beasts’. This ancient group split off from other mammals at a time when Africa was an island continent, probably during the Cretaceous geological period, tens of millions of years before Triceratops and Tyrannosaurus dinosaurs were thundering around the American plains!
Given the long evolutionary history of the Afrotheria, surprisingly few living mammals fall into this group, and those that do are exceptionally diverse. As well as the elephants, hyraxes, and manatees, Afrotheria also includes elephant shrews, golden moles, and tenrecs, which are shrew and hedgehog-like mammals that are mainly found on Madagascar. The group is unique in that is contains one of the smallest living mammals, the long-eared tenrec, which weighs just 5 grams – not much more than a penny coin – as well as the largest, the African savannah elephant. It was only thanks to scientific developments in genetics over the past twenty-five years that we had any idea that these animals were in one related group.
While rock hyrax and the other little creatures are native to the hills, plains and valleys of Africa and the Middle East, manatees and dugongs float around in the tropical waters of Central and South America and off the warm coasts of the Caribbean, Indian and Pacific Oceans. Yet, despite their obvious differences, these seas creatures share a number of traits with elephants: manatees are the only herbivorous marine mammal; they have four small nails at the end of each flipper that are very similar to the toenails of an elephant; and they also have a prehensile upper lip that they use to grasp hold of marine vegetation, much like a stubby trunk. They even have similar teeth, with incisors that resemble tusks, as well as the horizontal molar teeth displacement that also occurs in elephants.
Hyraxes have flattened nails, rather than the claws found on most similar-sized land mammals. They even have small tusks too that develop from incisors. And, like elephants and manatees, their mammary glands (which produce milk for their babies) are near their front legs. In all other mammals, except primates, milk teats are found between the rear legs. A final trait shared with elephants is that their testicles stay inside the abdomen, rather than swinging around like a monkey, bull or human. So, despite the aeons since the common ancestor of these species was alive in the swamps of North Africa, there are still plenty of visible clues to their shared heritage.
Fossil evidence helps us to work out when the anatomical features of living elephants evolved, and why. If we were to journey back over 35 million years ago to Northern Africa, we might be fortunate enough to see a pig-sized animal that looked somewhat like a modern-day tapir, foraging in the soft vegetation around rivers and lakes. This was Moeritherium, one of the earliest proboscideans – the group within Afrotheria that specifically contains elephants and their relatives.
Moeritherium died out without leaving any descendants, so it is not a direct ancestor of today’s elephant species, but they shared features with other proboscideans, like a flexible upper lip, which, like a modern trunk, was used for grasping and handling food. They also had short tusks, although these were more tooth-like than the tusks of a modern-day elephant.
Part of the skull and teeth of another very old proboscidean – Eritherium – was recently discovered in Morocco. It is dated to 60 million years ago, which was a time of rapid evolution and change for mammals following the demise of the dinosaurs. Eritherium was tiny, standing only 20 cm high, no bigger than a well-fed domestic cat, making it a thousand times lighter than a modern African elephant. But, despite appearances, it was its unique teeth that allowed scientists to identify it as the earliest ancestor of the elephant!
Other than humans, the evolutionary history of proboscideans is one of the best-mapped mammalian lineages, with around 175 species identified. They are divided up into five main groups, which are referred to as ‘super-families’ by biologists.
There are the early proboscideans (such as Eritherium and Moeritherium), the deinotheres, mastadons, gomphotheres, and elephantidae. Taxonomy is a complex business, though, particularly when dealing with creatures that have been extinct for millions of years and have left only a few fossilised fragments behind to help us. Every time a new fossil or thread of genetic evidence becomes available, scientists end up adjusting relationships between super-families and updating estimated ages, and we’re still a long way off from knowing the full story.
However, from the fossils we do have, we can see that the proboscideans were remarkably successful, having lived on every continent except Antarctica and Australia in their 60 million years on earth, in environments as diverse as deserts, tropical forests, mountain ranges and the Arctic tundra.
Around 20–30 million years ago, the deinotheres (‘terrible beasts’) appeared on the scene. Instead of having tusks in the upper jaw, like elephants, they had downward-curving tusks looping down from their lower jaw. They started small, but some grew quickly (in evolutionary terms) reaching an impressive shoulder height of four metres.
Deinotheres stuck around for about 20 million years; the equivalent group of our human ancestors has been around for only two million, and our species, Homo sapiens, only 300,000 years. Deinotheres were so successful because of their increasing body size, meaning they could tolerate lower quality diets such as fibrous, hard-to-digest plants, which allowed them plenty of flexibility because they could graze more widely.
Around 25 million years ago, the climate began to warm, and big, open grasslands and tundra appeared across the world. Mastodons and the fantastically named gomphotheres marched out from Africa, across Eurasia, and into this favourable new environment in North America, with some species – such as the American mastodon – dominating the landscape until around 10,000 years ago.
Like modern-day elephants, mastodons had tusks that emerged from the upper jaw, and the thick enamel and ridging on their teeth shows that they predominantly browsed on woody plants. The largest known of all these creatures, a mastodon called Mammut borsoni, was well over four metres tall and reached the colossal weight of 18 tonnes. This puts it in the same league as the hornless rhino, Paraceratherium, a monstrous beast that lived across Eurasia 34–20 million years ago and has been officially recorded as the largest mammal species that ever lived.
However, there is some tantalising evidence that a third species may outstrip both these giants. Partial leg bones discovered in the 1800s, from a straight-tusked Asian elephant group called Palaeoloxodon, suggest an animal with a height of over five metres and a body weight of 22 tonnes. They would make today’s elephants look like small fry.
The gomphotheres are the most diverse group of the proboscideans, first appearing in Africa 24 million years ago, then spreading across the globe, before mostly becoming extinct 11,000 years ago. Many gomphothere species had four tusks and while some had trunks that are similar to modern elephants, others had shorter snouts more reminiscent of today’s tapir, which is more closely related to rhinos and horses than it is to elephants.
This brings us to the Elephantidae – the group that includes the three remaining species of proboscidean alive today, as well as the extinct mammoths (Mammuthus) and Palaeoloxodons. Elephantidae emerged in Africa in the late Miocene period, somewhere between 6–8 million years ago. This was truly a time of trunks, when deinotheres, gomphotheres and mastodons all ranged far across the planet from the tropical forests of America to the arid grasslands of Africa and Asia.
We also know a little bit about the behaviour of these early elephants. Scientists recently used aircraft to study the ancient fossilised trackways of an unknown proboscidean species in the deserts of Eastern Arabia, near to modern-day Dubai. Seven million years ago, we know that a single group of around thirteen animals, of different ages and sizes, had moved across the muddy ground in a coordinated fashion, much like elephant families move across the savannah today.
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