Pleistocene (Pt 16): Giant Wombats and Marsupial Lions

While Australia is not the only continent to have marsupials today - they're also found in the Americas - it certainly has the largest ones. This was, perhaps, even more true during the Ice Ages than it is today.

Of course, being an arid, tropical to subtropical, continent the Ice Ages affected Australia rather less than they affected Europe or North America, or even southern South America. There were no glaciers to be seen, and not a lot of snow unless you wanted to climb a mountain. On the other hand, there were some pretty big animals, including lizards and flightless birds larger than anything we have today. And, yes, the marsupials were bigger, too.

Many weren't that much larger than their modern equivalents - although, to be fair, that's quite large in the case of a kangaroo. But not all of them, for this was also the time of the largest marsupial ever to have lived: Diprotodon optatum, the giant wombat.

Pleistocene (Pt 15): Ice Age Down Under

Procoptodon

The island continent of Australia has today what is probably the strangest mammalian fauna of any continent. Yet it is also the continent that has, perhaps, suffered the greatest number of mammalian extinctions over the last 50,000 years or so. Many of those are relatively recent, or at least after the end of the last Ice Age around 10,000 BC. But even compared with the Australia of, say, the 18th century, the wildlife of Ice Age Australia looked pretty odd.

In climactic terms, Australia didn't suffer too badly from the Ice Ages. It's too close to the equator to have had ice sheets get anywhere near it, although doubtless there was rather more snow on the mountains. (Although perhaps not too much - even today, Australia is the only continent to lack glaciers). Then, as today, much of the continent consisted of desert, and the bits that weren't were mostly arid grassland, albeit with denser woodlands around the eastern and northern coasts.

Pleistocene (Pt 14): Ice Age Africa

Giant warthog

In the earlier parts of this series, when I described the animals of Ice Age Europe, I said that the continent, at that time, had a feel reminiscent of present-day Africa. But, if that's so, what was Africa like during the Ice Ages?

The answer is, perhaps disappointingly, "not that different to how it is now". Indeed, of all the settled continents, it's probably Africa that has changed the least since the Ice Ages. You might think that this has something to do with Africa being close to the equator; in particular, that it's too close for whopping great sheets of ice to have rolled across the countryside.

Which they didn't, so that much is true. Indeed, the southern hemisphere in general had far less ice cover than Europe, Asia, and North America. That's due mainly to the way that the continents happen to be arranged, with glacial ice sheets only being able to get as far as southern South America (there are fjords in places like Tierra del Fuego). Presumably, sea ice extended much further across the Southern Ocean than it does now, but that would have little effect on land-based animals.

But that's not to say that Africa, or Australia, were unaffected by the Ice Ages. Africa was colder than it is today, and, to begin with at least, rather drier, too. The Sahara and Kalahari deserts were more extensive than they are today, with the semi-desert belt of the Sahel being quite a way south of its present position, running through what are now fairly lush countries such as Guinea, Nigeria, and northern Kenya.

Pleistocene (Pt 13): Giant Bears and Speedy Cats

The most famous predators of the North American Ice Ages were surely Smilodon and the dire wolves. But, of course, these were hardly the only carnivorous mammals on the continent at the time. For one thing, it's worth remembering that something like half of the species in North America in the mid Pleistocene are still around today. Even where modern species had yet to evolve, their immediate ancestors often had, and would have looked very similar to modern forms. So Ice Age North America would have had its share of coyotes, bobcats, and cougars, not to mention smaller creatures like badgers. And let's not forget jaguars, which entered South America from the north early on in the epoch, and are still found in parts of Mexico today.

But surely Smilodon was the most fearsome predator of its day? Well, probably... kind of. But it most certainly has a contender for that crown.

Pleistocene (Pt 12): Dire Wolf Redux

I have previously discussed the dire wolves of Pleistocene North America, but really only in the context of how even earlier dogs were much scarier. Those earlier, bone-crushing, dogs were still around in the early Pleistocene, but they didn't survive the early Ice Ages, possibly because they were too specialised to cope as the climate changed. The dire wolf, on the other hand, first appeared at around this time, and survived long enough to live alongside humans.

The dire wolf (Canis dirus) was a very close relative of the grey wolf that we're all familiar with today. Grey wolves, despite their broad modern distribution, first evolved in Europe and Asia. Indeed, the sudden appearance of the Etruscan wolf (Canis etruscus), thought to be a direct ancestor of the living wolf, in the so-called "Wolf Event" shortly before the dawn of the Pleistocene, had a dramatic effect on European wildlife. Modern wolves, however, while widespread in the Old World, did not enter the Americas until surprisingly late, and did not travel south of the Canadian Arctic until the Ice Ages were almost over, around 0.1 million years ago.

