The Upright Ape: A New Origin of the Species

by Aaron G. Filler, MD, PhD

Figure 5-3 Cladistic Classification From Hennig

Figure 5-3 – Hennig’s Methods for Cladistic Description of Lineages

A- A branching tree that represent the relationship among species is a cladogram. When character state a’ occurs in species B and D, where their common ancestor had character state a for that character, then we can call B and D sister species and call A the stem species. In this system we call a the original or plesiomorphic state and we call a’ the derived or apomorphic state.

B – Species can be classified into higher groups such as genus, family, order, etc. (for instance calling the group of apes and human species “hominoids”). Ideally 1 - every group name is made of species that arise uniquely from a common ancestor and 2 – the group includes all the species in that branch or “clade”. Hennig calls such a group monophyletic.

Figure credit -

Redrawn and modified by AGF after Hennig (1966), Phylogenetic Systematics. Urbana, University of Illinois Press, pages 89 and 148 .

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