Fins to Feet

Elephant Evolution
May 21, 2011, 5:10 pm
Filed under: Uncategorized

NOTE: Hurrah! I have returned!

Tusk met tusk on the arid fields of Rafiah, Palestine in 217 BC. Alexander’s great empire had fallen into the hands of a number of feuding successor dynasties that ruled all the known world between Macedonia and the Punjab. Syria was a disputed border-land between the imperial domains of two princes in particular, Antiochus III and Ptolemy V. Antiochus, who would later challenge the rising Roman superpower and acquired the epithet “the Great”, approached from the east with 62,000 infantrymen, a few thousand horsemen and over a hundred war elephants. Ptolemy fielded similar numbers of men, horses and elephants. The signal was given and the elephant contingents charged at one another. Antiochus’ Elephants were of Indian origin, while Ptolemy’s were North African. The ground rumbled and dust clouds leapt into the air as they thundered across the sand.

Things turned sour quickly. The North African elephants, spooked by the strange smell of their subcontinental adversaries – from whom they were separated, evolutionarily speaking, by a space of 7.6 million years – suddenly began to panic and retreat, throwing Ptolemy’s right wing into a dreadful rout. Greek troops fought in a closely-knit military formation called a phalanx, where the mobility of a single soldier was severely limited. It’s difficult to imagine the sheer horror of being stuck in a box of shields and spears while a 4 ton animal rampages towards your position, tearing through ranks of armed men with ease. The Battle of Raphia, as the engagement came to be known, is generally regarded as one of the largest elephant battles in the classical world.

Elephants were used to break formations and wreak havoc by many generals in the ancient world: most famously by Hannibal, who hurled them at the Roman legions – with varying degrees of success- during the second Punic War. The Romans themselves would later make use of elephants, albeit in far reduced numbers, against Celtic armies in Iberia and Britain.

Apart from their use as instruments of war, Elephants have been – in various times and places – objects of reverence, beasts of burden and symbols of imperial might. The caliph Harun-al-Rashid  gifted an albino elephant named Abu-Abbas to Charlemagne as a token of friendship. Legend has it that Charlemagne later called upon Abbas in a tremendous battle against the Viking Danes. That’s epic.

Depictions of Elephants from medieval Europe

Elephants were, apparently, quite mysterious to the writers of medieval bestiaries. They have this to say about the subject:

“They possess the quality of mercy. If by chance they see a man wandering in the desert, they offer to lead him to familiar paths. Or if they encounter herds of cattle huddled together, they make their way carefully and peaceably lest their tusks kill any animal in their way.” – Aberdeen Bestiary, 1200 CE.

 “There is an animal, which is called “elephant,” which possesses no desire for sexual intercourse … They live 300 years.” – Harley MS 3244, 1255 – 1265 CE

This one is trippy:

“Between elephants and dragons is everlasting fighting, for the dragon with his tail bindeth and spanneth the elephant, and the elephant with his foot and with his nose throweth down the dragon, and the dragon bindeth and spanneth the elephant’s legs, and maketh him fall, but the dragon buyeth it full sore: for while he slayeth the elephant, the elephant falleth upon him and slayeth him.” – Batholomaeus Anglicus, 13th century CE.

In fact, male Elephants have an incredible libido; have been seen killing livestock, live for about 60 years and only occasionally engage dragons in mortal combat.

Elephants … and Hyraxes?

Unlikely relatives: From left to right, a Hyrax, a Dugong and an Elephant

Bizarrely, the closest living relatives of modern Elephants are Dugongs, Manatees and Hyraxes. The evidence for this curious relationship comes from DNA/protein sequence data and shared anatomical/developmental characteristics like the late eruption of permanent teeth and undescended male gonads. They collectively belong to the Mammalian clade Afrotheria – so named because of the African origins of the group in the middle Cretaceous. Elephants belong to the subgroup Proboscidea, an order of animals that, until a few thousand years ago, inhabited a wide range of terrestrial environments across the globe – from icy tundra to tropical rainforest.

The tree of Elephant evolution

Where and when did Elephant evolution begin?

