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PCA Shows Genetic Neighborhoods, Not the Whole Story

PCA is a readable map of genetic structure. It is useful, but it should be read alongside pairwise similarity and branch views.

A PCA plot compresses genetic variation into a small map. Samples that appear near each other often share more genetic similarity than samples that are far apart, but the plot is still a summary of a larger dataset.

This makes PCA excellent for orientation. It can show broad neighborhoods, outliers, and whether a selected sample sits where the submitted name suggests it should sit. It should not be treated as a standalone identity decision.

How to use the PCA view

  • Start with the selected sample and look at its nearest visual neighbors.
  • Check whether those neighbors match the expected naming or source context.
  • Use similarity and branch views to inspect relationships that the map compresses.
  • Treat unexpected distance as a reason to ask a better question, not as the final answer by itself.
Apply the evidence

Start with the sample record.