Answer: Koalas

Textured ridges on the tips of the fingers, or fingerprints, are a common trait among primates. Humans, chimpanzees, and gorillas all have them. We could say that fingerprints are distinct to the primate family, except for their presence on koalas, those adorable Australian marsupials.

Even more interesting is that among all other animals with fingerprints, it is the koala that has fingerprints most similar to those of humans. So similar, in fact, that beneath the eye of a trained forensics specialist or even an electron microscope, they appear indistinguishable from each other. The photo above shows a comparison, both in standard fingerprint form and under an electron microscope, of human and koala fingerprints. The comparison, courtesy of researcher Macie Hennenberg, shows an adult male koala on the left and an adult male human on the right.

What’s particularly fascinating about koalas’ fingerprints is that they appear to be a recent (relatively speaking) evolutionary adaptation. While members of the primate family have fingerprints, other members of the marsupial family (to which the koala belongs) do not. This indicates that koalas developed fingerprints long after primates and modern koalas’ marsupial ancestors branched apart 70 million years ago. Like primates who have hands and digits adapted for grasping, the koala also spends much of its time grasping, and very sensitive and grippy fingertips, prints and all, help with that.