I was made in secret, and curiously wrought.
(Psalm 139:15)
At first the Biochemist didn't budge,
For he was sound asleep. He got a nudge
From the Cosmologist--then he awoke
With such a start he almost spilled his Coke.
"Just what is life?" asked the Geologist,
His question aimed at the Biologist.
"Why don't we start with that? Then this good man
Can go from there to how life first began,
If he's awake enough to tell us."
"Yes,"
Said the Biologist, "although I guess
There's no set definition. Lists of what
Life's attributes are--what life's forms have got
In common--seem the closest that we come
To saying what life is. Now I like some
Lists more than others; one I'm happy with
I credit to the late John Maynard Smith: 1
Life's properties are multiplication,
Heredity, and thirdly variation.
The list is short, it's clear just what it means:
What makes us life? We are the things with genes.
The same genetic code, four letters long,
Is shared by every life form--that's as strong
As evidence can be for the descent
Of all from one ancestral form. What's meant
By 'code', though? 'Letters' in our genes? I take
It, Biochemist, you're now wide awake,
So you explain it, that's enough from me.
Now let us hear some biochemistry."
The Biochemist's Tale
The preacher says, "God has a plan for you."
Well, maybe so. Your cells, though, really do,
Inside their nuclei. Yes, cells are homes
Of little bodies we call chromosomes
That house our genes; more strictly, there resides
Our DNA, made of nucleotides,
Four chemicals called cytosine or C,
A's adenine, guanine is G, and T
Is thymine. (DNA stands for deox-
Yribonucleic acid--a pox
Upon such words!) So right away we've seen
That by genetic "letters" what we mean
Are these four substances our DNA
Is made of. Now these letters come one way,
In groups of three, called codons (there
Are sixty-four of these). So that is where
The "code" comes in: three-letter "words" construct
The "sentences," the "blueprints" that instruct
Our cells on how to build our bodies. They
Do not instruct directly: RNA
Is sent out as a "messenger," but we
Will not go into that--this has to be
Kept simple, for genetics is the kind
Of thing can boggle anybody's mind.So what's a gene? A piece of DNA,
A section of three-letter words that say,
"Here this or that." That's roughly how the genes
Instruct the cells on how to make proteins,
Compounds essential to development
In organisms. Twenty different
Kinds of amino acids are the stuff
Proteins are made of. There are quite enough
Amino acid combinations (some
Ten trillion) to assure that proteins come
In great variety. 2 Genes dictate, then,
The sequence of amino acids in
Each protein, and that sequence is what makes
Each protein do its special thing.
Mistakes
Sometimes occur in the transcription of
The code. It also happens folks make love
And reproduce, and what the latter means
Is a recombination of their genes.
Two things, then, cause genetic variation:
Recombination and what's called mutation.
Now genes mutate--producing something new,
Recombination just reshuffles--due
Not only to transcription errors ("A"
Gets used where "C" or "T" was, let us say)
But also to such random radiation
As cosmic rays. 3 So usually mutation
Harms or is neutral. Still, within the range
Of possible mutations, some such change
Environment will favor now and then,
The mutants having some advantage in
Their "strangeness," that which helps them to survive
Conditions in which others cannot thrive.
That's natural selection. How do bugs
In us evolve resistance to the drugs
We take to kill them? Most, of course, will die,
But some will be immune, mutation's why;
They'll multiply, till almost all will be
Genetically immune, and that's when we
Must find another drug. 4 That's how besides
Insects become immune to pesticides.Mutation can be in the neutral range, 5
Resulting not in death or any change--
It stays, though, in the gene pool, thus on hand
Should there arise conditions that demand
That type of change if there's to be survival.
Mutation needn't be a late arrival
To play its vital role in evolution.
But understand, when life needs a solution
To some big problem if it's to adapt,
It can't just order a mutation apt
To fix things. It's a random situation,
And whether there exists a "right" mutation
Already in the gene pool will depend
On chance.Creationists, while they defend
Genetic variation as a fact,
Would limit it, they say all that we've tracked
Is microevolution, change confined
To an original created kind.
"No new kind has evolved, a moth," they say,
"Is still a moth. 6 Moreover, there's no way
Mutation and selection can produce
New kinds or any large-scale change of use.
