158 Evolution? The Fossils Say YES!
In the 1980s and 1990s, scientists thought that ammonia and methane were not common
in the early atmosphere. This does not invalidate the Urey-Miller experiment. It only makes
the task of creating organic materials a bit harder. Many later experiments have been tried
with atmospheric compositions lower in methane and ammonia, and they still produced the
same results as the original experiment. Since that time, scientists have returned to thinking
that the early earth’s atmosphere was indeed rich in methane, and probably ammonia, too,
so this criticism is no longer valid (Fegley and Schaefer 2005). In fact, the presence of amino
acids in many meteorites tells us that a wide variety of atmospheric conditions throughout
the universe are capable of producing them, not just the original conditions of the Urey-
Miller experiment. But the creationists like Wells only want to focus on old outdated objec-
tions to experiments that may or may not be representative of current thinking. As we shall
see throughout this book, creationists ignore more recent results if they can criticize outdated
results and appear to invalidate a whole field of study.
So the initial building blocks are incredibly easy to produce, and it’s a fair assumption
that the earth’s oceans had plenty of amino acids and other simple organic molecules float-
ing around. The next step is a bit more difficult: assemble the simple building blocks of life
into longer-chain molecules, or polymers. Amino acids link up to form longer polymers we
know as proteins, which are the fundamental components of most living systems (fig. 6.4A).
Simple fatty acids plus alcohols link up to form lipids, the “oils” and “fats” so common on
earth. Simple sugars like glucose and sucrose link together to form complex carbohydrates
and starches (fig. 6.4B). Finally, the nucleotide bases (plus phosphates and sugars) link up to
form nucleic acids, the genetic code of organisms, known as RNA and DNA (fig. 6.4C).
There are lots of ways of approaching this complex problem of linking simple molecules
into polymers like proteins, lipids, starches, and nucleic acids. Using the primordial soup
approach has produced some successes. In the 1950s, Sidney Fox showed that splashing
amino acids on hot dry volcanic rocks produced most of the proteins found in life instantly.
In the presence of formaldehyde, certain sugars readily form complex carbohydrates. Some
of Stanley Miller’s early experiments produced the components of nucleic acids, such as the
nucleotide base adenine (by heating aqueous solutions of cyanide) and adenine and guanine
(by bombarding dilute hydrogen cyanide with ultraviolet radiation).
It is even easier to polymerize lipids. We all know that “oil and water don’t mix,” but
most people don’t know why this is so. Fatty acids are polar molecules, with a “head” end
that is naturally attracted to water and a “tail” end that is repelled by water (fig. 6.5). As soon
as fatty acids are mixed with water, the individual molecules naturally line up with their
heads facing the water and their tails pointed away. These then clump together to form an oil
droplet (lipid in excess water) or a water droplet in oil. Once these droplets form, they have
an automatic outer membrane of fatty acids that link together to form a lipid. In fact, the cell
wall of most simple cells is composed of the same kind of lipid bilayer. When these lipid
droplets are dried and then rehydrated, they form spherical balls that also concentrate any
DNA present up to 100 times. Thus, little lipid bilayer droplets with nucleic acids trapped
inside have all the properties of “protolife.” In fact, Sidney Fox produced just such structures
that he called proteinoids, and Oparin produced droplets he called coacervates. These struc-
tures behave much like living cells, holding together when conditions change, growing, and
budding spontaneously into daughter droplets. They selectively absorb and release certain
compounds in a process similar to bacterial feeding and excretion of waste products. Some
even metabolize starch! Even though they are not living, they have most of the properties of
living cells—all without much more than simple chemical reactions plus heat.