Why Fingerprints Differ

No two fingerprints have ever been found to match — not even those of identical twins, who share the same DNA. Genes set the broad style of the ridges, but not the fine details.

The pattern is finalized in the womb, in the second trimester, as the developing skin folds against the fingertip. Tiny differences in pressure, fetal position, and growth nudge each ridge a little differently. Those conditions can never be repeated exactly, so every finger — even on the same hand — ends up unique.