Dire wolves, however, were there much earlier. So where did they come from? Although there was some suggestion back in the 1980s that they were actually South American in origin, the more modern consensus is that they were native to the northern continent. The most popular theory seems to be that dire wolves evolved from Armbruster's wolf (Canis armbrusteri). In fact, the latter continued to survive in its original form alongside its descendant until about 0.3 million years ago, although it does appear to have been steadily pushed eastward and southward during this time.

Pleistocene (Pt 11): Sabretooth Smilodon

Smilodon fatalis

Over the  course of the last three parts of this series, I have looked at the various large herbivores that lived in North America during, and between, the Ice Ages. Naturally, there were also predators feeding on these animals, and none is more famous than Smilodon, the sabretooth cat.

However, Smilodon was by no means the only sabretooth cat, even in Pleistocene North America. Indeed, the trend for large cat-like animals to evolve huge, sabre-like canines, is one that arose many times during the Age of Mammals. So there are a wide range of, often quite unrelated, animals that look like "sabretooths." However, when we refer to "sabretooth cats" in particular, we're generally referring to the group technically called the machairodontines.

The machairodontines are one of three main subfamilies within the cat family, and the only one to have gone extinct; the other two are the big cats (lions, tigers, etc.), and the "true" felines (everything from cougars to house cats). They first appeared about 10 million years ago, long before the Pleistocene, and represent a genuine group of cats, descended from a single ancestor, and about equally related to the other two kinds, which arose slightly later. In fact, they don't all have enormous teeth - at least, no more so than a tiger does, which is quite large enough, really - but most of the later forms do.

Pleistocene (Pt 10): Of Armadillos and Bison

Glyptotherium

When the continents of North and South America collided, shortly before the dawn of the Pleistocene, a range of creatures wandered across the newly formed isthmus of Panama. Most were heading south, giving us such "normal"-looking South American animals as jaguars, ocelots, and grey foxes. The ones heading north were a lot stranger, and many of them didn't do so well in the long term. These include such wonderfully weird creatures as the giant ground sloths, which managed to get as far north as modern Canada before dying out.

But they weren't alone, and not necessarily any stranger than some of their fellow immigrants. The same event that saw the arrival of the ground sloths also saw the coming of the armadillos. Today, there is only one species of armadillo in the United States, and only two outside of South America (the other gets no further north than southern Mexico). But, back during the Pleistocene, there were others, and some of them were not quite what we'd expect today.

Pleistocene (Pt 9): Before the Bison

Megatherium

The Pleistocene in North America can be divided into three 'land mammal stages', defined by the kinds of animal that inhabited the continent. The first, which was only recently added to the Pleistocene, is the one that comes before the Ice Ages proper, so that the Ice Ages themselves are, as I mentioned in part 8, divided into just two. As I said back then, the first of these starts with the arrival, not only of the ice, but also of the first American mammoths. The second, called the Rancholabrean after the famous tar pits, is much shorter, and essentially refers only to exceptionally bitter cold of the Last Ice Age. In terms of animal life, though, it is defined by the arrival of bison.

Today, when we think of America before the white man arrived, vast herds of bison are often part of our mental picture. And that, on the whole, is pretty much accurate, and is why their first appearance is deemed so significant in the ongoing evolution of North American wildlife. But what was the American wilderness like before there were any bison? What dominated the continent during the earlier, "Irvingtonian", stage?

As always, of course, the most common animals were the smallest. But, important though the teeth of (for example) voles are for the precise dating of geological deposits from this time, the eyes of any time travelling visitor would inevitably have been drawn to much larger animals. Obviously, mammoths and mastodons are a large part of the answer, and the presence of large elephantine animals crossing the plains would have been enough to tell our time traveller that, while he might still be in Kansas, it isn't really the same one he left. But there are many other beasts that would provide just as quick a clue.

Deer, peccaries, and horses are all examples of animals that aren't so unfamiliar today, although in many cases, the exact Pleistocene species were different from those alive now. Horses, for example, had, by this point, evolved to the modern single-toed form, but the last North American native horses died out around 12,000 BC, when the Pleistocene ended, leaving the ancestors of the domesticated forms behind in Asia. Exactly how many species of wild horse there were in America at this time, though, is unclear, with as many as fifty having been named - in my view, it's somewhat unlikely that they're really all distinct. There were, however, at least two broad types, one similar to the modern domestic horse, and the other, the so-called stilt-legged onager (Equus francisci, among others), which looked much more like a wild ass.

Pleistocene (Pt 8): Mammoths v. Mastodons

American mastodons

The arrival of the first mammoths in North America was a significant turning point in the development of the local wildlife. It's so important that this date, 1.9 million years ago, marks the beginning of the first of just two 'land mammal stages' that define North American wildlife during the Ice Ages. It used to also mark the beginning of the Pleistocene itself, but for various reasons, that's now been shifted a little further back.

