Why do you look the way you do? What determines the color of your eyes, your hair, your skin? What about your height, your build, or your resemblance to one or both of your parents? What tells the ends of your fingers to grow soft pads on one side and hard, protective nails on the other?
In Charles Darwin’s day, the answers to such questions were shrouded in mystery. Darwin himself was fascinated by the way traits are passed along from one generation to the next, but he knew little about the laws of genetics and even less about the mechanisms within the cell that govern heredity. Now, however, biologists have spent decades studying human genetics and the detailed instructions that are embedded in the amazing molecule called DNA (deoxyribonucleic acid). Of course, the big question is, Where did these instructions come from?
What do many scientists claim? Many biologists and other scientists feel that DNA and its coded instructions came about through undirected chance events that took place over the course of millions of years. They say that there is no evidence of design in the structure of this molecule nor in the information that it carries and transmits nor in the way that it functions.17
What does the Bible say? The Bible suggests that the formation of our different body parts—and even the timing of their formation—involves a figurative book that originates with God. Notice how King David was inspired to describe matters, saying of God: “Your eyes saw even the embryo of me, and in your book all its parts were down in writing, as regards the days when they were formed and there was not yet one among them.”—Psalm 139:16.
What does the evidence reveal? If evolution is true, then it should seem at least reasonably possible that DNA could have come about by means of a series of chance events. If the Bible is true, then DNA should provide strong evidence that it is the product of an orderly, intelligent mind.
When considered in the simplest of terms, the subject of DNA is quite understandable—and fascinating. So let us take another trip to the inside of a cell. This time, though, we will visit a human cell. Imagine that you are going to a museum designed to teach you about how such a cell works. The whole museum is a model of a typical human cell—but magnified some 13,000,000 times. It is the size of a giant sports arena, the kind that can seat an audience of about 70,000 people.
You enter the museum and stare awestruck at this wondrous place full of strange forms and structures. Near the center of the cell stands the nucleus, a sphere about 20 stories tall. You make your way there.
You go through a door in the nucleus’ outer skin, or membrane, and look around you. Dominating this chamber are 46 chromosomes. Arranged in identical pairs, they vary in height, but the pair nearest you is about 12 stories tall (1). Each chromosome has a pinched place near the middle, so it looks a bit like a link sausage but is as thick as a massive tree trunk. You see a variety of bands running across the model chromosomes. As you draw closer, you see that each horizontal band is divided by vertical lines. Between those are shorter horizontal lines (2). Are they stacks of books? No; they are the outer edges of loops, packed tightly in columns. You pull at one of them, and it comes free. You are amazed to see that the loop is composed of smaller coils (3), also neatly arranged. Within those coils is the main feature of all of this—something resembling a long, long rope. What is it?
THE STRUCTURE OF AN AMAZING MOLECULE
Let us simply call this part of the model chromosome a rope. It is about an inch (2.6 cm) thick. It is looped tightly around spools (4), which help to form the coils within coils. These coils are attached to a kind of scaffold that holds them in place. A sign on the display explains that the rope is packed very efficiently. If you were to pull the rope from each of these model chromosomes and lay it all out, from end to end it would stretch about halfway around the earth!*
One science book calls this efficient packaging system “an extraordinary feat of engineering.”18 Does the suggestion that there was no engineer behind this feat sound credible to you? If this museum had a huge store with millions of items for sale and they were all so tidily arranged that you could easily find any item you needed, would you assume that no one had organized the place? Of course not! But such order would be a simple feat by comparison.
In the museum display, a sign invites you to take a length of this rope in your hands for a closer look (5). As you run it between your fingers, you see that this is no ordinary rope. It is composed of two strands twisted around each other. The strands are connected by tiny bars, evenly spaced. The rope looks like a ladder that has been twisted until it resembles a spiral staircase (6). Then it hits you: You are holding a model of the DNA molecule—one of the great mysteries of life!
A single DNA molecule, tidily packaged with its spools and scaffold, makes up a chromosome. The rungs of the ladder are known as base pairs (7). What do they do? What is all of this for? A display sign offers a simplified explanation.
THE ULTIMATE INFORMATION STORAGE SYSTEM
The key to the DNA, the sign says, lies in those rungs, the bars connecting the two sides of the ladder. Imagine the ladder split apart. Each side has partial rungs sticking out. They come in only four types. Scientists dub them A, T, G, and C. Scientists were amazed to discover that the order of those letters conveys information in a sort of code.
