Koalas have almost identical footprints to ours | NOVA

In the mid-1990s, Maciej Henneberg was working with koalas in a wildlife park near Adelaide, Australia, when he noticed something odd: the animals appeared to have fingerprints.

As a biological anthropologist and forensic scientist, Henneberg knew that this made koalas unique, the only non-primates with fingerprints. “Nobody seems to have bothered to study them in detail,” he told The Independent in 1996, shortly before publishing a newspaper article announcing the discovery. Henneberg’s research indicated that not even a careful microscope analysis could help distinguish the wiggly, swirling ridges on koala toes from ours. The fingerprints were so similar to human ones that he feared they could be easily confused by investigators. (Even so, he acknowledged to The Independent, “it is extremely unlikely that koala footprints will be found at a crime scene.”)

While Henneberg’s discovery didn’t help decipher koala cold cases, it did add fuel to a decades-long debate about what fingerprints are for and how humans evolved to possess them.

When it comes to fingerprints, we know more how we develop them with respect to why. Scientists divide the intricate vortex of these unique patterns into broader categories: rings, spirals, and arches. They call the rest of the forms, places where the lines break, split in two or create concentric islands, “minutiae”. Although the general essence of your fingerprint is something you inherit from your parents, these minutiae come from the environment in which you developed as a fetus, including the composition of the amniotic fluid, how you were positioned and what you touched in the womb. That’s why everyone has slightly different footprints, even identical twins.

But what would make fingerprints useful from an evolutionary point of view? Prior to the discovery of the Henneberg koala, conventional wisdom held that fingerprints increased friction, helping humans grasp objects better. However, a handful of more recent studies indicate it’s more complicated than that.

In 2009, biologist Roland Ennos published a study according to which, in contact with an object, the skin of the fingertips behaves like rubber. This means that the friction between our skin and a surface increases in proportion to the total area in contact. And because the skin is puckered with loops, spirals, and arches, it actually has less contact with that surface than if it were smooth, meaning fingerprints could actually diminish friction.

But more recently, a study based on Ennos’ conclusions suggested that while fingerprints may not create friction on their own, they can help maintain grip by working together with the sweat glands. Researchers have found that our fingers release moisture when they come into contact with hard, waterproof surfaces. Moisture creates friction by softening the skin on the fingertips, with the help of the small grooves of the prints, which direct the liquid in order to allow maximum evaporation. (This is important because if sweat builds up too much, it could cause slippage.) The barely supple leather also allows for another built-in protection, as pressing against the surface eventually blocks the sweat-producing pores, allowing evaporation to escape. recover and helping to maintain the all-important friction.

“This dual moisture management mechanism gave primates an evolutionary advantage in dry and wet conditions, giving them manipulative and locomotive skills unavailable to other animals,” co-author Mike Adams said in a press release at the time.

And fingerprints can also provide crucial sensitivity at your fingertips. Physicists at the École Normale Supérieure in Paris found that fingerprint ridges can amplify the vibrations produced by rubbing the fingertip on a rough surface, transmitting those vibrations to the nerve endings of the fingers. This kind of insight has become increasingly important as designers of prosthetic limbs, adaptive technologies, and touch screens try to understand how our fingers and sense of touch help us interact with the world.

But our last common ancestor with koalas was, according to some calculations, more than 100 million years ago, when marsupials separated from the rest of the mammals. So how did we come to share this particular trait? The answer is what is called “convergent evolution,” when independent organisms evolve identical characteristics in response to similar evolutionary pressures.

There are so many ways animals can climb tall trees, live on cliffs, move underwater, or perform any of the specific tasks required by narrow evolutionary niches. Bat and bird wings evolved separately. As Live Science points out, sharks and dolphins come from divergent lineages hundreds of millions of years ago, but both developed smooth skin and sharp fins to help them stalk prey. And because marsupials branched out a long time ago, there’s even a parallel track of them in Australia that has evolved convergently with our placental mammalian cousins. Down Under marsupial moles, for example, are not related to moles in other parts of the world. Yet both are blind and boast very similar feet for a life digging underground.

Koalas are famous picky eaters who seek out eucalyptus leaves of a specific age. And as Henneberg points out in his 1997 article, koalas may also need to grasp each other in similar ways to humans, simultaneously, “climbing vertically up the smaller branches of eucalyptus trees, reaching out, grabbing handfuls of leaves and bringing them to their mouths.” He felt that koala fingerprints must have originated as an adaptation to this task, and relatively recent, since neither wombats nor kangaroos (both koala cousins) have them. delicate job of collecting particular leaves and discarding others, but hopefully not close to a crime scene.

Receive emails on upcoming NOVA programs and related content, as well as featured reports on current events through a science focus.

Leave a Comment

%d bloggers like this: