The two curled tusklike teeth of the male beaked whale (breaking the surface of the water above) evolved to attract females as well as to battle males, according to new research.

• 一项新的研究指出：突吻鲸（图中正在水面呼吸的动物）的一对卷曲的牙齿会不断进化，用于与其他的雄性鲸战斗，并借此吸引雌鲸的注意。