You may know that Morse code was invented in the 19th century so that people could communicate by telegraph. That code had only two “letters”—a dot and a dash. Yet, it could be used to spell out countless words or sentences. Well, DNA has a four-letter code. The order in which those letters—A, T, G, and C—appear forms “words” called codons. Codons are arranged in “stories” called genes. Each gene contains, on average, 27,000 letters. These genes and the long stretches between them are compiled into chapters of a sort—the individual chromosomes. It takes 23 chromosomes to form the complete “book”—the genome, or total of genetic information about an organism.*
The genome would be a huge book. How much information would it hold? All told, the human genome is made up of about three billion base pairs, or rungs, on the DNA ladder.19 Imagine a set of encyclopedias in which each volume is over a thousand pages long. The genome would fill 428 of such volumes. Adding the second copy that is found in each cell would make that 856 volumes. If you were to type out the genome by yourself, it would be a full-time job—with no vacations—lasting some 80 years!
Of course, what you would end up with after all that typing would be useless to your body. How would you fit hundreds of bulky volumes into each of your 100 trillion microscopic cells? To compress so much information so greatly is far beyond us.
A professor of molecular biology and computer science noted: “One gram of DNA, which when dry would occupy a volume of approximately one cubic centimeter, can store as much information as approximately one trillion CDs [compact discs].”20 What does that mean? Remember, the DNA contains the genes, the instructions for building a unique human body. Each cell has a complete set of instructions. DNA is so dense with information that a single teaspoonful of it could carry the instructions for building about 350 times the number of humans alive today! The DNA required for the seven billion people living on earth now would barely make a film on the surface of that teaspoon.21
A BOOK WITH NO AUTHOR?
Despite advances in miniaturization, no man-made information storage device can approach such a capacity. Yet, the compact disc offers an apt comparison. Consider this: A compact disc may impress us with its symmetrical shape, its gleaming surface, its efficient design. We see clear evidence that intelligent people made it. But what if it is embedded with information—not random gibberish, but coherent, detailed instructions for building, maintaining, and repairing complex machinery? That information does not perceptibly change the weight or the size of the disc. Yet, it is the most important feature of that disc. Would not those written instructions convince you that there must be some intelligent mind at work here? Does not writing require a writer?
It is not far-fetched to compare DNA to a compact disc or to a book. In fact, one book about the genome notes: “The idea of the genome as a book is not, strictly speaking, even a metaphor. It is literally true. A book is a piece of digital information . . . So is a genome.” The author adds: “The genome is a very clever book, because in the right conditions it can both photocopy itself and read itself.”22 That brings up another important aspect of DNA.
MACHINES IN MOTION
As you stand there in the quiet, you find yourself wondering if the nucleus of a cell is really as still as a museum. Then you notice another display. Above a glass case containing a length of model DNA is a sign that reads: “Push Button for Demonstration.” You push the button, and a narrator explains: “DNA has at least two very important jobs. The first is called replication. DNA has to be copied so that every new cell will have a complete copy of the same genetic information. Please watch this simulation.”
Through a door at one end of the display comes a complex-looking machine. It is actually a cluster of robots closely linked together. The machine goes to the DNA, attaches itself, and begins to move along the DNA as a train might follow a track. It moves a little too fast for you to see exactly what it is doing, but you can easily see that behind it, there are now two complete DNA ropes instead of one.
The narrator explains: “This is a greatly simplified version of what goes on when DNA is replicated. A group of molecular machines called enzymes travel along the DNA, first splitting it in two, then using each strand as a template to make a new, complementary strand. We cannot show you all the parts involved—such as the tiny device that runs ahead of the replication machine and snips one side of the DNA so that it can twirl around freely instead of getting wound up too tight. Nor can we show you how the DNA is ‘proofread’ several times. Errors are detected and corrected to an amazing degree of accuracy.”—See the diagram on pages 16 and 17.
The narrator continues: “What we can show you clearly is the speed. You noticed this robot moving at a pretty good clip, didn’t you? Well, the actual enzyme machinery moves along the DNA ‘track’ at a rate of about 100 rungs, or base pairs, every second.23 If the ‘track’ were the size of a railroad track, this ‘engine’ would be barreling along at the rate of over 50 miles (80 km) per hour. In bacteria, these little replication machines can move ten times faster than that! In the human cell, armies of hundreds of these replication machines go to work at different spots along the DNA ‘track.’ They copy the entire genome in just eight hours.”24 (See the box “A Molecule That Can Be Read and Copied,” on page 20.)
