The two curled, tusklike teeth of the male beaked whale evolved to attract females as well as to battle other 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。