Regarding the origin of the individual protein components, a paper on the evolution of dyneins shows that the more complex protein family of ciliary dynein has an apparent ancestor in a simpler cytoplasmic dynein (which itself has evolved from the AAA protein family that occurs widely in all archea, bacteria and eukaryotes). Long-standing suspicions that tubulin was homologous to FtsZ (based on very weak sequence similarity and some behavioral similarities) were confirmed in 1998 by the independent resolution of the 3-dimensional structures of the two proteins.