Primitive (phylogenetics)

Primitive (phylogenetics)

Primitive in the sense most relevant to phylogenetics means resembling evolutionary ancestors of living things and in particular resembling them in the nature of their anatomy and behaviour. For example, one might regard a flatworm, which has no legs, wings, or image-forming eyes, as more primitive than a beetle, that in its more advanced morphology has all these things. The term "primitive" might might suggest simplicity, but need not strictly imply it; many "advanced" organisms have lost complex structures that were present in some of their ancestral forms. For example, the jaws of mammals are simpler than those of their ancestral fishes, in that they include fewer bones and usually fewer teeth.