How can our personal DNA be so different and yet so similar? A good way to understand this surprising fact is by comparing DNA with the texts of books, and the Argentine writer Jorge Luis Borges (1962) has given us a little fable, “The Library of Babel,” that vividly illustrates the way this difference and similarity can coexist. Borges tells of the forlorn explorations and speculations of people who find themselves living in a vast storehouse of books, structured like a honeycomb, composed of thousands (or millions or billions) of hexagonal air shafts surrounded by balconies lined with shelves.
One of the important features of DNA is that all the permutations of sequences of adenine, cytosine, guanine, and thymine are about equally stable, chemically. All could be constructed, in principle, in the gene-splicing laboratory, and once constructed they would have an indefinite shelf life, like a book in a library. But not every such sequence in the Library of Mendel corresponds to a viable organism. Most DNA sequences—the Vast majority—are gibberish, recipes for nothing living at all. All the genomes that we see, that actually exist today, are the products of billions of years of adjustment and revision, a mindless editorial process that is effective because most of the gibberish is automatically discarded, while the rest is relentlessly reused, copied kazillions of times. You have more than a trillion copies of your genome in your own body right now, one copy in each human cell, and every day, as new skin cells and bone cells and blood cells are made, new copies of your genomes are installed in them. The text that can be copied—because it resides in a going concern, a living cell—is copied. The rest dissolves. Publish or perish.
Source:
Philosopher Daniel Dennett’s Book Intuition Pumps
