Thanks to Babbel, a language learning  app, for supporting this SciShow video.

As a SciShow viewer, you can use our link  to grow your language skills with Babbel for up to 60% off with a 20  day money-back guarantee. [♪ INTRO] Humans are pretty special among mammals. Like all the others, we have hair on our  bodies and feed our young breast milk.

But we have one anatomical  quirk that sets us apart. And, I’m not talking about our big brains. Or the “walking on two legs” thing either.

I’m talking about a muscle that sits  just under the skin of most mammals … I mean, most of them except us. The layer of muscle in question  is called the panniculus carnosus, which translates to “fleshy cloth” in Latin . True to its name, it’s a thin sheet of muscle  attached to the skin and connective tissue across the trunk, back, and upper parts  of the limbs in the animals that have it.

The muscle primarily just twitches really  fast, which jiggles the skin above it. This is the muscle that  lets a horse twitch the skin at the base of the neck called  the withers, for example. Those twitches help to dislodge  insects, birds, or other foreign objects so that animal doesn’t need to use its limbs  or turn its head to get rid of hitchhikers, which is especially great if you’re an animal  that’s somewhat lacking in shoulder mobility.

Not only that, but having a big sheet of  muscle could help with thermoregulation thanks to those fast twitches, and  might even speed up wound healing. And echidnas have taken the panniculus  carnosus muscle and really rolled with it. Echidnas are monotremes, which are  the group of mammals that lay eggs.

They have sharp spines all over their  bodies, kind of similar to porcupines. But unlike porcupines, echidnas have  adapted to roll into a tight ball and point their spikes outward  as a defensive strategy which they can do thanks to  their panniculus carnosus muscle. So if this muscle is so great for  other mammals, why don’t we have it?

Although we don’t have  skin-twitching muscle sheets, anatomists think we have several muscles  derived from panniculus carnosus, including some in our scalp, face,  neck, arms, trunk and scrotum. They don’t really do much though, and  most of us can’t move them at will. And how much of those panniculus  carnosus remnants are left in us varies from person to person, which further tells us  that it’s just not that big of a deal for humans.

It turns out that if we want to know  more about why we don’t have this muscle, we can look at our relatives, the apes. Most other primates do have this  muscle, including lemurs, lorises, and several species of monkeys. But it seems like somewhere along the evolutionary  line of apes, most of us have lost it.

Dissections have shown that  most gorillas don't have it, so for those that do, it's probably  vestigial or unimportant, like it is for us. And as it turns out, there’s a  pretty simple reason that we apes don’t really need to get rid  of bugs with skin-wiggling. Another thing that apes have in common  is our flexible forelimb and shoulders.

We can reach more parts of our  bodies with our upper limbs, which means that we can swat at bugs  more easily than, like, a horse. And if having a big sheet of muscle no longer  increased those apes’ chances of survival, natural selection wouldn’t keep that expensive  tissue around - it’s use it or lose it! So the next time you have to put  something down to swat at mosquitoes, you can thank evolution for  taking away the muscly fly-swatter you could have had under your skin.

Now, along with back scratching and fly swatting, we humans can also be really  good at communication. We have the ability to speak multiple languages  and talk to other people all over the world! Especially with the help of Babbel.

Babbel is the #1 language-learning  app in the world, with 14 different languages at your fingertips. We recently had a SciShow meeting  where we went around the room asking people what superpower they wish they had, and the most common answer was being  able to understand every language. We all want to know more languages,  but it takes a lot of time.

So Babbel forms their lessons  to be just 10 minutes at a time, giving more of us the chance to pick  it up little by little every day. After three weeks, you could be speaking  Norwegian or Portuguese or Indonesian. And after two months, you  could be speaking all three!

Conveniently, the 20 days that it takes to  start speaking one of those new languages is the window for Babbel’s money back guarantee. So if you’re looking to prepare for the year  ahead, you won’t lose anything for trying. And, as a SciShow viewer,  you can get up to 60% off when you sign up using the link  in the description down below.

You can choose from different subscriptions,  including a lifetime subscription, and even gift a Babbel  subscription to friends and family. Thank you for watching this SciShow video  and thanks to Babbel for supporting it! [♪ OUTRO]