Introduction

This chapter explores questions about the history of the size, spatial distribution, and behavior of the human population (Homo sapiens). We start with our origins in the great rift valley of East Africa and touch on our evolution and co-evolution with other Homo species. We explore ideas about how our cognitive abilities, behaviors, and cultural practices evolved over the last 200,000 years. We explore how H. sapiens has dramatically changed the number and distribution of other life forms on the planet and how the changes we are causing now present profound challenges for our continued existence.

Guiding Questions

How do we define the term species in general and H. sapiens in particular?

How has the size and distribution of the human population changed in the last 200,000 years?

What is the agricultural revolution, where did it occur, and how did it affect H. sapiens?

What evolutionary pressures may have caused H. sapiens to engage in cooperative behavior?

Define the term “Prehistory” and explain its classification by the “Three-Age System.”

How have humans transformed from “reactors” of environmental change to “causal agents” of environmental change?

How has our idea of human evolution from Australopithecus to Homo erectus to Homo habilis to H. sapiens evolved?

Learning Objectives

Demonstrate a basic understanding of what H. sapiens is and how we have evolved physically, cognitively, and behaviorally in the last 200,000 years.

Describe how and why human prehistory is characterized by physical artifacts.

Explain how changes in human behavior have resulted in global environmental changes.

Key Terms and Definitions

Homo sapiens, Homo neanderthalensis, Prehistory, Species, Linear notion of human evolution, Obstetrical dilemma, Three-Age System, Cognitive revolution, Agricultural revolution, Fertile Crescent, Boserup’s Hypothesis, Animal domestication, Bipedalism, Global biomass by species

1.1 Out of Africa—Where Did We Come From?

When and where did the first human being on earth exist? This sounds like a reasonable and interesting question; however, we will likely never have a definitive answer because the question itself raises more questions. For example—what constitutes a human being? Is it the use of language? Is it the use of stone tools? Some have argued that walking upright (bipedalism) is a fundamental human characteristic that provides for many interesting hypotheses about trade-offs in evolutionary adaptations and perhaps a mechanism of selection for prosocial or cooperative behavior (Wayman, 2012). Evidence suggests (e.g., the discovery of “Lucy” in 1974) that australopithecines walked upright prior to the development of large brains in hominids. However, these early hominids likely still spent a great deal of time in the trees. Homo erectus is generally regarded as the first hominid to grow to a longer-legged, taller, and completely terrestrial human. There are many theories as to why bipedalism evolved including the following: (1) Darwin’s suggestion that we needed hands and arms to develop and use tools, (2) climate change causing greater seasonal variability in food availability in the arboreal environments, and (3) a gender-based cooperation in which males gathered food for females and their young and needed arms to carry food gathered from both arboreal and terrestrial environments. One element of evolving toward bipedalism is changes to the pelvis and issues related to what has been referred to as the “obstetrical dilemma” (Obstetrical Dilemma, n.d.). There is a biological trade-off between two evolutionary pressures, that is, larger skull sizes and narrower birth canals. Did these changes create evolutionary selective pressure for cooperative behavior in humans? Catherine Ann Key suggests in her PhD thesis the following roots of the development of prosocial and collaborative behavior in humans (Key, 1998):

The theoretical and empirical evidence presented in this thesis suggests that sex differences in the energetic cost of reproduction determine the cooperative strategies, and ultimately the types of social groups, that evolve. It is proposed that during hominid evolution female energetic costs increased greatly, in comparison to male energetic costs, due to changes in body size dimorphism, diet and brain size. A two-stage model of hominid social structure is developed. The first stage, at the transition from the australopithecines to Homo erectus, would have involved an increase in female cooperation, especially food sharing. The second stage, occurring between 500,000 and 100,000 years ago, would have involved male care giving, the formation of pair bonds and the sexual division of labor within the context of a wider cooperative network.

Explaining the evolutionary processes that resulted in human language, bipedalism, the use of tools, and cooperative behavior are fascinating questions primarily in the domain of anthropology. We currently believe that bipedalism, the use of stone tools, cooperative behavior, and perhaps even pair bonding existed at the end of H. erectus’s presence on Earth. Should H. erectus be considered the first modern human? Video 1.1 provides a beautiful animation of 7 million years of human evolution to frame this chapter.

