Investigators have long believed that fish, birds and other migrating creatures oriented themselves along the earth's magnetic field and that they used magnetite crystals to aid in the process, but it was never clear how this was done. Now scientists have isolated the cells in anadromous trout that contain the mineral and are making headway in solving the riddle of how the earth's magnetism effects the crystals and how that interaction translates into instructions from the brain as to the direction in which the animal should move.
I wonder if they'll also make headway in explaining how such a system could have evolved by unguided forces and random mutations in most of the major phyla, but be employed by only some representatives of those phyla. Since, for example, not all butterflies or birds migrate do they all possess the magnetite system but only some of them use it, or do only some species in a taxon possess it? Whatever the answer, it raises the question why that should be.
Perhaps there's a compelling story of how this marvelous phenomenon could have evolved naturalistically. If so, I'd like to hear it.