this thing, and no resolution as to what it is. I decide to give in.
The numbers in the fieldbook identify which packages, wrapped in
toilet paper, were found near the skull. I select two: the ear and the
lower jaw. The floor of the veranda becomes littered with pink toilet
paper as I unwrap them.
The ear part puzzles me. It is the size and shape of a small potato, and
the bone is extremely dense, pachyosteosclerotic. One side is broken,
but a thin lip of bone must have been attached here. There must have
been a cavity there. The ears of elephants and sirenians look nothing
like this. I feel that I should recognize it, but I do not.
Next comes the jaw. It is partly encased in rock, but some black tooth
enamel is visible. I work on it with dental tool and toothbrush, exposing
the side. It too fails to match my expectations. I am expecting the flat
and squarish molar teeth of anthracobunids, but this tooth is exactly the
opposite: high and triangular, with a second small triangular expansion
behind. This is clearly not a sirenian relative. Then, what was it?
Suddenly, it hits me like a train. Whales have teeth like that. The
potato-thing is the involucrum of the ear, dense as it should be.
This is a whale—a whale with, well, hind limbs. The first whale that
walked. It is like a fog suddenly lifting, exposing a big city where there
seemed to be nothing before. I sag back against a pillar of the porch
with the jaw in my lap and the large orange setting sun stinging my face.
We have discovered the skeleton of a whale that could walk and swim—
the transitional form that paleontologists have wished for, and that
creationists said would never be discovered.
I slowly recover. Dramatic intermediate forms are so rare in the fossil
record that one really cannot count on ever finding one in one’s lifetime.
Understating the find, I write in the margins of my fieldbook for Febru-
ary 20:
Decided that Arif’s skeleton must be a whale (tooth and bulla). . . . There
may be more in the wall, deep to what we have. 5
It is clear that this is important and that more digging needs to be
done. However, not now—the layer in which the fossil sits goes deeper,
but it is difficult to access, and the field season is nearly over. The logis-
tical predicament of my situation also forces itself on me: I am broke.
Even if I dig all of it up, I will not be able to take it all home. As a mat-
ter of fact, I can’t even bring everything home that I have right now. This
48 | Chapter 3
skeleton needs three or more suitcases. Each extra suitcase means a fee
of about $100, which I do not have. Moreover, it will take several years
to get everything out of the rock, so even if it did come home, money
would be needed to hire a professional fossil preparator.
I have to make a choice, and I choose the skull. That is the part that
shows that this is a whale. The skull is also the part that is most difficult
to prepare, and without it, no publication is possible. After the skull is
out of the rock, the rest will be easy, and the excitement that it stirs may
make it possible to get more money and come back here.
Back in Islamabad, I carefully pack the other remains in extra layers
of newspaper and store them in two crates that used to hold oranges.
Arif will safeguard them. The skull is swaddled in my dirty field clothes
and goes in my suitcase.
Back in the United States, the work progresses slowly. I present my
find in October of 1992 at a convention in Toronto that is attended by
most vertebrate paleontologists. I am excited, and show lots of pictures
of the skull, but I cannot show the hind limbs, I can only talk about
them. Colleagues are polite but reserved. They buy the animal as a
whale; after all, I can show them the teeth and the ears. However, with-
out pictures of hands and hind limbs, they are unconvinced. True to
their scientist nature, they are skeptical, reserving judgment until the
bones can be viewed. The next year, Philip Gingerich, who collects in
central Pakistan, offers to bring my orange crates back for me if I give
him a sneak preview of what is inside. I gratefully accept, and the skull
is reunited with its feet.
Finally, in 1994, all is ready and the beast can be presented to the
scientific community and the public.6 I also get to give it a name (figure
19). The animal represents a new genus and species, and is so different
from all other whales that it is a new family of whales, too: Ambuloce-
tus natans, in the family Ambulocetidae. The genus name describes
what is most unusual about this fossil: it is a whale that walked. Ambu-
lare is Latin for walking, and natans means swimming. It is the walking
and swimming whale. In the week that my article is published, I spend
most of my days talking to journalists about the find and its importance.
