By Hore, Phil
Phil Hore traces the ancestry of big cats, elephants, rhinos, possums, kangaroos and echidnas across several ice ages and continents.
The “woolly” rhinoceros was covered in thick hair as an adaptation to living in a cold climate. This large mammal coexisted with the woolly mammoth Mammuthus primigenius, mainly in Asia and later in Europe. Its forebears lived in China. The woolly rhinoceros roamed about alone or in small family groups like present-day African rhinoceroses. Like the mammoth it died out when the climate became warm. DNA from an extinct woolly rhinoceros shows that it is the modern Sumatran rhino’s closest relative.
During the past 50 million years or so our planet has endured a number of ice ages, with some far more extreme and severe than others. During these times, many of our modern animal species, or relatives of modern species, migrated between continents as more and more of the world’s water became trapped in the ever-growing ice sheets.
This sudden drop in ocean levels up to an astonishing 70 metres in some areas – allowed remote groups of animals to merge and mingle for the first time. Even on some of the more secluded islands, animals that had been isolated for millions of years could unexpectedly enter new areas by walking across newly formed land bridges or wading across a shallow stretch of water.
This permitted many “new world” groups in North and South America to start mingling with “old world” ones in Africa and Eurasia, and explains why these continents today share species like cats, dogs, pigs and deer.
Eventually the ice sheets covering the northern hemisphere retreated, causing ocean levels to rise once more, covering the land bridges and separating these animals again. Over the following centuries, many of these pioneer species fell extinct in their traditional homelands yet managed to hold on in their new habitats.
An example of this are early horses that first evolved 60 million years ago in most of the northern hemisphere and then fell extinct everywhere except North America, where the modern horse (Equus) emerged some 35 million years ago. When an early Oligocne ice age began 30 million years ago (mya), ocean levels dropped and horses began spreading across the Bering land bridge that spanned today’s Bering Sea between Asia and Alaska. This enabled them to radiate into Asia, Europe and Africa again. In due course, however, the horse became extinct in America yet managed to hold fast in their new homelands.
The oddity is that when Europeans entered North America they came face to face with Indians on horseback! If America’s horses had become extinct, where did these horses come from?
The movie The Ghost and the Darkness is based on the true tale of two male lions that killed more than 130 people in a 9-month period during 1898 at a place called Tsavo in Kenya. As good as the movie was, it unfortunately got one major fact wrong by having the protagonists played by two large maned lions.
Male Tsavo lions are maneless. They’re also larger than most African male lions and have a proportionally smaller skull. The fossil record and cave paintings throughout Europe inform us that male lions with small skulls and no manes are cave lions (Panthera atrox)’. Could it be that cave lions like the one pictured above have managed to survive in isolated Tsavo, deep within Africa? As wild as this sounds, the possibility has sent several zoologists into Tsavo to find out if this could be true.
Remarkably, the horse had been reintroduced into the Americas some 200 years earlier when the Spanish conquistadors invaded South America and unwittingly re-established the species.
But this isn’t the only example of an old world species that actually originated in the new world. Camels, rhinos, wolves (indeed all canines) and even the cheetah evolved in North America, only to trek into Eurasia and Africa when the Bering land bridge formed. Out of all these species only wolves (the canines) can still be found in North America. All otheis are now extinct in their original homeland – except perhaps for one!
The cheetah’s (Arinonyx jubatus) fossil record in North America goes back over three million years to two large cats called Miracinonyx inexpectatus and M. trumani. Both were larger than the modem African cheetah and the now extinct European one (Roman circuses accounted for the extinction of most larger European species, including bears, lions and even a dwarf elephant from the Mediterranean). These American cats had the narrow bodies, elongated limbs, short faces and reduced whiskers of modern cheetahs yet were more primitive as they could retract their claws (unlike cheetahs, which are extremely specialised).
