Constraint and convergence in the evolution of vertebrate sound production

Understanding vertebrate sound production offers powerful insights into constraint and convergence in evolution. Sound production falls into two broad categories: muscle-driven and airflow-driven. Muscle-driven mechanisms, widespread among fish, are tightly limited by muscle contraction rates, producing lower-frequency signals that often radiate poorly. In contrast, airflow-driven mechanisms, especially those using myoelastic aerodynamic (MEAD) principles, overcome these limits, enabling long-distance communication across a vast frequency range. MEAD-based laryngeal sound production dominates in tetrapods and convergently evolved in novel vocal organs in birds and toothed whales-all supporting complex, long-distance communication and new acoustic niches. In this review, we show how physical and physiological constraints shaped convergent innovations, positioning MEAD as a central evolutionary strategy underlying the remarkable diversity of vertebrate sounds.