Sex, Time, and Power
Page 16
Somewhere between 1.5 million and 750,000 years ago, a Homo erectus decided not to do what every other creature instinctively did in the presence of flame. He or she did not flee. Although we can never know whether it was a male or a female who took this first step, the inherent recklessness of the act tends to suggest that only a young male Homo erectus would have been foolish enough to risk getting burned.
As his companions cringed in fear, this one intrepid ancestor edged closer to a burning brand at the perimeter of a brushfire that was probably ignited by lightning. In the moment that he vanquished his fear, grasped the lit branch, and then waved it triumphantly over his head, a new chapter in the story of evolution began.*
Homo erectus immediately put fire to a variety of beneficial uses. News of fire’s conquest would have spread to nearby bands among a primate species consummately skilled in the art of imitation. Yet, because of poor communication networks and the wide dispersal of Homo erectus throughout Africa and Eurasia, evidence of habitual fire use remains scant for hundreds of thousands of years after its discovery. Some groups were undoubtedly too dimwitted to master the techniques of making and tending a fire. Others were perhaps too fearful. Those few members of Homo erectus who knew the secret of keeping a flame alive were most likely the ones whose genes we now possess. Archeologists find blackened firepits sporadically among the excavated home bases of Homo erectus carbon-dated at 250,000 years ago. Not until modern Homo sapiens, however, is there ubiquitous evidence of the construction of hearths within encampments.†
Early on in the evolutionary story of life, plants evolved the complex biochemical pathway to harness the energy of the sun. When photosynthesis became widespread, sunlight, once removed, fueled an explosion of new species of plants and animals. Most flammable substances on the surface of the earth and beneath it have acquired their fuel load because they originally stored up sunlight in the interstices of their substance. When that nameless Homo erectus tentatively but valiantly reached for the Burning Bush, the second great evolutionary energy revolution began.
The hominid domestication of fire was a dramatic alternative to photosynthesis. A long fuse was lit that hissed down through all the generations to the present. The leaping flames arising from the first small bundle of superheated kindling transmuted into hearth, kiln, smelter, steam piston, electrical dynamo, lightbulb, and then spark plug. The stupendous event ignited by that archaic lit brand later detonated a staggering explosion at Alamagordo, New Mexico, in July 1945, followed by the first hydrogen fusion bomb in 1952. A life-form created by the energy of the sun had seen beyond sunlight to reveal the very secret of the sun.
From its earliest beginnings, the taming of fire provided hominids with an evolutionary edge. Warmth, light, parasite-free food, fire-hardened spear points, an opportunity for increased social interactions, a versatile new weapon, increased visibility of facial expressions and body language, the opportunity to make friends with a few other animals such as cats and dogs, and improved security make up the short list of fire’s benefits.
In Hebrew Genesis, the first gift that Yahweh conferred on Adam was to teach him how to name. Naming, Yahweh informs Adam, will provide him with the means to gain “dominion…over every living thing that moveth upon the earth” (Genesis 1:28). The more practical archaic Greeks believed that a more important boon was fire. In the Greek origin myth, Prometheus, the Titan, stole fire from Mount Olympus and gave it as a gift to mortals. Because the secret of fire belonged to the gods, Zeus punished Prometheus severely. Zeus and the other deities were keenly aware that Prometheus’ seditious act forever separated mortals from all other animals.
Fire initiated significant modifications in the dietary habits of the three hominid species to use it: Homo erectus, Homo neanderthalensis, and Homo sapiens. Cooking flame denatured proteins and magically converted meat that was tough as shoe leather into tender, delicious mouthfuls. Hominids who used fire evolved discriminating tastes and sought flavor. Eventually, recipes became de rigueur.
Cooking food introduced a revolutionary environmental factor in the life cycle of hominids.* Increasing reliance on fire, however, encouraged both beneficial and deleterious mutations in digestion, absorption, and internal biochemistry to replicate exponentially. Grilling meat and cooking tubers made both easier to digest, so the hominid gut began to shrink rapidly in both diameter and length, diminishing the number of the intestine’s convolutions. This in turn released a burst of excess metabolic energy that was quickly appropriated to meet the demands of a swiftly enlarging brain.
Homo sapiens’ gut handles essential nutrients in a manner that, when taken as a whole, represents a significant departure from the way every other creature digests its meals. All vertebrates require three basic foods to maintain a baseline healthy state: carbohydrates, proteins, and fats.
Digestive enzymes break complex carbohydrates into smaller and less complex molecules. When they have attained a size that is a minute fraction of the original, the cells of the small intestine’s lining absorb the byproducts of this reductive process and transfer these simple sugars into the intestinal capillaries on the other side of the gut-blood barrier. These short-chain sugars then can be easily and quickly converted to glucose by the liver.
Glucose is the fodder chiefly used to stoke metabolism to keep the home fires burning. Trillions of mitochondria within trillions of cells simultaneously throw glucose onto tiny cellular bonfires. The primary function of these mini-blazes is to heat and maintain the human body to a core temperature of 98.6°F.* This internal climate control is necessary because virtually all the body’s enzyme systems work optimally at this temperature.