Cheetahs crossed into Asia when the Bering land bridge appeared, eventually reaching as far as southern Africa When the land bridge closed, these cheetahs were left stranded. It’s believed that the original population then died out in America while the small populations left in places like Iran (where there are still around 100 alive today) and most of Africa became ever more inbred due to the lack of a stable population base.
But did the American cheetah die out, or did it change its spots? Recent studies point to the latter being the case. The American lion, puma, cougar or mountain lion (Felisjoncolor) has the distinction of having the most names given to any animal ever! These are large cats with short faces, white underbellies and teardrop markings running down their noses. The kittens are often spotted like a cheetah. The puma also has absolutely no fossil record past three million years ago – the earliest is a cat called Viretailurus schaubi. In fact, the only cat that could possibly be its ancestor is the similar-sized Miracinonyx. It’s also worth noting that there is no cat outside of America of the right age that could be its ancestor either.
Biological studies of pumas also strongly support this close relationship, so it seems the American cheetah may well have escaped the ice age extinctions, albeit in a larger form and hidden under a tawny coat.
For years anatomists have noticed similarities between the Asian elephant (Elephas maximus) and a European mammoth species (Mammuthus primigenius). Both have large heads with prominent bumps along the crest of their skulls. They also have high shoulders and a spine that slopes down from their large front legs to their short back ones. Asian elephants are also quite hairy, especially when they are young.
Now tests on woolly mammoth DNA have shown a close tie between the two – more so than with the African elephant (Loxodonta africana). It seems M. primigenus may have managed to slip into the 21st century as one of the only two species of elephants alive today. However, the scientists who managed to code this DNA warn that it is still reasonably fragmented and there could indeed be some differences between the two that they either haven’t seen or found yet.
The mammoth is not the only shaggy animal to survive. Other than perhaps the horse, rhinos have been one of the great mammalian success stories over the past 40 million years. These beasts managed to leave America and spread all the way to Africa, where they solely remain – or so many think!
Asia actually has three rhinoceros species with the largest in India (Rhinoceros unicornis), a second in Java (Rhinoceros sundaicus) and the third in Sumatra (Dicerorhimis sumatrensis). DNA from an extinct woolly rhinoceros (Coelodonta antiquitatis) shows that it is the Sumatran rhino’s closest relative. Calculations suggest the two diverged 20 mya when Sumatra was joined to Asia through land bridges as a result of low sea levels (Sumatra was actually part of Gondwana, just like Papua New Guinea and Australia). Although there are less then 300 left today, the Sumatran rhino looks like it is straight out of times past. They are large and often covered with thick, dense brown/reddish hair. They also have “formed” toes rather than the padded hoofs of modern rhinos.
Scientist examining carcass of baby mammoth. Tests on woolly mammoth DNA has shown a close tie with Asian elephants.
With only 300 left, the Sumatran rhino will join its long-dead relative in extinction within a generation unless radical action is taken immediately. A sad end to a long-time survivor!
Most of the examples of ice age survivors discussed above are still being argued about and should be considered “possible” survivors. There are, however, more “definite” ones than these. Ice age animals still roam in some of the colder regions of the north!
The musk ox (Ovibos moschatus) looks like a robust, shaggy cow but is instead the world’s largest goat. It’s a true ice age survivor that is so well-protected against the cold that it runs the chance of overheating if it exerts itself too much, even during the coldest winter. This is thanks to the extremely fine wool that makes up its thick coat, which is eight times warmer then sheep’s wool. In fact, the amazing properties of this wool has people scrambling to protect them – musk ox were all but extinct in Canada until some far- sighted farmers caught the few that were left and started breeding them.
Musk ox may well be one of the more intelligent animals on the planet as well. They are highly protective and caring of each other and have shown great problem-solving abilities and a talent for learning new things, including unlocki\ng gates and escaping!
