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Identical twins, from the same egg and the same sperm, share almost entirely identical DNA. Nevertheless, studies show that their fingerprints and iris patterns are not identical. The reason lies in a complex interplay between genetics and environmental factors during embryonic development, which shape these traits.
Fingerprints form between the 13th and 19th weeks of pregnancy. Although genetics determines their overall patterns (such as arches, loops, and whorls), environmental factors like the fetus’s position in the uterus, access to nutrients, and umbilical-cord length influence the microscopic details of the ridges. Research shows that these slight fluctuations create unique fingerprints, even in identical twins. In addition, subtle changes in finger shape and the timing of skin growth produce distinctive patterns. As a result, identical twins who share the same DNA still develop different fingerprints. After birth, factors such as injuries or skin conditions can add to this variability [1].
Iris patterns, on the other hand, begin developing from the third month of pregnancy. Genetics dictate the general structure and color of the iris, but epigenetic processes [2] – processes that affect gene expression without altering the DNA sequence – and environmental factors, such as the folding and expansion of tissues, create the iris’s intricate pattern. Studies emphasize that iris patterns are unique even to each of an individual’s eyes, and therefore identical twins do not share identical iris patterns [3]. The iris of every person, including identical twins, contains 266 unique features, compared with 16–20 features in fingerprints [4].
The uniqueness of fingerprints and iris patterns makes them effective tools in biometric identification. Fingerprint recognition systems can distinguish between identical twins, despite the initial similarity of their patterns. Similarly, iris patterns serve as even more accurate identifiers than fingerprints due to their high complexity [5]. These characteristics remain stable throughout life, unlike other traits that can change with age.
So if you were planning to commit a crime and counting your identical twin to take the fall, think again…
Hebrew editing: Shir Rosenblum-Man
English editing: Elee Shimshoni
References:
Netali holds a Master’s degree in Biology from Tel Aviv University. She spent ten years at the Weizmann Institute managing a laboratory in the Department of Molecular Genetics and is now a researcher at Da-Ta Biotech.
