How the whale learned to swim

A real Just So Story

The whale has not always been a giant of the ocean. Fifty million years ago, when the first whales appeared on Earth, they stalked the land, drifting through the deep shadows of the forests like the wolves and bears of today.

In those days, the different animals had not yet settled into the different roles that they occupy today. After the fall of the dinosaurs, the smaller animals that inherited their world had embarked upon a frenzy of exuberance and experimentation. Everywhere, there were hopeful new creatures seeking new and ambitious ways to make a living. New designs and new ways of life were tried, modified, tested and improved upon. The good ones survived and prospered. The bad ones were discarded into the dustbin of extinction.

It was a time of great opportunity in the world. For every possible way of life, there was an animal willing to give it a try. Some became browsers of leaves, and although at first they were not very good at browsing leaves, this did not matter, because in those days the leaves were soft and easy to reach. Some became hunters of other animals, and although at first they were not very good at hunting, this did not matter, because in those days the other animals were slow and easy to catch. Later on, the leaves would become tough and thorny, so that only those with the strongest teeth could chew them, and the animals would become swift and wary, so that only those with the sharpest wits and the sharpest teeth could catch them. As life became fiercer and more competitive, the animals would be forced to specialise in order to survive, and the age of experimentation would come to an end. But let us return to the story of the whale.

The first whale was an improbable and rather frightening creature. It was a hairy, four-footed beast, with an enormous, pointed snout like a crocodile's. It had legs like a goat's - complete with dainty hooves - and a long, muscular tail like a cat's. In its overall size and shape it resembled a wolf. Where this odd creature came from is a mystery, but some believe that it was a distant cousin of the hippopotamus.

The whale's story begins at a time in history when damp forests covered the entire world, from pole to pole, and even Antarctica was blanketed with trees. The whales lived along the banks of the dappled rivers and muddy pools that trickled through the forests, and ate the fish that swam there. At first the whales were not very good at catching fish, but this did not matter, because the fish were plentiful and the other animals of the forest were not very good at catching them either.

It was in those forest rivers and pools that the whales learned how to swim, and how to dive, and how to use their eyes and ears underwater. Their snouts grew longer, and their teeth became sharp and pointed for snatching at slippery fish. The whales' bodies became sleek and streamlined, allowing them to slide more easily through the water. Their legs became short and stumpy, and their feet became broad and paddle-like, with webbing between their dainty hooves.

Soon, the whales were masters of the waterways, expertly hunting fish and menacing any other animal of the forest that tried to cross the rivers in which they lurked. But the whales' new abilities came at a price. When a creature becomes adapted to a new lifestyle, it must leave its old one behind, and so it was with the whales. With their short legs and giant feet, they could no longer run through the forest, only waddle awkwardly up the riverbank. As time went by, the whales crawled onto land less often, and less easily, than before. They took to skulking beneath the water, where they lay in wait for their prey, alongside the crocodiles that shared their rivers and pools. The other animals of the forest learned to avoid the water's edge, for fear of being seized by the hungry whales and dragged into the depths.

As they lay in the murky water, perhaps the whales dreamed of the life they were leaving behind. Perhaps they imagined the rush of the wind through their fur, and the flutter of swiftly-trodden leaves beneath their hooves. Perhaps they dreamed of leaping and galloping. Perhaps they even wondered what it would be like to climb the trees whose branching outlines shimmered in the surface of the water. One thing they cannot possibly have imagined is that the sociable, monkey-like creatures that swung from those treetops would one day climb down and defy the whales' domination of the water. But that would not happen for a very long time yet.

The whales might have lurked in the rivers and pools forever, but instead some of them began to swim downstream. They swam to where the little forest rivers joined to form larger rivers, and onwards to where these rivers joined to form even larger rivers, and so on until the whales emerged into the shining blue expanse of the Tethys Ocean. The Tethys Ocean was one of those ancient seaways that disappeared long ago, erased from the map by the ceaseless movements of the Earth. Its waters teemed with silver shoals of fish, unlike anything that the whales had seen before. Once upon a time, the oceans had been the realm of giant cold-blooded monsters, such as the dragon-like mosasaur and the long-necked plesiosaur and the hideous pliosaur, but those creatures had died with the dinosaurs. When the whales arrived in the Tethys Ocean, they found themselves the masters of this vast and bountiful hunting ground. The whales gorged themselves on the silver shoals of fish. They grew larger and larger, and swam further and further from the shore.