The body expends the remaining dietary glucose to fuel enzymatic reactions critical to life processes. If a person ingests carbohydrates in excess of what is needed at the moment, the liver converts this surplus in several stages to fat, in which form, much to the dismay of modern humans, it is amply and conspicuously stored in buttocks, bellies, and breasts. The cells making up adipose tissue (fat) then patiently await orders from on high for their precious fuel, which the body can quickly convert to glucose.
Refined or pure sugar is the fastest absorbable source of glucose. Stripped of any other components, the simple sugars contained in its refined or pure form rapidly enter the bloodstream and can produce a “sugar high.” In the context of the Pleistocene, early Homo sapiens would have hungrily consumed any source of pure sugar. Honey, one of nature’s most concentrated forms of simple sugars, would have been particularly prized.
Proteins are the building blocks of the body. They are necessary to build, repair, and maintain tissues and organs. Pancreatic enzymes break these extremely complex protein molecules present in food down into much smaller components for easier absorption. The smallest absorbable unit is an amino acid. Once proteins are on the other side of the intestinal lining, blood transports these indispensable building blocks to the liver. There they enter various factory assembly lines so that they can be combined and recombined with other amino acids to form the very stuff of life. Albumin, serotonin, and immunoglobulins are just a few of the many intricate molecules fabricated from amino acids like Tinker Toys.
There are twenty distinct amino acids. Most animals can assemble any one of them on the backbone of the carbon, oxygen, and hydrogen present in the fats and carbohydrates in their diets. Homo sapiens, along with several other primate species, cannot manufacture eight of the twenty amino acids. These are called the “essential amino acids.” They must be ingested. Absence of any one of these eight over any extended period will have a negative impact on health. Besides the eight EAAs, two others are very difficult for the livers of adults to assemble, and children cannot make them at all. These two, arginine and histidine, are called the “semiessential amino acids.” Thus, nearly one-half of the protein building blocks critical to a sapiens’ well-being must come from his or her diet. Sapients must find their “missing pieces” in their external environment.*
In contrast, every single one of the essential amino acids is present in meat, fish, and fowl. Ironically, the most perfect protein food is the much-maligned egg. The yolk and white, intended to make an entire new organism, contain every necessary building block. If an egg is rated 3.92—highest on an overall scale for its food value, especially for the amino acids it contains—then wheat is 1.53 and peas are 1.57. By comparison, beef is 2.32 and fish is 3.55. The most complete vegetable food is the soybean, which equals beef in nutritional value.8
Vegetarians will eat dairy products, but vegans do not eat anything associated with an animal. Sue Rodwell-Wilton in her authoritative textbook on nutrition and diet comments, “A vegan diet is too poor in required nutrients to sustain childhood growth needs. Vegan children are stunted, and anemic.”*9 They also would not likely attain their full intellectual potential.
When sapients began their journey to lands less hospitable than equatorial Africa, they often found themselves in environments that had seasons during which the local plant stock was poor in the missing eight EAAs. Those ancestral humans who had access to meat protein would have been the most likely ones to make it to the next generation. Those who did not were at a major genetic disadvantage.
Women need protein more than men. Adequate estrogen levels (built up from proteins) are essential for a woman to synthesize properly her other proteins. Progesterone (built up primarily from proteins) plays a crucial role in ensuring that the proteins she manufactures last. Menses causes iron and protein loss. Men do not experience a comparable metabolic event that regularly loses protein.10
The challenge to a pregnant or nursing woman would have added an exceptional burden. She would have had not only to fuel her own body’s needs but also to participate in building a new one. Every one of the mother’s amino acids traversing the placental barrier is lost to her forever. At birth, a newborn plus its attached placenta carries out of the mother a huge amount of what had formerly been the mother’s total protein. To create a healthy baby, a woman must procure a diet rich in all the amino acids before, during, and after pregnancy.
Another vital component of the human diet is fat—a food providing the most concentrated energy per ounce. A wild elephant must spend its waking hours locating and eating six hundred pounds of green fodder daily to meet its minimal energy requirements.11 A wolf, after bolting down a meal of hapless prey, can go for days without eating again. The fat in its meat makes the difference. Fats are large, complex molecules that resist easy digestion and absorption. Enzymes excreted by the pancreas saponify the fats we eat; that is, they break the large fat globules one sees floating in a bowl of chicken soup into smaller and smaller droplets until they are tiny enough to be absorbed by the intestinal lining. The smallest component of dietary fats that can be absorbed is a fatty acid.
Once on the other side of the intestinal lining, fatty acids, like proteins, are transported to predestined storage areas. In a crisis, fats can be thrown into the metabolic furnace for a quick jolt of energy. Some fats that we eat, however, are too valuable to store or burn. These are earmarked for tiny assembly lines scattered in various tissues and organs, principally the liver. There, the special fat is annealed to a protein to become a component of an important class of compound molecules called “lipoproteins.”