The Proboscidea seem to have begun their divergence from the Sirenia (the group containing manatees and dugongs) in the Eocene along the swampy shores of the Tethys sea (now the Mediterranean rim) at sites like modern-day Fayoum, Egypt, where fossil specimens of the two groups can be found in close proximity to one another.  Global temperatures were much higher then than they are today and there were no ice-caps at the poles at that time.

Among the earliest members of the order Proboscidea was a hippopotamus-like creature named Moeritherium that lived about 35 million years ago. It had short,  stout  legs,  a long body and a short tail. The animal probably spent a great deal of time wading through swamps and riverine habitats, consuming fresh water-vegetation. It had two pairs of short tusks which, like the tusks of modern Elephants, were simply modifications of the second incisor. Tusks are the longest teeth in the animal kingdom!

They have trunks?

Moetherium had a flexible upper lip for grasping food, a sort of “proto-trunk” similar to what we see in modern tapirs. The trunk or “Proboscis” of an Elephant is a combination of the nose and the upper lip. The existence of a trunk in a fossil species can be inferred from the size and position of the nasal opening and the structure of a bone canal below the eye socket (called the infraorbital canal) which conveys nerves and blood vessels to parts of the face – in the case of elephants, to the trunk. The trunk is a phenomenal multi-purpose tool that can be used for everything from the delicate handling of branches to siphoning up water to drink.

Is Moetherium ancestal to the modern elephant? 

Semi-aquatic habits are seen in a number of early Proboscideans and many of them bear superficial resemblance to the modern tapir. Moeritherium is probably not a direct ancestor of the Elephantidae (which includes all living Elephants), but an offshoot on the family tree that has left no living descendants.

Paleomastodon, a possible ancestor of both mastodons and elephants and a close relative of Moeritherium, also had two pairs of the tusks. The lower pair was shovel-shaped and possibly used to scoop up freshwater plants. The trunk is more obvious in this species than in the roughly contemporaneous Moeritherium.


Mastodons? Are those like Mammoths?

Mammutidae is a major Proboscid family that (probably) owes its ancestry to Palaeomastodon.  It includes the iconic woolly Mastodon – which occupies a somewhat august position in the history of Paleontology as one of the earliest large fossil species to have its anatomy fully reconstructed and exhibited to the public. Thomas Jefferson used the past existence of the mighty Mastodon on American soil as an argument against the (primarily French) notion of American Degeneracy, the goofy idea that atmospheric conditions in the New World weakened both men and animals – making them smaller and less intelligent. It’s easy to confuse Mastodons with Mammoths, but the two are actually only distantly related and the superficial similarities between them are more the result of convergent evolution than any phylogenetic affinity. Mastodons were shorter than mammoths and had stockier legs. They browsed on shrubs and the crowns of their molars had pointed cusps for clipping leaves. The high crowned molars of mammoths were better suited for grinding down grass. They had longer and less curved tusks. They both survived to the end of the Ice Age and faced predation from human beings.

So, we’re done with proto-elephants – what sorts of Proboscideans have appeared since?

The order Proboscidea is notorious for its incredible experiments in tusk shape and length. A rapid proliferation of forms took place in the Miocene, producing shovel-tusks, downward curving tusks and a number of other strange parodies of the conventional spiral curved elephant tusk. We will deal with three major branches that evolved in the midst of this diversification, the Gomphotheres, Stegodons and Deinotheres.

From left to right: Deinotherium, Platybelodon (a shovel-tusked Gomphothere) and Stegodon

Deinotheres thrived during the Miocene. Some of them attained heights and lengths that dwarfed modern elephants. The best known of them, Deinotherium, stood at a shoulder-height of about 3.5-4.5 meters, making it about as tall as a double-decker bus. It is the third largest land mammal known to science. The build of its skull and its dentition was so unusual that it led one anatomist to suggest that it was an aquatic beast that anchored itself to the riverbed with the aid of its tusks. Deinotheres lack any upper tusks, but they sport a pair of dramatically downward-curving tusks that may have been used to dig up food or as a sexual display. The lower jaw is itself bent downwards and lacks any canines. The retracted facial and nasal bones also seem to indicate that these animals had trunks. Deinotheres were never very diverse and the only evolutionary trend they seem to display within the family is a general increase in size.

