The Walking Whales: From Land to Water in Eight Million Years

The Walking Whales: From Land to Water in Eight Million Years

by J. G. M. Hans Thewissen

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ISBN-13: 9780520959415
Publisher: University of California Press
Publication date: 11/13/2014
Sold by: Barnes & Noble
Format: NOOK Book
Pages: 248
Sales rank: 457,376
File size: 14 MB
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About the Author

J. G. M. "Hans" Thewissen is Ingalls-Brown Endowed Professor in the Department of Anatomy and Neurobiology at Northeast Ohio Medical University. His main research interest is the study of whales, particularly their adaptations to life in water and their origin as land mammals. He discovered in 1994 the skeleton of the first-known whale that could walk on land (Ambulocetus), and he has led more than ten field expeditions each to Pakistan and India, collecting fossil whales. He is coeditor of Encyclopedia of Marine Mammals (2002), Emergence of Whales (1998), and Sensory Evolution on the Threshold (UC Press, 2008).

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The Walking Whales

From Land to Water in Eight Million Years


By J. G. M. "Hans" Thewissen, Jacqueline Dillard

UNIVERSITY OF CALIFORNIA PRESS

Copyright © 2014 The Regents of the University of California
All rights reserved.
ISBN: 978-0-520-95941-5



CHAPTER 1

A Wasted Dig

FOSSILS AND WAR


Punjab, Pakistan, January 1991. I am excited beyond belief! The National Geographic Society is giving me money to collect fossils in Pakistan: my very own field project, the first time ever. For years, it has been great to collect fossils in exotic places—Wyoming, Sardinia, and Colombia. But this is different. Now I can run my own program, decide where to collect, and study what is found. It's exciting but also daunting. My friend Andres Aslan will come with me. We're perfect complements: he loves geology and I love fossils. We're both just out of school, freshly minted PhDs, and together we're ready and able to set the world on fire, or at least vacuum up any fossil between Attock and Islamabad.

It is Andres's first trip to Pakistan. I first went there as a paleontology student in 1985, during the Soviet occupation of Afghanistan, when the CIA channeled much of its support against the Soviets through Pakistan. Trucks full of equipment would travel the highway, the Grand Trunk Road, from Islamabad to the Afghan border at night—the very same road we took to our field area. The Soviet-backed Afghan government retaliated by trying to disturb the stability of Pakistan. Car bombs were the weapon of choice, and my hotel room in Islamabad offered an excellent view into the courtyard of the police station next door, where a line of charred, exploded mini-busses were evidence of their success. With mirrors tied to long poles, the police stopped every vehicle entering the city and checked the underside for bombs. This didn't bother me, as long as I could collect fossils, studying life from a very exciting period in earth's history, fifty million years ago.

Now, six years later, Andres and I arrive in Pakistan just before the New Year and receive our permits to work in the Kala Chitta Hills, west toward the Afghan border (figure 1). The television in our Islamabad hotel is showing CNN stories about the Iraqi invasion of Kuwait last year, but that conflict seems distant. I am here to immerse us in the greatest excitement paleontology has to offer: collecting fossils, being the first to see and figure out each one I pick up.

We check in at a hotel in the town of Attock, and fieldwork starts on January 1. We travel to remote sites that I chose from decades-old reports from other paleontologists. The rocks here in the shadows of the Himalayas have their own distinctive charms. They are gnarled, bent, twisted, and overturned, all the result of the mountain-building to the north. They are silent witnesses to the incredibly violent forces that raised the Himalayas to be the world's highest mountains. With a sense of poetry, my Pakistani colleague, Mr. Arif, calls the limestone that has been tossed into tight bends "the dancing limestone."

We search the dry scrublands every day, but fossils are rare; things take time. In my fieldbook I have logged fifty-one fossils. None seem exciting—small pieces of fishbone, crocodile armor, fish teeth, and a piece of the casing of the ear of a whale, the tympanic bone. It is not the first whale bone I ever found. Growing up, in Holland, I lived close to a fossil locality where my father used to take me. A river had dropped rocks there that it collected as it cut through mountains upstream, in Belgium, France, and beyond. There was everything from sea lilies hundreds of millions of years old, to plant fossils from coal swamps, and large fossil whale bones from when that area was covered by ocean, just a few million years ago. It cemented my interest in fossils, and for my twelfth birthday I got a rock hammer, which is still the hammer I use now.

