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How Did We Get Here?
Letter 1
Kenneth R. Miller, November 14, 1996
Dear Phillip,
I am always struck by the fact that human awareness of our place in
nature, like so much of modern science, began with the industrial
revolution. For much of history it was possible to believe that the
great diversity of life on Earth was a fixed creation, that the living
world had never changed. But when the first stirrings of industry
demanded that fuel be dug from the earth and hillsides be leveled
for roads and railways, the Earth's true past was dug up in
abundance. In a few short decades museums filled with fossils that
documented a living past dramatically different from the present-
day.
This record of past life demanded explanation, and naturalists
struggled to provide one. Georges Cuvier, the great naturalist of the
Napoleonic era, adamantly maintained that species were fixed and
unchangeable. His own studies of fossils, however, revealed a
pattern of extinctions and appearances so compelling that even
Cuvier had to propose a series of catastrophic extinctions and
renewals in which new species appeared. Etienne Geoffrey, his
contemporary, had a more direct explanation for the detailed
sequences of fossil crocodiles that he studied. Geoffrey noted that as
he went back in time, these fossils became less and less like those of
contemporary animals. Geoffrey was not sure how it had
happened, but the fossils left him with no doubt as to what had
happened. Present-day crocodiles were the descendants of these
ancient forms - crocodiles had evolved.
As you know, the fossil record includes not only the ancestors of
crocodiles and whales, but also the ancestors of human beings. And
this, of course, is why evolution remains controversial. The great
achievement of Charles Darwin was that he was the first to propose
a theoretical mechanism for the fact of evolution that is
documented in the fossil record. The operation of that mechanism,
natural selection acting over time upon the variation in species, is a
demonstrable fact. However, this does not mean that we fully
understand how new species are formed, that we can look to the
fossil record and always say with certainty what forces were acting
upon a particular species, or that we know enough to weigh the
relative importance of natural variation, mutation, gene transfer, or
geographic isolation in the process of evolution.
What is the current scientific status of evolutionary theory?
Biology is far from understanding exactly how a single cell develops
into a baby, but research suggests that human development can
ultimately be explained in terms of biochemistry and molecular
biology. Most scientists would make a similar statement about
evolution. We cannot yet explain everything about our natural
history, but we know enough to be sure that Darwin's mechanism
was at the heart of it. How did we get here? We were produced by
what Darwin called "descent with modification," a process of
change that links us with the grand story of life on earth. In other
words, like everything else on this warm and wonderful planet, we
evolved.
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