6 Evolution and the Fossil Record
evolution during his 1980 campaign) said, “Well, it is a theory. It is a scientific theory only,
and it has in recent years been challenged in the world of science—that is, not believed in
the scientific community to be as infallible as it once was.” Reagan (perhaps playing to his
fundamentalist audience) was voicing the common confusion in the public mind about the
two uses of the word “theory.” To scientists, a theory is extremely well supported, has sur-
vived hundreds of tests and potential falsifications, and is accepted as a valid explanation of
the world. But Reagan is confusing that meaning with the everyday meaning of theory as a
“wild harebrained scheme.” He is also showing his ignorance of another aspect of science.
Science is always about challenging hypotheses and trying to test them and never reaches a
point where a scientific idea is “believed” or is “infallible.” These are words used in dog-
matic belief systems, not in science. If scientists stop challenging theories and hypotheses,
they stop doing science.
There is also another public confusion embedded in this quote: the confusion between
the fact of evolution and the theory of evolution. The idea that life has evolved (and we can
still see it evolving) is as much a descriptive fact about nature as the fact that the sky is blue.
This was already established long before Darwin and represents an empirical observation
about nature, and it is no longer disputed within the scientific community. What Darwin
provided was a theory that included a mechanism for evolution he called natural selection.
There has always been debate within the biological sciences about whether that mechanism
is sufficient to explain the fact that life has evolved and is evolving. Argument and dispute
is good in science; it’s a sign that dogmas are being challenged and that no hypothesis is
being accepted without question. But even if Darwin’s mechanism, the theory of natural
selection, were to be rejected by scientists, it would not change the fact that life has evolved.
It is comparable to the theory of gravitation. We still do not have a full understanding of
the mechanism by which gravity works, but that does not change the fact that objects fall
to the ground.
Science and Belief Systems
A central lesson of science is that to understand complex issues (or even simple ones),
we must try to free our minds of dogma and to guarantee the freedom to publish, to
contradict, and to experiment. Arguments from authority are unacceptable.
—Carl SaganHumans have many systems of understanding and explaining the world besides science.
In most cultures, religious beliefs provide the role of explaining how and why things work
(“the gods did it”), and until the Enlightenment and Scientific Revolution, these beliefs tried
to explain the physical and biological world. In some parts of the world, Marxism is the
official “state religion,” and every aspect of life is subjected to “dialectical materialism” and
viewed through a Marxist filter. Likewise, there are many organizations (some would call
them “cults”) that explain the world through unusual perspectives, such as claiming that
aliens are responsible for most of what we don’t understand. These belief systems are not
necessarily good or bad, but they are not science, because they are not testable and their main
ideas cannot be falsified. Whenever a religious or Marxist dogma is challenged by some
observation, that inconvenient fact is explained away or dismissed or ignored altogether,