Human Errors: A Panorama of Our Glitches, from Pointless Bones to Broken Genes

by Nathan H. Lents

Nearsightedness is not caused by injury. It’s a design defect; the eyeball is simply too long. Images focus sharply before they reach the back of the eye and then fall out of focus again by the time they finally land on the retina.

Many birds can also see a broader range of wavelengths than we can, including ultraviolet light. In fact, migrating birds detect the North and South Poles with their eyes.

Somewhere around 6 percent of males have some form of colorblindness. (It’s not nearly as common in females because the screwed-up genes that lead to colorblindness are almost always recessive and on the X chromosome. Because females have two X chromosomes, they have a backup if they inherit one bum copy.)

The sinus passages, when working properly, keep the mucus flowing, which clears the bacteria and viruses before they can cause infections and prevents mucus from gumming up the whole system.

While the sinuses behind the forehead and around the eyes can drain downward, the largest and lowest two cavities must drain upward.

Human anatomy, however, has evolved to support our species’ standing upright, mostly by way of changes in the legs, pelvis, and vertebral column.

The ACL is vulnerable to tearing in humans because our upright, bipedal posture forces it to endure much more strain than it is designed to.

This straight-leg arrangement works out okay for normal walking and running. But for sudden shifts in direction or momentum—when you’re running and then stop short or when you make a sharp turn at high speed—the knees must bear the force of this sudden, intense strain.

To make matters worse, we as a species are getting heavier, so it’s even harder for the ACL to withstand the strain put on it during those sudden shifts.

Ironically, as posture straightened, the back had to become curvier, particularly the lower back, which took on a pretty sharp concave shape in order to help transmit upper-body weight to the pelvis and legs evenly.

There is a reason that twisted and sprained ankles are so common: the skeletal design of the ankle is a hodgepodge of parts that can do nothing except malfunction.

Humans have more dietary requirements than almost any other animal in the world. Our bodies fail to make many of the things that other animals’ do.

All vitamins are important, crucial even, to human health, but those that are essential are the ones that we cannot make ourselves and therefore must ingest.

In fact, nearly all animals on the planet make plenty of their own vitamin C, usually in their livers, and thus have no need for it in their diets.

The commonly ingested form of vitamin D is not fully active, which means that we can’t use it until it’s processed in the liver and kidney.

Without enough dietary vitamin D or enough sunlight, young humans can develop a disease called rickets, and older humans can develop osteoporosis.

Humans need calcium to keep bones strong, and we need vitamin D to help absorb calcium from food. We could eat all the calcium in the world, and none of it would be absorbed without sufficient vitamin D.

There are eight different B vitamins, which often go by other names, such as niacin, biotin, riboflavin, and folic acid (or folate). Each of these vitamins is required for various chemical reactions throughout the body, and each has its own syndrome associated with insufficiency.

Vitamin K, for example, is made by the bacteria in the gut, and we simply absorb it from there. You don’t need supplements or foods that contain it as long as you have the bacteria that produce it in your gut.

The next most famous B vitamin–deficiency syndrome is beriberi, caused by a lack of vitamin B1, also known as thiamine.

For reasons that are not always understood, nutrients are not spread evenly throughout a plant. For example, the skins of potatoes and apples are where most of their vitamins A and C are located, so peeling them can rob them of most of their nutrients.

Unrefined rice, or brown rice, is rich in B1.

All organisms use twenty different kinds of amino acids to build proteins. Humans have tens of thousands of different proteins in their bodies, all of which are made with the same twenty building blocks.

Our species has lost the ability to make nine of the twenty amino acids. Each loss is the result of at least one mutational event, usually more.

Further, chickpeas, also called garbanzo beans, contain large quantities of all nine essential amino acids all by themselves, as do quinoa and a few other so-called superfoods.

We don’t think of these minerals as metallic because we don’t consume or use them in their elemental forms. Instead, cells use metals in their water-soluble, ionized forms.

While infants can absorb a respectable 60 percent of the calcium they consume, adults can hope to absorb only around 20 percent, and by retirement age, that drops to 10 percent or even lower.

The most commonly known role of iron is in the functioning of hemoglobin, the protein that transports oxygen throughout our bodies. Red blood cells are absolutely packed with this protein, each molecule of which needs four iron atoms.

The most acute problem caused by iron insufficiency is anemia, a word that loosely translates to “not enough blood.”

In animals, iron is generally found in blood and muscle tissue, and it’s easy enough to process; humans usually have little trouble extracting iron from a nice hunk of steak.

For instance, we absorb iron best when it comes together with something else we readily absorb—for example, vitamin C.

Foods such as legumes, nuts, and berries—which we’re told to eat plenty of—contain polyphenols, which can reduce our ability to extract and absorb iron.

Thus, foods rich in calcium, such as dairy, leafy greens, and beans, should be consumed separately from foods rich in iron in order to maximize absorption, especially if the source of the precious iron in question is plant-based.

We need only the tiniest amounts of copper, zinc, cobalt, nickel, manganese, molybdenum, and a few others.

Intense exercise leads to intense hunger, which in turn leads to poor diet choices and chips away at the mental resolve to lose weight.

These nucleotides come in four flavors, abbreviated A, C, G, and T; A can pair only with T, and C can pair only with G. These are known as base pairs, and they are what make DNA such an incredibly effective carrier of genetic information.

(Mutagens are often called carcinogens due to the mutations’ tendency to cause cancer.)

Like many genetic diseases, sickle cell disease is recessive. This means that you need to inherit two copies of the mutant allele, one from each parent, in order to develop the disease.

The training of the immune system takes place in two phases, first in utero, then in infancy.

Several studies have now implicated an excessively clean environment during infancy in the development of food allergies later.

minimizing exposure to antigens will prevent children’s immune systems from getting accustomed to them.

Only a small minority of cancer cases are caused by viruses.)

Psychologists have used simulations to show how easily memories can be distorted after the fact, and these shed light on what is going wrong in the brains of many eyewitnesses.

Scars and tattoos should be covered, because if the witness remembers that the perpetrator had a neck tattoo and only one of the men in the lineup has a neck tattoo, there is a good chance she will identify that person, even if he is innocent.