I have never studied whales before, and now too, whale bones are no good for me. The money from the National Geographic Society is for studying how land mammals migrated between Indo-Pakistan and Asia across the Tethys Sea some fifty million years ago. Whales are of no use for studying migrations on land. I need land-dwelling mammals, and many more fossils, if this grant is to be successful. I am very aware that failing to deliver on a first grant can sink a career.

On day five the dream collapses. The United States is threatening to invade Kuwait, and the U.S. government is worried about the safety of its citizens. Mr. Arif is told by his superiors at the Geological Survey of Pakistan to escort us back to Islamabad, the capital. All my plans are crumbling before my eyes. The reason for going back to Islamabad seems ridiculous—the conflict is in the Gulf, not Pakistan. The physical dangers seem much smaller than when I first visited. Why should politics end the field season?

Reluctantly, Andres and I return to Islamabad and check into a hotel. The hotel is in the Blue Area, Islamabad's broad central avenue with shopping areas, as well as the buildings of the president, prime minister, and congress. It's a mile or so from the American embassy.

We hang around our hotel room, waiting for news. On TV, the foreign minister of Iraq, Tariq Aziz, and the U.S. secretary of state, James Baker, are sparring. Mr. Arif tells us that we will be kicked out of Pakistan if war breaks out, and we will not be allowed to go back to the field. We visit the American consulate, pleading, hoping they will support our cause. The consulate is a fortress, with a concrete moat around it, double gates with Pakistani guards, and a second gate with U.S. marines and watch towers.

Inside, the mood is tense. "Too dangerous for foreigners," says a trembling scientific attaché who seems younger than we are. "Who knows what might happen? They burned down the American embassy here in 1979."

I am Dutch by birth, so I also visit the Dutch consul, who works in a small office suite in the middle of the bustling Blue Area. Here the mood is different. He laughs at such comments. "There might be demonstrations, but it is unlikely that the Pakistanis will turn against foreigners if the United States attacks Iraq in Kuwait. Just keep a low profile and stay away from cities. In the countryside you will be fine."

Ironically, our Pakistani colleagues have moved us from the countryside into the city. I am so frustrated. I feel like an irrelevant extra in someone's movie script. In the hotel room we watch CNN nervously. The talks between Aziz and Baker collapse on January 9. We are told we must leave. Dejected, we wait as my Pakistani friends find a flight for us. It goes through Moscow. As the plane takes off from Islamabad International Airport, it flies right over our field area in the Kala Chitta Hills. I don't look out the window. On our second stopover, in Amsterdam, I hear that Operation Desert Storm has started: the United States is invading Kuwait.


A WHALE EAR

Our meager fossil finds travel back to the United States with us. Back at Duke University in North Carolina, where I am a postdoctoral associate, I slowly expose the fossils, carefully scraping the rock around them with dental tools and applying glue to cracks. None of them seem very exciting, but they are all we have, and it is good practice to take care of all fossils collected. The whale tympanic bone is a lot of trouble. For starters, this bone is already known to science from this region. In 1980, American paleontologist Robert West was the first to recognize, based on the teeth, that whales once lived in Pakistan. A year later, Philip Gingerich of the University of Michigan described a whale's braincase from a locality across the Indus River from West's. That fossil also had a tympanic bone, and Gingerich named it Pakicetus, Latin for "Pakistan's whale."

Although scientists agree that these finds are whales, and very primitive whales at that, little is known about them. For the most part, these fossils did not impress the general public or the scientific community. Creationists in those days used whales as a prime example of why the fossil record does not support evolution. "There are simply no transitional forms in the fossil record between marine mammals and their supposed land mammal ancestors," a leading creationist, Duane Gish, wrote five years after the discovery of those fossils in 1985. Whales have DNA similarities to artiodactyls (even-toed ungulates such as hippos, cows, and pigs), so they had long been considered the likely ancestors of whales. Gish ridiculed evolutionists for inferring from those molecular similarities that whales were derived from artiodactyls. He dubbed the idea the "Bossie-to-blowhole" transition and called it an "udder failure." As late as 1994, Gish called Pakicetus "a land mammal with no relationship to marine mammals."

The tympanic bone of a whale (figure 2) looks like half of a walnut shell, a bowl-shaped bone with a central cavity. In addition, it has a very thick wall on one side and a very thin wall on the other side. The thin part is called the tympanic plate, and attached to it is an S-shaped crest of bone, the sigmoid process. The thick wall, known as the involucrum, consists of dense bone, much denser than that of other parts of the body. These are the critical characteristics of a whale's ear bone, unique to whales and their relatives, dolphins and porpoises; together, all these mammals are referred to as cetaceans. All cetaceans have a tympanic with an involucrum, and no other animal is known to have one. There are other features that are present in all modern whales and present in no other mammal, such as a blowhole, which is essentially a nose opening located way back on the forehead—but ancient fossil whales don't have blowholes. Other features, including the S-shaped sigmoid process on the tympanic bone, are present in all modern and fossil cetaceans—but they aren't unique to whales: some other mammals have them too. So, for an anatomist, the ear makes the whale.

