EPQ: To what extent did agriculture cause a decline in the health of early human populations?

To what extent did the Neolithic Revolution cause a decline in the health of early human populations?

by Georgina Holmes

CONTENTS

ABSTRACT……………………………………………………………………….

INTRODUCTION……………………………………………………………...

DISEASE AND TRANSMISSION…………………………………………

1.1 Origins of disease

1.2 Transmission of disease within communities

1.3 Implications of disease on health

LIFESTYLE SHIFTS……..…………………………………………………..

2.1 Population growth, density and aggregation

2.1a Fertility and mortality trade-off

2.2 Sedentism, work load and physical activity

2.2a Stature, growth and body mass

2.2b Bone health and robusticity

2.3 Food Processing, food and technology

2.3a Dental health

2.3b Skull morphology

DIET AND NUTRITION…..…………………………………………………

3.1 Malnutrition & Nutritional Quality

3.1a Dietary diversity

3.1b Anaemia

CONCLUSION………………………………………………………………....

WORKS CITED……………………………………………………………….....

APPENDIX A: Source evaluation…………………………...………..

ABSTRACT

This report intends to explore the extent to which the adoption of agriculture negatively impacted the health of early human populations. Literature typically associates the transition to farming with a marked reduction in skeletal and dental health, widespread infectious disease and increased mortality rates. Rather than taking a broad generalising approach and assuming that all farming or all foraging populations are the same, this report explores the variability of subsistence methods and the lifestyle factors commonly connected to the different facets of poor health. Notably, how the varying levels of intensity of sedentism, aggregation, diet composition and domestication are more significant than the type of subsistence method in explaining patterns of health in past populations. In this report I outline why agriculture is not the sole cause of declining health and conclude that lifestyle factors play a more important role in determining whether health is adversely affected. Many of these factors are seen most commonly in farmers, largely explaining the connection between agriculture and declining health.

INTRODUCTION

It seems counter intuitive that health would decline following the adoption of agriculture. For reasons such as food security, energy-dense foods and decreased energy expenditure one could reasonably think that farmers were at a nutritional advantage. Evidence of population growth and increased life expectancy beyond the reproductive age, in turn accelerating fertility rates, seems to support this concept [1]. However, research increasingly shows health decreased following the adoption of agriculture; the prevalence of disease, physiological and nutritional stress all seem to be higher in agricultural populations [2]. Abundant skeletal remains from both hunter-gatherers and farmers show increased pathologies, bony lesions, dental and craniofacial adaptions and decreased stature and robusticity in the latter [3].

The term ‘Neolithic Revolution’ is the same as the adoption of agriculture, it does not mean that Neolithic populations are always agriculturalists. In this report, studies mentioning the Neolithic may represent either sedentary farmers or more mobile forager-farmers and the same goes for any period mentioned. All periods will be linked to the characteristics known about them from archaeological record, thus allowing conclusions to be drawn between lifestyle, subsistence methods and health, irrespective of the time period. An important note is that crop and animal domestication was a long process, intensify at different times in various regions of the world [4]. Consequently, the adoption and effects of the Neolithic Revolution span a wide period of history and arguably still continue in modern health today. Nevertheless, all studies have been critically analysed and none were found to be significantly out-dated or unreliable, with all being peer-reviewed, thoroughly researched and published in respected journals. Where an author or study may not be wholly relied upon, this will be mentioned within the report.

Subsistence methods such as agriculture are not uniform across the globe and different periods of time, with different dietary compositions and lifestyle factors which play a role [5]. Consequently, considering regional variation is of the utmost importance in understanding the impact of agriculture on health. This report considers variability in lifestyle factors, subsistence methods and the changing patterns of different facets of health.

DISEASE AND TRANSMISSION

1.1 Origins of disease

Many infectious diseases in human populations emerged during the transition to agriculture [2] [6] [7] [4] [8]. Arising mainly in the Old World – Africa, Asia and Europe – many ‘new’ infectious diseases (not found in early hunter-gatherers or non-human primates) came from domesticated animals during the Neolithic Revolution [2] [6] [9]. This evidence suggests health did decline following the adoption of agriculture.

However, it is important to note when citing Diamond’s works in the following paragraphs [2] [6] [10] that his view on agriculture is largely negative. He has previously considered agriculture ‘the worst mistake in the history of the human race’ [11] and often-times his own book ‘Guns, Germs and Steel’ (which is more of a popular science book) is used in his references. Ultimately, in rigidly viewing agriculture so negatively this overlooks a balanced view where the reality of variation can be assessed (where we see poor health in foragers, for example). Nevertheless, his academic work is peer-reviewed, researched, frequently cited, published in respected journals and an important source to take into consideration.

Domesticated animals are one of the main sources for the origins of new diseases (see Fig 1.) [4] [9] [6] due to the many ways in which zoonotic diseases can be transmitted to humans. The consumption of animal products (e.g. meat, milk); close contact with animal bodily fluids (e.g. mucus, blood, saliva); poor sanitation (e.g. animal faeces, waste accumulation, water bodies); animal vectors (e.g. mosquitoes, ticks, fleas) [7] [4] [12], are all potential vectors for the transmission of disease Moreover, domesticated animals lived close to agricultural communities; waste could accumulate nearby and the use of animals meant contact was frequent and prolonged, contact was prime cross-species transmission of pathogens [3, 13, 14, 15]. As a result, the transmission of a zoonotic pathogen to a human population is highly likely in a society which has adopted farming.

Further, the majority of diseases in temperate climates are crowd epidemic diseases. As crowd epidemic diseases require large populations to sustain the spread of the pathogen – and these numbers could not have been reached in communities until the human population grew after the Neolithic Revolution [2] [9] [6] [10] – many originated following the adoption of agriculture. Additionally, most diseases originated in the Old World, largely due to the higher number of domesticated animals that could act as vectors to pass pathogens to humans [6]. Consequently, more diseases arose in Old World agriculturalists.

These factors and opportunities for transmission are much less prevalent in dispersed and nomadic hunter-gather bands. Nevertheless, zoonoses did occur in pre-agriculturalists, the human journey exposed hominids to new animals with new parasites and infections [9]. However, pre-agricultural diseases were more likely received from animals phylogenetically close to hominids such as primates, or by consumption of hunted meat [9] [2]. Contact with other animals was not frequent or prolonged enough to make transmission of disease likely [4]. To this end, transmission of zoonotic diseases are less likely in foragers.

In some cases animals are not domesticated in the region they are used in but introduced from elsewhere [6]. This increases the likelihood of zoonotic disease transmission as pre-existing humans and animals may not have immunity to foreign zoonoses [4] [16] [10] [14]. Moreover, animals used for transport, alongside increased trade between agricultural communities, provided more opportunities for foreign pathogens to be introduced in neighbouring farming populations [4] [15]. Increased physiological stress, stunted growth and exostoses in domesticated animal remains reflects the poor living conditions of early domesticated animals [4]. This is suggestive of overcrowding, poor hygiene, nutritional deficiency and a loss of mobility – all of which provide opportunity for zoonotic diseases to be transmitted – which is strong evidence for the conditions being prime for infectious diseases in pastoral populations.

Fig 1. SOURCE: [4]

The number of diseases shared between domestic animals and humans

Whilst domesticated animals act as the vector to pass diseases on to human hosts, the domestication of crops result in host vulnerability (due to the nutritional deficiencies of a less diverse diet) [7] [4]. When an organisms cannot adapt to changes in its internal environment immunity and response is insufficient, such changes are often a result of an imbalance of external factors such as malnutrition [17]. Therefore, due to the increased malnutrition in early agricultural populations, vulnerability to infectious disease also increased suggesting the transition to agriculture made it easier for health to be affected by pathogens. Additionally, the likelihood of disease transmission rose from what it was for the hunter-gatherer to the farmer.

