Humans, for the most part, are trichromats. That means that we have three kinds of cone cells in our eyes to interpret and identify colors. There are those, however, that have four kinds of cone cells in their eyes, known as tetrachromacy. They can’t see colors that don’t exist, but they can perceive the differences in colors much closer.
Is that couch dark brown or black? We don’t know, but tetrachromats will be able to tell us. It was the normal condition of most mammals in the past, but they have lost one or two of their cones by now.
An Extra Neck Rib
More prevalent in women, having an extra rib near the cervical spinal region (or “neck” for us dum-dums) is known as a cervical rib. Somewhere between one and three percent of the people in the world have a cervical rib on one side or both. They may reach down to connect to the first rib, or they may not be fully formed.
Often the bone is tiny and hard to notice even on x-rays, but they can sometimes cause complications. A cervical rib means higher chances of nerve or blood vessel compression between the rib or its muscles since the ligamentous connections take up a smaller space.
Less Means More for the Heart
All of us have the PCSK9 gene in us, but some of us have it in a lesser amount, somehow. Maybe it's just a weaker version? It's hard to have less of a gene – you either have it or you don't. Those that lack it, or present the deficiency somehow, have a ninety percent less chance of heart disease, and hardly have to bother with cholesterol at all.
The gene provides instructions on how to make a protein that regulates the amount of cholesterol in your bloodstream. You might know there are two forms of cholesterol, good and bad, but even bad cholesterol has some uses.
Get Those Elizabeth Taylor Eyes
Having long, beautiful lashes is something that everyone wants if they want to look their best. What about a double layer of eyelashes? This is called distichiasis, and it does just that. There's a technical way to describe this, but really what it does is make your upper lashes thick, full, and popping.
Actress Elizabeth Taylor, known as one of the most beautiful women in the world, sported this to make things, frankly, a little unfair. This is a good boost, but it can create a sensitivity to light, irritation, sties, and droopy eyelids. It is still a rare trait.
The Rare Genetic Condition Known as...Red Hair
This one is pretty well known. In fact, we wouldn't be surprised if there's someone in your family that has it. But natural red hair is a lot rarer than you might think. It only occurs in about two percent of the population, most common in northern and western Europe. It's a recessive gene, beaten by every other color.
For someone to have natural red hair, both parents have to have it. You may wonder why they seem far more common, but it turns out something like thirty percent of advertisements feature models with red hair. Plus, there's hair dye and plenty take the opportunity to try out this fiery shade.