62 Self and the Phenomenon of Life
b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”like DNA.) In the absence of cellular components, multiple copies of
Q-beta RNA can be made in a test tube in the presence of a protein
enzyme called RNA-replicase. Their experiment consisted of incubating
the RNA with the enzyme (along with the required raw materials for
RNA synthesis) and letting the RNA multiply in number. After a fixed
period (say, 20 minutes), a minute amount of the mixture (containing
the replicated RNA product) was transferred to seed another test tube,
where a fresh preparation of the enzyme and the precursors were again
added. Upon further incubation, a tiny amount of the newly replicated
RNA was in turn transferred to a third tube for reaction with a new
preparation of the enzyme and precursors. The transfer of tubes went
on and on, and the experimenters shortened the time of incubation in
each step. After many transfers, the final product was a mutant RNA that
replicated many times faster than the starting RNA. What happened was
that, when a replicator (RNA or DNA) divides, a copying error (muta-
tion) normally occurs, at the rate of one per 100,000 nucleotides. Since
the mutations are random, in this experiment some mutants would pro-
mote the replication rate, while others would not. By stepwise shorten-
ing the incubation time, the experimenters selected those RNA variants
that multiplied faster than others, and this favored trait was accumulated
over succeeding transfers. In the end, a fast replicating RNA came out
the winner of the race. Spiegelman himself dubbed this process “Dar-
winian evolution.”^82
Let me analyze how well this experiment agrees with the Darwin-
ian concept of evolution. On the positive side, the experiment shows the
ability of genes (here represented by RNA) to change (mutation), and
that some of these changes can be preserved by external selective pres-
sure (here imposed by the experimenters). What it did not demonstrate
is that the abundance of a replicating molecule leads to the survival of a
cell (since there is no cell involved), let alone the making of one. A rep-
licating molecule, taken alone, does not translate into a functioning pro-
tein useful for metabolic purposes. Piling up tons of DNA (or RNA) is
not the same as making a live cell. At best, Spiegelman’s experiment is