What makes the flu virus such a good subject for studying molecular evolution?
A. Over the last 30 or 40 years, we’ve sequenced thousands of flu viral genomes. By comparison, we have sequenced only a handful of human genomes. And more importantly, over the last few decades, 20 percent of sites in the flu genome have undergone mutations, which is roughly the equivalent of several million years of evolution in typical human protein. In other words, over a few decades, we can see in influenza the rough equivalent of millions of years worth of evolution in humans. Because we have a full historical record of all these mutations, we have a tremendous opportunity to learn about molecular evolution, given that the laws of physics and protein folding are the same, to generalize our conclusions to all of life. Q. Why is the flu virus changing so fast? A. There are really two reasons. First of all, its mutation rate is higher than that of humans. But the second reason, which is actually far more important, has to do with natural selection. Not only does it acquire mutations
