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Time Frames is the story of the making of a revolution
-- a revolution in evolution. Dr. Niles Eldredge, chairman and curator of invertebrates
at the American Museum of Natural History, challenges Darwin's slow, steady and
gradual view of change with a new theory called Punctuated Equilibria. This view
of the evolutionary process contends that species, once evolved, typically remain
stable for five or ten million years -- or even longer. When new species
arise, they do so relatively quickly, in evolutionary terms -- over an interval
of five to fifty thousand years. Eldredge's paleontological field work suggests
that, from looking at the fossil record of invertebrates (specifically his specialty,
trilobites), the conclusions that must be reached do not agree at all with the
standard expectation of gradual change that is central to Darwinian evolution.
Darwin's theory propounds the notion that life forms will almost always change
given the passage of sufficient chunks of time, and that their evolution will
typically appear as a smoothly progressive, gradual transformation through time.
In Time Frames Eldredge describes the research and field work that led
him to the radical conclusion that "once a species evolves, it will usually
not undergo great change as it continues its existence." This
scientific adventure story gives the reader a close look at how research work
in the field is done, and the excitement that surrounds new results that push
forward or poke holes in the prevailing wisdom. "In my research, collecting
trilobites," Eldredge writes, "I tried in vain to document any evolution
in them at all in their eight-million-year history in the seas that covered the
eastern and central United States around three hundred and eighty million years
ago. I finally decided that the pattern of obdurate stability interrupted only
rarely by brief spurts of change should after all be taken seriously: it told
us all something real about the nature of the evolutionary process."
Time Frame is the story of Punctuated Equilibria -- what
it is, how it came to be, and what it means for modern evolutionary thinking.
The development of the theory is symptomatic of the general upsurge of critical
analysis going on in virtually every corner of biology. The conclusions that arise
from this theory leads us to a much more complex view of evolution than Darwin
ever expected. Niles Eldredge has his A.B. and Ph.D.
from Columbia University. He is currently the Chairman and Curator of Invertebrates
at the American Museum of Natural History in New York City. He is the author of
many books on paleontology and evolution. His most recent work for a popular audience
was The Monkey Business.
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