The Limited Loss of Large Species in Africa & Southern Asia
The incredible devastation wrought by the megafaunal extinctions in Australia, where around 90 per cent of large species went extinct, was the subject of last month's post so it might be instructive this month to take a look at two regions which were far less severely affected – Africa and southern Asia. Compared to other parts of the world, these two regions escaped very lightly from the megafaunal apocalypse, although southern Asia was the worst affected of the two and may hold a special place in the megafaunal extinctions in that one of the species lost from this region could have been the largest land mammal to ever live. The survival of so many large species in Africa is truly astonishing, obviously indicating that the forces pushing large beasts to extinction in the rest of the world were not as powerful on this great continent. Clearly, then, in Africa and southern Asia, something unusual must have facilitated this great escape.
As southern Asia was the most heavily affected area of the two, we might begin by taking a look at what lands are actually included in this region and follow this with an overview of the great mammals it lost during its megafaunal extinctions.
Southern Asia is an extensive and very diverse region, stretching from the Indian subcontinent through southern China and Southeast Asia, all the way east to Indonesia as far as Wallace's Line and the Philippines. Wallace's line is a faunal boundary identified by the aforementioned Alfred Russel Wallace which runs between Borneo and Sulawesi, Bali and Lombok, with organisms of Asiatic character lying to the west while those to the east are a mixture of Asian and Australian origin.
Although there is an abundance of evidence of megafaunal species from southern Asia dating to the Pleistocene, unfortunately the dating of these fossils is quite poor so it is unknown exactly when many of them went extinct. Nevertheless, a number of species are thought to have suffered extinction in southern China in the late Pleistocene, including Ailuropoda baconi, a giant panda related to our modern form Ailuropoda melanoleuca, as well as the large and grandly-titled tapir, Megatapirus augustus (although it should be noted that most would now place Megatapirus in the modern tapir genus, Tapirus). A subspecies of the spotted hyena, Crocuta crocuta ultima, is also generally thought to have gone extinct at the end of the Ice Age, although there have been some suggestions that it persisted into the Holocene until around 7,800 years ago.
But other members of southern Asia’s megafauna to disappear from the face of the Earth in the late Pleistocene would have utterly dwarfed these creatures, not surprisingly perhaps as these were relatives of our modern elephants. One, Stegodon orientalis, was itself a large form, but in southern China in the late Pleistocene there was no question over who was truly the Big Kahuna, the ground having shook under the enormous feet of perhaps the largest land mammal to ever live – the Asian straight-tusked elephant, Palaeoloxodon namadicus.
It is often stated that the largest land mammal ever to have inhabited the Earth was the indricothere – a gigantic, long-necked rhino which lived in Asia around 30 million years ago that towered above its contemporaries, resembling a strange love-child of a giraffe and a rhino. However, a recent study examining the size of proboscideans – the order that our modern elephants are the only surviving members of – found that Palaeoloxodon namadicus may well have been significantly larger than indricotheres. This study concluded that indricothere bulls likely weighed around 17 tonnes and stood 4.8 metres tall at the shoulder, but that P. namadicus bulls may have been as much as five tonnes heavier, while the top of their shoulders stretched five metres or more into the sky.
Thus, the taller, 22-tonne P. namadicus may well be the largest land mammal ever to walk the Earth, and it is incredible to think that a giant of such amazing dimensions lived not millions of years ago but only thousands of years ago, surely striking awe into the hearts of our ancient relatives – those modern humans who had already begun their great colonisation of Asia.
But while P. namadicus is no more, some of its relatives ducked the scythe of the megafaunal extinctions in southern Asia, their descendants now having assumed the title of the largest mammal in this region – the Asian elephant, Elephas maximus. However, the title of largest land mammal on Earth has now passed to its slightly larger relative, the six-tonne African elephant, Loxodonta africana, which, of course, lives in that great continent to the west – Africa.
As regards the megafaunal extinctions, ‘Africa’ as a region is deemed to refer only to sub-Saharan Africa, as North Africa is considered as part of northern Eurasia, even though a number of sub-Saharan mammals can be found there.
What is most remarkable about Africa in terms of the megafaunal extinctions is the fact that all of the largest mammals known to have populated the continent in the late Ice Age can still be found there, including not only the elephants but the giraffes, the rhinos, and the hippos. And of those African megafauna that did go extinct, many only disappeared in the Holocene (c. 11,700 years ago–Present), including the giant long-horned buffalo, Syncerus antiquus, and possibly the giant wildebeest, Megalotragus priscus. Also, although future finds may expand the number of megafaunal species known to have gone extinct in Africa, these would probably do little to change the overall picture that Africa was far less affected by the megafaunal extinctions than most other regions.
However, this clearly begs the question: why did Africa, and to a lesser extent southern Asia, escape the worst excesses of the megafaunal extinctions? Well, there have been some attempts to answer this question, most notably in a sort of super-charged version of the overkill hypothesis called the ‘Blitzkrieg hypothesis’, its name being derived from the ‘lightning war’ engaged in by the Nazis at the outbreak of the Second World War.
According to this theory, the megafauna and humans in Africa and Eurasia had lived together for a very long time and so had evolved behavioural strategies which allowed them to co-exist. However, as humans spread across the globe and reached continents like Australia, North America, and South America, they encountered large beasts which were naive to the dangers humans represented and lacked behavioural and evolutionary adaptations to deal with them. Thus, according to the theory, the megafauna on these continents were rapidly overhunted and driven to extinction by the newly-arrived humans.
However, as neat a theory as this is, it has not found widespread support, not least for the reason that there is little in the way of archaeological or fossil evidence to support such an incredibly rapid extinction, although the proponents of this view counter that the lack of evidence is a direct result of this extinction happening so quickly. In any case, whatever about the merits of this particular theory, it is undeniable that whatever conditions prevailed in Africa and southern Asia in the late Pleistocene, they helped to ensure that our modern world would not be utterly bereft of giants.
When you think that the difference in weight between the mighty Palaeoloxodon namadicus and the indricotheres was almost the same as the weight of the largest land mammal on Earth today, the African elephant, it really hits home that we now live in a much-diminished world, where the truly gigantic mammals that once were have now all left the stage. Yet, the story of the megafaunal extinctions in Africa and southern Asia also highlights something else: that we should be extremely thankful that the world we live in today has any massive mammals at all. And, of course, this realisation is swiftly followed by a disturbing thought – did the megafauna of Africa and southern Asia truly escape from a sentence of execution or were they only granted a temporary reprieve?
Will we soon see a day when all of the great mammals of our modern world have also been consigned to extinction; relegated to an afterlife as dry bones in museums, footage on screens, and denizens of the netherworld that is the human memory, the stories we tell being some of the only remnants of the titans we once shared the Earth with? If we allow that to come to pass, we will truly live in an impoverished world – and this will be a form of poverty which no amount of material wealth can overcome. Ensuring this does not happen is the responsibility of us all – not just those who live in Africa and southern Asia, not just governments, states, and international bodies – but of every person on this planet, and the Irish must play their part too. There is still time left to ensure our giants make a great escape.