At first the whales would lumber onto the beach to rest and to rear their young, as the seal and the sea lion do today. Yet soon the whales became so good at swimming that they could swim without ever stopping, from the moment of birth to the moment of death. From then onwards, they would never need to come ashore again.

At this point, the whales still had their four legs, with their big webbed feet and the tiny hooves on the tips of their toes. But nature is seldom extravagant, and equips creatures only with the things that they need in order to survive. When the whales no longer needed to walk on land, their legs began to shrink away. Instead of paddling with their feet, they learned to propel themselves with their thick tails, which grew immensely powerful, and sprouted triangular flukes from the sides. Eventually, the whales' hind legs shrank so much that they disappeared completely. As for their front legs, they lost their webbed toes and those dainty hooves, and became so thick and stumpy that they were no longer legs, but paddle-like flippers.

As the whales grew larger and more abundant, the fish they ate became scarcer and harder to find. The smaller whales cried out in search of food, and their cries were answered by a distant cacophony of echoes from the depths of the ocean. Sometimes an echo would be heard nearby, as the sounds were reflected from the silvery mirror created by a shoal of passing fish. The whales gradually learned that they could use these watery echoes to track down the shoals, and this is how sonar was invented. Such technology transformed these small whales from wandering hunters into precision-guided torpedoes, which could home in on their prey with military precision.

Meanwhile, the larger whales had developed a more leisurely way of finding their food. They learned to take great gulps of seawater and strain it through their gargantuan jaws, using their enormous tongues to lick up any fish trapped between their teeth. A mass of thick, hairy brushes sprouted between their teeth, so that even the slenderest fish could be strained from the water. The teeth themselves began to shrink away. Eventually, the whales' mouths were transformed into broad, hairy sieves, which could filter enormous amount of sea water and sift out not only fish, but also the clouds of tiny shrimp that swarm in the oceans. The whales began to migrate north and south, towards the polar waters in which the tiny shrimp were most plentiful. They became fat and blubbery, which helped them to keep warm in these icy regions (as the Earth was cooler now, and the coastlines of Antarctica were no longer warm and forested).

With such efficient ways of plundering nutriment from the oceans, the great whales grew to be the largest animals that had ever lived. For millions of years they ruled the depths. It seemed that they were invulnerable, but then came new sea monsters: metal hulks, equipped with sieves even larger than the whales', which emptied the fish from the waters. The new monsters had teeth, too, sharp teeth on sticks that pierced the whales' bodies and dragged their corpses back onto the shores from which their ancestors had long since departed.

That, perhaps, is the end of the whale's story.


The science behind the story

The earliest known 'whale' is a wolf-like beast called Pakicetus, whose 52 million year-old fossil remains were discovered recently in Pakistan. The skeleton of Pakicetus looks much like that of an ordinary land mammal, yet its skull has certain characteristic features that identify it as an ancestral whale. It possessed hooves on its feet and was clearly related to the ancestors of hoofed animals such as pigs and deer, although exactly where it fits into the family tree is unclear. Until recently it was believed that the ancestor of the whales belonged to a group of primitive hoofed animals called the mesonychids, but evidence now suggests that the mesonychids were the whales' cousins, not their direct ancestors. By comparing DNA sequences, some scientists have concluded that the hippopotamus is the modern hoofed animal most closely related to whales, which does not mean that whales evolved from hippos, but does suggest that the ancestor of whales was related to the animal that ultimately evolved into hippos.

A couple of million years after Pakicetus came Ambulocetus (whose name literally means "walking whale"), a weird beast almost perfectly intermediate between terrestrial animals and aquatic whales. Ambulocetus was three metres long with a flattened body and large carnivorous jaws, and may have lived like modern crocodiles, lurking in rivers where it ambushed its prey. It had enormous, paddle-like hind feet, with which it swam like an otter, and it could crawl awkwardly onto land.

Over the next few million years, whales became progressively more aquatic. By 40 million years ago, marine mammals appear in the fossil record that clearly resemble today's whales, although they retained tiny vestigial hind legs (which would have been useless for walking but may have been used to assist in copulation). Fossil whales from this period include the 18-metre giant Basilosaurus and the dolphin-sized Dorudon. Later, these primitive whales were replaced by the two great groups of modern whales: the baleen whales, and the toothed 'whales' (including dolphins and porpoises).



A while ago I had the idea of re-writing Kipling's Just So Stories so as to incorporate actual scientific knowledge about how the world came to be the way it is. This is a draft attempt at one of the stories; please let me know if you have any comments.

© Andrew Gray, 2005