58 Evolution and the Fossil Record
Most single-celled organisms, like amoebas and paramecia, are soft-bodied and never
fossilize. But a few groups, such as the amoeba-like foraminiferans and radiolarians, have
beautiful shells made of calcium carbonate or silica that fossilize very well (fig. 8.1). These
single-celled protistans live by the millions in the oceans, and their shells are so abundant
that on many parts of the seafloor the entire sediment is made of nothing but the shells of
foraminiferans. The coccolithophorid algae secrete tiny button-shaped plates of calcite only
a few microns in diameter. In shallow marine waters, however, coccolithophorids can live in
enormous densities, and they accumulate thick piles of the limy sediment we know as chalk.
For organisms as abundant as these, the fossil record is extremely good. All the micro-
paleontologists need do is collect a few grams of sediment from the outcrop or from a core
drilled in the deep-sea bottom and put them on microscope slides and they have thousands
of specimens spanning millions of years of time. With a record as good as this, micropaleon-
tologists can document evolution in great detail and tell how old the sediment is and show
how the microfossils respond to climate change and whether the ocean waters in a given
area grew deeper or shallower. Indeed, micropaleontology is the single largest subfield in
paleontology because the work is indispensable to oil companies who need to know the age
of the rocks that produce oil. In addition, micropaleontology is critical to marine geology in
studying how climates and oceans have changed over geologic time. Without microfossils,
we would have no oil and would still not understand the causes of the ice ages or earth’s
past climatic changes. We will look at some of the amazing examples of evolutionary change
in microfossils in chapter 8, but microfossils are the ultimate answer to the usual complaint
that the fossil record is too incomplete to document evolution.
Faunal Succession or “Flood Geology”?
Let us now see whether the several facts and laws relating to the geological succes-
sion of organic beings accord best with the common view of the immutability of spe-
cies, or with that of their slow and gradual modification through natural selection. . . .
Yet if we compare any but the most closely related formations, all the species will
have been found to have undergone some change. When a species has once disap-
peared from the face of the earth, we have no reason to believe that the same identical
form ever reappears.
—Charles Darwin, On the Origin of SpeciesOne of the common myths that creationists spread about the fossil record is that geologists
shuffle the layers of strata and their sequence of fossils to prove evolution, and then the evo-
lutionists point to the sequence as proof of evolution (Gish 1972; Morris 1974:95–96). Accord-
ing to creationists, this is a circular argument. But it is manifestly untrue and shows how
little creationists actually know about the history of geology—and creationism.
The geologists who first discovered the fact that assemblages of fossils change through
time, or faunal succession, were actually devoutly religious men who were not trying to prove
evolution (an idea that would not be published for 50 to 70 years after they discovered fau-
nal succession). One of them was William Smith, who was not an independently wealthy
gentleman-scientist (like most of the early geologists and paleontologists) but a humble