Who were we 40k+ years ago?
Many of us believe our ancestors lived much shorter lives than we do. Archaeology shows otherwise.
Don’t confuse lifespan with life expectancy. The latter includes infant mortality. The maximum human lifespan (approximately 125 years) has barely changed since humans arrived.
Our ancestors had a higher probability of death at every age than we do, but they lived a smaller portion of their lives in disability. Modern humans live longer but age more rapidly than our prehistoric ancestors, and we live more of our lives in chronic illness.
So, who were we 40,000 years ago? Our ancestors of that era were tall, muscular, and lean. Food was often scarce. Exercise (meaning the physical activity required to survive) was made up of heavy labor plus intense but brief “fight-or-flight” emergencies. Our ancestors retained their health throughout their lives, though their life spans were considerably shorter than ours because of greater incidences of infection, infant mortality, predators, and accidents.
Homo erectus, our ancestor from almost 2 million years ago, could go out today and buy a suit (42 long) at Ralph Lauren and walk the streets of New York with little notice. He would be tall and lean, built like an NBA guard. A more modern Cro-Magnon, who roamed the earth 40,000 years ago, might buy an Armani (44 long)—he would have a better sense of style than Homo erectus, as evidenced in the art objects and cave paintings he left behind. A Cro-Magnon might look more like a rugby player; he would be taller than most males now and would be lean, muscular, and very powerful—a devastating athlete. He would also have a bigger brain than we have. All this can be inferred from Cro-Magnon skeletons, from the capabilities of contemporary hunter-gatherers, and through comparisons between other animals living in the laboratory and in the wild.
Similarly, a female Cro-Magnon would be slender and a bit taller than a modern female, with the classic hourglass shape and posture of a graceful woman. Based on the depictions of shapely females found in Cro-Magnon art, she might look like a supermodel,… Some highlights have been hidden or truncated due to export limits.
Modern humans carry a copy of the same genes as our Cro-Magnon ancestors from 28,000 years ago. At least 70 percent of European humans alive today can trace their genes to the small band of Cro-Magnon humans who managed to survive the last Ice Age. The origins of the seven tribes of humans living in Europe can be traced to seven males who lived between 100,000 BC and 40,000 BC.
Why, then, does this same genetic material, which once expressed health and muscular leanness in our ancestors, now express obesity and chronic illness? The answer, of course, is the environment in which our genes express themselves—meaning our modern, affluent society.
In short, we are genetically engineered to thrive in a different world. I believe that if you took prehistoric hunter-gatherers and placed them in our environment, they would behave just as we do and would eventually suffer the same problems. We know this is true because we are hunter-gatherers and we do suffer. We also know that when contemporary hunter-gatherers enter industrialized society, they end up with our bad habits and chronic ailments.
This brings us to a key concept to keep in mind as you read on: We humans evolved when food was scarce and life was full of arduous physical activity. Hence, our bodies instruct us to eat everything we can lay our hands on and to exert ourselves as little as possible.
That’s right. We are, in essence, hardwired to be lazy overeaters.
This was a perfect strategy for success thousands of years ago. No human could survive in 40,000 BC unless he or she ate anytime food was available. Our ancestors knew that famine was always close at hand—feast now or suffer tomorrow. They were also careful to expend as little energy as possible, because burning more calories than absolutely necessary was a threat to survival. There were unpredictable intervals of low food intake, even occasional starvation, interwoven with times of abundance.
In the modern world, a hunter-gatherer would follow those same principles: He’d eat a lot and move a little. And he would suffer the same ills we do, living in a modern environment where food is abundant and physical activity is more or less voluntary. Most diet and exercise plans ask us to move more and eat less—a direct contradiction of our genetically engineered impulses. No wonder most diets don’t work.
Our forager ancestors also sought out high-energy (meaning high-calorie, high-fat) foods that could be obtained at the lowest energy cost. They would eat or not depending on what they could find or kill, meaning mealtime was a fairly unpredictable thing. They would move when hungry (or when being pursued) and relax once fed—like wild animals do today. Their physical activity would be sporadic, meaning short bursts of intense activity (hunting, hauling, climbing, running) separated by long stretches of languid rest and play. This is the environment for which our behaviors and our metabolism are designed. For all our genes can tell, this is still the way of the world. Only we know different.
Why do we get fat and sick? This is an odd question from an evolutionary perspective, because ancestral humans were not overweight. Nor did they suffer the ailments that are so prevalent in our civilized world. We began getting heavier and developing new diseases once we ceased to live as hunter-gatherers and instead became farmers (or more specifically, once we started eating the food we grow rather than gathering food).
Now we suffer from a host of chronic “Western” diseases that were virtually unknown among our early ancestors and are largely absent even among today’s hunter-gatherers living in traditional ways. The list is long and depressingly familiar: obesity, adult-onset (type 2) diabetes, high blood pressure, heart disease, Alzheimer’s, and on and on.
The origin of these modern ailments can be linked, to some degree, to problems with human metabolism and inflammation. Something in modern life is disturbing the internal systems that evolution handed down to us.
In general, our bodies do not thrive on modern life, where inactivity is imposed by desk jobs and where alcohol, drugs (prescription and otherwise), and even food are abused. Nor do our minds seem to enjoy contemporary living. Humans today likely experience more chronic stress than did our ancestors, whose stresses would have been acute and episodic. The fight-or-flight instincts our ancestors relied on to escape danger are triggered in us today by innumerable and certainly less grave circumstances that have no resolution. The resulting chronic stress is a potent source of misery and disease. Even our wealth and possessions cannot ease this never-ending stress—and in fact, often seem to exacerbate it.