The mammoths in question arrived from Asia, crossing over the Bering land bridge, the recurring appearance and disappearance of which greatly influenced North American wildlife during this time. They were southern mammoths (Mammuthus meridionalis), the dominant species of mammoth in Asia at the time, but they quickly evolved into a home-grown American animal: the Columbian mammoth (Mammuthus columbi).

It used to be thought that, even ignoring any late-surviving southern mammoths, there were at least two different species of mammoth living in North America in the early to mid Pleistocene. We're now pretty confident that they're all just examples of Columbian mammoth. Nonetheless, you will often see references to the "Imperial mammoth" (Mammuthus imperator). Perhaps the biggest elephant that has ever lived - they were about thirteen feet tall at the shoulder - these were probably just really big Columbian mammoths. Not that that's anything to sneeze at, mind you.

Pleistocene (Pt 7): Meanwhile, Across the Atlantic...

Columbian mammoth
(It's likely that the real animal was hairier than the one in
this reconstruction, but it shows the tusks effectively)

Over the last five parts of this series I have described the history of Pleistocene Europe, describing some of the ways that the animal life of the continent changed over those thousands of millennia, and looking at a few particular animals in more detail. But one doesn't need a degree in zoology to notice that today, the wildlife of North America, for example, is different to that of Europe. North America has coyotes, raccoons, cougars, armadillos, and pronghorn antelope, to name just a few animals that are simply absent in Europe. (Or, in the case of raccoons, were absent until somebody made the mistake of releasing some of the furry nuisances in 1930s Germany).

It's hardly surprising that that continent also had different wildlife during the Pleistocene. One notable difference, for instance, is that we humans weren't there. Obviously, neither Columbus nor Leif Ericsson were genuinely the first person to discover America. But even whichever long-lost group of Native Americans was actually the first to discover the great western continent, they did so long, long, after the first Europeans discovered Europe. While Europe had at least some species of human inhabiting it for about two-thirds of the Pleistocene, nobody reached America until the epoch was all but over.

Pleistocene (Pt 6): Lions, Hyenas, and Bears, oh my

Cave lions
(original artist unknown, c. 33,000 BC)

The iconic Ice Age carnivore is, of course, the sabretooth cat. However, as I mentioned when discussing the Mid Pleistocene, sabretooth cats when extinct in Europe well before the Last Ice Age. (Well, maybe not... but at any rate, they seem to have been very rare). So what were the dominant predators in Europe during that final, and most extreme, period of intense cold?

It probably depends on how small a predator you're willing to count. Animals like weasels, stoats, and shrews were presumably very numerous, even if their skeletons are often too delicate to preserve well. Moving up the scale, the most numerous carnivoran fossils from the time belong to foxes. Both the modern red fox and the Arctic fox were widespread in central Europe at the time, although the latter was presumably more comfortable.

Another modern animal that we wouldn't be surprised to find among the snowy forests and open tundra was the grey wolf. Indeed, grey wolves may well have originated in Europe from an American ancestor, before heading back over the Bering land bridge. If so, they were probably quite quick about it, since they are found across the Arctic on both sides of the Pacific from an early date.

All of these are creatures that are still found in Europe today, although not necessarily in large numbers - wolves are more common in the wilds of Asia and North America than they are in densely settled Europe. But I've been harping on through this series about how "African" European wildlife looked at the time, and that's as true of the big carnivores as it is of herbivores such as elephants/mammoths and rhinos. One of the clearest instances of this is the presence in Pleistocene Europe of lions.

Pleistocene (Pt 5): Giant Deer and Woolly Rhinos

There were a number of Ice Ages during the Pleistocene, but the most severe of them all seems to have been the most recent one - the Last Ice Age. Or, perhaps more accurately, the Last Ice Age So Far, since there's no particular reason to assume there won't be another one along in a few thousand years time. This was the time when the earlier steppe mammoths were replaced by their more famous descendants, the woolly mammoths. But woolly mammoths did not live in isolation. With what other creatures did they share their world?

Even today, deer are relatively common animals in the wilder forests of Europe. In the Pleistocene, before the spread of farms and towns, they would have been even more so. At the height of the last Ice Age, however, there were relatively few forests in Europe, and many of the deer we are familiar with - red deer, roe deer, and so on - would have been sheltering in warmer climes. Reindeer and moose, on the other hand, were doing well, with the former, in particular, being widespread across the continent.

Throughout the course of the Pleistocene, however, there had been another kind of deer in Europe, one that is no longer with us. These were the "giant deer" of the genus Megaloceros. Some species, isolated on islands created by the rising melt-waters of the glaciers between the Ice Ages, were unusually small, but, in general, they had been getting larger as the Pleistocene went on. Before the last Ice
Age, the largest species, slightly bigger than the primitive moose of the day, had been M. verticornis. Now that was replaced by an even larger species, the Irish elk (Megaloceros giganteus).

