Hunter-Gatherer Population Effects

At some point in time, human populations decided to settle down and harvest their own food instead of searching for it in the woods. In modern times, people tend to view this as a great advancement or revolution. Why would people want to search for food daily and forage for tubers or berries when they could just head to the supermarket or their own backyard? Scientist have determined, however, that this development brought many negative effects to the human population. The societies who adopted agriculture were malnourished and unhealthy, but they gained enough of an advantage over hunter/gatherer populations that the benefits outweighed the cost – at least in their eyes. Our society today has been shaped by this “revolution” and its effects,

both good and bad, can still be seen.
Plant and animal domestication began around ten thousand years ago. Up until then, humans lived a nomadic hunter/gatherer lifestyle. This time period before agriculture is known as the Paleolithic period (Stein). This time period was cold and dry, but there was plenty of large game (Diamond, “Evolution”). Groups of people would spend their days hunting prey and gathering a wide variety of wild plants and typically migrated with each season.
About ten thousand years ago, the earth began to warm. In some areas of the world the local plants and wild game grew to abundance. In these areas, the local food supply was so great that it allowed some populations to remain in one place, or become sedentary. These groups would often give up the nomadic hunter gatherer lifestyle and create villages or base camps (Stein). In other areas, unpredictable climates and a decrease in preferred large game led those populations to broaden their food sources in an effort to avoid unpredictable starvation. This sometimes led them to purposely cultivate certain plants (Diamond, “Evolution”). Regardless of the reason, agriculture was independently started in at least five (nine at most) different areas of the world. This worldwide adoption of agriculture is considered the beginning of the Neolithic era, or the Neolithic Revolution.
Early farmers selected edible plants for domestication based on their growing habits, their ability to adapt to farmland, and the ease of breeding out undesirable traits (Zeder, 227-259). Animals were chosen for domestication based almost entirely on behavior. Wild animals became candidates for domestication if they had an easily supplied diet, a good disposition, a hierarchal group system, a relatively calm demeanor, or a lower fear of human interaction. Other aspects of behavior such as sexual behavior and parent-young interactions affected the success rate as well. Species of plants or animals with the least desirable attributes are either never domesticated, or they experience the most biological changes (Diamond, “Evolution”).
Only a handful of plant and animal species were successfully domesticated. Hundreds of edible or useful species were left alone in the wild. Some animals didn’t meet enough (or any) of the requirements of successful domestication. There is evidence of rather brave attempts at taming ospreys, hyenas, grizzly bears, and even multiple known attempts at taming zebras (Diamond, “Evolution”). Shortly after a species was tamed, they began to go through the process of artificial selection. Their owners began selectively breeding them for desired characteristics. This often meant encouraging traits that could prove lethal in the wild. For instance, corn with tight thick husks and the non-shattering fruit heads of wheat and other grasses would prevent the dispersal of seeds in the wild. In domestication, however, these traits allow for easier collection (Levetin and McMahon, 177-186). Over time, farmers selected for larger edible portions of the plant. An excellent example is the wild plant Brassica oleracea (wild cabbage). In different parts of the world, it was artificially selected for different edible features and eventually became kale, cabbage, broccoli, cauliflower, and Brussel sprouts, depending on the desired traits of the region that cultivated it!
During the process of domestication, plants underwent a change in starch and sugar content due to a conscious or unconscious effort at controlling desired traits such as size or seed dispersal (Zeder, 227-259). Domesticated plants generally have larger and more plentiful fruits or seeds than their wild ancestors. Seeds of domesticated plants also do not have a dormant seeds. Wild plant seeds will wait to grow until the proper season arrives, but domesticated plant seeds can be planted immediately (Levetin and McMahon, 177-186).
