112 Evolution and the Fossil Record
Darwin’s proposed mechanism or by some other, yet to be discovered. . . . Scientists
regard debates on fundamental issues of theory as a sign of intellectual health and a
source of excitement. Science is—and how else can I say it?—most fun when it plays
with interesting ideas, examines their implications, and recognizes that old informa-
tion might be explained in surprisingly new ways. Evolutionary theory is now enjoy-
ing this uncommon vigor. Yet amidst all this turmoil no biologist has been lead to
doubt the fact that evolution occurred; we are debating how it happened. We are all
trying to explain the same thing: the tree of evolutionary descent linking all organ-
isms by ties of genealogy. Creationists pervert and caricature this debate by conve-
niently neglecting the common conviction that underlies it, and by falsely suggesting
that evolutionists now doubt the very phenomenon we are struggling to understand.
—Stephen Jay Gould, “Evolution as Fact and Theory”How can we talk about “the fact that evolution has occurred”? On what evidence can we
make that statement? As we saw in chapter 1, scientists must use the word fact cautiously, as
a description of nature, an observation, or hypothesis that has accumulated so much over-
whelming evidence without falsification that it is a fact in common everyday parlance. As
Gould (1981) put it,
Moreover, “fact” does not mean “absolute certainty.” The final proofs of logic and
mathematics flow deductively from stated premises and achieve certainty only
because they are not about the empirical world. Evolutionists make no claim for
perpetual truth, though creationists often do (and then attack us for a style of argu-
ment that they themselves favor). In science, “fact” can only mean “confirmed to
such a degree that it would be perverse to withhold provisional assent.” I suppose
that apples might start to rise tomorrow, but the possibility does not merit equal
time in physics classrooms.In this sense, the idea that life has evolved and is evolving is “confirmed to such a degree that
it would be perverse to withhold provisional assent.” We see life evolving all around us, and
we have abundant evidence that it has done so in the past. Creationists may put religious
blinders on and refuse to face reality, but to the unbiased observer, the fact of evolution is as
clear as the fact that the sun rises in the east or that objects fall to the earth. Some “evolution
deniers” cannot live with this reality, but their denial won’t stop viruses and bacteria from
evolving new ways to attack us.
Ironically, the evidence that life had evolved was accumulating long before Darwin, as
we saw with our discussion of faunal succession (chapter 3), Chambers’s premature efforts
to document evolution in 1844 (this chapter), or the evidence that Philip Henry Gosse tried
to explain away with his Omphalos hypothesis (chapter 1). But the great strength of Darwin’s
book is that it accomplished two different functions: it laid out a huge amount of evidence
that life had evolved, thereby establishing the fact of evolution; and it proposed a mechanism for
how it had occurred (the “theory” of evolution), which was Darwinian natural selection. As
we have just discussed, Darwin’s mechanism is still being debated as to whether it explains
everything, but Darwin’s evidence that life has evolved is still valid. Much new evidence
has accumulated in the past 150 years that Darwin could only have dreamed about. What