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

by Nathan H. Lents

Vertebrates were not so lucky, and we are still suffering from the consequences of this evolutionary fluke; most ophthalmologists agree that the backward retina is what makes retinal detachment more common in vertebrates than in cephalopods.

The human maxillary sinus cavity. Because the mucous collection duct is located at the top of the chamber, gravity cannot help with drainage. This is part of the reason why colds and sinus infections are so common in humans but unheard of in other animals.

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. The precursor of the vitamin is also generated in the skin, providing the individual gets enough sunlight, but it still needs to be processed into the active form. Without enough dietary vitamin D or enough sunlight, young humans can develop a disease called rickets, and older humans can develop osteoporosis.

A large dose of vitamin C can increase iron absorption sixfold. Unfortunately, the opposite is also true; a diet poor in vitamin C makes iron absorption more difficult, often leading to the double whammy of scurvy and anemia.

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. Similarly, whole grains, nuts, and seeds are high in phytic acid, which tends to prevent iron from being absorbed by the small intestine.

Another dietary component that interferes with iron absorption is calcium, which can reduce iron absorption by up to 60 percent. 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. If you go to the trouble of eating iron-rich foods but pair them with calcium-rich foods, you’ve negated your efforts.

Because of its late onset, Huntington’s can be passed on with natural selection having little to say about it.

In gorillas, average birth spacing approaches four years, except when a nursing infant dies, at which point the mother almost immediately goes into estrus.

There is an even rarer, stranger, and more dangerous form of ectopic pregnancy. Very seldom, when an egg is ejected from the ovary, it does not make it into the fallopian tube at all. This is because, quite oddly, the fallopian tube is not actually connected to the ovary. Rather, the opening of the fallopian tube envelops the ovary, sort of like a too-large garden hose resting on a too-small spigot. The two are not actually attached, and sometimes an egg gets squirted out of the ovary and into the void of the abdominal cavity instead of into the fallopian tube.