Le Maître Anne, Grunstra Nicole D S, Pfaff Cathrin, Mitteroecker Philipp
Department of Evolutionary Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.
Department of Palaeontology, University of Vienna, Vienna, Austria.
Evol Biol. 2020;47(3):187-192. doi: 10.1007/s11692-020-09502-0. Epub 2020 May 27.
Encapsulated within the temporal bone and comprising the smallest elements of the vertebrate skeleton, the ear is key to multiple senses: balance, posture control, gaze stabilization, and hearing. The transformation of the primary jaw joint into the mammalian ear ossicles is one of the most iconic transitions in vertebrate evolution, but the drivers of this complex evolutionary trajectory are not fully understood. We propose a novel hypothesis: The incorporation of the bones of the primary jaw joint into the middle ear has considerably increased the genetic, regulatory, and developmental complexity of the mammalian ear. This increase in the number of genetic and developmental factors may, in turn, have increased the evolutionary degrees of freedom for independent adaptations of the different functional ear units. The simpler ear anatomy in birds and reptiles may be less susceptible to developmental instabilities and disorders than in mammals but also more constrained in its evolution. Despite the tight spatial entanglement of functional ear components, the increased "evolvability" of the mammalian ear may have contributed to the evolutionary success and adaptive diversification of mammals in the vast diversity of ecological and behavioral niches observable today. A brief literature review revealed supporting evidence for this hypothesis.
耳朵包裹在颞骨内，是脊椎动物骨骼中最小的组成部分，它对多种感官起着关键作用：平衡、姿势控制、凝视稳定和听力。原始颌关节向哺乳动物听小骨的转变是脊椎动物进化中最具标志性的转变之一，但这一复杂进化轨迹的驱动因素尚未完全明了。我们提出了一个新的假说：将原始颌关节的骨头纳入中耳，极大地增加了哺乳动物耳朵的遗传、调控和发育复杂性。遗传和发育因素数量的这种增加，反过来可能增加了不同功能性耳朵单元独立适应的进化自由度。鸟类和爬行动物较为简单的耳朵解剖结构可能比哺乳动物更不易受到发育不稳定和紊乱的影响，但其进化也受到更多限制。尽管功能性耳朵组件在空间上紧密缠绕，但哺乳动物耳朵增加的“可进化性”可能促成了哺乳动物在当今可观察到的广泛生态和行为生态位中的进化成功和适应性多样化。简要的文献综述为这一假说提供了支持证据。