Artificial selection for desirable behavior in animals ultimately led to a decrease in wariness or attention to external stimuli. This decrease in brain activity leads to decreased brain size that can be seen even in animals domesticated as recently as one hundred years ago (Zeder, 227-259). Domesticated animals also tend to have generally under-developed sense organs when compared to their native ancestors as well. When comparing domestic animals and their wild counterparts we can also see that chickens were bred to be larger, cows were bred to be smaller, and sheep were bred for their softer fur (Diamond, “Evolution”). The most significant difference between wild and domesticated livestock is their fat content. Farm animals get less exercise and eat mostly grain, while their wild counterparts run around and eat plants (Gadsby, 48-54). This can cause tame livestock to have not only more fat in general, but also contain fat consisting mostly of saturated fats (Eaton et al, 52-55). These kinds of fats are not healthy and contribute to coronary disease. Wild animals in comparison are leaner and have little, if any, saturated fat. Their fat mostly consists of Omega three and Omega six fatty acids which are essential for proper nutrition because they are good for human hearts and brains (Tally).
Despite human bravery and ingenuity, nutrition in agricultural societies was very poor. This is partially due to people consuming a much narrower variety of plants and animals. The diet in these societies relied heavily on one or two crops–usually either rice, wheat, legumes, or corn. By relying on one or two major crops, these societies ran the risk of starvation if one crop failed–like the Irish potato famine (Diamond, “Worst Mistake”). Also, these high-carbohydrate staple crops are usually deficient in nutrients or essential amino acids. For example, corn lacks several amino acids, wheat has little to no iron, and rice inhibits the absorption of Vitamin A and is deficient in protein (Larsen, 185-213). The nutritional differences in wild and domesticated food and lack of variety in diet lead to a cornucopia of health issues.
Most of what we know about biological changes caused by the adoption of agriculture comes from studying the skeletal remains. By comparing the skeletons of hunter/gatherer societies with those of agricultural societies, we can create a picture of the general health experienced by people in these societies. Dental health in agricultural societies saw a major decline, largely due the increase in carbohydrates and sugars. Agriculture brought higher rates of cavites, tooth loss, dental chipping, enamel defects, and tooth crowding along with a lower average life expectancy (Diamond, “Worst Mistake”). Proof of malnutrition in agricultural societies can be seen in the increased incidences of anemia and enamel defects along with decreased cortical bone thickness, tooth size, and average height (Larsen, 185-213). Bones can also show muscularity, so scientists have noted that hunter-gatherers were generally physically stronger than farmers and didn’t suffer from the wear of the repetitive motions of farming (Eaton et al, 52-55).
Permanent places became organized (“Ancient Culture”) and domesticated food provided enough surplus food to support a larger population. The people in these settlements were also able to spend more time specializing in one area other than food production. This led to priests and specialists, which eventually caused the emergence of financial inequalities and stratification. Royal or elite people in these societies ate better than the general populations of these settlements. We know this because their bones show less signs of malnutrition and disease (Diamond, “Worst Mistake”). These agriculture dependent settlement areas became centers of religion, wealth, technology, power, and large collections of people (Stein).
Agricultural communities had a higher birthrate than hunter/gatherer societies. In a nomadic lifestyle, the mother has the job of carrying the younger children until they are able to keep up with the group. In a sedentary lifestyle, this is not necessary (Diamond, “Worst Mistake”). An increase in ceramic technologies and starchy foods created an increase in the availability of soft, easily digested foods. This allowed women to wean their children off of breastmilk sooner (Larsen, 185-213). Because farming is easier with more people, women were encouraged to have more kids (“Ancient Culture”). This encouragement combined with earlier weaning and decreased child transport responsibilities led to a decrease in birth spacing. These shorter intervals between pregnancies lead to even greater malnutrition in women. This also led to an increase in population. As the population in these settlements continued to grow, the demand for more food grew as well. This in turn led to warfare over farmland between neighboring societies (Diamond, “Evolution”; Kolbert).
This sedentary lifestyle also lead to infectious diseases that were not seen in the Nomadic hunter/gatherer lifestyle (Diamond, “Evolution”). The standing water commonly found at agricultural sites was the perfect breeding ground for mosquitos, which could sometimes lead to malaria. Human waste would build up at these sites, causing a decrease in sanitation and serving as homes for microbes and worm larvae. Permanent settlements also attracted vermin. The close proximity of humans with domesticated animals and vermin lead to animal diseases mutating and infecting humans. The measles, for instance, came from close contact with dogs. The common cold arose from horses, the black plague was thanks to rats, influenza originated from pigs and ducks, and cattle gifted humans with Tuberculosis, smallpox, and measles (“Ancient Culture”).
The increasing population often led to increased physical contact and overcrowding, which only made things worse.

