How Similar Are Human and Chimpanzee Genomes?

When people say human and chimpanzee genomes are “98.8% the same,” they usually mean single-letter similarity in regions that can be aligned directly. Whole-genome comparisons also involve insertions, deletions, repeats, and structural rearrangements, so the percentage depends on the method. A 2005 study estimated an average difference of about 1.23% in individual letters, but that figure does not describe every genomic difference. More complete assemblies show how difficult some regions are to compare. So 96–98% is only a rough summary, not one unconditional measure. The illustration is AI-generated.