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07/11/2002
Gaps- Filled and Otherwise
Last week we discussed gaps (missing links) in the fossil record
and Eldredge and Gould''s "punctuated equilibrium" as a possible
explanation for these gaps. The gaps that concerned Gould were
relatively short, geologically speaking. I may be wrong, but I
doubt that a gap of 20 million years would be one that would be
considered "short". I''m talking of course about Romer''s Gap.
You never heard of Romer''s Gap? I hadn''t either until I read an
Associated Press article in our newspaper, the July 4 Star Ledger.
The article spurred me to search the Web sites of PBS, BBC and
the Geological Society in the UK. I''m sure that you''ll be happy,
as I was, to know that Romer''s Gap has finally been filled.
Last week also saw the filling of another gap, this one a gap in
the history of manned flight filled by Steve Fossett''s remarkable
solo trip around the world in a balloon. I was born in 1927, the
year of Lindbergh''s epic solo flight across the Atlantic. The fact
that it took three quarters of a century more to achieve an
around-the-world solo in a balloon indicates the magnitude of
Fossett''s feat.
Last week also saw the creation of a gap, this one in baseball
history, with the passing of Ted Williams, the last of the .400
hitters. Regretfully, I never saw Williams in action. When I was
a teenager, some buddies and I took the train from Harrisburg to
Philadelphia to see the Red Sox play the Philadelphia Athletics
(they weren''t in Oakland then). However, Ted Williams was off
flying a fighter plane in World War II. After the game, we were
standing on the platform waiting for our train when we realized
that the whole Red Sox team was on the same platform waiting
for their train. For a rabid baseball fan, this was heaven,
especially since my hero, Indian Bob Johnson (traded to Boston
from the A''s), was there. I got Bob, Joe Cronin and Bobby Doerr
to sign my scorecard. It was the highlight of my life to that
point. Sadly, one of the worst moments of my life occurred on
the train trip home. Someone stole my scorecard while I was
dozing! That missing scorecard gap has never been filled.
Oh, you''re right, what about Romer''s Gap? Before I answer, I
should note that one reason for my concern with evolution and
the fossil record was an editorial by "the editors" in the July issue
of Scientific American. The editorial cited two polls, a Gallup
poll in 1999 and a National Science Board poll in 2000, both of
which showed that nearly half of the American public does not
believe in evolution. Even today, some boards of education or
lawmakers are trying to mandate the teaching of creationism or
"intelligent design" as an alternate theory to evolution. To me,
this is a shocking and sad commentary on the scientific literacy
of a large fraction of the U.S. population.
To my mind, few things bolster the fact of evolution more than
the filling of a gap in the fossil record. Certainly one of the most
dramatic and key events in evolution was when the first creature
of the sea developed the ability to move out of the sea and walk
on the land. Without that development we wouldn''t be here
today. One of those specializing in the study of that exciting
period is Jennifer Clack. Jenny is a Reader in Vertebrate
Paleontology and a Senior Assistant Curator at the University of
Cambridge''s Museum of Zoology.
One of Jenny Clack''s discoveries was a fossil nicknamed
"Boris". Boris lived some 360 million years ago. The striking
feature about Boris was that he had four appendages, or limbs.
However, it was clear from the design of these limbs that they
were not made for walking but for maneuvering in the water.
Boris was a swimmer, not a walker. Nevertheless, Boris could
be classified as an incipient tetrapod, defined as a creature with
four legs. We are tetrapods, our four limbs fitting the definition.
Ok, Romer''s Gap. Harvard scientist Alfred S. Romer first
pointed out that there was a gap in the fossil record for at least
some 20 million years. In other words, after the appearance of
fossils such as Boris, there weren''t any tetrapod-like fossils found
that lived in the 20 million years or so before real tetrapods that
were at home on land. Jenny Clack was also one of those who
had found examples of these walking landlubbers, in her case in
ancient footprints off the coast of Ireland. But there was still this
gap of nothing for at least 20 million years.
Now comes Pederpes finneyae, let''s call it Peder for short. Peder
is a fossil of a fish that was found in Scotland in 1971. For the
next three decades Peder appears to have hung around in the
Hunterian Museum in Glasgow. Peder didn''t arose any particular
excitement, being just a fish, albeit a very old one. I should have
mentioned that Peder wasn''t a freestanding fossil but spent its
time embedded in the rock in which it was found.
Recently, it was decided to carefully chip away the rock and, lo
and behold, Peder turned out not to be a fish at all! Peder had
legs and one of the legs had a well-preserved foot with five
digits. Not only that but Peder turns out to have lived during
Romer''s Gap. Peder was a fairly large guy, about three feet long,
and resembled a clumsy sort of crocodile. He was not very agile
on land.
Peder differed from his aquatic predecessors such as Boris in that
the bones of Peder''s legs had a twist that allowed it to bring its
foot forward to walk on land. The earlier animals that stuck to
the water had their feet pointed to the sides or backward so they
were used as paddles rather than to walk. Peder is apparently the
earliest true amphibian fossil that has been found that could find
itself at home both in the water and on land. Some animals that
followed Peder developed legs that were much more adapted to
walking on land and these vertebrates were on their way to
becoming other land-based critters like ourselves. But Peder has
filled Romer''s Gap.
Do you have a laughter gap that needs to be filled? I''m not
normally a movie critic and go to very few movies but if you
haven''t seen "The Big Fat Greek Wedding", you''re missing the
funniest movie in decades. Strangely, the reason I saw this
movie stems from the environmental consequences of an event
hundreds of miles away. My wife insisted that we go to the
movie, saying she needed some laughter; it was such a gloomy
day. The day was strange in that the humidity was low, the
temperature quite comfortable and the sun was shining. Yet
there was a haze in the air that one normally associates with a
sticky hot humid day.
Sure enough, there are fires burning in Canada north of Montreal
and even though we''re some 900 miles south of the blazes we''re
getting the smoke! With more than 30 inches of rain in Texas,
fires and bone dry conditions in the West and in Canada, can we
be seeing the extremes of weather predicted as the consequences
of global warming? If so, we''re in for times that may intrigue
any creatures exploring the fossil record of our own era some
millions of years from now. Recollection of the stolen scorecard
has put me in a pessimistic mood and I''m assuming Homo
sapiens won''t last another million years.
Allen F. Bortrum
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