Densely packed people only made the spread of disease easier for those pesky little parasites and microbes (“Ancient Culture”). The spread of these diseases were made even more dangerous when combined with the general malnutrition of agricultural societies because malnourished bodies have a weaker defense (Diamond, “Worst Mistake”). Disease is one of the main killers of humans since the start of agriculture and most of them would not exist in a hunter/gatherer society (Diamond, “Evolution”). Populations that survived disease epidemics would develop immunities and pass those immunities onto their offspring. Later, these diseases and immunities served as powerful methods of conquest. This is especially true for Eurasia whose oversea expansion lead to the deaths of indigenous people in Australia, the Pacific Islands, Africa, and the

Americas.
The question remains then, if the adoption of agriculture had such negative repercussions, why did the practice of plant and animal domestication continue? The simple answer is that the advantages of this lifestyle outweighed the disadvantages. As Jared Diamond describes it, this transition was “auto-catalytic” (“Evolution”). Domesticated plants provided villages with food surpluses and animals provided fertilizer, food, and strength for farm labor (“Ancient Culture”). The surplus of food could be used to feed full-time inventors, which led to many technological advances such as metal tools or writing (Kolbert). The new sedentary lifestyle allowed for the production of heavier technologies (like the forge or the printing press). Farming populations grew to become a powerful force and it was not uncommon for a homeland in agriculture to develop tools of conquest.
The hunter/gatherers in this time were either converted to agriculture or driven out by the farmers in search of more fertile land. Some hunter/gatherer populations living near agricultural sites didn’t like what they observed and rejected the lifestyle (Diamond, “Evolution”). Still others were run out before they even had the chance to convert. Early deaths due to warfare were common during this time as farmers often competed with hunter/gatherers or other farmers for land (Larsen, 185-215). These sickly and short farmers defeated the more robust hunter gatherers because they outnumbered them. In the end, hunter/gatherer societies were forced to make do with the land the farmers didn’t want (Diamond, “Worst Mistake”).
Small numbers of hunter/gatherer societies still exist today. Due to land restriction and encroaching Western practices, they cannot live the same way their Paleolithic ancestors did. Their diets vary and offer great insight into nutrition. The !Kung (! is pronounced as a click) in Africa spend an average of 2.5 days a week foraging and hunting for food. They eat a varied diet of plants and animals. The Hazda in Tanzania and are mostly vegetarian and the Inuit in the Arctic eat mostly meat (Levetin and McMahon, 177-186; Eaton et al, 52-55).
The Inuit only eat roots, berries, and greens that grow during the subarctic summers.

The rest of their diet is meat. This is an incredibly odd because if human bodies get more than forty percent of their energy from protein, it will suffer from protein poisoning. The Inuit are able to survive on this diet due to the high amounts of fat they consume (enough to account for the other sixty percent of their energy). Most people get vitamins A, D, and C from fruits and vegetables. The Inuit get vitamins A and D from eating animal skin and liver and Vitamin C from raw animal organs. Studying this diet has shown that it’s not what types of foods you eat, but what types of nutrients you get that matters (Gadsby, 48-54). Hunter /gatherer diets typically have less saturated fats, no trans fats, and more omega three and omega six fatty acids. They also consume more red meat and dietary fiber along with less salt, sugar, and flour (Eaton et al,

52-55)
As more and more human populations are introduced to the modern Western diet, their health subsequently suffers (Diamond, “Evolution”). Even today, starchy, nutrient deficient foods like wheat, rice, and corn still make up a majority of the diet and humans have only recently caught up to cavemen in height. Diet-related diseases like diabetes and coronary disease are constantly on the rise (Diamond, “Worst Mistake”). These diseases have been named “mismatch diseases,” so called because their high frequency in human populations is because our lifestyles do not match the lifestyle our genetics were built for (Eaton et al, 52-55; Kolbert). Lieberman writes “I don’t think it is possible to overemphasize just how important mismatch diseases are. You are most likely going to die from a mismatch disease.” (qtd. in Kolbert). Diabetes, heart attacks, strokes, vascular disease, hypertension, emphysema, and even certain forms of cancer are all known forms of mismatch disease.
Scientist have been looking into a simple remedy for this problem, and they may have found one. The paleo diet is a diet that tries to emulate what our ancestors ate. People on this diet cut out potatoes, corn, legumes, grains, salt, sugars, and most vegetable oils (Kolbert). Multiple studies have shown that even healthy adults who spend a short period of time on this diet show improved blood pressure, glucose tolerance, lipid profiles, and insulin sensitivity and secretion (Frassetto et al, 947-955; Osterdahl et al, 682-685).
This diet does not solve all the problems, however. The earth is overcrowded and overworked. We cannot revert back to foraging because a plowed field provided more food acre for acre than foraging alone (Diamond, “Worst Mistakes”). The high protein paleo diet could offer a solution if it weren’t for livestock production using more land, energy and water than wheat production. Plus livestock are a major source of greenhouse gas emissions (Kolbert). Diamond best states the problem:
Humanity’s greatest risk today is of our growing numbers and aspirations ultimately destroying our society by destroying our environment. Providing undernourished people with more food would be a laudable goal if it were inexorably linked to reducing our numbers, but in the past, more food has always resulted in more people. Only when crop and animal breeders take the lead in reducing our numbers and our impacts will they end up doing us net good. (“Evolution, Consequences, and Future of Plant and Animal Domestication”)