6 Terrifying Mutations With Awesome Historical Explanations

6 Humans With Tails

If you're familiar with medical oddities, or at least the Jack Black movie Shallow Hal, you know that occasionally a human will be born with a tail. While these individuals can't use their gift to hang from low-lying branches, their tails are more or less as anatomically correct as that of any monkey from your local zoo. Some people can actually move the damn thing (fair warning, this video is incredibly gross).

You might, however, have thought that this was just a freak accident, like being born with a sixth finger or webbed genitals. Actually, all human babies start life with a stubby little tail while they're in the womb -- it's an evolutionary leftover from when we all had tails. In fact, scientists now think that our early ancestors might have been squirrel-like creatures with tails so long that they were mostly tail.

Obviously, the no-tail side won the evolutionary battle, presumably because it has to be next to impossible to bone a female squirrel monster with a tail in the way that's longer than your goddamned body. It's hard not to miss it a little bit, though. Sure, it would make driving a car impossible, but do you ever find yourself standing in line at the DMV and wishing you had a giant limb that you could use to smack somebody across the room? That's you subconsciously missing your phantom tail (that's our theory, anyway).

And in some cultures, being born with a tail can earn you some perks. In India, Chandre Oram is believed by many to be the incarnation of the Hindu monkey god Hanuman because of his 13-inch tail. It's a comparison that he encourages by climbing up trees and eating bananas. That's right, buddy, just go with it.

5 Dolphin Legs

One of the first animal facts you learn in grade school is that whales and dolphins are mammals and actually more closely related to you than to the fish they resemble. They can't even breathe underwater -- they have lungs just like us. What this actually means is that, millions of years after animals first crawled onto land, the whales decided "Screw everything about this," regrew their fins, and slunk back into the ocean, flipping us the middle finger they no longer have.

These days, whales and dolphins are still occasionally born with stubby little legs, like this one that Japanese researchers caught in 2006 (pictured above), an apparent throwback to ancient times when they may have looked like this:

You can see not only where they had back legs, but also that their front fins used to be webbed paws like the Creature from the Black Lagoon:

Which is kind of terrifying if you're imagining them, you know, whale-sized. In fact, even normal whales have rudimentary leg bones crammed into their backsides, as you can see floating under the lower left of this killer whale skeleton:

You can also see its freaky "hands" where you thought it just had flippers. That's what their front limbs actually are -- evolved hands (or paws, whatever):

The pictures only get freakier from there. Here's the giant skeleton hand of a sperm whale:

And here's a killer whale with both skeleton hands and huge teeth included in the frame so you can imagine it grabbing you by the neck and biting your head off:

We'd point out how terrifying it would have been to live in an era when killer whales could come flopping out of the ocean to munch on land prey, but we have a feeling the things would have been slow as shit.

4 Chickens With Teeth

Dinosaurs are every child's introduction to the idea that evolution has no interest in making things more awesome. For instance, the dinosaurs were so huge and terrifying that evolution decided to punish them for their hubris by turning them into birds. It's difficult to imagine now, but the humble chicken once towered over the savannah as a Tyrannosaurus rex. Now we cut off their wings and make women in tiny shorts serve them to us as food.

Sometimes, though, the chickens are granted a nostalgic throwback to their badass past with a little help from modern science. In 2006, mad scientists working on chicken embryos managed to grow chickens with teeth by coaxing their DNA to recall their ancient evolutionary origins.

After all, there were a lot of steps in between "building-sized lizards with murderous jaws" and "sad lumps of feathers that eat worms." For instance, there was once a time when they looked like this:

That's Sulcavis geeorum, the 125-million-year-old ancestor of modern birds, which nature wisely saw fit to eliminate from the gene pool and humanity has decided to tease back into existence by way of the world's most non-threatening species. So modifying a chicken embryo to make it grow teeth just involves using a few tricks to bring out the dormant genetic traits that are still hiding in there.

Somewhere, a young writer has already started on his screenplay about hordes of genetically modified dino-chickens descending upon KFC headquarters to exact their violent revenge. And the poster will be a big KFC bucket full of severed human limbs.

3 Horses With Toes

We mentioned in a previous article that horses are distantly related to rhinos on the evolutionary tree, and you can tell if you look closely at their feet. Rhinos have three huge toes ...

... and horses have just a hoof, but the horse's hoof is actually one giant toe. There was a time in history when each evolved from a common multiple-toed ancestor, and the horse's middle toe evolved into one big one that we're referring to as a hoof. But, once again, occasionally freak horses will be born with multiple toes sticking awkwardly out of the sides of their feet.

And just as the man with the tail has been worshiped as a mystical being, multiple-toed horses were often regarded as magical status symbols among warriors. Julius Caesar and Alexander the Great were both said to have owned one. The Romans were so impressed by the "toes on a horse thing" that Caesar's was rendered as having at least five, and also a unicorn horn for good measure:

To be clear, the toes did NOT look like that -- the Romans were so fascinated by horse toes that they just couldn't help going overboard with it.

2 People With Reptile Hearts

Imagine you're struck one day with the most crippling chest pains and you race to the hospital, fearing the worst. The doctor tells you that there's good news and bad news. The good news is that you're not having a heart attack. The bad news is that inside your chest beats the cold heart of a reptile.

That's exactly what happened to a 59-year-old man who was admitted to the hospital with mysterious symptoms that had medical professionals puzzled until they gave him an X-ray and found that he had a full-blown case of snake heart -- a reptilian heart with only three chambers, instead of the usual four.

Again, this isn't just a freak deformity that happens to resemble a lizard's heart in the body of a man -- studies of the organ found that it was a genuine genetic throwback, a simple case of evolution getting drunk and forgetting which eon it is. Because we know you think we're making this up, let us just quote the scientists:

"In early stages of embryonic development, the human heart resembles that of a fish .... In later stages of development, the human heart -- now with fully separated atria and a partially separated ventricle -- resembles a reptilian heart. ... To our knowledge, this is only the second reported case of an unusual morphologic variant involving a non-mammalian, reptile-like cardiac anatomy ...."

Wait, you mean this has happened more than once?

And while this sounds like the origin story for a supervillain (this was the plot of the Spider-Man reboot, right?), the only superpower the patient got from it was a horrible pain in the chest and a dependence on prescription medication. We're assuming that if he complained, the doctor's only response would have been "Dude, count your blessings. You made it to age 59 with a snake heart."

1 People With Multiple Sets of Boobs

Come on, you knew this was where the article was going. Other mammals have multiple breasts, humans are mammals, you can put two and two together.

So, yes, there have been people who were born with more than just the factory standard two breasts. The hilariously named accessory breast syndrome (we're going to guess a male came up with that) is a throwback to an earlier human ancestor who, like other mammals, had several breasts each so that they could feed a whole bunch of offspring at the same time. Humans tend to only give birth to one or two kids at a time, though, so evolution has decided that we only need an upper limit of two boobs per person.

But, as with all of the other cases on this list, the genes are still hiding in there somewhere, and occasionally they pop up and decide to award someone the grand prize in the boob lottery.

If you're wondering why Internet porn isn't just packed full of four-breasted women, it's because nature, in her infinite wisdom, made it so that accessory breasts are more common among men than women. It's typically harmless, and the extra breasts often aren't even detectable without an MRI (the thing where some men have an extra nipple is not really the same thing). Women often have them removed because they're in the way (sometimes located in the armpit), and because they probably get tired of dudes who hear about it immediately picturing a Total Recall situation.

For more strange wonders of nature, check out 7 Animals That Are Evolving Right Before Our Eyes and 15 Animals You Won't Believe Aren't Photoshopped.