Occupying the same region as the musk ox is the bizarrelooking Saiger antelope (Saiga tatarica), which is so ancient it seems to fit somewhere between true antelopes and sheep. To retain heat, the Saiger has a gigantic bulbous nose that traps and holds the heat from its breath when it exhales. The Saiger also faces extinction now as starving farmers in places like Russia and Mongolia are unmercifully poaching them.
Pangolins (Manis gigantea) are a group of armoured mammals found in both Asia and Africa and are often misidentified as part of the family Edentata, which includes antealers. In fact, these odd creatures belong to the family Xenarthra, making their closest living relative the sloth. Although it is no longer found around Germany, these animal oddities first evolved there. The fact that they eat ants (or termites) and have armoured bodies like armadillos is a matter of convergent evolution. To put it simply, they look like an anteater because they eat ants! Pangolins are rare today, yet who can look at their scaly body and not see images of the armoured giants that once roamed our world?
One of the more unusual survivors Ls a living creature whose behaviour and physical attributes are a “carry-over” from this unusual time. The pronghom antelope (Antilorapm Americana) from North America is celebrated as one of the fastest animals alive today. It can run at 95 km/h for as far as 15 km. But why would an animal devote so much energy to speed when there’s no predator alive that even comes dose to it in the Americas?
Alive today there isn’t, but the pronghom evolved in an ancient savannah that was patrolled by the American cheetah, an animal more than capable of catching a pronghom in full Sight – if it could get close enough.
This is where the second of the pronghom’s special features comes in to play, as it possesses the best vision of any mammal alive or dead. It can pick up movement as far as 5 km away. Its eyes are located high on its head, helping it to keep watch while its head is down during feeding -just the thing you need to spot a pesky cheetah trying to move within sprinting range.
Two unusual survivors aren’t animals at all but plants, one of which is so common that you may have eaten one in the past week or so. The avocado (Persea Americana) is a South American fruit that has survived until modem times thanks to the intervention of humans and fanning. The seed inside the avocado fruit is gigantic and needs to be swallowed and excreted for it to germinate in the wild. However, no modern herbivore in South America can swallow such a seed without choking to death.
This may be the case today, but 10,000 years ago South America had some of the largest mammalian herbivores ever, including the enormous ground sloth (Megatherium americanutn), which could grow as tall as two stories. Coprolites (fossilised poo) reveal that these sloths ate everything in their region, including the humble avocado.
Here is a classic case of parallel evolution, where two organisms evolved alongside each other in a symbiotic relationship. The loss of one almost caused the extinction of the other.
Likewise the osage orange tree (Madum pomtfera), which is found on the North American plains, also yields gigantic fruits that were once eaten (and similarly distributed) by the American sloth and mammoth – some of the only herbivores at the time that could manage the tough-skinned fruit
Luckily both the avocado and the osage live for a long time, and both managed to survive just long enough for humans to unwittingly save them. In the case of the avocado it was farmers cultivating them for their fruit, while the osage was saved by the reintroduction of the horse by the conquistadors.
Australasia also has its out-of-place survivors thanks to the bizarre geological connections in the area The closest and most obvious are the bonds that tie Papua New Guinea (PNG) and ancient Australia together. Both islands share several animals including cassowaries, possums, kangaroos and even dingoes (in PNG they are called singing dogs).
One of the most “obviously” Australian animals is the echidna – more precisely the short-beaked echidna (Tachyglossus acuieatus). PNG not only shares the short-beaked echidna with Australia but also has a dwindling population of the larger and less spiky long-beaked echidna (Zaglasssus bruijni). This rarely-seen monotreme is one of the last survivors of a time when both regions were populated by the megafauna
The modern Tbchyglossus is physically very similar to the giant echidna (MegalibgirUia rainsayi) that lived in Australia 20,000 years ago. It may well be a dwarf species that shrunk to the smaller environment of PNG to survive (a process also seen in the recently described dwarf human species from Indonesia called hotnofloresiensis).