The DNA-replicating robots trundle off the scene. Another machine appears. It too moves along a stretch of DNA, but more slowly. You see the DNA rope entering one end of this machine and emerging from the other—unchanged. But a single strand, a new one, is coming out of a separate opening in the machine, like a growing tail. What is going on?
Again the narrator provides an explanation: “DNA’s second job is called transcription. The DNA never leaves the safe shelter of the nucleus. So how can its genes—the recipes for all the proteins your body is made of—ever be read and used? Well, this enzyme machine finds a spot along the DNA where a gene has been switched on by chemical signals coming in from outside the cell nucleus. Then this machine uses a molecule called RNA (ribonucleic acid) to make a copy of that gene. RNA looks a lot like a single strand of DNA, but it is different. Its job is to pick up the information coded in the genes. The RNA gets that information while in the enzyme machine, then exits the nucleus and heads to one of the ribosomes, where the information will be used to build a protein.”
As you watch the demonstration, you are filled with wonder. You are deeply impressed by this museum and the ingenuity of those who designed and built its machines. But what if this entire place with all its exhibits could be set in motion, demonstrating all the thousands upon thousands of tasks that go on in the human cell at the same time? What an awe-inspiring spectacle that would be!
You realize, though, that all these processes carried out by tiny, complex machines are actually going on right now in your own 100 trillion cells! Your DNA is being read, providing directions to build the hundreds of thousands of different proteins that make up your body—its enzymes, tissues, organs, and so on. Right now your DNA is being copied and proofread for errors so that a fresh set of directions is there to be read in each new cell.
WHY DO THESE FACTS MATTER?
Again, let us ask ourselves, ‘Where did all these instructions come from?’ The Bible suggests that this “book” and its writing originate with a superhuman Author. Is that conclusion really out-of-date or unscientific?
Consider this: Could humans even build the museum just described? They would run into real difficulty if they tried. Much about the human genome and how it functions is little understood as yet. Scientists are still trying to figure out where all the genes are and what they do. And the genes comprise only a small part of the DNA strand. What about all those long stretches that do not contain genes? Scientists have called those parts junk DNA, but more recently they have been modifying that stance. Those parts may control how and to what extent the genes are used. And even if scientists could create a full model of the DNA and the machines that copy and proofread it, could they make it actually function as the real one does?
Famous scientist Richard Feynman left this note on a blackboard shortly before his death: “What I cannot create, I do not understand.”25 His candid humility is refreshing, and his statement, obviously true in the case of DNA. Scientists cannot create DNA with all its replication and transcription machinery; nor can they fully understand it. Yet, some assert that they know that it all came about by undirected chance and accidents. Does the evidence that you have considered really support such a conclusion?
Some learned men have decided that the evidence points the other way. For example, Francis Crick, a scientist who helped to discover DNA’s double-helix structure, decided that this molecule is far too organized to have come about through undirected events. He proposed that intelligent extraterrestrials may have sent DNA to the earth to help get life started here.26
More recently, noted philosopher Antony Flew, who advocated atheism for 50 years, did an about-face of sorts. At 81 years of age, he began to express a belief that some intelligence must have been at work in the creation of life. Why the change? A study of DNA. When asked if his new line of thought might prove unpopular among scientists, Flew reportedly answered: “That’s too bad. My whole life has been guided by the principle . . . [to] follow the evidence, wherever it leads.”27
What do you think? Where does the evidence lead? Imagine that you found a computer room in the heart of a factory. The computer is running a complex master program that directs all the workings of that factory. What is more, that program is constantly sending out instructions on how to build and maintain every machine there, and it is making copies of itself and proofreading them. What would that evidence lead you to conclude? That the computer and its program must have made themselves or that they were produced by orderly, intelligent minds? Really, the evidence speaks for itself.
The textbook Molecular Biology of the Cell uses a different scale. It says that trying to pack these long strands into a cell nucleus would be like trying to pack 24 miles (40 km) of very fine thread into a tennis ball—but in such a neat, organized way that each part of the thread remains easily accessible.
Each cell contains two complete copies of the genome, 46 chromosomes in all.