The Gomphotheres represent a diverse collection of elephant-like animals that appeared on the scene in the Miocene. They originated in Africa and radiated out throughout Eurasia and the New World. They bear four substantial tusks, two upper and two lower. Some specialized forms developed shovel-shaped lower tusks that might have been used to scrape up plants for consumption.

Modern elephants posses a gland called the “musth” gland on the side of the face that produces chemicals during heightened sexual activity. These chemicals are associated with agitation and violent outbursts – and elephants in musth on an elephant farm are usually kept under lock and chain because they have an increased likelihood of going on a stampede. The musth gland first appears in the Miocene and can be inferred in fossil species from the shape of the sides of the skull.

One common feature among shovel-tusked Gomphotheres is a long lower jaw – something that contrasts strongly with the greatly reduced lower jaw of modern elephants. A short, strong neck was necessary to hold the head and dental apparatus up.

Both Stegodonts and modern Elephants are derived from Gomphotheres. Stegodonts differ from Elephants in the structure of their teeth, but generally resemble modern Elephantidae. A pair of vestigial tusks remained in the lower jaw. The upper tusks were long and nearly touched the ground. In an interesting case of island dwarfism, one species of Stegodon seems to have undergone a dramatic reduction in size on the Indonesian island of Flores. It is comparable in size to a small water buffalo. Interestingly, they lived contemporaneously with a species of dwarf Hominid named Homo florensis (often dubbed “Hobbits”) on the same island. And, while Homo sapiens took on Mammoths in Eurasia and North America, hobbits may well have speared and killed pygmy elephants in the tropical mists of Flores (evidence to this effect has been uncovered).

A number of general trends can be observed throughout the course of elephant evolution:

1) A general increase in size

2) The loss of teeth. The typical mode of replacement of teeth seen in most mammals (including ourselves) was abandoned for a system where older worn out teeth in the front of the jaw are replaced by newer teeth from the back of the jaw – rather like a conveyor belt. The old tooth drops out or is swallowed. Each half-jaw of an adult elephant bears upto three teeth– the foremost one on its way out and the hindmost one on its way in. An elephant will run through 6 or, if it’s very lucky, 7 sets of molars in its life time. The destruction of the final tooth means certain death.

3) An increase in the complexity of teeth and the length and diameter of tusks.

4) A transition from browsing to grazing that roughly coincides with the spectacular rise of grasses across the planet as CO2 levels and global temperatures dipped in the Miocene.

By 11,000 BC, Gomphotheres still roamed the forests of South America, Mastodon herds still rolled across the frozen wastelands of North America and Stegodons could still be found in island forests in Indonesia. In fact, there may have been well over a dozen Proboscidea species on the planet when Humans first started migrating out of the African continent. Unfortunately, there are barely 3 species left today. In the next post, we’ll deal with the Elephantidae: the Wooly Mammoth, the Asian elephant and the African elephant.


14 Comments so far
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great post!

Comment by frinz

Thanks for reading!

Comment by arvindpillai

Regarding war elephants, I recall reading of an occasion when the commander of a besieged city ordered his elephants to sally forth to attack the encircling armies. The elephants, after thinking this over, ran as one straight through the opposition and disappeared into the surrounding countryside. The besiegers (who may have been Mongols) stood aside and let them go. Unfortunately I’ve been unable to re-locate the reference. Apologies for the rather tenuous link but have you ever come across this story before?

Comment by Gav

I’ve actually never heard of that story – though it sounds interesting! It seems plausible too. Scipio Africanus’ troops, as I recall, simply stood aside or gave way as Hannibal’s elephants plowed through the ranks – allowing them to attack the animals from the flanks with spears and swords. The Elephants essentially charged into a death-trap!

I don’t remember reading that in any of the Mongol campaigns I’ve studied in any detail – but I’m no expert. Sorry I couldn’t be of more use! 😦

Comment by arvindpillai

new post soon?

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