As remarkable as the relationship between Australia and PNG is, another island hidden away in the Indonesian archipelago is truly an ark from the last ice age. Called Sulawesi, this small island is home to dozens of amazing species that are completely out of place in our modem world The island has had few predators over the past 50 million years and has managed to keep many species that have long since disappeared from the rest of the world. Early explorers of the area, like Alfred Russel Wallace, noticed the uniqueness of the area’s flora and fauna and drew a line through the region called “Wallace’s line”. On one side of this invisible divide you’d find Asian and European animals while on the other side are native Australian and Pacific species.
The clouded leopard has the longest canines of any living cat relative to its body size. These long teeth are reminiscent of the sabre-toothed tiger.
Recent geological surveys have shown that the islands along this part of Indonesia (like Sumatra) were once part of Gondwana, an ancient supercontinent that included most of the land masses that make up today’s continents of the southern hemisphere. Sulawesi is actually the most northern part of this group, so instead of being an Asian island it should be thought of as the most northern part of Australasia
Sulawesi’s ancient forests are home to “old world” primates like macaques and primitive tarsiers. Tarsiers are tiny – some weigh as little as 7 grams – and have massive eyes and incredibly manipulative hands. The fossil record for the group is poor but the remains that have been unearthed suggest they first appeared around 70 million years ago – around the time Tyrannosaurus rex was terrorising the planet.
But the wonders don’t stop there. Rummaging through the forest floor is the most primitive pig on the planet called babirusa (Babyrousa babyrussa) or deer pig. These are so archaic that the male’s upper canines grow up through the roof of their mouth and curl just in front of their eyes, giving them a demonic look.
For some time is was supposed their closest relative was a European pig that died out 35 million years ago, but new evidence suggests they’re actually closer to hippos then they are to any modern pig species. A miniature hippo relative, horned like a demon from hell, stuck on a tiny island in Indonesia? Who’d have thought?
But where Sulawesi becomes important to Australia is in its trees. This distant island is home to the largest and most primitive species of possum on the planet. Called the bear cuscus, this is a 10 kg possum with a bear-like face, front hands like a koala and a hairless prehensile tail. The fossil record tells us these cuscuses died out on mainland Australia millions of years ago, yet here on this island, thousands of kilometres away, the most primitive member of the family is still alive and doing reasonably well.
Sulawesi is truly a unique island that deserves a lot more attention then it’s been getting, especially since almost every one of its amazing animal species is close to extinction due to poaching.
Australia also has its own share of hidden treasures. Concealed away in Queensland’s dense rainforests is the smallest and most primitive of all kangaroos, the musky rat kangaroo (Hypsiprymnodon moschatus). At only 0.5 kg in weight, this tiny macropod still possess several features that reveal the close ties between kangaroos and possums. These include a long, prehensile tail, opposable digits and multiple births. Most of these features are important if you live in trees, which early kangaroos did.
There was also once a second group of kangaroos that roamed Australia called the Sthenurinae. These were far more robust then modern species, with shorter faces, powerful arms and stronger tails. Their extinction, however, seems to have been short-lived with the classification of the banded harewallaby as the only known surviving species of Sthenurinae. Unfortunately these tiny 3 kg wallabies have become extinct on mainland Australia, but luckily can still be found on several islands around Shark Bay in Western Australia where no predators (like cats and foxes) have been able to reach and wipe them out.
I find it incredible that almost every iconic animal from the ce age is still with us today – with the exception of maybe one. Sabre- tooth tigers (Smilodon) may be long dead and buried, but if you’re hoping they might still be hidden away in some distant jungle then I suggest you try something.
Research the planet’s rarest cat species – the clouded leopard (Neofelis nebulosa) from South-East Asia – and have a look at the size of its teeth! Smilodon may be extinct but there’s still a silhouette of this great carnivore staring out at us from the edge of a forest with a killer’s eye and an ancient smile.
Phil More is manager of the National Dinosaur Museum (www.nationaldinosaurmuseum.com.au).
Copyright Control Publications Pty Ltd Sep 2005
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