I am not ready for all the press attention—my early interviews are
clumsy—but the excitement it stirs up is exhilarating.
Scientist colleagues are excited now, too. Stephen Jay Gould devotes an
essay to the find.7 He writes, “If you had given me a blank piece of paper
and a blank check, I could not have drawn you a theoretical intermediate
any better or more convincing than Ambulocetus. ” Discover magazine
figure 19. Life reconstruction of the fossil whale Ambulocetus natans, which lived in
what is now northern Pakistan approximately forty-eight million years ago.
Ambulocetus spent most of its life in water, but was able to come onto land, too.
50 | Chapter 3
includes whale origins in its top science stories of 1994. Ambulocetus
opens the door to the recognition that the origin of whales is indeed
documented in the fossil record. It is an exception to the common wisdom
that transitional forms are difficult to find. I am excited about the oppor-
tunity to study how organ systems were transformed as whales evolved to
become aquatic, from land to water. The first system I want to study is
locomotion.
Chapter 4
Learning to Swim
meeting the killer whale
Stephen Jay Gould’s essay in Natural History 1 highlighted one phrase in
the article describing Ambulocetus: the phrase “the feet are enormous.”
He liked it because it cut through jargon and expressed some excitement.
Indeed, Ambulocetus’s hind feet are as big as clown shoes, presumably
because they become powerful oars in the water. The hands (or forefeet)
are much smaller. In modern days, seals have feet bigger than their hands2
because they use the former for propulsion when swimming, not the lat-
ter.3 But seals and whales are not related, and all modern whales swim
with their tails, so it is surprising that Ambulocetus had large feet. Also,
in true seals (Phocidae in Latin), the feet move side to side in swimming,
whereas a whale’s tail moves up and down. Whales descended from
quadrupedal (four-footed) land mammals, and that implies that their
propulsive organ changed from limbs to tail. Ambulocetus showed that
the feet were important in swimming, and thus, foot-propelled swim-
ming came before tail-propelled swimming. But that leaves the question
as to how those feet moved—was it up and down, like the tail in a mod-
ern whale, or side to side, like the feet in a swimming seal?
The fossils only go so far regarding those kinds of questions. Instead,
one has to understand swimming in living mammals. I contact Frank
Fish, who has studied swimming in mammals for most of his life. Frank
is an avid swimmer himself, and, incidentally, knows all the jokes that
people make linking his name with his field of research. Frank puts
51
52 | Chapter 4
animals in a flow tank, which is an aquarium or pool where he can
change the water flow, and films them swimming. Then he analyzes their
movements in slow motion at different flow speeds, and applies his
engineering knowledge to understand why which parts move. Musk-
rats, for instance, swim by paddling with their feet. Their tail is flat from
side to side, and it moves through the water like a corkscrew that bal-
ances the animal but contributes little to propulsion.4 Frank’s tank is
too small for big mammals, so those he studies in marine parks. Frank
is intrigued about Ambulocetus and invites me to come out and see his
operation filming killer whales in a marine aquarium.
The filming is done early in the morning, before the park opens to the
public. The trainer opens a door so we can go behind the scenes. As I
walk in, a large black head suddenly emerges from the holding pen next
to me and its eye stares directly at me. The killer whale has realized that
we are not his trainers and caretakers, and checks us out. I am not used
to having such a large living animal so close. It is unsettling.
Frank sets up cameras on long extension poles and arranges ladders
to stand on while the trainers play with the whales. When they are
ready, Frank mans the camera, shouting requests to the trainer.
“Now I want him to come full speed right underneath the camera.”
With hand and sound signals, the trainer transmits the command,
and the whale obliges.
“He just turned a bit when he was under the camera, can we do that
again?”
