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Exhale, Why?

Koalas have fingerprints so much like a human they’ve tricked CSIs

Here’s something weird to think about the next time you are watching CSI. No, it’s not a critique of David Caruso’s use of cheesy one liners – Jim Carrey beat us to that – it’s about koalas, humans, crime scenes… And fingerprints.

Koalas have fingerprints. Not only that, they have fingerprints that are so human-like, that crime scene investigators have actually got them confused.

(That has never been a plot for CSI, but it totes should be, except that there are not so many koalas in Las Vegas or Miami – although isn’t that exactly what these scofflaw criminal koalas want you to think?)

Koala fingerprints are like human fingerprints not only in their shape, but also in the way they differ from koala to koalas – i.e. the combination of whirls, swirls and loops that make human fingerprints so unique.

This diagram illustrates how close they are.

Koala left, human right. Or is it human left, koala right? Most crime scene investigators don’t know either.

Similar, huh? But now that we have blown you collective minds and solved the mystery at the centre of Enid Blyton’s as-yet-unpublished The Great Eucalyptus Heist Of Myrtletown, the next question is ‘why?’

Why do koalas – who are generally otherwise non-humany – have humany fingerprints?

Before you counter with “all animals have fingerprints”, that isn’t true. Plenty of animals, including mammals and marsupials, have zero fingerprints.

Second (and this probably should have been first) the answer given by scientists is “we don’t really know, soz”. As yet, there is no scientific consensus on why koalas have fingerprints, let alone ones that resemble people’s.

Koala fingerprints have confused scientists and researchers for a number of reasons, but primarily because they are rare among tree-going mammals. Most monkeys do not have fingerprints – although chimps and gorillas do. However, chimps and gorillas are much closer to humans on the evolutionary scale, making koala fingerprints even weirder.

Also, the fingerprints aren’t to add grip to help them climb trees. Koalas use their clawed hands to grip branches rather than the extra traction provided by fingerprints, so there is little evolutionary benefit.

The best guess as to the reason for koala fingerprints is that they help in leaf selection. Koalas are fussy eaters, eating only particular leaves and only when the leaves reach a certain stage of maturity, and the extra sensitivity provided by fingerprints may help them select leaves better.

The phenomenon is otherwise put down to convergent evolution, which is the theory which explains why completely different animals who have little to do with each other on an evolutionary basis have developed the similar characteristics.

Dolphins and bats, for instance, have the same inner-ear proteins which enable them to find their way around, but dolphins and bats haven’t evolved from one another and rarely hang out together. Fish in both the North and South Poles have developed methods of preventing their blood from freezing – even though they never get to chill with each other because the swim is too long and too warm.

So, the next time you are carried out of your house by the police while screaming “the koala did it, the koala did it, why does no one believe me?”, remember that koalas’ human-like fingerprints would allow you to crack the case and overturn your wrongful conviction (provided you have the time to assemble a fingerprint database of Known Koala Offenders beforehand).

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