I would suggest that the answer to the question—When and where did the first human being on earth exist?—is the earliest born infant that could be time-warped to a hospital nursery today and would grow up to do regular human things and be indistinguishable from any other humans. H. erectus probably does not fit this bill. An argument could be made that the earliest member of the genus and species Homo sapiens would meet that criteria. If you accept that definition, then our best estimate of the answer to the question is roughly 200,000–300,000 years ago in East Africa. However, by that time, other members of the genus Homo (e.g., Homo neanderthalensis) were using fire and stone tools and likely burying their dead (Than, 2013). The use of fire is not a trivial matter associated only with staying warm. It allowed for the cooking of food, which made many foods more edible and killed parasites.

The evolution of H. sapiens and the development of their brains are intricately linked to the discovery and mastery of cooking (Zohar et al., 2022). The ability to cook food marked a crucial turning point in human evolution, influencing both our physiology and culture. Cooking enabled our ancestors to extract more nutrients from their food, making it easier to digest and providing a more efficient energy source. This shift from a raw to a cooked diet is believed to have played a pivotal role in the expansion of the human brain. The increased availability of energy-rich, easily digestible cooked food allowed for the development of larger brains that demanded substantial energy resources. The coevolution of cooking and brain size reflects a mutually reinforcing cycle, with a bigger brain driving the need for more sophisticated cooking methods, and improved cooking facilitating the growth of a larger, more complex brain. Which may have been the impetus for fostering technological innovation to secure more energy-dense resources (e.g., the development of agriculture and the exploitation of fossil fuels).

Furthermore, cooking had profound social implications, shaping the structure of human societies (Wrangham, 2009). The communal act of gathering around a fire to cook and share food fostered cooperation, communication, and the formation of social bonds. This communal aspect of cooking contributed to the development of complex social structures, cooperation in hunting and gathering, and the sharing of knowledge, skills, and resources. The ability to cook not only transformed the human diet but also laid the foundation for the cultural practices and rituals that define human societies.

The impact of cooking on human evolution and brain development cannot be overstated. It likely not only provided a nutritional advantage that fueled the expansion of our brains but also shaped our social structures and cultural practices. The discovery and mastery of cooking were pivotal moments in our evolutionary history, influencing the trajectory of H. sapiens and setting the stage for the complex societies and advanced cognitive abilities and affiliated technological developments that define us as a species today (Video 1.2).

It is becoming a virtual certainty that H. neanderthalensis interbred with H. sapiens (Than, 2010). This raises interesting and thorny questions about the very definition of a species. A longstanding definition of “species” has been “a group of individuals that actually or potentially interbreed in nature.” By this definition, H. sapiens and H. neanderthalensis would be the same species (Video 1.3). Needless to say—defining the term “species” is contested and complex (Understanding Evolution).

In the not too distant past, the evolution of H. sapiens was often depicted as a linear process typically starting with Australopithecus afarensis to Homo habilis to H. erectus to H. neanderthalensis to H. sapiens (Figure 1.1). There are a host of textbooks, posters, and bumper stickers with myriad representations of this sort of linear evolution. Perhaps this image of our evolution meets the criterion of H.L. Mencken’s oft-paraphrased quote: “For every complex question there is an answer that is clear, simple, and wrong.”

[figure number=Figure 1.1 caption=Antiquated Ideas of Linear Evolution of the Homo Genus filename=Fig_1.1.jpg]

This linear notion of human evolution is almost certainly oversimplified if not outright wrong. Contemporary understanding of the nature of the evolutionary process that resulted in H. sapiens is much more complicated and will undoubtedly continue to evolve as more archaeological evidence manifests and technology (e.g., paleogenomics) develops. A nice distillation of the state of knowledge regarding a more complex understanding of the evolution of the genus Homo is provided by Jordi Agusti (Agusti, 2018). The surprising nature of our current understanding is that H. neanderthalensis and H. sapiens likely coexisted for tens of thousands of years. It is also likely another species of Homo (Homo floresiensis) was also a contemporary (in time but perhaps not in space) of H. neanderthalensis and H. sapiens. It is believed that H. neanderthalensis evolved mostly in Europe and Asia. H. sapiens (current global population roughly 8 billion and counting) seems to be the winner of this “survival of the fittest” competition.

