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How does cladistics differ from phenetics in classifying organisms?

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A diagram showing the tentative evolutionary relationships among hominid species over the past four million years, with skull images and labeled species names connected by solid and dotted lines to indicate proposed evolutionary pathways. — phylogeny Tentative phylogenetic scheme for the evolution of the human lineage. Solid bars indicate the time ranges during which species are thought to have existed, based on fossil evidence. Dotted lines signify evolutionary relationships between hominin species that have been proposed on the basis of the fossil evidence.

In the field of phylogeny, cladistics and phenetics represent two distinct approaches to biological classification.12

Phenetics

Phenetics, or numerical taxonomy, classifies organisms based on overall similarity. It relies on the tabulation of as many phenotypic characteristics as possible, regardless of evolutionary history. In this system, the more characters two organisms share, the more closely they are classified together. Because it ignores ancestry, phenetics is often criticized for being subjective, as the definition of a "character" and the assessment of similarity can vary.123

Cladistics

Cladistics, or phylogenetic taxonomy, classifies organisms based solely on their most recent common ancestor. Developed by Willi Hennig, this method uses synapomorphies—shared derived characteristics that indicate descent from a single common ancestor. By focusing on these unique evolutionary markers, cladistics creates a branching hierarchy that reflects evolutionary relationships.124

While phenetics treats all shared traits as equal for grouping, cladistics prioritizes historical, derived traits to infer evolutionary lineage. Consequently, cladistics has become the dominant approach in contemporary systematics.12