Pleistocene (Pt 4): Time of the Woolly Mammoths

The second-to-last Ice Age ended around 0.13 million years ago, a full 95% of the way through the Pleistocene. As I've described in Part 3, it was just one of a series of Ice Ages stretching back nearly two million years, and separated by relatively warm 'interglacials'. For much of this time, European wildlife had had a distinctly 'African' flavour, with lions, hyenas, hippos, and elephants, among others, inhabiting the continent alongside the ancestors of more familiar European animals.

Such animals prospered during the warmer gaps between the Ice Ages, and this, the last full interglacial, was no exception. The phrase 'hippos in the Thames' is often used when talking about this time, and its perfectly accurate. The climate of the day was, if anything, slightly warmer than it is now, with the ice retreating far into the Arctic. All that melting ice had to go somewhere, of course, and the sites of modern day coastal cities such as Amsterdam and Copenhagen would have been underwater. On land, much of the northern continent was covered by dense oak forests, a green wilderness yet to be cleared to make way for farmland or towns.

Pleistocene (Pt 3): Ice Ages and Interglacials

Life-size reconstruction of a steppe mammoth
(compared with a 3-year old human)

When the Pleistocene began, Europe's climate was much the same as it is today, and the general shape of the continent would also have been instantly recognisable from space. The animals however, were different, many of them being ones we would now associate with Africa - rhinos, elephants, hyenas, and cheetahs, among others. In part 2, I described how that began to change 1.8 million years ago (which, incidentally, was once defined as the beginning of the Pleistocene - see part 1 for why that changed).

This was a time of cooler weather, as the Ice Ages began to dawn. Forests retreated in the face of advancing tundra, and musk oxen, bison, and (strangely) European hippos began to make their appearance. The cold snap was prolonged, and, so far as we can tell, the fauna of Europe remained relatively stable for the next 600,000 years. That's still a very long time - if we go back to my analogy where we get just one minute to watch the events of a decade, with the whole of written history thereby spread out into a nine hour spectacular, this phase of European history would last a full six weeks.

1.2 million years ago, half way through the Pleistocene, the climate changed again, and mammals (and other animals) were forced to adapt. However, the change wasn't towards yet colder weather, but back towards a warmer, more pleasant climate. The forests grew back, with all their dense undergrowth in attendance, and the harsh steppe-lands retreated into the north. As had been the case at the dawn of the Pleistocene, European weather would have been much as it is now.

Pleistocene (Pt 2): Europe at the Dawn of the Ice Ages

Pachycrocuta brevirostris, a European hyena

The Pleistocene is the time of the Ice Ages, when great ice sheets rolled across much of the northern hemisphere. Nothing much lived on the ice sheets themselves, just as there is very little today in the heart of Greenland. But, as we've seen, not only were their wide bands of tundra and pine forest reaching across much of today's 'western' world (and, of course, a fair chunk of the Orient), but the ice ages weren't continuous; there were many warm gaps between them.

The mammals of the Pleistocene include what are surely the most familiar fossil mammals to most people, the ones we generally think of when we think of 'after the dinosaurs'. For this was the time of the mammoths and sabretooths. They're familiar to us because, aside from the tiny sliver of warm weather we currently live in, the Pleistocene is the most recent, and therefore the best preserved and the most easily analysed, of all the epochs of the Age of Mammals. It's been the setting for a number of films, books, and TV series - to name just two, the Ice Age cartoons, and the Earth's Children series.

Yet, when we think seriously about Pleistocene animals, there are a couple of important points to bear in mind.

Age of Mammals: the Pleistocene (Pt 1)

A scene from northern Spain

The "Age of Mammals" is the informal name for the Cenozoic era, the 65 million year slice of Earth's history from the extinction of the dinosaurs to the present day. It is so named because mammals have been the dominant large, land-dwelling animals throughout the era.

Of course, "large, land-dwelling" is something of an arbitrary qualification, and one more rooted in the natural prejudices of our own species than in an actual reflection of Earth's biodiversity. The most numerous animals throughout the era, and, for that matter, through the Age of Reptiles that preceded it, would have been insects. But, unless you're standing in the middle of a swarm of midges, most people don't notice insects in the same way they would notice, say, a herd of antelope, or a prowling tiger. Mammals aren't even the most numerous vertebrates today, and, by sheer species count, it's the fish that are dominant, and some of those are pretty big.

Even on land, in terms of number of species, mammals are the least numerous of the four vertebrate classes - birds come in first, and reptiles still hold on to second place, followed by amphibians. Of course, most of those reptiles are small lizards, and birds are also generally quite small. Even so, there are ostriches, crocodiles, and anacondas, among others, and, in fairness, most mammal species are mouse-sized. So there's a reasonable case that what this should really be is the Age of Birds. But I, for one, am going to stick with the standard term.