“I said, did I not, that he was a very cautious man. But as regards that
question, he did permit himself to propose what one might call a qualified
guess. He wrote:
If (and O, what an if!) we could picture some hot little pool in which all
manner of ammoniacal and phosphorous salts, light, heat, electricity and so
forth were present, and that a protein compound were to be chemically
formed in it, ready to undergo even more complicated changes ...”
“What then?”
“What Darwin was philosophizing on here was how the first living cell
might have been formed out of inorganic matter. And again, he hit the nail
right on the head. Scientists of today think the first primitive form of life arose
in precisely the kind of ‘hot little pool’ that Darwin pictured.”
“Go on.”
“That will have to suffice because we’re leaving Darwin now. We’re
going to jump ahead to the most recent findings about the origins of life on
earth.”
“I’m rather apprehensive. Does anybody really know how life began?”
“Maybe not, but more and more pieces of the puzzle have fallen into
place to form a picture of how it may have begun.”
“Well?”
“Let us first establish that all life on earth—both animal and vegetable—
is constructed of exactly the same substances. The simplest definition of life is
that it is a substance which in a nutrient solution has the ability to subdivide
itself into two identical parts. This process is governed by a substance we call
DNA. By DNA we mean the chromosomes, or hereditary structures, that are
found in all living cells. We also use the term DNA molecule, because DNA is
in fact a complex molecule—or macro-molecule. The question is, then, how
the first molecule arose.”
“Yes?”
“The earth was formed when the solar system came into being 4.6 billion
years ago. It began as a glowing mass which gradually cooled. This is where
modern science believes life began between three and four billion years ago.”
“It sounds totally improbable.”
“Don’t say that before you have heard the rest. First of all, our planet
was quite different from the way it looks today. Since there was no life, there
was no oxygen in the atmosphere. Free oxygen was first formed by the pho-
tosynthesis of plants. And the fact that there was no oxygen is important. It is
unlikely that life cells—which, again, can form DNA—could have arisen in an
atmosphere containing oxygen.”
“Why?”
“Because oxygen is strongly reactive. Long before complex molecules
like DNA could be formed, the DNA molecular cells would be oxydized.”
“Really.”
“That is how we know for certain that no new life arises today, not even
so much as a bacterium or a virus. All life on earth must be exactly the same
age. An elephant has just as long a family tree as the smallest bacterium. You
could almost say that an elephant—or a human being— is in reality a single
coherent colony of monocellular creatures. Because each cell in our body
carries the same hereditary material. The whole recipe of who we are lies
hidden in each tiny cell.”