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Authors: Brian Stableford
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luck."
I didn't ask him to explain the mathematics of this remarkable
calculation, but I took it with a pinch of salt. The trouble with the calculus
of probability is that you can easily get silly answers if there are factors
operating which you don't know about. Ludicrous improbabilities are ten a penny
in scientific research.
"Does that explain why the life-systems of the homeworlds
of all the
galactic races are so very similar?" I asked.
"Not in itself," he told me. "If your world and mine had
simply received the same elementary biochemical system, in the form of bacteria
and virus-like entities, natural selection might have built very different
systems. The fact that the pattern is repeated so closely, to the point where
the insects of Tetra are very similar in their range to the insects of Earth—and
so on for all the other major groups—implies that each of our worlds was seeded
more than once. We think that new genetic material drifts from the outer to the
inner regions of solar systems more-or-less constantly, and that this provides
a major source of variations upon which natural selection can work, but we also
think that seedings of more complicated genetic packages have occurred two or
three times in recent galactic history—within the last billion years, that
is."
"So you think that the humanoid gene-complex was actually dumped
on the inhabited worlds we know—by godlike aliens using the whole galactic arm
as a kind of garden?"
Tetrax can't frown, but I could tell that he thought I was going way
over the top, and he clearly didn't want such implications read into his
argument. "We could not isolate the humanoid gene-complex as such,"
he said. "At present, our best theory is that the last seeding may have
been done at the time when, in Earthly terms, the dinosaurs died out. That radical
break in the evolutionary story is something that recurs on many worlds. But
there is no reason to suppose that alien intelligences were responsible for the
seeding."
"But you are saying that the mammalian gene-complex came from
outer space, not from the DNA that already existed on Earth or Tetra?"
"That seems to be the case," he confirmed. He looked at me
carefully for a minute or two, perhaps wondering how much I would be able to
understand. I got the feeling that we were now getting close to his own
hobby-horse. "Do you know what is meant by the phrase 'quiet DNA'?"
he asked.
"No," I replied. I began to suspect that we mightn't get much
further. Pan-galactic parole is a language designed to be easy to use. It isn't
geared up for complicated scientific discourse, and my limited mastery of it
might soon come up against its limitations.
"Your gene-mappers, like ours of a few centuries ago, have now
succeeded in locating on mammalian chromosomes—including human chromosomes—the
genes which produce all the proteins which make up your bodies."
He paused, and I said: "Okay—I understand that."
"Those genes," he said, "account for somewhere between
five and ten percent of the DNA in your cells. The rest is 'quiet DNA.' "
"What you mean," I said, in order to demonstrate my intelligence,
"is that nobody knows what it does."
"Quite so. Our scientists thought for some time that it must be
made up of genes to control other genes. You see, there is more to building an
organism than a mere chemical factory. An egg-cell, as it develops into a whole
organism, must not only produce the proteins it needs, but must organise them
into a particular structure. For many years our biotechnologists have tried to
discover how it is that an egg is programmed to develop into a particular kind
of organism. We had always assumed that the answer lay in the quiet DNA. We
have failed to solve the problem. Your own biotechnologists are just beginning
to be frustrated by that barrier to progress. We have found many practical
applications for our biotechnology, and have been able to accomplish many
things in spite of our incomplete understanding,
I didn't ask him to explain the mathematics of this remarkable
calculation, but I took it with a pinch of salt. The trouble with the calculus
of probability is that you can easily get silly answers if there are factors
operating which you don't know about. Ludicrous improbabilities are ten a penny
in scientific research.
"Does that explain why the life-systems of the homeworlds
of all the
galactic races are so very similar?" I asked.
"Not in itself," he told me. "If your world and mine had
simply received the same elementary biochemical system, in the form of bacteria
and virus-like entities, natural selection might have built very different
systems. The fact that the pattern is repeated so closely, to the point where
the insects of Tetra are very similar in their range to the insects of Earth—and
so on for all the other major groups—implies that each of our worlds was seeded
more than once. We think that new genetic material drifts from the outer to the
inner regions of solar systems more-or-less constantly, and that this provides
a major source of variations upon which natural selection can work, but we also
think that seedings of more complicated genetic packages have occurred two or
three times in recent galactic history—within the last billion years, that
is."
"So you think that the humanoid gene-complex was actually dumped
on the inhabited worlds we know—by godlike aliens using the whole galactic arm
as a kind of garden?"
Tetrax can't frown, but I could tell that he thought I was going way
over the top, and he clearly didn't want such implications read into his
argument. "We could not isolate the humanoid gene-complex as such,"
he said. "At present, our best theory is that the last seeding may have
been done at the time when, in Earthly terms, the dinosaurs died out. That radical
break in the evolutionary story is something that recurs on many worlds. But
there is no reason to suppose that alien intelligences were responsible for the
seeding."
"But you are saying that the mammalian gene-complex came from
outer space, not from the DNA that already existed on Earth or Tetra?"
"That seems to be the case," he confirmed. He looked at me
carefully for a minute or two, perhaps wondering how much I would be able to
understand. I got the feeling that we were now getting close to his own
hobby-horse. "Do you know what is meant by the phrase 'quiet DNA'?"
he asked.
"No," I replied. I began to suspect that we mightn't get much
further. Pan-galactic parole is a language designed to be easy to use. It isn't
geared up for complicated scientific discourse, and my limited mastery of it
might soon come up against its limitations.
"Your gene-mappers, like ours of a few centuries ago, have now
succeeded in locating on mammalian chromosomes—including human chromosomes—the
genes which produce all the proteins which make up your bodies."
He paused, and I said: "Okay—I understand that."
"Those genes," he said, "account for somewhere between
five and ten percent of the DNA in your cells. The rest is 'quiet DNA.' "
"What you mean," I said, in order to demonstrate my intelligence,
"is that nobody knows what it does."
"Quite so. Our scientists thought for some time that it must be
made up of genes to control other genes. You see, there is more to building an
organism than a mere chemical factory. An egg-cell, as it develops into a whole
organism, must not only produce the proteins it needs, but must organise them
into a particular structure. For many years our biotechnologists have tried to
discover how it is that an egg is programmed to develop into a particular kind
of organism. We had always assumed that the answer lay in the quiet DNA. We
have failed to solve the problem. Your own biotechnologists are just beginning
to be frustrated by that barrier to progress. We have found many practical
applications for our biotechnology, and have been able to accomplish many
things in spite of our incomplete understanding,
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