Myosins are a diverse family of actin-based molecular motors that appeared early in eukaryotic evolution. Just how early, and how diverse, has begun to become clear from work that appears in this issue of PNAS (1) and recent work from Nature (2). For most of its existence, the term “myosin” applied only to the actin-activated ATPase that forms the bipolar thick filaments of muscle and the cytokinetic furrow. This biochemical definition has given way to a bioinformatic one based on presence of a canonical 80-kDa motor domain related to that of other myosins.