I just stand around, absorbing the scene. The whales seem happy
with the attention. This routine is different from what they usually do,
and they appear eager to be part of it. As a matter of fact, one of the
whales not involved in Frank’s movie is looking over the wall between
the two tanks. His trainer does not want him to feel ignored and throws
a fish. The whale dives down and picks up a yellow maple leaf from the
bottom of his tank. He sticks out his tongue to the trainer with the leaf
on it. The trainer takes the leaf and throws it back in the water. A game
of fetch starts. The trainer gently tugs the whale’s tongue. The whale
pulls back, but immediately sticks its tongue out again. Killer whales
like having their tongue massaged.
from dog-paddle to torpedo
Frank has studied many whale and dolphin species, and they all swim
similarly. When they propel themselves in a straight line, whales and
Learning to Swim | 53
dolphins use their tail, not their forelimbs (the flippers).5 The fluke is
pushed through the water, up and down, and both the upstroke and the
downstroke help propel the whale. That is unlike swimming in humans.
When humans do the breaststroke, the part of the stroke that closes the
legs provides propulsion. It is called the power stroke. The rest of one
cycle of the legs is the recovery stroke; it does not help with propulsion
but just brings the legs back into position to be able to initiate another
power stroke. A swimmer’s speed falls during the recovery stroke. In the
movement of whale flukes, there is no recovery stroke. It is obviously a
much more efficient way to move, and similar to flapping bird wings6
and fish tails,7 even though those move very differently from flukes. Engi-
neers call the force that moves the animal the lift force, and the surfaces
that make lift (feet in seals or tail in cetaceans) are called hydrofoils. A
special shape makes it possible to reorient the hydrofoil in such a way
that propulsion is generated throughout the cycle. The movement
through the water is complex, too. Hydrofoils differ in this way from
paddles such as the oars of a rowboat or the feet of a human doing the
breaststroke.8
Frank refers to the whales’ mode of locomotion as caudal oscillation,
because the tail is the hydrofoil ( cauda is Latin for tail) and it swings
back and forth. Most of the movement occurs in one area at the root of
the tail, right where the ball vertebra is located, and known to exist in
basilosaurids (see chapter 2). It works much like the hinge of a door.
A whole new world opens for me as I help Frank. My previous
insights into locomotion came from the perspective of the boxes full of
bones in museums and labs. That perspective leads to insights. It makes
sense that seals have short legs with large feet. They can make short but
powerful strokes, which is good for moving in a dense medium like
water, but bad for land locomotion. But Frank’s way of looking at the
whole animal adds the actual movement, a new dimension.
Frank’s work shows that mammals swim in very different ways.
Whales and dolphins, and also manatees and dugongs (figure 12), swim
by caudal oscillation when they go in a straight line. They keep their
body stiff, streamlined like a torpedo. Seals are pelvic oscillators: their
hind limbs move through the water side to side, without involvement
from the tail.9 Sea lions drag the back of their bodies when swimming,
and are propelled by their large, wing-like forelimbs. The movements of
those forelimbs resemble the wing beat of a bird;10 that mode of loco-
motion is called pectoral oscillation. Cetaceans, sirenians (seacows),
seals, and sea lions are the most aquatic mammals, but there are many
54 | Chapter 4
other mammals that are good swimmers. Polar bears and some moles
drag their hind limbs and paddle with the forelimbs (pectoral paddling),
whereas beavers hold their forelimbs close to the body and paddle with
their hind limbs (pelvic paddling).11 There is a diverse world of swim-
mers out there that should help us understand why the fossils of past
swimmers looked the way they looked.
Frank had thought about evolution, too, and after collecting data on
lots of swimming mammals, he put it all together (figure 20), proposing
how more efficient ways of swimming evolved from less efficient ones.12
For the caudal oscillation of whales, understanding the swimming
modes of otters and their relatives proved to be key.
The otters are in the same family of carnivorous mammals as com-
mitted landlubbers such as badgers, skunks, and wolverines, and that
family also includes sleek-bodied weasels and martens. The otters all
look similar in form—long and narrow bodies with short legs—but
their extremities are very different. River otters have a short but rela-
tively muscular tail and limbs. Sea otters are large-bodied, and they have
very large, asymmetrical hind feet, with the little toe much longer than
any of the others, and a little stub-like tail. Finally, in South America
lives the giant freshwater otter, Pteronura brasiliensis. It is as big as a sea
The Walking Whales Page 8