Books

'The Walking Whales' Is an Exceptional Example of What Accessible Scientific Literature Can Do

Evolutionary biology requires nimble flexibility of mind. Thewissen's engaging The Walking Whales: From Land to Water in Eight Million Years stretches its reach well beyond the arguments of calcified Creationists.

The Walking Whales: From Land to Water in Eight Million Years
J. G. M. Hans Thewissen

University of California Press

April 2019 (paperback)

Other

Even moreso than dinosaurs, the whale has long been a darling child of Creationists. To those who believe only what their eyes tell them (and what their hearts want to), the notion that the ocean's most massive and mighty creatures once started out on land, with fully functional limbs, seems a truly audacious claim. Particularly so given the lack of a clear intermediate-stage creature in the fossil record showing the whale ancestor in progress to its current form.

While the dwindling ranks of Creationists cling to their fictions even today, the fossil record is gradually being filled in. It hasn't been an easy process. Although ancient thinkers – including Aristotle – knew whales to be mammals, even this fact was disputed until recent times. Even Herman Melville's classic Moby Dick features a conversation among whalers who scoff at the notion the whale is a mammal, and argue vehemently that it is a fish. The chaotic early days of palaeontology didn't help, either. One famous 19th century fossil exhibit produced by entrepreneur Albert Koch purported to be that of an ancient sea serpent. It riveted the world for decades. But it was only a mash-up of various bones, including those of whales.

Fortunately, palaeontology is a much more systematic science these days, and one of the world's experts on whale evolution has penned a delightful book (now accessibly available in paperback) filling in much of the lesser-known details that have been uncovered in recent years. J. G. M. "Hans" Thewissen's The Walking Whales: From Land to Water in Eight Million Years chronicles what scientists have learned about that elusive intermediary stage between land and water. This work helps to reveal what the fossil record suggests about whales' early land-based ancestors, over 40 million years ago. Thewissen was responsible for many of the key breakthroughs, both in the field and in the lab, and his accessible yet scientific discussion of whale evolution is complemented by richly described narratives of field expeditions to the ancient graveyards of prehistoric whales: India, Pakistan and the Himalayas.

Evolutionary biology requires nimble flexibility of mind; figuring out which animals and species to fit into evolution's blank spaces is evocative of solving a crossword puzzle. Sometimes this means not going for the answer that appears most obvious but thinking through alternate possibilities. In the case of whales, researchers like Thewissen used computer simulations as well as live observation to study the swimming techniques of a broad range of animals in their quest to understand how a land mammal like the whale became an aquatic swimming mammal.

Otters proved to be a surprisingly useful guide. They're a fraction of the size of contemporary whales, but when you consider the broad type -- an animal that's sleek and graceful in the water, yet also functional on land, with tiny limbs. For which some species are more aquatic than others -- they're a helpful model. Their modes of locomotion -- which differ depending on the particular species -- reveal a lot about how a land mammal takes to the water, and how the early ancestors of whales probably learned to propel themselves in the seas. Much like otters and crocodiles (another useful model in some respects) some of these early whale ancestors were probably ambush hunters. Not particularly adept at hunting and eating either on land or in the water, they were likely best at ambushing prey by the water's edge, a liminal space between land and sea where their versatility came in handy.

How and why did they take to water? There's still much to determine, but Thewissen imagines a scenario in which the probable early ancestors of modern whales – a small raccoon-sized creature that resembles the mouse deer -- lived mostly on land, near the water, but when frightened or avoiding predators would hide in the water (as mouse deer do today). Eventually, this led to hunting in the water and greater overall proficiency in the water. Over subsequent millions of years the creature spent less and less time on land, and more in the water, shedding physical and biological traits it had used on land and honing new ones for its increasingly aquatic existence. A key turning point was the early whales' ability to operate in saltwater, as opposed to the freshwater environment in which they originated. The early proto-whales appear to have largely been limited to freshwater locales around what is today India and Pakistan, and so it was the ability to operate in saltwater that enabled whales to break out from that cetacean homeland and eventually conquer the oceans of the world.

