Evolution And History

The Rise of the Primates 135

Biocultural Connection

Why “Ida” Inspires Navel-Gazing at Our Ancestry by Meredith F. Small

One long line of evidence that supports
evolution is the ongoing discovery of
“transitional” fossils that bridge the gap
between one obvious kind of species and
another. Nowhere are these transitional
animals more interesting than when
looking backwards through time at the
human lineage.
This week, scientists from the Univer-
sity of Oslo announced the discovery (or
re-discovery since the fossil was dug up
in 1983) of a 47-million-year-old female
primate known as Ida. This almost com-
plete female animal appears to represent
the transition between what are often
called “primitive” primates, such as le-
murs and lorises (known as prosimians),
and the more “lofty” monkey, apes, and
humans. And even more interesting, this
transition was in place long before any-
one realized.
We love this stuff because humans
are a self-interested species, and some
of that navel-gazing has been directed
toward our ancient past. Luckily for us,
we have living examples of our history
still with us today.
Usually, the cycle of life involves
repeated speciation, extinction, and
survival of modified forms, so that what
we see today is not anything like what
came before. But as the human lineage
went through a prosimian phase, then a
monkey phase, then an ape phase over
time, those branches didn’t completely
die off. Instead, representatives of every
historical stage can still be found in
forests, savannahs, and zoos around the
world.
The ancient forms, of course, have
been modified by natural selection
during the millions of years they have
survived, and their reign is not what it
used to be. Prosimian primates were
once found all across North America and
Europe, and now they have retreated to
specialized niches in Africa (especially
Madagascar) and Asia. Monkeys ruled
the Earth 34 million years ago during
the Oligocene, but now they mostly rule
forests that cling to the equator. And
during the Miocene, about 23 million
years ago, apes were all over the place
until they fell from grace leaving only
four endangered species.
That kind of ancestral mirroring is
not so common. If, for example, we were
modern horses, we wouldn’t be able to
find decent representatives of the vari-
ous stages of horse evolution galloping

across a field. We’d have to deduce

everything about our horsy past from the

fossils that happened to be preserved

and unearthed.

But we humans have these living

primate templates and so we know

something about how the long line of our

ancestors not only looked in the flesh,

we also have an idea of how they be-

haved, ate, socialized, and mated.

And that’s also why Ida is such a spe-

cial find. She seems to be covering the

entire history of primate anatomical evo-

lution all on her own. She was the size

and build of modern lemurs but lacked

the “tooth comb” that prosimians use

to clear their fur, which makes her more

like a monkey. Ida also had the flat face

of monkey, and, oddly, she had the heel

bone of a human.

Ida seems to be cobbled together by

evolution and looks like she could take

off in any and all species directions.

The mishmash of Ida’s features is a re-

minder that although we have living exam-

ples of our past, the story might be more

complicated than we think. Sometimes it

takes an animal that was buried long ago,

had the unusual experience of becoming a

fossil, was unearthed in Germany in 1983,

sold off in parts, put back together, and

then presented as the biological Rosetta

stone for the Primate Order to make us

take another look, and revaluate, our past.

BIOCULTURAL QUESTION

What cultural factors make the biology of

the Ida specimen capture our collective

imaginations?

Adapted from Small, M. F. (2009,

May 15). Why “Ida” inspires

navel- gazing at our ancestry. Live

Science. http://www.livescience.com/

history/090520-hn-ida.html

Due to the fragility of Ida’s remains, scientists have been using CT scan technology to

study her. The radiographic image in Plate B reveals that parts of this image have been

forged (compare it to the chapter opener photo). Only the true remains show up as white

because the mineralized bones and teeth in fossils, as in living creatures, are opaque in

an x-ray.

Courtesy of PLoS