It must not be overlooked that non-human primates and hunter-gatherer groups were still afflicted by parasites and diseases which could be sustained in small and dispersed human populations [7] [2]. Many specific infections are inherited from early hominids and primates such as Malaria and Leprosy [9] [14]. Equally, with the journey out of Africa, hominids were exposed to environments with new microbes – new diseases arose in the early hominids, but viruses and pathogens had not evolved to be human specific [9]. Consequently, non-agricultural populations are not a model of perfect health as they are sometimes made out to be. To this end, it is the lifestyle factors which allow for diseases to originate and not the subsistence method. Although these factors tend to apply to farmers, they can also be linked to settled foragers and perhaps not applied to more dispersed/early farmers. In spite of this, the origins of many human infectious diseases stem from the Neolithic Revolution due to the lifestyle changes which make transmission more likely.

1.2 Transmission of disease within communities

The adoption of agriculture caused an increase in population numbers and density [18]. Consequently, diseases that depend on hosts or large populations in order to maintain transmission within a community increased. The aggregation of human populations increased the likelihood of transmission within human communities as contact between individuals increased; decreased sanitation and the accumulation of waste/faeces provide conditions for microbial growth; poor diet increases human susceptibility to infection; trade provided cross community transmission and crowd epidemic diseases could be sustained [4] [7] [9] [12] [3] [14] [15] [17] [19] [20] [1] [21]. Infected humans and animals sharing the same space can also spread pathogens by sneezing or coughing [4] [22] [21]. Sedentism (which is commonly associated with the agricultural lifestyle) both increases population density, and thereby contact and transmission of disease, but also means the population suffers repeated infection by the same strains of parasites (these parasites like mosquitoes become specialised to humans as there is a constant food source which allows for easy breeding and a lack of variety in species to infect) [9] and a host-pathogen relationship has time to develop and establish prolonged illness [23]. All of these papers which provide this insight are peer-reviewed, published in respected journals and not of questionable provenance, which supports the link between settlement and pathogenic transmission. Sources by Cockburn T [9] and Lallo et al. [23] do date to the 1970s, but this research still remains valid and continues to be cited, once again supporting the point.

As a result, the frequency of disease in a population increases alongside increased population numbers, settlement and density [4]. This is because there are more hosts to sustain transmission of the pathogen, thereby acting as a ‘reservoir’, and due to domesticated animals and a constant food source the vectors of disease increase [24]. This supports a connection between disease prevalence in a population and agriculture because all of these causes increase with farming more so than in foragers (even settled foragers).

Thus, settled and aggregated communities are more likely to be afflicted with diseases. These lifestyle factors will vary in different geographic regions over time, as result one subsistence method cannot be the sole cause of declining health but rather the presence of these lifestyle shifts within a population. As the sedentary and densely populated lifestyle is often associated with agriculture and the domestication of animals increased the opportunity for diseases to originate, the agricultural lifestyle is more likely to be prime for disease transmission. Namely because most hunter-gatherers are mobile, sparse and do not remain in long and frequent contact with the same animals.

1.3 Implications of disease on health

The impact of increased pathogen load with agriculture can be seen in the osteological record [23] – abundant bony lesions denote a marked decline in the health [4] [20].

Human remains show lesions from infections increased with the adoption of farming [7], for example tuberculosis (TB, from cattle) and brucellosis (from sheep/goat milk) cause bony lesions [4]. From modern day case studies, tuberculosis rarely occurs in wild animals (if it does occur they have often been exposed to captive mammals) and is associated with domestication and crowding [22]. Although early strains of TB have been identified in human evolution, [25] and neutrophilia associated with TB can survive in small populations suggesting it predates agriculture [1], the main cause of transmission is domesticated livestock (see Fig 2.) which suggests the health of early agriculturalists is more likely to be affected by TB. Consequently, tuberculosis is linked to the rise of agriculture - the abundance of bony lesions in Neolithic skeletons from around 8000 B.C. and Ancient Egyptians from around 3700 - 1000 B.C. is proof of the link between the effect of domestication on human health [22].

Fig 2. SOURCE: [6]

Zoonotic diseases which originated from domesticated animals and are now human diseases

Moreover, in Middle Mississippian agricultural samples 84% of examined bones show signs of infection compared to the earlier (and more nomadic/less crop dependent) Mississippian Accultured Late Woodland sample where only 26% of the bones contained signs of infection [23]. Although more bones were examined in the latter study – likely providing more oppourtunity for dilution of the results – more severe cases were seen in the farming sample suggesting that disease afflicted agriculturalists more than foragers. Equally, a modern study of the Agta (although a modern population their lifestyle provides insight into pre-industrialised life and so it remains a useful source) has indicated helminthic intestinal parasites increases in sedentary camps (and these are rarely seen in archaeological evidence predating the rise of agriculture), this is evidence of a greater pathogen load afflicting sedentary farmers more than foragers [1].

There is strong evidence to suggest that the Neolithic Revolution caused a substantial decline in health as a result of disease. It is clear that diseases did not just affect agricultural populations, nor did they all stem from the transition to agriculture. The types of diseases do vary between foragers and farmers; viruses with a longer latency cycle and less rapid transmission are more common in hunter-gatherers to suit the sparse and nomadic lifestyle, the opposite is true in agriculturalists [7]. Consequently, the arrival of agriculture meant pathogen-load could increase and return repeatedly. In spite of the presence of parasites and pathogens prior to the adoption of agriculture, the abundance and frequency of new diseases affecting farmers is far greater than in foragers – the Neolithic Revolution did cause a decline in human health with regards to diseases.

LIFESTYLE SHIFTS

2.1 Population growth, density and aggregation

Population numbers and density increased with agriculture, as a result of: decreased birth intervals; increased life expectancy beyond the reproductive age; increased fertility rates; a decreased energy expenditure deficit [1] [3] [17] [19] [20] [24]. This pattern of population growth appears to imply that the health status of agriculturalists improved. However, establishment of settlements, alongside increased interaction and trade with neighbours increases the opportunity for the transmission of new diseases [23]. The effect of increased disease (particularly infectious disease in dense sedentary populations) evidently results in a decline in human health and increased mortality.

2.1a Fertility and mortality trade-off

The increased fertility and population growth with the transition from foraging to farming came with a higher mortality rate trade-off [14] [1]. In a study of Agta camps by Page et al., 2016 [1], higher fertility rates were observed in the sedentary mothers. The data shows that settled mothers have a 16.7% higher Total Fertility Rate (TFR) of 7.7 than mobile mothers who had a 6.6 TFR. This can be linked to the fact that forager mothers have lower BMI scores, whereas sedentary mothers expend less energy and consume more carbohydrates. Thus, the birth interval is reduced in sedentary mothers resulting in this higher fertility rate and, by extent, a population growth.

As has been established, the benefit of growing civilisations perpetuated the transmission of disease and therefore physiological stress increases. European civilisations quickly became densely populated after the Neolithic Revolution, this was a catalyst for the transmission of diseases and decline in sanitation and they were therefore afflicted with infectious diseases [6]. In the study, large camps with low mobility were 2.8 times more likely to display lymphocytosis, with only severe eosinophilia (showing extreme helminth infestations) and highest infant mortality found in the completely settled Agta [1]. To this end, as fertility rate increases with the degree of sedentism and population growth, so does the mortality rate. This trade-off explains the contradiction between global population growth and indicates health declined and pathogen load increased with the adoption of agriculture.