Technological developments in the field of evolutionary biology in recent years have been remarkable. Thewissen recounts – in prose that starts off accessible enough for the novice yet gradually becomes complex enough for the expert – how some of these developments work and how they've aided his studies. It is possible, for instance, to do a range of studies on bone, allowing scientists to determine a great deal about the environment in which its owner lived, and to speculate quite reasonably on some of the types of tissues contained within and through the bone.

Final ambulocetus illustrattion by © Jacqueline Dillard courtesy of California University Press

All of these techniques enable a tremendous amount of information to be extrapolated about how now-extinct species grew, developed, and lived. Where once palaeontologists had to struggle to piece together evolutionary lineages by hand and on paper, now computers are able to compare vast numbers of traits among fossils to determine which biological development most likely led to others, and thereby which fossil species are most closely related to each other, and to living species in the present. Hippos, surprisingly, turn out to be the closest living land mammal to the early terrestrial ancestor of both whales and hippos.

Palaeontology is a beautiful combination of biology and geology, two seemingly disparate sciences that come together in the study of ancient life forms and evolution. Biology is obviously necessary to understand how an ancient animal lived, moved, ate, and reproduced. Geology is necessary for understanding how fossils formed from the remains of the animal; and also for understanding the ancient ecology of the fossil's environment, which was tremendously different from its provenience -- the location in which the fossil is found today.

In the case of whales' ancient forebears, many of their fossils have been found in the dry, wind-swept mountains and deserts of Pakistan. But millions of years ago, this area was a vast sea. Thewissen, describing his field trips in pursuit of fossils, chronicles the dramatic transformation of this environment in riveting detail, complementing it with lively on-the-spot descriptions as he traverses remote valleys and terrifying mountain passes. Millions of years ago, India and Africa were divided by a vast sea, and it was here that the ancestors of modern whales thrived. But the Earth's restless tectonic activity drove Africa relentlessly toward Asia, filling in the sea, crushing a range of islands between them, and spouting volcanoes as the land moved. Eventually Africa crashed into Asia, and the resulting impact created the Himalayas, pushing the earth upward where the two land masses collided.

This is the landscape in which Thewissen and others now hunt for the fossil remains of early whales, discovering evidence of the ancient sea in the cliffs of remote mountain valleys and wind-swept deserts in which the sands capriciously reveal hidden secrets of the vibrant life that once inhabited this place. Much as the processes of biology and geology shape the context in which palaeontologists work, there is an important human dimension at play as well. Key expeditions to follow up on important fossil finds are disrupted by outbreaks of violence, militarism and geopolitical machinations. Thewissen eventually had to give up much of his work on important sites in Pakistan, pursuing ancient whales in neighbouring India instead.

Even there, important discoveries were subject to the capricious vagaries of human nature. He recounts in one chapter his efforts to cajole the idiosyncratic German widow of an Indian fossil-hunter to allow him to study the vast caches of fossils that have lain unexamined in bags strewn around her property for years. He succeeds, against the odds, and the resulting finds proved worth the complex years of effort it took to secure permission.

Likewise he visits Japan, eager to study a biological anomaly that has been captured there – a live dolphin with limbs – which promises to teach a great deal about how whales' 'missing link' probably lived. Yet here his efforts are stymied: Japan is a whale-hunting, dolphin-hunting nation, and the politics of its powerful whale lobby produce a stand-offish attitude to the interests of western, whale-conserving scientists. Of course, not all Japanese scientists adhere to the politico-industrial whale complex that still grips their nation, and Thewissen provides a nuanced vantage into how the complex politics of whale conservation affect even his research on ancient whales.

The Walking Whales is a masterpiece of accessible palaeontology. Easily understandable to the interested novice, Thewissen also provides ample scientific detail for the expert or student wishing to build on his work. The full-colour, full-page illustrations produced by Jacqueline Dillard are nothing short of stunning. The book's proliferation of scientific illustrations (charts, skeletons, evolutionary diagrams, close-up comparisons of different body parts and fossils), coupled with gorgeously reconstructed scenes of ancient whales and their habitat, render the book both profoundly educational and a deeply pleasurable experience to read. This is an exceptional example of what accessible scientific literature can do, and a great model for other scientists to follow.

It's also a reminder for those hiding their heads in the Creationist sand that everything has a scientific answer – even if it just takes a while to get there.

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