population of caribou in the far north of north America has managed to adapt to tundra conditions and is still present in relatively large numbers.  For example, the arctic national wildlife refuge at 78,000 km2 contains about 150,000 caribou. This is still a far, far lower density (approximately 1/40th for similar sized grazers, to say nothing of the total absence of larger ones) than that of the Serengeti.


[iv] It’s worth noting that Africa did suffer a megafauna extinction and that it’s own animal density is still significantly lower than it used to be. Africas megafauna extinction included giant buffalo, giant tortoise, giant baboon, saber toothed cats, dinotherium (an enormous elephant like animal) and a type of Asian Elephant called Elephas Recki. Perhaps the strangest of the extinct African megafauna is the chalicothere. It roamed in herds and looked somewhat like a horse, except it had hands instead of hooves and used them to pull down branches to eat.


Africas megafauna went extinct more gradually and over a longer period of time than in the rest of the world. If North Americas assemblage of animals seems even more incredible than Africas then this is the reason why. Eg Africa now contains either one or two species of elephant (depending on how they are classified). North America contained Woolly Mammoths, Colombian Mammoths Mastodons, Gomphotheres and pygmy elephants. This greater elephant diversity might seem unusual given that the continent is smaller and that elephants evolved on Africa. This can only be understood if we realise Africa has lost a lot too, just not nearly as much as the other continents. It provides the best glimpse at a true picture of nature.









[viii] Image due to the brilliant paleoartist Mauricio Antón.  Wikipedia:ón . Personal Website:

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