Every fingerprint is unique, but that doesn’t mean they’re easy to tell apart — especially since humans aren’t the only species that’s developed them. Chimpanzees and gorillas have fingerprints too, but it’s actually koalas — far more distant on the evolutionary tree from humans — whose prints are most similar to our own. This was first discovered by researchers at the University of Adelaide in Australia in 1996, one of whom went so far as to joke that “although it’s extremely unlikely that koala prints would be found at the scene of a crime, police should at least be aware of the possibility.”
That discovery lent support to one of the primary theories in the centuries-long debate over the purpose of fingerprints and their swirly microscopic grooves: They help grasp. Koalas’ survival depends on their ability to climb small branches of eucalyptus trees and grab their leaves to eat, so the fact that they developed fingerprints — which assist in that action — independently of primates millions of years ago is likely no coincidence.
In 1879, several decades before the use of fingerprints became widespread, a French criminologist named Alphonse Bertillon developed a system based on body dimensions to identify and catalogue criminals and suspects. The five main measurements were head length, head width, length of the middle finger, length of the left foot, and length from the elbow to the end of the middle finger. Each of these was classified as being either small, medium, or large. Despite his insistence that “every measurement slowly reveals the workings of the criminal,” the system was imprecise, and eventually law enforcement agencies turned to fingerprinting instead.