Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to [email protected] do we get the fingerprints we have? – Oscar V., age 8, Somerville, MassachusettsFingerprints are those little ridges on the tips of your fingers. They’re essentially folds of the outer layer of skin, the epidermis. The “prints” themselves are the patterns of skin oils or dirt these ridges leave behind on a surface you’ve touched.Your fingerprints began to form before you were born. When a fetus starts to grow, the outside layer of its skin is smooth. But after about 10 weeks, a deeper layer of skin, called the basal layer, starts growing faster than the layers above it, which makes it “buckle” and fold. The expanding lower layer ends up scrunched and bunched beneath the outside layer.AdvertisementAdvertisementAdvertisementAdvertisementThese folds eventually cause the surface layers of the skin to fold too, and by the time a fetus is 17 weeks old – about halfway through a pregnancy – its fingerprints are set.Although this folding process might sound random, the overall size and shape of fingerprints are influenced by the genes you get from your parents. So you probably share some fingerprint patterns with your family members.But the details of your fingerprints are influenced by many other factors besides genes. For example, the shape and size of the blood vessels in your skin, how fast the different layers of skin are growing, and the chemical environment inside the womb all play a part. No two people end up with exactly the same fingerprints, even identical twins.It was only in 2015 that a big long-term study showed that fingerprints are stable over a person’s lifetime. The ridges of a fingerprint are visible on the skin’s surface layer, but the pattern is actually “encoded” below that. Even if you have a major skin injury, your prints will come back when the outer layer heals – though you might have a scar, too.AdvertisementAdvertisementAdvertisementAdvertisementSo your fingerprints are totally unique to you and have been since before you were born. No matter how much you change as you grow up, you’ll always have the s …
