MARGINALIA
Missing Links and Found Links
In and out of the water, transitional forms from the fossil record illuminate the nuts and bolts of evolution
Pat Shipman
Grasping the Brass Link
Finding a missing link is a life's ambition for many
paleontologists, often taking years of hard work, travel to remote
regions and more than a generous dollop of luck. The aftermath of
finding a missing link is more subtle than might be supposed. The
paleontological record will always be sparse compared to the total
number of creatures that ever lived, because fossilization is a very
rare event. Millions of animals are born and die every day, but only
a few of their bodies find habitats suitable for fossilization and
preservation. Of those few creatures that die in the right place at
the right time, many are preserved in places so thinly inhabited by
human beings that no one who could recognize the fossil for what it
is will ever see it. Not only does an organism have to be
fossilized, but it must be found and recognized by a trained eye to
add to the sum of scientific knowledge.
Although the discovery of a missing link is cause for celebration,
it is also cause for more and deeper studies. Ironically, even as
one link is found, two new missing links are
"created"—one the immediate ancestor and one the
immediate descendent of the newly found creature. But slowly, as
discoveries proceed, paleontologists are able to compile an
ever-clearer record of the evolution of life on Earth.
The discovery of Tiktaalik will encourage paleontologists
to continue their intrepid searches in far-flung areas. With luck,
its existence may spark others to rethink their position, too.
Intelligent design advocates and creationists claim that too many
links are missing for evolution to be credible; they see only the
abrupt appearance of new forms created by an Intelligent Designer.
Stephen Meyer, director of the Center for Science and Culture of the
Discovery Institute, asserts that "the transitional life forms
that ostensibly occupy the nodes of Darwin's branching tree of life
are unobservable...."
The highly observable Tiktaalik is exactly the sort of
transitional form that Meyer maintains does not exist. The fossils
are real and solid evidence that you can hold in your hand. If you
are willing to take the time to study their anatomy, you can see for
yourself the evolutionary adaptations that were made over time. This
ancient fish mutely tells a story of mosaic changes, of piecemeal
adaptation to a new ecological niche. It joins myriad other
"found links" that document transitions from one type of
creature to another or from one habitat to another. Together these
found links form a stony edifice in support of evolutionary theory.
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