Although a report on modern Agta communities, those who were in settled camps in the study had abandoned foraging for a cultivated life. Thus, the correlation observed can be applied to the Neolithic Transition and early agriculture communities due to the interplay between agriculture and sedentism. Moreover, the research is peer-reviewed, frequently cited and there are no conflicts of interest. Therefore, the study is both relevant and reliable in provenance to be used as evidence.

Furthermore, reproductive, air and water-borne diseases are easily transmitted within aggregated human populations. As an example, gut rotaviruses kill lining cells and prevent absorption and retention of fluids causing diarrhoea. With each gram of faeces containing 109 viruses, microbes could thrive in such settled and confined communities with poor sanitation – large, settled populations live amongst their waste and ill, unlike nomads [21]. As a result, the growth in the successful reproductive turnover of humans is a hotspot for diseases, this demonstrates the feedback loop of declining health with population growth in agriculturalists.

Despite mortality rates generally being high in farmers, hunter-gatherers have a low life expectancy at birth [26]. This demonstrates that prior to the adoption of agriculture the risk of death was likely to be equally high. However, the mobile nature of small foraging groups means that they are less likely to be affected by diseases and parasitic infectious as has been seen in agriculturalists. To this end, population dynamics play an important role in determining the health status of a community and while sedentism is not exclusive to farmers, and population varies regionally, the general trend is increased aggregation and a greater decline in health with farming.

2.2 Sedentism, work load and physical activity

One of the key features of the Neolithic Revolution was the change from a nomadic to a sedentary lifestyle. The shift from changing location regularly and mobile activity to staying in one location brought many causes of declining health [27] [28].

Low levels of cardiovascular disease are associated with high mobility in the Tsimane and Hadza foragers with over 135 minutes of activity per day [26]. However, modern studies do not perfectly replicate past conditions and endurance running was likely more common in ancient populations than to modern ones [26]. It is possible that prehistoric foragers were even more mobile and active than present ones, naturally this sort of evidence has not preserved distinctly in the archaeological record. Nevertheless, it offers evidence towards a mobile lifestyle being healthier.

A study by Raichlen et al. [29] suggests that hunter-gatherers are sedentary for a similar amount of time as industrialised populations, but their mode of sitting such as squatting and interrupted sitting increases muscle activity. The decrease in sustained muscle activity with the move away from foraging decreases metabolism in muscles, lipid and glucose metabolism, blood flow and worsens inflammation, many of which are factors associated with cardiovascular disease. Thus, the change in the way in which humans are sedentary is more significant than the time spent resting. Although this is early research published just this year, it provides a possible insight into how sedentism changed with agriculture and the reasons why it would cause a decline in health. Whilst this study utilises modern comparisons, it provides evidence that sedentism was not so much of a problem regarding the amount of energy expended (which would likely also hold true given the labour intensity of early farming) but the mode of energy expenditure.

Consequently, decreased physical activity and sedentism are associated with decreased health. The lifestyle shift to sedentism, and not necessarily the mode of subsistence, led to a decline in health – these lifestyle aspects will be present in forager-farmers and farmers and vary in intensity regionally. Overall, the transition to agriculture amplified these activity changes and therefore contributes to poor health.

2.2a Stature, growth and body mass

Declining stature is another possible consequence of the transition to agriculture, and it had been seen in skeletons globally and across any period where farming was adopted [30] [31].

During periods of undernourishment, stress leads to the release of catabolic hormones in order to release energy, preventing anabolic growth [32]. It has been observed in both modern and ancient studies of individuals affected by famine and malnourishment that long bone growth is retarded, which in turn leads to decreased stature [31]. Consequently, growth inhibition can also be evidence of malnutrition. Such inadequate nutrition and periods of famine may seem likely in hunter-gatherers. Contrarily, due to their dietary breadth – compared to the farming reliance on monoculture which can result in crop failures and famines – there is often a wide variety of food available to consume sufficient energy and micronutrients all year round for foragers [3]. Moreover, decreased protein consumption and early crop-based agriculture (particularly with regards to maize, wheat and rice) depletes iron abundance, resulting in anaemia and not providing adequate amino acids for growth [3] [31]. As a result, poor dietary changes are commonly associated with decreased stature. Although not exclusive to agriculture, the increased likelihood of malnutrition suggests a decline in health with farming.

It is important to note that temperature, genetics, disease and work load are also linked to changes in stature, and in some cases stature increases following the adoption of agriculture (such as in the Lower Illinois Valley [33]) [31]. A study by Macintosh A. et al. [34] found significant stature and body mass reduction in early LBK Neolithic farmers compared to preceding semi-sedentary Mesolithic hunter-gatherer-fishers, but this was then followed by recovery in later agricultural populations. These results suggest that the inclusion of protein in pre-agricultural and dairy in late agricultural (Iron Age and Bronze Age) diets helped protect against stunting, along with sanitation and technological improvements and increased immunity to pathogens which would have physiologically stressed the initially unimmune Neolithic farmers. Moreover, sedentism during the initial Neolithic transition led to high population densities which could promote pathogen transmission, and high physical stress from a younger age could deplete energetic resources at the vital period of growth. A similar pattern is observed by Piontek J. and Vančata V. [27] where the shortest bone lengths, lowest robusticty, stature and body mass is observed in the early LBK Neolithic groups compared to Palaeolithic, Mesolithic and late CWC Neolithic due to the lack of meat consumption, increased disease vulnerability, young labour, rapid maturation and decrease mobility of the early LBK farmers. It is important to note that these latter studies focus on Central Europe, but they are recent and reliable sources of information to provide an insight into how the early transition to agriculture, and the intensity of the lifestyle changes, are the most likely factors in decreased skeletal health.

The pattern of stature and agriculture is not a clear one, and an interplay of factors contribute to final adult height, in some cases stature declines initially when agriculture is adopted but rebounds over later and more established periods [31]. Equally, catch-up growth during adolescence means full adult height can be reached despite deficiencies in childhood [3]. The pattern of stature across prehistory is confusing, and its relationship with a particular subsistence method of lifestyle shift is unclear. However, it is likely that in the majority of cases, when agriculture is initially adopted a combination of increased aggregation, sedentism, pathogen load, nutritional (protein) deficiencies and famine would contribute to stunted childhood growth more often than in hunter-gatherers, but as time progressed the sophistication of agriculture and increasing animal domestication/dairying and technology prevented nutritional deficiencies.

2.2b Bone health and robusticity

A far better indicator of the effects of subsistence strategies is skeletal robusticity and health. Larsen C.S. [3] explains how osteoarthritis and spondylolysis in the archaeological record can provide an insight into the work load of past populations, but concludes that there is no clear evidence that it is any more prevalent in agriculturalists as in hunter-gatherers [3][20]. Larsen’s research is thorough, his conclusion well-informed, and is known for leading research in the field which supports the use of his work. Therefore, the frequency of such conditions appears to be related to the intensity of physical activity and load, more so than to the method of food acquisition. Importantly, variations in physical activities, mechanical load and the work load intensity between populations ultimately leads to varying degrees and frequencies of skeletal defects [20]. A comparison of fisher-farmers to inland agriculturalists showed higher rates of osteoarthritis and spondylolysis in the fisher-farmers, and the males particularly, associated with higher mechanical load [35]. Ultimately, the patterns of bone health vary between different regions of the world due to the lifestyle differences. Consequently, rather than deducing that agriculture led to decreased bone health the argument should be that higher mechanical load is the root cause, and this pattern is often seen in intensive agriculturalists or fisher-farmers.

