At one time, chondrichthyes were thought to have split off from other vertebrates before the evolution of bone. now we have concluded that the chondrichthyes split off after the evolution of bone had started. this change demonstrates ________. at one time, chondrichthyes were thought to have split off from other vertebrates before the evolution of bone. now we have concluded that the chondrichthyes split off after the evolution of bone had started. this change demonstrates ________. cartilage contributes to keeping sharks light so they do not sink evolution is one-way and straight line characteristics can be lost in evolution hagfishes and lampreys have ancestors with bone