[figure number=Figure 1.2 caption=Evolution of the Genus Homo filename=Fig_1.2.jpg]

The competition may have been “nasty” and “brutish” but it was not “short” by any stretch of the imagination. As further evidence is discovered, we may find that other hominids (individuals of the genus Homo) existed contemporaneously with sapiens, neanderthalensis, and floresiensis. This precis of human origins is a good example of the scientific method at work. Physical evidence, such as bones and their geographic location and context, is interpreted using (hopefully) methods (e.g., carbon dating), logic, and reason to build theories about the unfolding of human evolution that took place deep in the past. The nature of scientific understanding evolves with new evidence, new technology, and even new ideas. This evolution is not haphazard because it is typically based on the consensus of myriad scientists engaged in the process.

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1.2 Prehistory

Prehistory is the events that occurred before the invention of written records. Written records from Egypt date back to 3,200 BCE. Consequently, many regard 3,200 BCE as the “beginning of history” and prehistory is the time before that (Video 1.4). So, if we regard H. sapiens as having been on earth for 200,000 years, then roughly 97% of “human” history is prehistory. Most of human history is very very different from the lives we live today. However, it is poignant to realize that a human baby snatched from 190,000 years ago and adopted by a modern family would be indistinguishable from you or me or anyone else for that matter. We call on science more than historical archives to develop a narrative of human prehistory because ancient humans did not leave us with any written documentation or YouTube videos of their thoughts and lives.

Several narratives of prehistory and history have been proposed. Archaeologists have long used the “Three-Age System,” which divides human prehistory into the “Stone Age,” “The Bronze Age,” and the “Iron Age.” The Three-Age System basically follows a chronological development in time of technology as measured by the physical artifacts from those times that modern archaeologists can get their hands on. The Stone Age is further subdivided into the Paleolithic, the Mesolithic, and the Neolithic (Figure 1.2).

[figure number=Figure 1.3 caption=The Fertile Crescent filename=Fig_1.3.jpg]

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Table 1.1. The Three-Age System

In general, the further back in time we go, the less we know about what human civilization was like. Stone tools likely go back millions of years, whereas the controlled use of fire may only go back 125,000 years. The origins of language use by H. sapiens appear to be close in time to the controlled use of fire, occurring around 125,000 years ago (Video 1.5).

Another narrative spanning from prehistory to recorded history is suggested by Yuval Noah Harari in his widely acclaimed book Sapiens: A Brief History of Humankind (Harari, 2015). Harari suggests that human history has been significantly shaped by three major “revolutions”—The Cognitive Revolution (~70,000 years ago), The Agricultural Revolution (~10,000 years ago), and The Scientific Revolution (~500 years ago). The Cognitive Revolution occurs in prehistory. It represents what appears to be a uniquely human ability to believe in things that only exist in one’s mind (e.g., abstract ideas such as gods, nations, and money). Harari goes on to argue that our newfound ability to believe in “abstract ideas” subsequently fostered the development of larger scale human cooperation enabling the establishment of religions, political structures, trade networks, nations, and legal institutions. This allowed for shared myths or belief systems that brought humanity to the point of overcoming biological evolution and becoming responsible for its own destiny through cultural and technological evolution. Another interesting and controversial hypothesis about the origin of consciousness related to Harari’s idea of a “cognitive revolution” was posited decades earlier by Julian Jaynes in his book, The Origin of Consciousness and the Breakdown of the Bicameral Mind (Jaynes, 1976). Jaynes posits that a fundamental change to the nature of consciousness in H. sapiens occurred much more recently (~3,000 years ago). In any case, the transition from prehistory to recorded history is closely associated with a significant development in technology that has driven significant changes in culture. A case in point is the agricultural revolution. This key turning point in human history dates to roughly 10,000 BCE—domestication of plants and animals. Agriculture began near the transition from the Paleolithic to the Mesolithic and is likely a cultural/technological adaptation that allowed for changes to what humans actually used their brains for.

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1.3 The Agricultural Revolution

The agricultural revolution had many dramatic effects on the character of human existence. Prior to the agricultural revolution, H. sapiens likely went through a dietary evolution from vegetarian-gathering to scavenger-gathering to hunter-scavenger-gathering with scavenging subsequently fading away over time (rotting meat does not taste as good?; Robinson, 2014).

