Primordial Soup Experiment
So much of the work until the early 1950's that was done in
laboratories was of a rather hypothetical nature. Indeed even possibly
speculative, highly controversial, but nevertheless quite speculative.
Then, in 1953 there was a major breakthrough. Stanley Miller, a student
of Harold Urey's at the University of Chicago, published a two page
paper in Science in which he did the experiment. If one goes back and
reads the early literature, translations of Oparin, Haldane, and indeed
one of the interesting things is that Harold Urey speculated on the
composition of the early atmosphere on the primitive earth. So Miller
was in good company working with Harold Urey. And Miller, what he did
was, he did the experiment. I'll say "The" with capital letters. The
experiment to take the speculation, the hypothesis, and put it to the
He created this vessel and in that vessel there was no oxygen.
Molecular oxygen was excluded. And he used gasses that were thought
to occur on the primitive earth at the time, early in the history of the
earth: hydrogen, methane, ammonia, and water... a carbon source, a
hydrogen source, a nitrogen source and an oxygen source. And he had an
electric spark in this vessel. After several days, it started to be
covered with some brown material, the liquid became brownish in color.
When the material in that vessel was analyzed, there was found to
contain amino acids.
So, here is the experiment that basically says you can take non-living
material, material that was on the early earth--hydrogen, methane,
ammonia, and water--and you can provide an energy source and you can
produce organic compounds. You can produce amino acids, building blocks
of what we know today that are proteins. So this is the experiment that
took speculation into the laboratory. And since that time, since 1953,
there have been numerous experiments around the world using different
model gasses, producing a variety of organic compounds. I'm not an
organic chemist and my research area does not include chemical
evolution. My interests are mainly once life evolved. What does that
tell us? And once it appears in the fossil record, what does that tell
us about life's origins?
My research interests are also: "What were the chemical/physical
conditions on that primitive earth that would allow for or prevent,
inhibit, chemical evolution?" It's from this perspective, from not the
test tube tapping experimental perspective but from a different
perspective that I want to draw your attention to some of the very
exciting things that are going on in studies of the origin of life.
This goes back to astrobiology. Astrobiology is extremely
inter-disciplinary, extremely multi-disciplinary. It takes researchers
in the traditional fields of science and indeed we hope to include other
fields like social sciences, religion, to bring them in under this
umbrella of astrobiology and try to get at some of the exciting
questions. The origin of life is probably one of the most exciting
questions facing science. To put that in the broad perspective, to
understand the history of the universe, etc., as well as what went on on
Earth billions of years ago is a challenge before us.
Let us go back to Stanley Miller's experiment because he's so important.
He found that at least 10 percent of the carbon was converted into a
small number of organic compounds and about two percent went into amino
acids. Hydrogen, cyanide, and aldehydes were also produced. Glycine
was the most abundant amino acid produced. You go back to Darwin's 1871
letter, the experiments of Stanley Miller and the first one reported in
1953 and subsequent experiments. It appears that proteins, or at least
getting amino acids, getting them to polymerize, you have all the basic
structure there that goes on. But that's only one half of life. What
about the replication that is so important for life and evolution?
Juan Oró, in 1961, took some of the materials that were produced in
the Miller experiments and he took hydrogen cyanide, one of these
compounds produced, along with ammonia and left out the aldehyde. So he
kind of organized the experiment in a certain way. He produced some
amino acids but he also got some adenine, one of the nitrogen containing
bases. Later experiments by him and others were actually able to
produce the other nucleic acid bases. So now we see there's another area
of chemical evolution experiments going on to get at replication. Also,
it was found that sugars could be produced. Formaldehyde is one of
these monomers produced in the Miller experiments and other experiments.
The formaldehyde could polymerize to form a ribose. And indeed, in
various kinds of experiments, ribonucleotides are more readily
synthesized than the dioxyribonucleotides. Therefore, it started to
appear that maybe, if that's the case, the ribonucleotides, that RNA may
have appeared early, that the early world was an RNA world.
But this leads to a paradox because today nucleic acids are only
synthesized with the help of proteins and the proteins are synthesized
only if their corresponding nucleotide sequence is present. So we have
sort of a chicken and egg problem. It's improbable that proteins and
nucleic acids arose spontaneously, at the same time and at the same
place. It seems implausible to have one without the other.
In 1986 Tom Cech discovered something called a riboenzyme, basically,
enzymes made of RNA. They could do little more than cut and join
preexisting RNA, but until then proteins were thought to carry out all
the catalytic activities in an organism. So, now we see since 1953,
since the experiment of Stanley Miller, some extremely interesting
directions in which chemical evolution has moved. A great deal of
information, a great deal of organic compounds have been produced yet no
self replicating life or organism or cell has yet been produced in the
laboratory. And that's often a criticism that is aimed at chemical
evolution studies by the creationists: "Well, why haven't you produced
life in the laboratory?" But it's only been 44 years since Stanley
Miller's experiment was published in Science. And although there may
have been and still are many laboratories around the world that are
involved in experiments to produce organic compounds from various kinds
of gases that may have existed on the primitive earth, it's not like
what probably occurred on the early earth back four or more billions
years ago. Forty four years isn't a lot of time.