Meeting Abstract
Skeletal evolution is better documented than any other system of the vertebrate body, including abundant data from the fossil record. Many studies show how the evolution of the musculoskeletal system has been channeled by adult function, but the evolutionary consequences of Embryonic Muscular Activity (EMA) are less discussed. EMA is ubiquitous across vertebrates, and is involved in normal development of functionally important structures. The mechanical forces of EMA can directly affect the shape of skeletal elements, their articulations, fusion patterns, and growth. Recent advances in the study of bony eminences at tendon insertion sites show common developmental mechanisms with sesamoid bones that involve EMA. This allows a renewed understanding of trends in the evolution of these structures. The effects of EMA are regulated by factors such as embryonic muscular arrangement (including secondary degeneration), and the progress of skeletal development, which determines plasticity upon mechanical forces. EMA can have its most significant effect during discrete periods or “decision points” of skeletal development. Regulation of EMA by these factors can affect the course of evolution, allowing the emergence of characters that may have not evolved otherwise, despite their high adaptive value after birth/hatching.
