Illustration of George and Lenny from Of Mice and Men

President Bush's State of the Union address highlighted several key policy issues, such as America's dependency on foreign oil, the ongoing war in Iraq and Baby Boomers' impact on Social Security. But the president's call for legislation to prohibit scientists from creating "animal-human hybrids" caught many by surprise; the term was one of the most popular Internet searches in the hours following his speech. Many wondered "What is the president talking about?" or "Why is he using his most important speech of the year to come out against science fiction?"

Bush's remarks may very well have been prompted by a recent article in the Proceedings of the National Academy of Sciences, which reported that researchers at the Salk Institute in La Jolla had created the first set of fully functioning human nerve cells in an animal by injecting human embryonic stem cells into mouse embryos. These mice now experience the world, at least in part, with cells similar to those you are now using to read this article. This is the first time human embryonic stem cells have...