Last month I wrote an essay about the future of evolution for Science. I paid particularly close attention to what will happen to our own species, describing some recent research and ideas from scientists. Natural selection will not stop, nor will the emergence of new, neutral mutations.

But this week, the evolutionary biologist Michael Lynch has published a provocative paper (to mark his inauguration into the National Academy of Sciences) in which he makes another kind of forecast. Our future evolution, he warns, is going to lead to a devastating decline in our health.

The idea is not new. Hermann Muller, who won the Nobel Prize for his work on mutations, first raised the specter of