Using the principle of parsimony, construct the most likely phylogenetic tree for the following four primates: Homo sapiens, Pan troglodytes, Gorilla gorilla, Pongo abelii, and explain your reasoning.
Answer
Homo sapiens and Pan troglodytes form a clade; Gorilla gorilla and Pongo abelii form another clade; the two clades share a common ancestor. The most parsimonious tree has two splits: first separating H. sapiens + Pan from Gorilla + Pongo, then separating H. sapiens from Pan.
Step-by-step solution
- Identify shared derived traits: humans and chimpanzees share many derived features indicating a recent common ancestor.
- Note that gorilla and orangutan share fewer derived traits and diverged earlier, forming a separate clade.
- Construct a tree with a first split separating human+chimp from gorilla+orangutan.
- Introduce a second split that separates human and chimp within their clade.
- This arrangement minimizes the number of evolutionary changes, satisfying the principle of parsimony.
Common mistake: Assuming equal evolutionary distances without data
Concept tested: Parsimony in phylogeny
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