The Secret of Life

Any 4-year-old who likes ladybugs and lightning bolts can tell you that life is wildly beautiful as far as the eye can see. But it took the geniuses of our time to reveal how beautifully ordered life is deep down where we can't see it at all--in the molecular workshop where we become who we are. James Watson and Francis Crick did not discover the existence of DNA; they discovered its structure, which means they unveiled its power as well as its beauty. If you could uncoil a strip of DNA, it would reach 6 ft. in length, a code book written in words of four chemical letters: A, T, G and C. Fold it back up, and it shrinks to trillionths of an inch, small enough to fit in any one of our 100 trillion cells, carrying the recipe for how to make a human being from scratch. The ingredients are the same for everything that lives; we are cousins to sequoias, and slugs--one life, one creation.

"The molecule is so beautiful," Watson once observed in a chat with TIME. "Its glory was reflected on Francis and me," and the two scientists have spent their lives since then trying to live up to its standards. They marveled that something so vital could be so simple and such a surprise. When they toasted their discovery in a pub one February night 50 years ago, Watson and Crick had no idea that not only biology but also the drugs we take and the machines we build, the food we eat and the choices we face when we decide to have a baby would be changed forever by what they had found.

Now, at the golden anniversary, we celebrate how much we have learned since then, including how little we know. For years scientists thought we human beings must have about 100,000 genes stitched onto our 23 pairs of chromosomes, only to discover that the number is less than a third of that. Like a vaccine against pride, the sublime achievement of the human intellect reveals that we have only twice as many genes as a roundworm, about three times as many as a fruit fly, only six times as many as bakers' yeast. Some of those genes trace back to a time when we were fish; more than 200 come directly from bacteria. Our DNA provides a history book of where we come from and how we evolved. It is a family Bible that connects us all; every human being on the planet is 99.9% the same.