The cavity in my tympanic bone is filled with rock, and that rock needs to come out. In the morning, I put the bone in a little jar of weak acetic acid, which is similar to very strong vinegar. The acid eats the rock, which fizzes like soda as it dissolves, and exposes the bone. The fossil comes out in the late afternoon and is rinsed under running water overnight. Then the newly exposed bone is dried and a layer of glue applied, to keep the acid from eating the bone. Then the fossil is ready for its next acid bath. This is slow: a layer thinner than a fingernail is removed by the acid in each bath. But week by week, the cavity in the tympanic is emptied of rock. I watch the process under the microscope. The acid is revealing a small lump of bone, inside the tympanic, which I assume was a loose bit of bone that got trapped there before fossilization. As the weeks wear on, the acid exposes more parts of this internal bone, revealing its odd shape. It is triangular, with a joint at its broadest side, and a thin bony bar coming off another side. The joint is not a simple round depression, but rather two depressions joined by a low crest. This is intriguing; it livens up the dull acid preparation process. I perk up, and look forward to seeing if each acid bath will reveal more of it.

Acid preparation is tense. Things can go wrong. If a crack in the bone goes unnoticed, the acid can slip behind the protective glue and crumble the specimen itself. Thankfully, this doesn't happen. After innumerable acid baths, eventually the entire bone is released from its forty-nine-million-year entombment in rock. It falls out of the tympanic shell into my palm, and I inspect the fossil under a microscope. I now see what it is: one of the three little ear bones, ossicles they are called, that transmit sound from the eardrum to the center of the ear. This tiny bone, the size of a grain of rice, has been preserved inside this ancient whale's ear since it died (figure 3).

These three bones are rarely preserved in fossils because they are so tiny and easily lost. But they are both important and diagnostic. They are called the hammer, anvil, and stirrup (or the malleus, incus, and stapes in scientific texts), and their names loosely describe their shapes in land mammals. By vibrating, the bones transmit sound from the eardrum to the fluid-filled cavities near the brain, where the vibrations are translated into signals that are passed on to the brain. The ear ossicles of some marine mammals, like whales and seals, look very different from those of land mammals. This probably has something to do with hearing sounds in water, but no one knows exactly what. I realize that because Pakicetus was a very early whale, its ear ossicles might be important. But I wasn't looking for fossil whales, and I don't know enough about them. I need some bones to which I can compare my discovery.

I read and read, and set off on a trip to the National Museum of Natural History at the Smithsonian Institution to study bones and fossils. The vaults behind the public exhibits there have scientific treasures—drawers full of fossil bones and teeth. The basement of another wing holds cabinets full of skulls and skull parts of modern cetaceans and seals. It becomes clear that whale ossicles are different from those of land mammals, but that all known whales have similar-shaped ear ossicles, including the gigantic blue whale, the modest-sized porpoise, and all fossil whales.

The Pakicetus ossicle turns out to be an incus—the anvil. But it is different from the incus of a cetacean, as well as from that of a land mammal. The incus of land mammals has two thin bars of bone sticking out of it; they are called the crus breve and the crus longum. Brevis and longus mean short and long in Latin, and that is indeed their relation in most mammals. But the relation is opposite in the little bone I have found in Pakicetus. The crus longum in this bone is fat and short compared to that of land mammals. Although different from most land mammals, the relative length of the crus longum and breve is actually similar to that of some even-toed ungulates, like deer and hippos. The position of the joints is different, too: they face differently in Pakicetus than in land mammals, and are oriented in a third way in in whales.

We write up a short paper about the bone, which makes it into the prestigious scientific journal, Nature. Our five-day field season was not a complete bust after all: our wasted dig vindicated itself, although in an unexpected way.

CHAPTER 2

Fish, Mammal, or Dinosaur?

THE KING LIZARD OF CAPE COD


Exciting though it was, that single ear bone from Pakicetus did not help us understand just what the earliest of whales looked like. For that, you need entire skeletons. And in 1992, the only ancient whale skeletons known were around forty million years old, compared to Pakicetus's forty-nine million, and they were from other continents—Africa and North America. Finally, they looked quite a bit like modern whales.

