Identical twins share the same DNA but have different fingerprints.
Fingerprint ridges form in the womb between about the tenth and sixteenth week. Genes set the general pattern, but the fine details are shaped by tiny differences in pressure, position and growth.
Why is this true?
That randomness is what makes fingerprints useful for identification: even the same person's two thumbs are different. Fingerprints also stay the same from before birth until death.
More facts in this category
More about human body
Your own body is a reliable source of surprises. It replaces cells by the million every second, keeps bacteria that outnumber human cells, and runs sensory tricks that make the world feel smoother than the raw signal ever is. The facts collected here stick to mainstream physiology, avoid the wellness myths that circulate alongside them, and explain the underlying mechanism rather than just quoting a startling number.