Thus macroevolution cannot be." 7
Till lately our camp tended to agree
Mutation and selection by themselves
Don't bring about new species. (God or elves
Don't either.) They may lead to adaptation,
But we have thought some form of isolation
Might play a role in any new species
Arising. Changes, too, in frequencies
Of genes occur, one generation to
The next, at random, something we can view
Especially in isolated, small
Inbreeding groups. This random change we call
Genetic drift. 8 But that's not all the story
Now, for Hox genes (these are regulatory
In the development of embryos)
Can mutate (as a recent study shows),
Affecting other genes, cause such a stir
That macroevolution can occur
In animal body plans. 9 So large-scale change
In creatures turns out not to be so strange,
When Hox genes may rewire, as they mutate,
Expression of the genes they regulate.And now for "kinds"--a concept from the Bible
With no scientific meaning. Here I'm liable
To get upset, but let me tell you what
Creationists are up to. They have got
To prove, they think, that Noah's flood's a fact,
That Noah had this ark in which he packed
A pair of every "kind," for such a flood,
With all Earth's creatures buried in the mud,
Is their "scientific" explanation for
The fossil record. 10 (And they're out, what's more,
To prove that all of Genesis is true--
Creation coming first, of course, God through
In seven days.) Now fossils aren't my field,
On fossils and the flood I'll gladly yield
To someone else. I've got credentials, though,
To talk of species, and I'll have you know
A species is an interbreeding group
That doesn't breed with others. 11 Now this troop
From Dallas, Texas, hasn't yet defined
Exactly what is meant by saying "kind"--
A dog's a dog, I guess, a cat's a cat-- 12
But here is what they're really getting at:
Old Noah had no trouble putting all
Those pairs of kinds on board (he had a stall
Even for dinosaurs!), 13 because a kind
Is something that's so broad and ill defined
It cuts down greatly on the total hoard
Of critters Noah had to get on board,
While species number in the millions. Folks,
It's nonsense, but the flood and ark aren't jokes
To them--their trips to Turkey aren't a lark,
They're climbing Ararat to find that ark! 14Creationism! Now I'm out of joint.
But I hate pseudoscience, that's the point.
There's nothing that will make me pound a fist
More than a Bible-bound creationist
Who'd have you think he knows more than I do
About what's science! He's just conning you,
He's out to save your soul. Creation is
Religion, it's straight out of Genesis.
I've read the First Amendment, I'm no fool!
That stuff does not belong in public school. 15Now how did life begin? I've got a story
To tell you, one redounding to the glory
Of chemists everywhere--I wonder why
They haven't made a film about this guy,
His story's true, as good as any thriller.
It's 1952, young Stanley Miller
Is hard at work to earn his Ph.D.
Up in Chicago. Stan's in chemistry;
He works for famous chemist Harold Urey,
Who thinks Earth's early atmosphere--the jury
Was still out on this--had to contain,
Like Jupiter's, ammonia and methane
Along with hydrogen. What does that say,
They ask, about life's origin? One day
Young Stan does an experiment, 16 a task
Thought out with Urey: Stanley boils a flask
Of water, and the vapor from it passes
Into a larger flask filled with the gases,
The hydrogen, ammonia, and methane
That Urey figures must have in the main
Composed the early atmosphere; to zap
This circulating mix, sparks shoot the gap
Between electrodes, this to represent
Some lightning bolts. In Stan's experiment,
The products will condense and flow into
The water flask--in Stan's and Urey's view
The ancient ocean. This continues for
A week, till Stan can't stand it anymore--
He has to find out what he's got, enough!
He pumps the gases out, and then the stuff
That's left inside the flask he analyzes.
And what does Stanley find? A few surprises:
Amino acids (glycine, alanine,
And others)--building blocks, as we have seen,
Of proteins and of life. Now Miller's found
In history books, experiments abound, 17
Though with new mixtures--chemists now maintain
There wasn't such ammonia and methane
As Urey thought. (The atmosphere back then
Was not like ours, though, it was lacking in
Free oxygen.) 18.) In these experiments,
Nucleotide bases (constituents
Of nucleic acid) get produced as do
Amino acids."Though that may be true,"
Creationists will say, "look what's left out!
Amino acids you have talked about,
And bases for nucleotides, but those
Are hardly life! Are we now to suppose
The building blocks just somehow got together
(If lightning's needed, in some stormy weather) 19
And then voilà! proteins and DNA?"
