and all modern and fossil cetaceans are characterized by the shape of one of the bones of
the ear, the tympanic bone, shown here. (In cetaceans, the tympanic bone can also be
called the bulla.) This bone has a thickened inner lip, the involucrum. In addition,
modern toothed whales have a very thin wall on the outside of the tympanic bone: the
tympanic plate. The tympanic bone cradles the middle ear cavity, in which the little bones
(hammer, anvil, and stirrup, together called the ear ossicles) that transmit sound reside.
their supposed land mammal ancestors,” a leading creationist, Duane
Gish, wrote five years after the discovery of those fossils in 1985.3
Whales have DNA similarities to artiodactyls4 (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 artio-
dactyls. 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.”5
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
6 | Chapter 1
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.6 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 open-
ing 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 over-
night. 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 emp-
tied of rock. I watch the process under the microscope. The acid is reveal-
ing 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 depres-
sion, 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).
Branches
(labeled cb and cl) are intermediate
These tiny bones transmit sound
Pakicetus
incus was discovered.
Pakicetus
All bones shown are from the left side but at different scales.
Note how the two projections of the incus of
Branching diagram (cladogram) that shows the relationships among whales and their relatives and the ear e 3.ru
fig
ossicles known for early fossil whales at the time the
through the ear in all mammals.
in proportions between a deer and a modern whale.
of the diagram left unnamed will be discussed in future chapters.
8 | Chapter 1
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 ear-
drum 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 Natu-
ral H
istory 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 cabi-
nets 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 com-
pared 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.7 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 Animal-
ium, 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.”1 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.2 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 oth-
ers think that Aristotle wrote mus, which means mouse or muscle).3
9
hairy fringe
faces tongue
right baleen rack
palate
left baleen rack
part anchored in palate
figure 4. Palate of a bowhead whale with baleen rack on both sides and lower
jaws removed. Water is gulped in through the gap between the racks at the tip of the
snout (on right of left photo) and is filtered through the baleen plates on left and
right sides (toward top and bottom of photo), which are not connected to each other
(as shown by Steve Ward). The hairy fringes of the plates form a matted sieve (visible
on left rack) used to strain food out of the water. These whales have more than three
hundred plates on each side of the jaw. This was a small, young whale. Older whales
have longer plates (right photo, author for scale).
figure 5. Head of a fetus of a bowhead whale showing areas that have hair (yellow
ovals) and close-up of hair on the chin of an adult bowhead whale.
Fish, Mammal, or Dinosaur? | 11
So, even in the fourth century b.c., scientists knew the critical features
that characterize a mammal: hair and nursing with milk. The great sys-
tematist 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 evo-
lutionary 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.” 4 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. 5
Thus, even people intimately familiar with whales, such as the crew
of Melville’s ship the Pequot, counted them as fish. Darwin’s Origin of
Species was published in 1859, eight years after Moby Dick. If the place
of whales in nature was a problem before the Origin, it got much worse
now. Mammals, fossil and recent, lived on land. If whales are mammals,
then their ancestors must have been land mammals. Darwin had diffi-
culty imagining a scenario in which evolution could shape a mammal’s
body to make it fit to return to the water. He describes one possibility in
the first edition of the Origin:
In North America the black bear was seen by Hearne swimming for hours
with widely open mouth, thus catching, like a whale, insects in the water.
Even in so extreme a case as this, if the supply of insects were constant, and
if better adapted competitors did not already exist in the country, I can se
e
no difficulty in a race of bears being rendered, by natural selection, more and
more aquatic in their structure and habits, with larger and larger mouths, till
a creature was produced as monstrous as a whale. 6
Of course, bears do not gather food this way, but Darwin did not
know that. The statement drew ridicule, and in subsequent editions it
gets shorter and shorter, and eventually disappears from the Origin
altogether. Darwin wrote in a letter to his friend James Lamont in 1861,
12 | Chapter 2
“It is laughable how often I have been attacked and misrepresented
about this bear.”7 Although he was convinced that whales, being mam-
mals, had ancestors that were derived from land mammals, the fossil
record did not preserve any intermediates. All known fossil whales were
obligate marine mammals. In Darwin’s time, the oldest cetaceans known
were basilosaurids—large whales with a streamlined shape easily recog-
nizable to anyone familiar with modern whales. One hundred and thirty
years later, when we found the Pakicetus incus, those were still the old-
est whales for which skeletons were known.
But when those first basilosaurid skeletons were found, they were not
immediately identified as whales. In 1832—before Darwin—twenty-
eight giant vertebrae washed out of the banks of the Ouachita River in
Louisiana. One of the vertebrae ended up with Dr. Richard Harlan in
Philadelphia, who published an account of the find in 1834.8 Harlan
said that the vertebra pertained to a giant lizard. He called it Basilosau-
rus, after the Greek basileus, king, and saurus, lizard. This was a mistake—making an ancient aquatic mammal sound like a terrestrial liz-
ard—but it was an understandable one. Whale vertebrae look different
from those of land mammals, and Harlan had only one. Additional
remains of a similar beast were found in 1834 and 1835 on an Alabama
The Walking Whales Page 2