Robusticity does generally see a trend with the transition from mobile foraging to sedentary farming: there is a decrease in structural robusticity in early agriculturalists. A sedentary lifestyle with decreased physical activity results in less robusticity, in the Baltic the increased sedentism and malnutrition in the Neolithic farmers is associated with a decline in humeri robusticity compared to the preceding Mesolithic and following Iron Age periods where food supplies were more stable and diverse [28]. However, evidence that this is regionally variable is seen in the decreased robusticity of coastal fisher-farmers in Georgia as they transitioned to maize agriculture compared to increased robusticity in inland Alabama as foragers transitioned to agriculture [3]. Consequently, the subsistence method is less significant than the decrease in physical activity when it comes to decreased bone health and robusticity. Generally, farmers are more sedentary and therefore robusticity decreases with the Neolithic Revolution, but as this is not uniform across the globe the extent to which agriculture plays a role is minimised.

2.3 Food Processing, food and technology

2.3a Dental health

One of the main causes of dental caries is believed to be cariogenic foods such as carbohydrates and sugars [3]. The fermentation of sugars on the surface of teeth by bacteria causes demineralisation, whilst the sticky nature of sugars are prime for bacterial growth [36] [3]. Proteins and lipids have the opposite effect and high fluoride levels in water can also prevent the development of dental caries [3] [36]. In addition to this, food processing softens food before they are consumed and consequently promotes bacterial growth [3] [36].

In the Danube Gorges, only 2.5% of the Mesolithic population were found with evidence of dental caries compared to 15% in the Neolithic groups [36]. This correlates with the increased carbohydrate and plant consumption in the Neolithic Danube, contrasted with the higher fish and protein consumption in the Mesolithic [36]. This would support the idea that a diet based on cariogenic food is associated with abundance of dental caries, whereas a high protein and aquatic diet (particularly containing fluorine) is cariostatic [37]. Jovanović [36] notes that the results from the Danube Gorges are in fact lower than expected and rates of caries in the Neolithic should be significantly higher. This indicates that fisher-farmers had lower rates of caries due to the lack of cariogenic food, and fluorine from aquatic foods could prevent caries. As a result, these regions demonstrate diet plays a significant role in dental health, and though this will depend on each population, cariogenic food consumption increases in agriculturalists (but not fisher agriculturalists) suggesting terrestrial agriculture does cause a decline in oral health to some extent.

Archaeozoological evidence and stable isotope analysis also shows that the Neolithic communities in the area were not entirely dependent on farming, and still somewhat reliant of foraging [36]. This still implies that a degree of cariogenic food in the diet, even if it is not the main food source, has adverse effects on dental health compared to a protein rich diet (as represented by the Mesolithic populations). The example provides a useful insight into how the transitional stages into farming began a trend of declining health, as opposed to forager health.

On the contrary, there is evidence of caries prevalent in hunter-gatherers in North Africa [37]. Of 52 individuals analysed in North Africa, only three did not show signs of carious lesions, equal to levels in agricultural populations [37] [38]. Similarly, carious lesions are found in foragers from the Pecos region in Texas for much the same reason – a highly cariogenic carbohydrate diet [3]. This seems atypical compared to the general association of agriculture with poor oral health, but examining the lifestyle factors of these hunter-gatherers explains this situation. In the case of Iberomaurusian foragers of North Africa, they had developed selective systems of obtaining and preparing terrestrial foods [37]. Agriculture is clearly not the only method of obtaining food that causes a decline in health: the cariogenic diets explain why hunter-gatherers may have poor dental health. Moreover, examining lifestyle factors within hunter-gatherer groups demonstrates they were foragers beginning to develop agricultural techniques. The Iberomaurusians left evidence of burials, food storage (deposits of acorn cups suggest harvesting and storage of acorns before they were ripe, as the cups would then fall off naturally) and processing (fragments of grasses indicate the whole plant was utilised for baskets and tools) [37] [39]. These subsistence techniques bridge the gap between hunting and farming, demonstrating that even among nomadic populations there is some element of selective food production. To this end, it is the use of methods of food production commonly attributed to farming – but not the adoption of agriculture itself – that negatively affect oral hygiene. Therefore, prior to the adoption of agriculture we can see trends in declining health showing the Neolithic Revolution was not such a sudden radical compromise to human health as previously thought, but rather a gradual and progressive decline.

Studies of modern day hunter-gatherers transitioning to farming also support the idea of a progressive decline in oral health, attributed to lifestyle shifts. Crittenden et al. [40] observe high rates of caries, periodontal disease and antemortem tooth loss amongst Hadza bushmen, attributed to their cariogenic diet, particularly honey which is a staple part of their foods [26]. There were sexual differences, with bush women having relatively good oral health compared to village women, whilst the opposite was true of men, with bushmen having the worst levels of dental hygiene and the least sexual dimorphism was observed in the forager-farmers, suggesting a more equal food system. It is important to note that the Hadza do not perfectly reflect prehistoric foragers: none rely solely on wild food - each year 15% of individuals in Hadza bands move to rely on cultigens and sedentism - and the sample is short-term and small [40]. Nonetheless, this is still a useful comparison as it provides tangible evidence for health during the transition to farming, which is perhaps less distinct in the archaeological record.

Fisher-farmers also see an unexpected trend, whereby carious lesions are less abundant than their hunter-gatherer predecessors [3] [28]. In the Baltic, the Neolithic fisher-farmers have low dental caries, as well as other oral pathogens. Mesolithic predecessors have marginally higher rates of caries and the Bronze Age successors have significantly higher rates of caries and periodontal disease [28]. Equally, the frequency of dental calculus was highest in Neolithic fisher-farmers and Iron Age populations but lowest in the Bronze Age sample. Both of these trends can be explained by the high protein-aquatic diets in fisher-farmers (which also contain high levels of fluoride) and the increase in farmed meat and milk in the Iron Age sample compared to the soft and cariogenic Bronze Age diet. High protein diets promote high rates of calculus, but decrease the presence of caries, periodontal disease and antemortem tooth loss [41] [42]. This demonstrates that variations in the lifestyle and diet of agriculturalists are more important factors in determining the impact of subsistence strategies on health. Rather than grouping agriculture as a whole, considering how lifestyle varies regionally and globally is more informative when assessing the underlying causes of declining health.

In some cases caries increased five-fold since the adoption of agriculture, compared to the 2% abundance seen in Palaeolithic and Mesolithic remains [40]. However, the role of dietary change is still more significant because caries prevalence is highest in agricultural populations subsisting off maize, whereas in some rice-consuming populations there are fewer cases of caries [40]. To this end, the transition to agriculture is not the sole cause of declining health and the variability of regional diets play a large role in the pattern of health from foragers to farmers.

Thus, the pattern of declining dental health is more likely linked to the adoption of agriculture where more cariogenic foods were consumed. However, the Neolithic Revolution cannot be pinned as the main cause of dental caries when diet is very variable in different regions of the world, as well as between different individuals and sexes in the same community. The composition of a diet and methods of food preparation are the most significant factors in determining caries prevalence, and not agriculture alone.

