While the avid dieter obsesses about reduction of different body parts, permanent reduction of many structures seems to be achieved relatively effortlessly (though much more slowly) throughout evolution. In a recent article in Nature, Shapiro et al. examine one such example, the genetic basis of pelvic reduction in the threespine stickleback fish (2004). They conclude that a regulatory mutation in the Pitx1 gene is responsible for the pelvic reduction.