THOUGHTS ON GERM LINE GENETIC ENGINEERING: “Why improve our genomes? Because some stuff in them is just broken. We all have harmful mutations. They are called genetic load. The problem is that evolution can not select harmful mutations out of existence at a fast enough rate to prevent them from surviving, in some cases for many generations. So every one of us might have hundreds or even thousands of mildly harmful mutations. Even worse for future generations, our rate of accumulation of harmful mutations has accelerated as a result of industrialization and modern medicine. People who are less healthy due to lousy genes are more likely to survive and reproduce. We should not let our genomes decay across generations.”

So if nature’s not weeding ’em out, I guess it’s up to us.