You Inherit Part of Your Fingerprint from Your Parents

2 minute read
Originally posted here: https://mcgill.ca/oss/article/did-you-know/you-inherit-part-your-fingerprint-your-parents

Our fingerprints are a one-of-a-kind pattern, so unique to an individual that even identical twins don’t share them. And yet I’m here to tell you that you inherit part of your fingerprint from your parents. Huh?

If you look closely at your fingerprints, you’ll notice that their patterns are one of three main types: loops, whorls or arches.

If you were to look at your fingerprint under a microscope though you’d see that while the ridges on your fingers follow one of the patterns, there are small variations in them, like breaks, forks and islands.

While the general shape of your fingerprints is heritable, these small details, often called minutiae, are not. Why that is comes down to how fingerprints are formed.

When a fetus is about 7 weeks old, they begin to form pads on their hands and feet called volar pads. These pads only exist for a few weeks, because at around 10 weeks they start to be reabsorbed into the palms of the hands and feet.

Around this time, the very bottom layer of the epidermis begins to form folds due to pressures from the growing skin. These folds are the precursors to your finger ridges, or fingerprints, and the pattern they take depends on how much of the volar pad has been absorbed when they begin to form. If the volar pad is still very present, then you’ll develop a whorl pattern. If the volar pad is partially absorbed, you’ll form a loop pattern, and if it’s almost entirely absorbed, you’ll form an arch pattern.

So how do genetics come into this? Well, the rate of volar pad reabsorption and the specific timing of the creases in the epidermis appearing are genetically linked. However, these events only determine the general shape of the fingerprint. The minutiae are influenced by things such as the density of the amniotic fluid, where the fetus is positioned and what the fetus touches while in utero. Since every fetus will grow in a different environment, their minutiae will differ. Even twins that share a uterus will interact with their surroundings differently. So even if your fingerprint shape matches that of your parents, if you look closer, you’ll see the differences that make your prints uniquely yours.

Did you know that fingerprints aren’t only a human feature? To read about fingerprints in koalas, click here!

Koalas Have Fingerprints Just like Humans

2 minute read
Originally posted here: https://mcgill.ca/oss/article/did-you-know/koalas-have-fingerprints-just-humans

In 1975 police took fingerprints from six chimpanzees and two orangutans housed at zoos in England. They weren’t just looking for a unique souvenir; they were testing to see if any unsolved crimes could be the fault of these banana-eating miscreants.

While these primates ended up being as innocent as they seemed, the police did determine that their fingerprints were indistinguishable from a human’s without careful inspection.

A few years later, in 1996, a different type of mammal came under police suspicions: a koala!

While it makes sense that orangutans and chimpanzees would have fingerprints like us, being some of our closest relatives, koalas are evolutionarily distant from humans. It turns out that fingerprints are an excellent example of convergent evolution, or different species developing similar traits independently from each other.

Another example of convergent evolution is seen in the bony structure supporting both birds’ and bats’ wings.

Fingerprints are thought to serve two purposes. First, they aid in grip, allowing an animal to better hold onto rough surfaces like branches and tree trunks. Second, they increase the sensitivity of our touch and allow us a finer level of perception regarding the textures and shapes of the things we hold.

Why this is useful for humans is obvious. Our hands are made to grasp, hold and manipulate objects. Whether it’s some nuts we foraged for or our Xbox controller, we humans spend all day every day relying on our sensitive sense of touch.

For koalas, it’s not really so different. They are incredibly picky eaters, showing strong preferences for eucalyptus leaves of a certain age. It seems that their fingerprints allow them to thoroughly inspect their food before they chow down.

Police aren’t exactly worried about koala bank robbers, but it is possible that koala fingerprints could be found incidentally at a crime scene and be mistaken for a human’s, making it pretty difficult to find a match.

To read about how fingerprints form, how parts of them are genetic, and why identical twins have different ones, click here!

Platypus are Electrifying

Originally posted here: https://mcgill.ca/oss/article/did-you-know/platypus-hunt-tracking-their-preys-electrical-outputs

If you thought that echolocation or vegetarianism were the only options available to vision-impaired animals, you’re in for a surprise.

Platypuses (the plural “platypus” is also correct, but technically “platypi” is not) have almost 40,000 special cells in their bills called electroreceptors that are activated by the electric fields created by other marine animals’ muscles moving. This is quite useful for the platypus, who tend to live in murky or dark waters but are able to follow the electric fields of their prey to catch their dinner.

It’s not only platypuses that can sense electricity: there are many electric fishthat also do this, as well as some sharks, bees, echidnas and a newly discovered species of dolphin!

While platypuses might not be blind, they are functionally blind when hunting. They close their eyes, noses and ears whenever they dive, and then swing their heads back and forth to sense electrical currents and move towards them (here’s a great video of that!)

But why are there only 3 species of mammals with these electric abilities? Well, it’s partly due to ecological niches. If a species develops a method to hunt where no others can (like in dark murky water) they flourish, but since that niche is now filled, the new skills don’t extend beyond that species.

Otherwise, you can thank evolution for non-electric animals. Sensing electric fields is only really useful if you live in the water (like electric fish) or at least hunt in it (like platypuses). Once you live and eat on land, there’s no real reason to keep your electroreceptors, and with less water comes even fewer reasons. This is reflected in echidnas: Western long-beaked echidnas have about 2,000 electroreceptors on their beaks (20x less than platypuses), and the short-beaked echidnas, who tend to live in even drier climates, have only about 400.

It’s worth pointing out, though, that all animals use electric signals to make their muscles work, so in a sense, we’re all electric!