172 Evolution? The Fossils Say YES!
are nearly always microscopic. It wasn’t until the 1940s and 1950s that Stanley Tyler and Elso
Barghoorn found cherts and flints like the 2-billion-year-old Gunflint Chert in Canada that
preserve these delicate microfossils and made it possible for us to study them. So the answer
to the first creationist misconception about the Precambrian fossil record is yes, there are
many fossils before the trilobites—but you need a microscope to see them, and they’re only
preserved in certain circumstances.
We have already discussed in chapter 6 the evidence for the earliest fossils (fig. 6.2) from
rocks 3.5 billion years old in Australia and 3.4 billion years old in South Africa, as well as
organic carbon and possible stromatolites from rocks 3.8 billion years in age. These fossils are
all of simple prokaryotic bacteria and cyanobacteria (formerly but incorrectly known as “blue-
green algae”). Their equivalents among the modern cyanobacteria are virtually indistinguish-
able from their fossil counterparts, showing that they have evolved very little (at least in the
external anatomical sense) for the last 3.5 billion years. The earliest forms of life made simple
microbial mats on the seafloor, and that way of living was so successful that they saw no reason
to change it since.
As it was in the beginning (3.5 billion years ago), so it was for almost another 2 billion
years. There are hundreds of microfossil localities around the world (see Schopf [1983] and
Schopf and Klein [1992] for documentation of these fossils) in rocks dated between 3.5 and
1.75 billion years ago, and they yield plenty of good examples of prokaryotes (and occasion-
ally their macroscopic sedimentary structures, the layered fossilized bacterial mats known
as stromatolites). Schopf (1999) calls this extraordinarily slow rate of evolution hypobradytely,
after George Gaylord Simpson’s (1944) term for slow rates of evolution (bradytely) with the
additional prefix “hypo-” (meaning “below”) to indicate that cyanobacteria evolve slower
than anything we know. Indeed, they show almost no visible change in 3.5 billion years.
Everywhere we look in rocks between 3.5 billion years old and about 1.75 billion years old,
we see nothing more complicated than prokaryotes and stromatolites. The first fossil cells
that are large enough to have been eukaryotes do not appear until 1.75 billion years ago, and
multicellular life does not appear until 600 million years ago. For almost 2 billion years, or
about 60 percent of life’s history, there was nothing on the planet more complicated than a
bacterium or a microbial mat, and for almost 3 billion years, or 85 percent of Earth’s history,
there was nothing more complicated than single-celled organisms. It was truly the “planet
of the scum.” If aliens existed and had visited the planet long ago, odds are they would
have come at a time when there was nothing more interesting to see (fig. 7.1) than mats of
cyanobacteria—and they would have probably blasted off immediately because this planet
was so boring (unless they studied cyanobacteria, in which case it would be exciting).
Humans like to think of themselves as special and the center of creation, but that anthro-
pocentric view of the universe has been shocked again and again by the discovery (starting
with Copernicus) that the earth is a minor planet in a small solar system on the fringe of an
immense universe, and the discovery (starting with Hutton) that geologic time is immensely
long and humans appeared in only the very last part of the age of the earth. Add to that
the fact that most of life’s history is characterized by nothing more complicated than pond
scum and that humans appeared in a tiny fraction of the final 1 percent of life’s history, and
the blow to our cosmic arrogance is complete. Mark Twain said it best, “If the Eiffel Tower
were now representing the world’s age, the skin of paint on the pinnacle-knob at its summit
would represent man’s share of that age, and anybody would perceive that that skin was
what the tower was built for. I reckon they would, I dunno.”