Another indicator of health is periodontal disease, it is an inflammation of the gum caused by bacterial build up in plaque [36]. With more intensified farming in the Kerma and Medieval Period in Sudan, compared to the foraging-farming pastoral diet and semi-nomadic lifestyle in Neolithic Sudan, the prevalence of periodontal disease increases [47]. Whiting R. et al. [47] suggests the increased grain consumption over the period could have changed plaque-based bacteria and thus the risk of periodontal disease. However, the pattern is not uniform and the late Medieval Period in Sudan is characterised by comparatively better health than the Kerma and early Medieval samples. This implies that the initial transition to agriculture caused the greatest decline in health, due to a combination of lifestyle shifts, and was then followed by recovery over time.

Equally, linear enamel hypoplasia (dental enamel indicative of malnutrition and disease) increases from Palaeolithic to Neolithic Egypt but then decreases with the rise of the Egyptian state, which Stock J. T. et al. [5] propose is evidence that the impact of agriculture was brief and other factors such as culture also contribute to dental health. The proposal put forward by Stock J. T. et al. is supported by reliable evidence and the trustworthy provenance of this research puts it in a strong position to be used. Consequently, the pattern of an initial decline in health with the adoption of agriculture followed by years of recovery demonstrates the complexity of lifestyle factors at play and the reason agriculture should not be generalised because it evolves over time as well as varies globally.

Further regional variation is seen elsewhere. Antemortem tooth loss and periodontal disease incidences increased in farmers in Greece, the Pica-Tarapaca and Maya but decreased in the Levant [30]. Consequently, the use of different food processing mechanisms (such as abrasive ceramics which can allow bacterial growth in the microwear of teeth) and dietary compositions of different regions are more significant than the method of subsistence.

2.3b Skull morphology

Reduced skull size and craniofacial structures are commonly associated with the adoption of agriculture. Related to the use of food processing and consumption of softer foods masticatory stress reduced, as a result bone mass and masticatory muscles decreased and consequently negatively affected health [3] [28] [30] [43] [44]. Dental crowding and malocclusion increase with these factors due to an incompatibility between the size of the teeth and jaw, despite decreased tooth size, which promoted bacterial growth and caries [30]. The changes in skull morphology are frequently seen in the transition from foraging to farming in many geographic populations, yet there is evidence which sees the opposite pattern [43]. The main morphological change is the edge-to-edge bite in hunter-gatherers is replaced by an overbite in agricultural populations (see Fig 3. [44] and Fig 4. [45]) [3].

Fig 3. SOURCE: [44]

Summary of morphological changes observed in Nubian skulls through time from the Mesolithic (solid line) through to the Meroitic–Christian period (dashed line).

Fig 4. SOURCE: [45]

A) Female around 30 years old, Arene Candide Cave (Italy), late Upper Palaeolithic, displaying edge-to-edge bite

B) Female around 30 years old, Schela Cladovei (Romania), Mesolithic, displaying edge-to-edge bite

C) Male around 40 years old, Hainburg (Austria), Early Bronze Age (3600 BP), displaying overbite and overjet

Katz et al. [43] report more significant morphological changes in dairy-based diets than cereal-based diets related to the greater softness of dairy products, this exhibits the variability of subsistence methods and human health. To support evidence for a strong forager to farmer change, studies of the same geographical location show this same pattern of decreased facial structure – supporting the effect of diet on morphology [44]. Evidence also suggests the change is weak in transitional/semi-sedentary populations but strong in intense agricultural groups, intimating the role of lifestyle variability on health [46]. Moreover, changes in skull morphology are typically due to “phenotypic plasticity” adapted to softer foods than genetic adaptations, indicating a short-term model for such changes and thus the significance of the immediate effects of the agricultural transition [43] [44] [46]. However, it is important to note that food processing was developed before the Neolithic Revolution, which attests to a long-term model for morphological skull adaptations. All of these sources are reliable and have been well-regarded, thoroughly researched and the authors are non-biased, therefore this evidence can be incorporated into the argument. The main takeaway is that reduced dietary load and masticatory stress results in decreased/changed craniofacial structures and thus increased malocclusion and dental crowding. Agriculture in this case does play a large role in facial adaptations due to the dietary and technological changes which followed, notably later agriculture where even softer and more processed foods are associated with greater changes. Thus, over the long-term the transition to agriculture brought about the necessary lifestyle shifts to induce skull and dental morphological changes, but these changes are related to the dietary and processing shifts and not solely the agricultural subsistence method.

It is important to note that environmental factors, such as aridity or temperature, will also affect health and development. To this end, agriculture can never be the sole cause of declining health. It also means that studies considering various periods of history and subsistence methods will never fully represent the extent to which lifestyle or subsistence affects health; the human environment will also change with time and in different ways in different regions which then also effects disease prevalence etc. Nevertheless, research is not invalidated by uncontrollable factors in a sample, it is something that must be held in mind when drawing conclusions as there is always an element of uncertainty.

DIET AND NUTRITION

3.1 Malnutrition & Nutritional Quality

3.1a Dietary diversity

The lack of diversity in early agricultural diets may have led to nutritional deficiencies, namely the lack of macro and micronutrients. Inadequate nutrition from diet results in poorer health biologically and increased vulnerability to disease [23].

A study by Lallo et al. [23] looked at the diet and health of the Mississippian Acculturated Late Woodland populations combined compared with the Middle Mississippians. Life expectancy was lower and infectious lesions were more frequent and severe in the Middle Mississippian sample. Compared to the Late Woodland populations, the Middle Mississippian diet lacked plant diversity including high maize consumption and decreased animal protein which (as well as their high population density, sedentism and trade) can explain the health differences between these two farming populations [23]. There are evidently variable levels of health within agricultural (and any subsistence method) populations, and a multitude of factors which can influence health status, and not just the change from foragers to farmers. Communities with more intensive agricultural practices – particularly where the diet is less varied, lacks animal protein and the population density is greater – see a decline in health to a much greater extent compared to less intensive agricultural communities.

Evidence of health and dietary differences between foragers and farmers can be seen in modern-day Hadza foragers who have extremely low rates of cardiovascular disease, type 2 diabetes and healthy low body fat percentages and BMI compared to present Western populations and rates seen in the USA [26]. However, total energy expenditure of these foragers and modern industrial populations are the same so the evidence suggests dietary composition plays a key role. The Hadza have a carbohydrate focused diet with honey as a staple food, despite this typically being the proposed cause of poor Western health, the Hadza have much greater dietary diversity and fibre-rich foods than agricultural populations [26] [40] [48]. Fibre of Palaeolithic hunters is estimated to be 100-159gd-1 and similar results for the Hadza, with significantly less fibre in modern populations (20gd-1 in USA) [26]. Dietary fibre and diversity is associated with a more varied gut microbiota, and this holds true in research, such gut microbiome diversity is associated with strong resistance to metabolic, infectious and immune disease [14] [48]. This provides a dietary explanation for the observed health of modern-day hunter-gatherers such as the Hadza, which can be applied to explain the increased immune vulnerability associated with a shift to farming. It is important to note that this is a modern day comparison, and this report intends to explore how agriculture affected early human populations. However, this approach provides a good model for the differences in lifestyle, diet and health between hunter-gatherers and farmers in prehistory so it remains a valid piece of evidence. To this end, the transition to agriculture (or a lifestyle with a less diverse diet) is linked to increased susceptibility to disease.

