198 ■ CHAPTER 11 Evidence for Evolution
EVOLUTION
tipped with hooves, lived close to and had an
affinity for the water.
The first clues about Indohyus’s lifestyle came
from its teeth. Oxygen in the molecules that
make up teeth comes from the water and food
that an animal ingests. Levels of oxygen isotopes
in Indohyus’s teeth match those of water- going
mammals today, suggesting that Indohyus
lived near and potentially spent a significant
amount of time in the water. It also had large,
crushing molars with levels of carbon isotopes
that suggest it grazed on plants, as do hippo-
potamuses and muskrats that graze near and in
water (Figure 11.8).
Lisa Cooper, a graduate student in Thewis-
sen’s lab at the time, identified another adapta-
tion to the water: Indohyus’s leg bones. From the
outside, the limbs of Indohyus look like those of
any other mammal walking around on land. But
on the inside, it’s another story. Cooper cut out
a section of bone from a limb, ground it down
until she could see light through it, and then
looked at the bone under a microscope. She saw
that a thick layer of bone was wrapped around
the bone marrow.
“Hans already had lots of bones of the earli-
est whales, and they all had extraordinarilyanimal that preceded them all—the ancestor
that lived on land. If Thewissen had to guess
where those fossils might be, it was Kashmir,
and potentially in Ranga Rao’s basement.
Unfortunately, Ranga Rao’s widow was
protective of the fossils, worried that someone
might steal her husband’s property and legacy.
But each year, Thewissen visited her, chatted
with her, and gained her trust. When she passed
away in 2007, she made Thewissen cotrustee of
her estate, and suddenly the fossils, which had
sat in dusty piles for 30 years, were available
for study.
“I focused on taking the rocks back to the
U.S., and having my fossil preparers remove the
fossils from the rocks, which is very difficult,”
says Thewissen. From Ranga Rao’s collection,
Thewissen identified more than 400 bones that
belonged to Indohyus. By collecting a thighbone
here and a jawbone there, his team compiled a
Frankenstein-like skeleton of a single Indohyus
individual (Figure 11.7). After the discovery of
the whalelike ear, the researchers looked even
more carefully at the features of the fossils and
found additional evidence that Indohyus was
a relative of whales. This unassuming little
animal, with a pointy snout and slender legsFigure 11.7
Fossilized skeleton of Indohyus, oldest cousin of the whales
A reconstructed fossilized skeleton of Indohyus was compiled from multiple sources and locations. The illustration is an artist’s
depiction of the living animal about 47 million years ago. (Source: Photo courtesy of Thewissen Lab, NEOMED.)
15 cm