Whales, together with dolphins and porpoises, make up the Cetacea, and cetaceans are mammals, not fish. This was known at least as early as in Aristotle's time (384–322 B.C.). He wrote, in his Historia Animalium, that whales have lungs, and that "the dolphin is viviparous, and accordingly, we find it furnished with two breasts, not situated high up, but in the vicinity of the genitals ... and its young have to follow after it to suckle." He also distinguished two groups of cetaceans. These are now called suborders: baleen whales (Mysticeti), like humpbacks, and toothed whales (Odontoceti), like killer whales. Toothed whales usually do have teeth. Aristotle observed that mysticetes had no teeth, but had "hairs that resemble hog bristles." Mysticetes have baleen in their mouth, plates of a horny material used to filter food (figure 4). Aristotle's "hog hairs" refer to the occasional hair on the upper lip and chin of some mysticetes (figure 5).Mustax in Greek means moustache, and ketos, sea monster, so he called mysticetes mustached sea monsters (although others think that Aristotle wrote mus, which means mouse or muscle).

So, even in the fourth century B.C., scientists knew the critical features that characterize a mammal: hair and nursing with milk. The great systematist Linnaeus cemented this view in the eighteenth century. But even though scientists knew that whales were mammals, laymen did not. For many, whales' complete adaptation to life in the water blurred their evolutionary origins. Herman Melville published Moby Dick in 1851 and Melville's protagonist, the whaler Ishmael, takes on the scientists:

In his System of Nature, A.D. 1776, Linnaeus declares, "I hereby separate the whales from the fish." But of my own knowledge, I know that down to the year 1850, sharks and shad, alewives and herring, against Linnaeus's express edict, were still found dividing the possession of the same sea with the Leviathan. The grounds upon which Linnaeus would fain have banished the whales from the waters, he states as follows: "On account of their warm bilocular heart, their lungs, their movable eyelids, their hollow ears, penem intrantem feminan mammam lactantes," and finally, "ex lege naturae jure meritoque." I submitted all this to my friends Simeon Macey and Charley Coffin, of Nantucket, both messmates of mine in a certain voyage, and they united in the opinion that the reasons set forth were altogether insufficient. Charley profanely hinted that they were humbug. Be it known that, waiving all argument, I take the good old fashioned ground that the whale is a fish, and call upon holy Jonah to back me.


(Continues...)

Excerpted from The Walking Whales by J. G. M. "Hans" Thewissen, Jacqueline Dillard. Copyright © 2014 The Regents of the University of California. Excerpted by permission of UNIVERSITY OF CALIFORNIA PRESS.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

Table of Contents

1. A Wasted Dig
Fossils and War
A Whale Ear

2. Fish, Mammal, or Dinosaur?
The King Lizard of Cape Cod
Basilosaurid Whales*
Basilosaurids and Evolution

3. A Whale with Legs
The Black and White Hills
A Walking Whale

4. Learning to Swim
Meeting the Killer Whale
From Dog-Paddle to Torpedo
Ambulocetid Whales*
Ambulocetus and Evolution

5. When the Mountains Grew
The High Himalayas
Kidnapping in the Hills
Indian Whales

6. Passage to India
Stranded in Delhi
Whales in the Desert
A 150-Pound Skull

7. A Trip to the Beach
The Outer Banks
A Fossilized Coast

8. The Otter Whale
The Whale with No Hands
Remingtonocetid Whales*
Building a Beast out of Bones

9. The Ocean Is a Desert
Forensic Paleontology
Drinking and Peeing
Fossilized Drinking Behavior
Walking with Ambulocetus

10. The Skeleton Puzzle
If Looks Could Kill
How Many Bones Make a Skeleton?
Finding Whales’ Sisters

11. The River Whales
Hearing in Whales
Pakicetid Whales*
September 11, 2001

12. Whales Conquer the World
A Molecular SINE
The Black Whale
Protocetid Whales*
Protocetids and History

13. From Embryos to Evolution
A Dolphin with Legs 
The Marine Park at Taiji 
Shedding Limbs 
Whaling in Taiji
 
14. Before Whales 
The Widow’s Fossils 
The Ancestors of Whales 
Indohyus* 
A Trust for Fossils 

15. The Way Forward 
The Big Question 
Tooth Development 
Baleen as Teeth 

Notes 
Index 
*These six headings summarize the biology of the six fossil groups that form the transition between whales and their terrestrial ancestors. Their relationships to each other and to the living families of cetaceans (whales, dolphins, and porpoises) are given in figure 66.

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