Homologous structures. are similar structures that related species have inherited from a common ancestor. Organisms with homologous structures might have evolved from the same ancestor. The more similar these structures are, the more closely related the organisms probably are.The same is true for molecular evidence.re similar structures that related species have inherited from a common ancestor. Organisms with homologous structures might have evolved from the same ancestor. The more similar these structures are, the more closely related the organisms probably are. The same is true for molecular evidence.