In respect to regressive changes, EvoDevo has much to offer beyond a conceptual framework, especially in those cases in which a regressive change is apparently due to gene loss. This has been tentatively suggested (Aboobaker and Blaxter 2003a ; Minelli 2009 ) as a possible explanation for the relatively simple organization of the nematodes, compared to most ecdysozoans, which possibly correlates with a reduction in the number of Hox genes (which is coupled, however, with a very high rate of evolution of the surviving members of this gene family; Aboobaker and Blaxter 2003b ).