A study of the earliest case of rickets found in Neolithic Britain epitomises the integration of dietary, environmental and lifestyle factors in health [55]. The skeleton found with rickets likely had a terrestrial plant and animal based diet, despite living coastally, the lack of aquatic food could be a cause of vitamin D deficiency but calcium from dairy was not lacking and there is no evidence of famine-related stress. In this case, rather than diet, cultural factors such as restrictions to the outdoors could have led to vitamin D deficiency and therefore rickets, but given the outdoor nature of Neolithic communities this is questionable. Equally, this is not firm evidence as the report is based off of a single skeleton – it may not be representative of lifestyle factors. Another paper argues that osteoporosis and osteopenia, as well as Harris lines, are indicative of vitamin D and calcium deficiency and this can often be seen in the Neolithic (particularly early on) as agricultural societies had not incorporated dairying/domestication of animals into their lifestyle [30]. As a result, not all facets of poor health can be put down to subsistence methods or nutrition, malnutrition is variable over time and regionally, and agriculture can therefore not be fully responsible for declining health when there are so many contributing strands.

3.1b Anaemia

Within the archaeological record, cases of anaemia can be identified from osteological effects such as porotic hyperostosis and cribra oribitalia, alongside evidence of expanded bone marrow [3, 49, 50, 51, 20]. Factors responsible are associated with a diet deficient in iron, poor absorption of iron, parasitism and infantile diarrhoea [18, 3, 49, 19, 4].

Porotic hyperostosis as an effect of anaemia is sometimes considered by anthropologists to be an indicator of nutritional stress, particularly a diet low in iron [20]. However, some studies propose diet is not the most significant factor in causing anaemia, and instead it is more likely a result of high pathogen load alongside an iron-deficient diet [3, 18, 49, 19]. Thus, porotic hyperostosis is not solely an indicator of malnutrition but other contributors such as a high pathogen load [52]. Both factors are nevertheless associated with the intensification of agriculture in different ways.

Pathogen load did increase with the adoption of agriculture. The consequent increase has a significant effect on anaemia because microbes use iron to grow, the body’s defence is to decrease iron in blood plasma [18]. As such, it is proposed that hypoferremia is an immune response to microbial infection and is an adaption to high pathogen load more than the consequence of diet [18]. As well as the body’s response to microbes, parasites like hookworm [49, 53] and diseases such as malaria can also negatively affect blood cells and cause anaemia [54]. Microbial infection can also cause chronic diarrhoea and, in turn, anaemia [19]. In a study of the prehistoric Anasazi of southwestern North America, abundant cases of porotic hyperostosis are proposed to be due to sedentary aggregation which allowed an increase in microbial infection (from poor hygiene, diarrhoea and close proximity of hosts) [19]. Similarly, the intensive period of agriculture in the Bronze Age Baltic, where rates of cribra orbitalia and porotic hyperostosis increased, relates to increased population density and is likely due to parasitic infection as their high-protein diet contained adequate amounts of iron [28]. This is evidence of the variability of a health defect and the complexity of contributing factors, suggesting that anaemia can be found regardless of malnutrition or a particular subsistence method.

When nutritional stress is severe, iron-deficient diets play a large role in anaemia too. Iron-poor diets include plants which contain tannins that decrease iron absorption (such as millet and sorghum) and plants low in iron (exemplified by wheat, rice and most often maize) [49, 3]. In the archaeological record of North American populations, nutritional stress is the leading cause of anaemia [20]. A study by Lallo et al. [51] demonstrated that the Late Woodland population of the Dickinson Mounds – which had a high dietary iron intake – had fewer cases of porotic hyperostosis than the three agricultural populations relying on maize. Porotic hyperostosis was also more severe in the Middle Mississippians, whose diet had less animal protein and a less diverse plant intake [23]. To this end, a diet based around a limited range of iron-poor plants increases the risk of iron-deficient anaemia.

The parasitism model tend assumes that diet has very little impact on iron-deficient anaemia and that hypoferremia is an physiological advantage in some cases. This is problematic because any form of iron deficiency is a health problem regardless of the cause [49]. Iron-deficiency anaemia does not demonstrate the negative effects of iron deficiency without anaemia [50].

As a result, research that focuses on anaemia as evidence of the significance of iron deficiency does not clearly demonstrate the extent to which agriculture had a negative impact on health. This is because porotic hyperostosis and cribra oribitalia are more frequent in sedentary agricultural populations than mobile foragers in some studies, in other cases anaemia is low in farmers and high in foragers and iron abundance in the diet does not always correlate with cases of anaemia [3, 18]. Other factors may not be taken into consideration in these studies, as anaemia is a complex problem and can be influenced by a multitude of variables [49]. Even if geographical and microbial factors are more important factors in porotic hyperostosis than diet as Stuart-Macadam [18] proposes they are, iron-deficient diets have negative, and sometimes severe, health effects [50]. These effects cannot be overlooked just because they are not associated with anaemic health conditions, and are not easily identifiable in the archaeological record, otherwise we overlook the significance of diet in the agricultural transition and how undernutrition impacts health. Stuart-Macadam’s research may overstate the significance of parasitism, and too quickly dismiss diet as a leading cause of iron-deficiency. It is not unless the significance of iron deficiency is considered alone, regardless of whether anaemia is prevalent, that a clear conclusion can be drawn on the relationship between agriculture (particularly with regards to diet) and health.

Agriculturalists were undernourished and had iron-poor diets compared to their forager counterparts, it is clear they would have suffered health effects associated with malnutrition. Even without anaemia, iron-deficiency can cause fatigue, shortness of breath, heart beat irregularity and more because iron is a vital cofactor in haemoglobin and thus the transport of oxygen [50]. Additionally, an individual with iron-deficiency is likely to suffer other forms of malnutrition and ill health [20] [24].

In short, the conditions for porotic hyperostosis include: iron-poor diets, poor hygiene levels (such as infantile diarrhoea) and high levels of parasitism [49]. In sedentary agriculturalists, where plants were the dietary staple over animal protein and populations could grow and settle due to surplus crops and small land cultivation [6], such conditions for anaemia would be prevalent in a high number of societies. Both nutritional and non-nutritional factors of anaemia and iron-depletion are most prevalent in sedentary agriculturalists, and the archaeological record demonstrates such cases of ill health increase from foragers to farmers [19, 51]. There is a statistically significant increase in the prevalence, as well as severity, of porotic hyperostosis and anaemia from hunters to agriculturalists [20] [19] [51]. Consequently, despite variations and the complexity of factors involved, it is clear that the Agricultural Revolution did negatively affect the iron health of early human populations (regardless of whether anaemia is present in the archaeological record).

A study of the earliest case of rickets found in Neolithic Britain epitomises the integration of dietary, environmental and lifestyle factors in health [55]. The skeleton found with rickets likely had a terrestrial plant and animal based diet, despite living coastally, the lack of aquatic food could be a cause of vitamin D deficiency but calcium from dairy was not lacking and there is no evidence of famine-related stress. In this case, rather than diet, cultural factors such as restrictions to the outdoors could have led to vitamin D deficiency and therefore rickets, but given the outdoor nature of Neolithic communities this is questionable. Equally, this is not firm evidence as the report is based off of a single skeleton – it may not be representative of lifestyle factors. Another paper argues that osteoporosis and osteopenia, as well as Harris lines, are indicative of vitamin D and calcium deficiency and this can often be seen in the Neolithic (particularly early on) as agricultural societies had not incorporated dairying/domestication of animals into their lifestyle [30]. As a result, not all facets of poor health can be put down to subsistence methods or nutrition, malnutrition is variable over time and regionally, and agriculture can therefore not be fully responsible for declining health when there are so many contributing strands.

