If you search for decent definitions of evolution, the chances are that you’ll see genes mentioned somewhere. The American Heritage Dictionary talks about natural selection acting on “genetic variation”, Wikipedia discusses “change in the genetic material of a population… through successive generations”, and TalkOrigins talks about changes that are inherited “via the genetic material”. But, as the Year of Darwin draws to a close, a new study suggests that all of these definitions are too narrow.

Li has found that variation can creep into populations of initially identical prions. Their amino acid sequence stays the same but their already abnormal structures become increasingly twisted. These “mutant” forms have varying degrees of success in different environments. Some do well