Geoscience Reference
In-Depth Information
but in fossil pollen spores. One of the most beneficial by-products of
the Alvarez theory is the way in which it has brought together sci-
entists from an unprecedented variety of disciplines. Pollen special-
ists, for example, have found themselves for the first time in the
same room with dinosaur experts, chemists, physicists, and astron-
omers, all discussing supernovae, precious metals, impact explosions,
and mass extinctions. Advances have been made that would have
been impossible had only one group been involved. In this sense,
few theories in the history of science have been as fertile as the
Alvarez theory.
Two vertebrate paleontologists, William Clemens and David
Archibald, along with plant specialist Leo Hickey, were among the
first to speak up in opposition to the Alvarez theory, though in much
less detail than did Officer and Drake. Only months after the original
Alvarez paper appeared in
Science,
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Clemens, Archibald, and Hickey
published "Out With a Whimper Not a Bang."
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This 1981 paper and
its title have become metaphors for the initial reaction of paleontol-
ogists to the proposal that meteorite impact caused the K-T mass
extinction. They closed with this paraphrase of T. S. Eliot's lines:
This is the way Cretaceous life ended,
Not abruptly but extended.^
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Although plants have received far less notice than the more fas-
cinatingly popular dinosaurs, paleontologists have known for a long
time that many plant species also failed to survive the K-T bound-
ary. The lack of attention is unfortunate, for fossil plants can tell us
a great deal about mass extinctions. First, as the base of most food
chains, plants determine much of what happens in the entire realm
of biology. Second, because they are so different from animals and
are sensitive environmental indicators, fossil plants reveal a lot about
the nature of extinction events. Third, pollen and leaf fossils can be
present in large numbers, reducing sampling errors and allowing the
statistical techniques that add confidence to conclusions about
extinction rates and timing.
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"On the whole the pattern of change in land plants and the
increasingly cooler affinities of the latest Cretaceous to early Pale-
ocene [earliest Tertiary] palynofloras [pollens] are compatible with a
gradualist scenario of extinction possibly related to climatic cooling,"
Clemens, Archibald, and Hickey concluded.
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That same year, Hickey
wrote that the evidence from land flora, together with the difference
in the time of extinction of plants and dinosaurs, "contradict hypo-
theses that a catastrophe caused terrestrial extinctions."
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He based