CONCLUSION

The extent to which agriculture impacted human health depends on the extent to which it is adopted. Comparisons are all relative, whilst a hunter-gatherer group may be in poorer health than one less intense agricultural population, they may be considerably more healthy than an intense farming population. To this end, rather than making a broad generalisation which assumes all agricultural populations are the same and equally so for hunter-gatherers, it should be the lifestyle factors within a population which are the reason behind the levels of health in a population.

The factors which cause adverse health effects remain the same, but the environment and lifestyle these causes come from can vary. For example, cariogenic foods cause caries, but these foods could be consumed in either forages or farmers. Thus, presence of caries is not solely related to the method of food sourcing but the diet and lifestyle adopted by a particular population in a particular region. In general, the majority of the causes of disease and decreased health stem from lifestyle factors which people who adopt terrestrial agriculture tend to integrate into their life. Consequently, agriculture itself did not cause adverse health effects, rather the lifestyle shifts associated with agriculture are more likely to play a role.

It is important to note that regional variation is a foremost factor to consider when exploring the relationship between declining health and agriculture. Cultural, environmental and lifestyle factors which aren’t preserved in the archaeological record are also at hand. Some farming populations are seasonal, have lower population densities and varied diets whilst others establish permanent, densely settled communities and have limited nutritionally insufficient diets. Equally, aspects of the fisher-farmers can be seen in either hunter-gatherers or agriculturalists, and fishing groups experience relatively improved health and protection from caries. On the whole, diseases arise and afflict (pastoral) agriculturalists and robusticity, craniofacial morphology, dental health, nutritional status and life expectancy all decrease initially in farming populations. Though there are exceptions where this does not apply, and some health effects such as stature are less divisive, in general, increasing intensification of agriculture relates to a greater decline in health. All-in-all, the initial transition to agriculture transformed human lifestyle and it is to a significant extent that the Neolithic Revolution did cause a decline in human health.

Works Cited

[1]

A. E. Page, S. Viguier, M. Dyble, D. Smith, N. Chaudhary, G. D. Salali, J. Thompson, L. Vinicius, R. Mace and A. B. Migliano, "Reproductive trade-offs in extant hunter-gatherers suggest adaptive mechanism for the Neolithic expansion," Proceedings of the National Academy of Sciences, vol. 113, no. 17, pp. 4694-4699, 2016.

[2]

N. Wolfe, C. Dunavan and J. Diamond, "Origins of major human infectious diseases," Nature, vol. 447, pp. 279-283, 2007.

[3]

C. Larsen, "Biological changes in human populations with agriculture," Annual Review of Anthropology, vol. 24, no. 1, pp. 185-213, 1995.

[4]

L. K. Horwitz and P. Smith, "The contribution of animal domestication to the spread of zoonoses: a case study from the Southern Levant," Ibex, Journal of Mountain Ecology, vol. 5, pp. 77-84, 2000.

[5]

J. T. Stock and R. Pinhasi, "Changing Paradigms in Our Understanding of the Transition to Agriculture: Human Bioarchaeology, Behaviour and Adaptation," 2011. [Online]. Available: https://media.wiley.com/product_data/excerpt/07/04707473/0470747307-110.pdf. [Accessed February 2020].

[6]

J. Diamond, Guns, germs and steel: a short history of everybody for the last 13,000 years, Penguin Random House, 2017.

[7]

R. Barrett, C. W. Kuzawa, T. McDade and G. J. Armelagos, "Emerging and Re-Emerging Infectious Diseases: The Third Epidemiologic Transition," Annual Review of Anthropology, vol. 27, pp. 247-271, 1998.

[8]

M. Zuckerman, K. Harper, R. Barrett and G. Armelagos, "The evolution of disease: anthropological perspectives on epidemiologic transitions," Global Health Action, vol. 7, no. 1, p. 23303, 2014.

[9]

T. A. Cockburn, "Infectious Diseases in Ancient Populations," Current Anthropology, vol. 12, no. 1, pp. 45-66, 1971.

[10]

J. Diamond, "Evolution, consequences and future of plant and animal domestication," Nature, vol. 418, pp. 700-707, 2002.

[11]

J. Diamond, "The Worst Mistake in the History of the Human Race," Discover Magazine, 1999.

[12]

S. Morse, "Factors in the Emergence of Infectious Diseases," Emerging Infectious Diseases, vol. 1, no. 1, pp. 7-15, 1995.

[13]

A. Pedersen and T. Davies, "Cross-Species Pathogen Transmission and Disease Emergence in Primates," EcoHealth, vol. 6, no. 4, pp. 496-508, 2009.

[14]

E. Karlsson, D. Kwiatkowski and P. Sabeti, "Natural selection and infectious disease in human populations," Nature Reviews Genetics, vol. 15, no. 6, pp. 379-393, 2014.

[15]

G. Fournié, D. Pfeiffer and R. Bendrey, "Early animal farming and zoonotic disease dynamics: modelling brucellosis transmission in Neolithic goat populations," Royal Society Open Science, vol. 4, no. 2, p. 160943, 2017.

[16]

J. Lindahl and D. Grace, "The consequences of human actions on risks for infectious diseases: a review.," Infection Ecology & Epidemiology, vol. 5, no. 1, 2015.

[17]

J. P. Mackenbach, "The origins of human disease: a short story on "where diseases come from"," Journal of epidemiology and community health, vol. 60, no. 1, pp. 81-86, 2006.

[18]

P. Stuart-Macadam, "Anemia in past human populations," in Diet, demography, and disease: changing perspectives on anemia, P. Stuart-Macadam and S. Kent , Eds., New York, Transaction Publishers, 1992, pp. 155-166.

[19]

S. Kent, "The Influence of Sedentism and Aggregation on Porotic Hyperostosis and Anaemia: A Case Study," Man, vol. 21, no. 4, pp. 605-636, 1986.

[20]

D. Martin and A. Goodman, "Health conditions before Columbus: paleopathology of native North Americans," Western Journal of Medicine, vol. 176, no. 1, pp. 65-68, 2002.

[21]

D. H. Crawford, Deadly Companions: How Microbes Shaped out History, Oxford Landmark Science, 2018.

[22]

C. O. Thoen and D. E. Williams, "Tuberculosis, Tuberculoidoses, and Other Mycobacterial Infections," in Handbook of Zoonoses, Section a: Bacterial, Rickettsial, Chlamydial, and Mycotic Zoonoses, CRC press, 2019.

[23]

J. Lallo, G. J. Armelagos and J. C. Rose, "Paleoepidemiology of Infectious Disease in the Dickson Mounds Population," Medical College of Virginia Quarterly, vol. 14, no. 1, 1978.

[24]

F. Guo, T. Bonebrake and L. Gibson, "Land-Use Change Alters Host and Vector Communities and May Elevate Disease Risk," EcoHealth, vol. 16, no. 4, pp. 647-658, 2018.

[25]

M. Barberis, "The history of tuberculosis: from the first historical records to the isolation of Koch's bacillus," Journal Of Preventive Medicine And Hygiene, 2017. [Online]. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5432783/. [Accessed June 2020].

[26]

H. Pontzer, B. M. Wood and D. A. Raichlen, "Hunter-gatherers as models in public health,," Obesity Reviews, vol. 19, pp. 24-35, 2018.

[27]

J. Piontek and V. Vančata, "Transition to Agriculture in Central Europe: Body Size and Body Shape Amongst the First Farmers," Interdisciplinaria Archaeologica: Natural Sciences in Archaeology, vol. 3, no. 1, pp. 23-42, 2012.

