For years, farmers have been growing genetically-engineered cotton plants that exude an insecticide known as Bt. But now, a pest called the bollworm moth has evolved a resistance to Bt -- and the altered bugs have already spread across part of the southern United States. This is the first-known example of bugs evolving resistance to an insecticide in the wild. It proves that natural selection can outrun genetic engineering in terms of its ability to transform a species quickly.
Another example of natural selection working this fast can be seen among elephants, who were hunted for their ivory tusks in the ninteenth and twentieth centuries. Over the course of a century, a "tuskless" mutation in a few elephants spread across the population like wildfire. While only 1% of elephants were born without tusks in 1930, in 1998 15% of female and 9% of male elephants were.