You can see the evolutionary history of our species in the development of the human fetus. The child in gestation looks like a minnow at first, then like a tadpole, then like a frog or maybe a large shrimp. Little buds poke out where limbs develop; the ribs of the fishlike skeleton fuse to form a pelvis; the head enlarges and eye buds pop out, and the fetus starts to resemble a pale, curled-up dolphin. Only gradually does the fetus develop into something that looks human.
A human baby born today would just as easily thrive 40,000 years ago, and a baby born in 40,000 BC would look just like a baby born today. They would have the same genes and develop into normal children and adults in either era. Each child born today carries genes that prepare him or her for the life of a hunter-gatherer, the occupation of every human who has ever lived except for those of us who were born after the recent invention of agriculture 10,000 years ago.
The remarkable thing is that we do so well in the modern world. That little baby born today has no more genetic instructions on how to live and survive now than the one born 40,000 years ago had. Today’s baby is no stronger, smarter, or better suited for life than one who was born in the distant past. Even though Paleolithic children grew up to make stone chips and spears and to hunt mammoth, they used the same neural pathways and learning skills that allow modern children to grow up to make computer chips and business deals. They have the same brain and the same body and can therefore have the same thoughts, and with enough training, can do the same things. They are different only because they live in different worlds, and there is the rub.
But even if some of our evolutionary adaptations no longer work to our advantage, our quality of life today is better than ever. We are safer and more comfortable, and we are all but free of the many pathogens and parasites that threatened our ancestors. Far fewer infants die now than did in the Paleolithic or Old Stone Age. Life expectancy is higher not only at birth but also at all ages now (although not by as much as you might expect in the later years).
Our ancestors had a higher probability of death at every age than we do, but they lived a smaller portion of their lives in disability. Modern humans live longer but age more rapidly than our prehistoric ancestors, and we live more of our lives in chronic illness. (Though this, arguably, is better than not living at all.) Our forebears were fit well into their advanced years. They aged well. A good deal of what we call normal aging is a modern condition that is more akin to disease than any natural state of growing older.
There is a reason for this. In scientific jargon, we are active genotypes trying to live as sedentary phenotypes. In plain English: We are not living as we were built to live. Our genes were forged in an environment where activity was mandatory—creating a strong selective pressure for genes that encoded a smart, physically adept individual capable of very high activity levels. Historically, humans have ranked among the most active animal species, and we carry energetically expensive brains to boot. The sedentary phenotype, Homo sedentarius, is the typical modern human who gets no exercise, becomes overweight or obese, is unfit and chronically ill, and ages rapidly. He ignores his biological need for activity. Inactivity and obesity alter the expression of our genes, making us more susceptible to an array of modern debilitating ailments.
So regular exercise is not just something you do to improve your health and drop a little weight. It is not an “intervention,” as some health professionals call it. It is absolutely essential to a healthy life—as necessary as food, water, and air. You exercise because the length and quality of your life depend on it.
A forager may spend many fruitless hours in search of high-energy animal foods, subsisting on plants until the next kill. I think human metabolism is adapted to this pattern of intermittent variety in food sources and periodic fasting mixed with varying activity levels. The chronic routine of three balanced meals and two snacks a day combined with the chronic routine of repetitive exercise just does not square with how our metabolism is built to function. There must be a periodic emptying of energy reserves through activity and intermittent hunger. Unless we do this, I don’t think it is possible to overcome the instinct to eat more than we burn that allowed our hunter-gatherer ancestors to survive and pass their genes on to us.
Darwin wrote, “Reproduction is how life commutes its death sentence.” What he meant was that our DNA has to decide whether our genes will repair themselves or depend on our sexual reproduction to carry our genes forward. During times of plenty, our DNA allows us to reproduce. When resources are scarce, it focuses on self-repair, which extends our good health and longevity. DNA takes its signal from carbohydrate—if it exists in abundance, our DNA assumes that food is plentiful, and so it can rely on our reproduction impulses. That mechanism is a powerful reason for restricting our carb intake—doing so may trigger our self-repair processes. It may also help us to control our weight.
N.B.:
Michael Gurven and Hillard Kaplan, in “Longevity Among Hunter-Gatherers: A Cross-Cultural Examination,” Population and Development Review 33, no. 2 (2007): 321–65
, show that the rate of life expectancy at ages from 1 to 80 is lower among hunter-gatherers than that in 18th-century Sweden, but the curve declines less steeply among hunter-gatherers beginning at the age of 25. The modal age at death—roughly, the most frequent age of death—is slightly higher among hunter-gatherers than those in 18th-century Sweden. The modal age at death is close to 80 among hunter-gatherers who survive infancy, which is not far below that in the United States in 2002, which is 85. The mortality hazard ratio for hunter-gatherers and those in the United States is high at early ages and falls to a value close to one, indicating equal hazard of death in both populations, by the age of 45.
Hunter-gatherers are 20 percent stronger than age- and weight-matched Westerners and approximately 50 percent more fit aerobically. The skeletal remains of late Paleolithic humans are comparable to those of Olympic athletes. Hunter-gatherers have a high proportion of muscle relative to fat mass. See S. Boyd Eaton and Stanley B. Eaton III, “An Evolutionary Perspective on Human Physical Activity: Implications for Health,” Comparative Biochemistry and Physiology 136, no. 1 (2003): 153–9.
Hunter-gatherers rarely develop chronic degenerative diseases such as rising blood pressure, increased adiposity, deficient lean body mass, elevated cholesterol, atherosclerosis, or insulin resistance; see Staffan Lindeberg et al., “Evolutionary Health Promotion,” Preventive Medicine 34, no. 2 (2002): 119–23.