Here's something else that is interesting...."The study suggests a way mutations could build up in a population, says Nipam Patel, an evo-devo researcher at the University of Chicago. If good nutrition can mask harmful genetic changes, mutations might accumulate unnoticed. Should diet then change, the mutations would exert their influence, possibly changing the animals' physical or behavioral traits. Then evolution could take its course, selecting against some of these traits while favoring others."
http://sciencenow.sciencemag.org/cgi/content/full/2002/507/4