Evolutionary processes have increased the complexity and functional capability of the vertebrate heart. This includes the transformation of the single chambered found in tunicates heart to the teleost heart with one ventricle and one atrium to the four-chambered organ found in mammals and birds. Associated with these anatomical changes was a parallel increase in heart rate that enabled increased cardiac output. What is the same, however, in all myocardium is that contraction is generated using a similar collection of component proteins. Muscle contracts when intracellular Ca increases and binds to the contractile element via cardiac troponin C (cTnC). The activation of cTnC triggers a series of conformational changes through the components of the thin filament that results in the generation of force by the myocyte. While all muscle contraction is powered by this mechanism, comparison of contractile function between vertebrate species reveals significant variation. This includes differences in the rate of myocyte contraction and relaxation, in the strength of contraction as well as in functional response following the activation of protein kinases with β-adrenergic stimulation. This seminar will examine the functional basis for these differences and how these have evolved within the vertebrate heart. Specific focus will be placed on cardiac troponin I (cTnI) and cardiac myosin binding protein C (cMyBP-C) and how these proteins have evolved to regulate contractile function in the vertebrate heart. Both cTnI and cMyBP-C are targets for phosphorylation following β-adrenergic stimulation in the mammalian heart. The influence of the evolution of endothermy on the function of the contractile element is also considered, as is the ability of hearts from specific species to function over a variety of physiological conditions. This analysis is completed through the integration of functional studies that have examined the role of specific proteins in regulating cardiac function with studies that have utilized phylogenetic approaches to examine the evolution of specific proteins and how this relates to key functional traits. It is generally found that as the heart became more complex in both anatomy and functional capacity, changes in protein sequence enabled improved control of the contractile reaction. In addition, the evolution of endothermy appears to have driven changes in the function of specific proteins including cTnC, cTnI and cMyBP-C. It is hoped that this integration of functional and phylogenetic studies will provide new insight into the role that the contractile element plays in regulating cardiac function and how this has evolved in vertebrates.