SCIENCE FILE / An exploration of issues and trends affecting science, medicine and the environment

Q: Do identical twins have identical fingerprints?

A: No. Like many things about our bodies, fingerprints are not determined by genes alone, according to scientists at San Francisco’s Exploratorium. Random chance and environmental factors also play a role. Most researchers believe that pressure on the skin of the embryo between the third and fourth months of gestation, when fingerprints are laid down, governs their exact shape. Identical twins have different positions in the womb and are thus subject to different pressures.