Lipoproteins are what give life its sponginess. The integrity, shape, and form of every cell membrane depend on lipoproteins. The greatest concentration of lipoproteins exists in the human brain. Sixty percent of brain tissue by weight is fat—but a very interesting, intelligent fat.12 If neurons can be compared to the transmission wires of an electrical grid, the entire infrastructure—the towers, insulation, and way stations—is constructed primarily of lipoproteins. Biochemist Michael Crawford, who has written extensively on the importance of diet in human evolution, observed, “The real value in animal products may well lie in the fact that they contain a spectrum of structural fats not found in vegetation.”13
Human metabolism can manufacture all fatty acids the body needs from the materials it has on its internal shelves except one. Linoleic acid is a long-chain fatty acid that many other animals can make with ease. Humans lost the ability to join together the atoms of this one essential fatty acid. Linoleic acid is found in many but not all vegetable oils. Corn, soybean, and canola, to name a few, contain rich lodes of it.* Raw seeds and leaves are another good source.
A much simpler dietary strategy to acquire this essential fatty acid is to eat an herbivore. Leaf- and seed-eating animals expend prodigious amounts of metabolic energy converting linoleic acid into incredibly complex fatty-acid chains. A carnivore can simply bypass all the intermediate steps and devour the finished product. The fat marbling a steak is visible linoleic acid that has been considerably upgraded. Liver and all dairy products are also very rich in this essential fatty acid. This element, so crucial in the construction of a fetal brain, must be in abundant supply during and right after pregnancy in order for a newborn to build out the potential intelligence programmed in its DNA.
The most crucial member of this family of important compounds, the one without which human life is not possible, is cholesterol. The liver and intestinal wall manufacture the necessary minimum requirement of this compound molecule. Most animals can make all the cholesterol they need “in-house.” But human metabolism requires so much of the golden substance that it welcomes an outside assist. The liver consumes an enormous amount of energy and resources to build the basic cholesterol molecule. Supplemental dietary cholesterol was an important adjunct to good health for ancestral humans.*
In modern times, people view cholesterol as a villain, because its overabundance has been implicated in atherosclerosis, the leading cause of coronary artery disease, heart failure, and strokes. At the dawn of our species, these modern pathologic conditions competed as a chief cause of death with an attack by a saber-toothed tiger, a goring by an auroch, and starving in the clutch of a relentless ice age. Cardiovascular disease came in last.
Cholesterol plays an indispensable role in everything from the basics of nerve transmission to the parameters of intelligence. It is the precursor molecule to all the steroid hormones: cortisone, estrogen, progesterone, and testosterone are all cholesterol-based. Fleeing, fighting, feeding, and sex are central activities driven by steroid hormones. The brain has more cholesterol in it than any other organ. There is suggestive evidence that high cholesterol levels sustain the mental states of happiness, equanimity, and optimism. Similar studies suggest its deficiency may induce the opposite mood states. Men exhibiting impulsive, antisocial, and violent behavior more commonly have lower cholesterol levels than the population at large, as studies of violent prisoners and inmates of mental institutions have shown.14 The 25 percent of men with the lowest cholesterol count are four times more likely to commit suicide than the 25 percent of men with the highest cholesterol count.15
Because cholesterol is the precursor molecule for the manufacture of testosterone, estrogen, and progesterone, any process that diminishes serum cholesterol or interferes with the normal conversion of cholesterol to the sex hormones will lessen a man’s or woman’s libido. Many medical conditions that have low serum cholesterol as part of their clinical picture, such as Addison’
s disease (a malfunctioning of the adrenal glands), are characterized by a low libido. A woman experiencing low cholesterol will have menstrual irregularities, and these in turn diminish her chances for a successful pregnancy.
There is zero cholesterol in 99.9 percent of plant foods. Cholesterol and the precursors necessary for its manufacture are overabundant in animal foods. I speculate that, in the evolution of our species, Natural Selection favored men who ate high-cholesterol foods because they were, on average, slightly more effective hunters and ardent lovers. A female who mated with a man who shared his high-cholesterol bounty with her had a healthier body, a slightly more exuberant sex drive, higher fertility rates, and slightly more intelligent children. Each feedback loop would have had the effect of encouraging humans to stray away from the plant foods that were their primate heritage and develop a hankering for fatty meats.
One need not be a biochemist to assess the importance of cholesterol to the male’s sex drive at the moment his testosterone level skyrockets. Simply observe the dietary volte-face of boys at the point in their development when they begin to turn into men. Young boys do not particularly like red meat. Ordering a steak for them in a restaurant, as any parent can attest, is a waste of money. Most boys would be perfectly happy subsisting on peanut-butter-and-jelly sandwiches. However, once the pistons of puberty begin to rev, a startling transformation occurs to male taste buds. Peanut butter is relegated to the back of the pantry, and teenage boys hunger for red meat—the greasier and bloodier the better. A significant component of this change in culinary tastes is due, I believe, to the male interest in sex. Men seem instinctively to understand that red meat increases their sexual stamina. And the cholesterol in his hamburger may be one among a series of vital components a young man wolfs down because he is unconsciously driven to satisfy his restless, ever-pacing libido.