Figure 17

One could certainly argue that there was nothing particularly “brilliant” in Pauling’s blunder—after all, his model was built inside out and with the wrong number of chains. But it was Pauling’s method, way of thinking, and previous incredible success with complex protein molecules that inspired and informed Watson and Crick. In a short article published on March 21, 1999, Watson wrote about Pauling, “Failure hovers uncomfortably close to greatness. What matters now are his perfections, not his past imperfections. I most remember Pauling from 50 years ago, when he proclaimed that no vital forces, only chemical bonds, underlie life. Without that message, Crick and I might never have succeeded.”

The discovery of the structure of DNA had flung open the doors to a limitless range of research that to date culminated in April 2003 with the formal completion of the Human Genome Project—the decoding of the complete DNA of a human (although analysis of all the data will continue for many years). Along the way came many surprises. For instance, prior to the year 2000, biologists believed that the human genome contained about one hundred thousand protein-coding genes. Findings from the International Human Genome Sequencing Consortium published in October 2004 reduced the estimate to fewer than twenty-five thousand—only a little more than the gene count of the simple roundworm C. elegans! Cheaper and faster genetic sequencing technology has recently helped scientists to draw a new picture of human origins. The new view that emerges from the genetic analysis of the tip of a girl’s forty-thousand-year-old pinky finger found in a Siberian cave, is that modern humans did not simply march out of Africa. Rather, they probably encountered and bred with at least two other groups of ancient, now-extinct humans.

The discovery of the structure and function of DNA has also shed light on evolution by clarifying the nature of the hereditary variations on which natural selection can operate. Pauling’s proclamation that life processes are the consequence of the laws of chemistry and physics became verifiable through an understanding of the forces that shape and can vary DNA patterns. (Figure 18, a picture of some of the participants in the Pasadena Conference on the Structure of Proteins that took place in September 1953, shows many of the major players in the discovery of the alpha-helix and the double helix.)