Evolution Gone Wrong: The Curious Reasons Why Our Bodies Work (Or Don't)

by Alex Bezzerides

The mass extinction event that occurred at this time is known as the K–Pg boundary or the K–Pg extinction event (for defining the border between the Cretaceous and Paleogene time periods).

The problem with meat is that it does not want to be eaten.

The brain accounts for about 2% of human body mass but uses up to 20% of our caloric intake.

That, right there, is one of the most important features of evolution. Lousy function trumps no function. Every time.

Without tapeta lucida, in humans, bright light reflects off the many blood vessels at the backs of the eyes, leading to the red-eye effect commonly seen in flash photography. Cameras with anti-red features use short flashes of light, before the real flash, to get the irises to constrict and make the pupils small, limiting the amount of light from the real flash that gets to the backs of the eyes.

Even though we have only three color pigment types, the most recent split set us up with a keen ability to discriminate more shades of green than any other color. We can distinguish tens of thousands (some even argue hundreds of thousands) of shades of green, and we have those early salad-eating primates to thank for this now-much-less-necessary skill. These days it’s maddening because it means there are way too many color swatches available when deciding which exact green to paint the guest bedroom.

Not every human is a trichromatic primate. Color-blind individuals produce two fully functional types of cones and one mutated version that is deficient in its ability to discriminate either red or green.

They are dichromatic, walking around seeing a limited number of shades, like they are looking through the eyes of a dog or a grizzly bear.

Many safety advocacy groups have tried to simplify things for parents by recommending that small children should not have access to any toy capable of fitting inside a toilet paper roll.

Because of the epiglottis, nonhuman mammals are terrifically unlikely to choke on their food. It can happen, but it does not happen with anywhere near the regularity seen in humans. The epiglottal seal with the soft palate also provides nonhuman mammals the ability to eat and breathe at the same time.

the quantal vowels [i], [u], and [a].

The generally accepted time for the appearance of Homo sapiens is approximately 200,000 years ago, though some researchers in the field suggest early Homo sapiens may have transitioned away from other hominins by 300,000 years ago.

For many people, the anatomy allowing for speech totally fails them when they lie down and attempt to rest. Sleep-disordered breathing (SDB) is the technical name of the condition, and it is shockingly common.

In fact, before surgical techniques became more refined and effective, it was not unheard of for professional athletes to carry on with their careers in spite of torn-up knees. Several athletes, including Mickey Mantle and Joe Namath, are believed to have played large stretches of their careers with torn ACLs.

the most common cause of injury in the non-sporting group was crouching. Yes, crouching.

With bipedalism and long-distance foraging, males may have shifted away from beating their chests and baring their teeth to impress females to figuring out which type of food gifts were the perfect ones for getting potential mates in the mood. A few million years later and males are still trying to figure that one out. In my experience, potato and leek soup with chopped chives and crumbled bacon gives you a good chance.

Believe it or not, there is an established human world record for the fastest 100 meters running on all fours. The Usain Bolt of four-limb running is Kenichi Ito from Japan, who holds the world record with a time of 15.71 seconds (compared with Bolt’s 9.58 seconds running bipedally). Just as it is somewhat striking to see a nonhuman great ape amble around on two legs, it makes you do a double take to see a human sprinting down the track using all four limbs.* It also stresses, in a very visual way, the notion that our quadrupedal past is, in fact, not so very deep in the past.

Proprioception is the awareness of the position of the various parts of the body.

Each human foot has 26 bones.

Even the holy grail of hominin fossils, Lucy, had only three of the possible 52 foot bones with her skeleton.

Adaptations like our abundant sweat glands, lack of hair, and ability to breathe heavily while running allow humans to chase and eventually kill large prey with a method deemed persistence hunting.

Taking advantage of their modified forelimbs, birds took flight and have colonized every corner of the globe. By sheer numbers, they are the most successful group of terrestrial vertebrates, and it is not even close.

The notion that correlation does not imply causation is one of the most important principles students can learn in an introductory statistics class.

tertiles (a new word for me—it’s the same idea as quartiles or quintiles but with three groups instead of four or five).

There are only five liters of blood in the average adult.

The phenomenon of ingesting non-nutritious items is known as pica.

One of the most commonly craved and ingested substances in these situations is dirt.

The first step to understanding a difficult topic is accepting and leaning into some level of confusion.

Some 30% of successfully implanted embryos never make it to six weeks of gestation.

The answers may lie in the shape of the brains rather than the size.4 Neanderthals dedicated a much larger proportion of their brains to visual input and had a smaller cerebellum than humans. The cerebellum has, in the last generation, become recognized as an important area of the brain for cognition, and researchers believe humans may have had a greater ability to think on their feet, problem-solve, and in short, be cognitively flexible compared with Neanderthals. Cognitive rigidity is fine until new challenges arise. New challenges require adaptability, and Neanderthals eventually met a novel situation they could not overcome. Their final failed test may very well have come from humans, with our flexible brains and penchant for establishing dominance over all other species.

Among mammals, humans have the largest brain-to-body-mass ratio. Dolphins come in second place, and no other mammal is even close.5* Humans and dolphins seem to suggest that exposure to a novel environment is a critical ingredient in the evolutionary recipe for extreme intelligence.