No, origin-of-life research, I'd say,
Has run into a problem here, it's this:
For all our laboratory synthesis
Of building blocks, we can't make DNA
And proteins with the blocks. 20 There seems no way,
Moreover, DNA could first arise
Without some proteins there (they catalyze),
And how did any proteins ever start
Without some DNA there to impart
Instructions? ("Which came first, the chicken or
The egg?") 21 So science still is looking for
The way the blocks were forged into the first
Self-reproducing molecules--at worst
A plausible hypothesis 22 of how
It worked, we may not ever know, for now
Four billion years have passed. Did God create
Those molecules? One's free to speculate
(And while you're at it, who created God?),
But scientists at work can't give a nod
To supernatural concepts, for our task
Is to find natural causes. 23 So don't ask
Why I get mad about creationism,
It's clear that it's not science, it's an ism,
It says "God did it." That is fine for Sunday
School, but not for science class on Monday.
A sample, what they'd teach in public school:
"Look at the simplest protein molecule;
The sequence of amino acids in it
Could not arise by chance." 24 Now wait a minute!
The original did not arise full blown,
Of course not. Step by step, as time went on,
It formed, by natural laws of chemistry,
And no one sequence was required. We see
The same thing with nucleic acids: no
First acid had to be composed just so,
One nucleotide sequence excluding all
The rest. Some sequence, that's all time would call
For. Probability of course was low
One certain sequence would arise; but no
Such sequence was required, for life, you see,
Would use whatever sequence came to be. 25
Thus probability was plenty high.
See how they twist things? I won't say they lie.Now back to Stanley Miller: if a meek
Young student can produce in just a week
Amino acids using water, gas,
And sparks, then might not nature bring to pass,
In several million years, a replicator,
That first self-reproducing cell, with later
Complexity evolving? Surely this
Hypothesis--abiogenesis
Is what it's called, this theory I am giving
You that life arose from the nonliving--
Is not far-fetched at all, it's chemistry. 26
And furthermore, that's how it has to be
Because we know that life arose! Now ask:
"If you mean that it was an easy task
For nature, given chemistry and time,
To create life back then, why is it I'm
Not seeing nature create life today?"
I'm glad you asked me that! The ancient way
Could not now reoccur: free oxygen,
As I've already mentioned, wasn't then
Found in the atmosphere--by "then" I mean
About four billion years ago. The scene
Was changed by life (some added "atmosphere"),
It's life that helped make oxygen appear, 27
Through photosynthesis (then life had to
Adapt). Today life can't arise anew,
For it would be destroyed by oxidation 28
(As well as by a thing that's called predation).Research into life's origin goes on.
Tom Cech and Sidney Altman made it known
In 1983 that RNA
Can do more than just take a message: they
Found that like proteins it can catalyze.
This news won Tom and Sid a Nobel Prize;
Now many origin researchers think
Some ancient form of RNA's the link
We're looking for between nonlife and life. 29
But there's no guarantee, ideas are rife,
Some argue that clay minerals are what
Helped life emerge, 30 still others go for hot
Sea vents. 31 Were life's precursors seeded here
By asteroid or comet? 32 (Such, I fear,
Does not explain how life itself arose.)
An alien spacecraft brought it? (One of those
Suggesting this was Francis Crick.) 33 Some say
That even if we synthesize someday
Life in the laboratory, we won't know
How life began without our help. 34 That's so,
There's no way to go back four billion years
In time and study life while it appears;
But we can come up with a pretty darn
Good theory and not settle for a yarn
The Hebrews borrowed from what's now Iraq.
(Our Bible Scholar knows there is no lack
Of evidence on that.) 35 It's chemistry,
As kinds of molecules we know to be
Important for life's synthesis are found
Not just on Earth; in atmospheres around
The outer planets they're detected, in
Gas clouds in outer space, in comets; 36 when
Meteorites have fallen from the blue,
Guess what has been discovered in a few:
Amino acids, nucleotide bases 37--
It may well be it's off to the races
As far as life throughout the cosmos goes.Consider one more thing--on this I'll close.
When we began, our good Biologist
Noted the fact that we are each a twist
Of just one plot: there's one genetic code.
Well, it's the evolutionary road
That leads us to the only explanation
That's scientific--all talk of creation
Has a religious, not scientific, sense.
(Along that road there's much more evidence
Than just the code, of course, that things evolved.)
A question, then, is more or less resolved,
Which is: did life start more than once? Perhaps, 38
But through selection, many past mishaps,
One ancient form survived. And that is why
All present life forms are distinguished by
The same four-letter code: all beings share
One family tree, all started out back there
With that one little molecule that could.
And that, friends, is what I call brotherhood.