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How can a phylogenetic tree be used to identify an organism's closest relatives?

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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.

A phylogenetic tree is a diagram used to represent the evolutionary relationships among organisms. To identify an organism's closest relatives using such a tree, you must trace the branches back to their point of intersection, known as a node.123

In phylogeny, relatedness is determined by the recency of a common ancestor. The fundamental principle is that the more recent the common ancestor shared by two organisms, the more closely related they are. When reading a tree, you should trace from the nodes to the tips rather than simply looking at which branches are positioned next to each other, as the visual layout or orientation of the branches does not dictate relatedness.32

Scientists often construct these trees using cladistics, which focuses on shared derived characteristics, or by analyzing molecular data, such as DNA or protein sequences, to estimate the evolutionary distance between species. By identifying these shared ancestral points, researchers can objectively map the evolutionary history and kinship of different life forms.342