[28]

M. B. C. Rivera, "Exploring diachronic changes in human activity, diet and health on the prehistoric Baltic coast," University of Cambridge, 2018.

[29]

D. Raichlen, H. Pontzer, T. Zderic, J. Harris, A. Mabulla, M. Hamilton and B. Wood, "Sitting, squatting, and the evolutionary biology of human inactivity," Proceedings Of The National Academy Of Sciences, vol. 117, no. 13, pp. 7115-7121, 2020.

[30]

K. J. Latham, "Human Health and the Neolithic Revolution: an Overview of Impacts of the Agricultural Transition on Oral Health, Epidemiology, and the Human Body," Nebraska Anthropologist, vol. 187, 2013.

[31]

A. Mummert, E. Esche, J. Robinson and G. J. Armelagos, "Stature and robusticity during the agricultural transition: evidence from the bioarchaeological record.," Economics & Human Biology, vol. 9, no. 3, pp. 284-301, 2011.

[32]

G. J. Armelagos and M. N. Cohen, Paleopathology at the origins of agriculture. Bioarchaeological interpretations of the human past., University Press of Florida, 2013.

[33]

D. C. Cook, "Subsistence and Health in the Lower Illinois Valley: Osteological Evidence," in Palaeopathology at the Origins of Agriculture, University Press of Florida, 2013, pp. 235-269.

[34]

A. A. Macintosh, R. Pinhasi and J. T. Stock, "Early Life Conditions and Physiological Stress Following the Transition to Farming in Central/Southeast Europe: Skeletal Growth Impairment and 6000 Years of Gradual Recovery," PloS one, vol. 11, no. 2, 2016.

[35]

P. V. Ponce, "A comparative study of activity-related skeletal changes in 3rd-2nd millennium BC coastal fishers and 1st millenium AD inland agriculturists in Chile, South America," Durham University, 2010. [Online]. Available: http://etheses.dur.ac.uk/546/1/PONCE_PhD_Thesis.pdf?DDD6+. [Accessed 4 April 2020].

[36]

J. D. Jovanović, "The diet and health status of the early Neolithic communities of the central Balkans (6200-5200 BC)," University of Belgrade Faculty Of Philosophy, Belgrade, 2017.

[37]

L. T. Humphrey, I. De Groote, J. Morales, N. Barton, S. Collcutt, C. B. Ramsey and A. Bouzouggar, "Earliest evidence for caries and exploitation of starchy plant foods in Pleistocene hunter-gatherers from Morocco," Proc Natl Acad Sci U S A, vol. 111, no. 3, pp. 954-959, 2014.

[38]

A. Botelho, "Ancient hunter-gatherers had rotten teeth," New Scientist , 6 Januray 2014. [Online]. Available: https://www.newscientist.com/article/dn24817-ancient-hunter-gatherers-had-rotten-teeth/ . [Accessed 2 April 2020].

[39]

K. Sheridan, "Eating nuts caused tooth decay in hunter-gatherers," Phys org, 6 January 2014. [Online]. Available: https://phys.org/news/2014-01-nuts-tooth-hunter-gatherers.html. [Accessed 2 April 2020].

[40]

A. N. Crittenden, J. Sorrentino, S. Moonie, M. Peterson, A. Mabulla and P. S. Ungar, "Oral health in transition: The Hadza foragers of Tanzania," PloS one, vol. 12, no. 3, p. e0172197, 2017.

[41]

J. Littleton and B. Frohlich, "Fish-eaters and farmers: dental pathology in the Arabian Gulf," American Journal of Physical Anthropology, vol. 92, no. 4, pp. 427-447, 1993.

[42]

R. Macchiarelli, "Prehistoric Fish-Eaters along the Eastern Arabian coasts," American Journal of Physical Anthropology, vol. 78, pp. 575-594, 1989.

[43]

D. C. Katz, M. N. Grote and T. D. Weaver, "Changes in human skull morphology across the agricultural transition are consistent with softer diets in preindustrial farming groups," Proceedings of the National Academy of Sciences, vol. 114, no. 34, pp. 9050-9055, 2017.

[44]

N. von Cramon-Taubadel, "Measuring the effects of farming on human skull morphology," Proceedings of the National Academy of Sciences, vol. 114, no. 34, pp. 8917-8919, 2017.

[45]

D. E. Blasi, S. Moran, S. R. Moisik, P. Widmer, D. Dediu and B. Bickle, "Human sound systems are shaped by post-Neolithic changes in bite configuration," 15 March 2019. [Online]. Available: https://science.sciencemag.org/content/363/6432/eaav3218?rss=1/share. [Accessed 2 August 2020].

[46]

R. Pinhasi, V. Eshed and N. von Cramon-Taubadel, "Pinhasi, R., Eshed, V., & von Cramon-Taubadel, N. (2015). Incongruity between affinity patterns based on mandibular and lower dental dimensions following the transition to agriculture in the Near East, Anatolia and Europe," PLoS One, vol. 10, no. 2, p. e0117301, 2015.

[47]

R. Whiting, D. Amtoine and S. Hillson, "Periodontal Disease and “Oral Health” in the Past: New Insights from Ancient Sudan on a Very Modern Problem," Dental Anthropology, vol. 32, no. 2, pp. 30-50, 2019.

[48]

S. L. Schnorr, M. Candela, S. Rampelli, M. Centanni, C. Consolandi, G. Basaglia, S. Turroni, E. Biagi, C. Peano, M. Severgnini, J. Fiori, R. Gotti, G. De Bellis, D. Luiselli, P. Brigidi, A. Mabulla, F. Marlowe, A. G. Henry and A. N. Crittenden, "Gut Microbiome Of The Hadza Hunter-Gatherers," Nature Communications, vol. 5, no. 1, 2014.

[49]

T. D. Holland and M. J. O'Brien, "Parasites, Porotic Hyperostosis, and the Implications of Changing Perspectives," American Antiquity, vol. 62, no. 2, p. 183–193, 1997.

[50]

E. T. Soppi, "Iron deficiency without anemia - a clinical challenge," Clin Case Reports, vol. 6, no. 6, pp. 1082-1086, 2018.

[51]

J. W. Lallo, G. J. Armelagos and R. P. Mensforth, "The Role of Diet, Disease, and Physiology in the Origin of Porotic Hyperostosis," Human Biology, vol. 49, no. 3, pp. 471-483, 1977.

[52]

P. Stuart‐Macadam, "Porotic hyperostosis: a new perspective," American Journal of Physical Anthropology, vol. 87, no. 1, pp. 39-47, 1992.

[53]

Centers for Disease Control and Prevention, "Hookworm," 2020. [Online]. Available: https://www.cdc.gov/parasites/hookworm/index.html. [Accessed 3 July 2020].

[54]

K. Haldar and N. Mohandas, "Malaria, erythrocytic infection, and anemia," Hematology Am Soc Hematol Educ Program 2009, vol. 1, pp. 87-93, 2009.

[55]

I. Armit, F. Shapland, J. Montgomery and J. Beaumont, "Difference in Death? A Lost Neolithic Inhumation Cemetery with Britain’s Earliest Case of Rickets, at Balevullin, Western Scotland," Proceedings of the Prehistoric Society, vol. 81, pp. 199-214, 2015.

[56]

J. Piontek and V. Vančata, "Transition to agriculture in Central Europe: Body size and body shape amongst the first farmers," Interdisciplinaria Archaeologica: Natural Sciences in Archaeology, vol. 3, pp. 23-42, 2012.