The consumption of meat by hominins predates H. sapiens (Pobiner, 2013) and the agricultural revolution. Eating meat has been a significant factor in the evolution and development of the human species. Early humans, as opportunistic omnivores, incorporated meat into their diets. It has been hypothesized that this played a crucial role in shaping both their physiology and cognitive abilities (Zink & Lieberman, 2016). However, these ideas remain contested (Barr et al., 2022). The nutrient density of meat, particularly in terms of protein and essential fatty acids, provided a more concentrated and accessible source of energy compared to a plant-based diet. This increased energy intake from meat consumption is thought to have supported the growth of the human brain. The high metabolic cost of maintaining a large brain demands a substantial and efficient energy source, and the incorporation of meat into the diet likely played a pivotal role in meeting these nutritional demands.

The consumption of meat not only contributed to the expansion of the human brain but also influenced social and cultural aspects of early human societies (Leroy & Praet, 2015). Hunting and sharing meat fostered cooperation among individuals, as it required collaborative efforts in hunting, processing, and distributing the food. The development of tools for hunting and butchering, along with the sharing of meat within social groups, encouraged the formation of complex social structures. These communal activities around meat consumption played a role in shaping the social dynamics and cooperation that are characteristic of human societies.

However, it is important to note that the impact of meat consumption on human evolution is a subject of debate, and various theories exist. Some argue that the incorporation of meat was a catalyst for the development of larger brains, while others emphasize the role of a broader dietary shift, including the consumption of cooked foods. Regardless, there is a consensus that the inclusion of meat in the human diet has had a profound impact on our evolutionary trajectory, influencing both our physiology and social behaviors. It is likely that eating meat provided high energy density input to hominins that allowed for dramatic growth in cognitive ability. A significant subsequent development is the high energy density available from agriculture, which allowed for significant growth in the population of H. sapiens.

Agriculture also likely developed as an evolutionary process in which we gathered grains, noticed them growing near our waste mounds (middens), and got ideas for fostering the growth of preferred plants and so on. The cognitive ability to “notice” these phenomena that led to agriculture may be predicated on brain growth resulting from eating meat. Just as our understanding of the story of human evolution is complex and unfolding—our understanding of the nature of the development of agriculture is complex and unfolding (History of Agriculture, n.d.). There is some controversy about what brought about the agricultural revolution—Did a growing human population create a demand for more food or did a growing food supply enable the growth of the human population? The answer to this question relates to a student’s humorous answer to an exam question I once gave: Q: Why did agriculturalists ultimately replace hunter-gatherers? Student’s answer: They outbread them.

It is estimated that the size of the human population at the onset of the agricultural revolution was somewhere between 1 and 10 million individuals (Historical Estimates of the World Population, n.d.). Agriculture increased food availability that allowed for a significant increase in the growth rate of the human population. There is little doubt that the “invention” of agriculture took place independently in many places throughout the world. The “Fertile Crescent” is often described as the “Cradle of Modern Civilization” and sole location in which agriculture developed. The Fertile Crescent consisted of rich river valleys in the Middle East including the Nile, Tigris, and Euphrates rivers (Figure 1.3).

[figure number=Figure 1.4 caption=Primary Regions of Diversity of Major Agricultural Crops Worldwide from “Origins of Food Crops Connect Countries Worldwide” filename=Fig_1.4.jpg]

However, we now believe that agriculture developed independently in several locations likely including what is now Mexico, the southeastern United States, China, sub-Saharan Africa, Indonesia, Australia, and other areas (Figure 1.4).

[figure number=Figure 1.5 caption=Current Patterns of Agriculture Around the World filename=Fig_1.5.jpg]

Thus, the Fertile Crescent is but one of many (albeit perhaps the first) independent developments of agriculture using a variety of plants. The pattern or geographic distribution of edible plants that eventually were domesticated is clearly not uniform. Barley, wheat, oats, lentils, and rye were the early domesticates of the Fertile Crescent, while other edible plants are native to other agricultural hearths. Note, for instance, that the potato is not native to Europe (home of the infamous Irish Potato Famine) but from Latin America. Many excellent books have been written about the history and geography of major foods and their impact on human culture, economy, and civilization (e.g., Mark Kurlansky’s Cod: A Biography of the Fish That Changed the World & Salt: A World History, John Reader’s Potato: A History of the Propitious Esculent; Kurlansky, 1997; Reader, 2009). A full exploration of all of these fascinating stories is beyond the scope of this text; nonetheless, the interested student is encouraged to explore sources in the bibliography to dive deeper.

The agricultural revolution is not just about the domestication of plants. The domestication of animals is also significant. Also, we should be careful about the idea that we (H. sapiens) were the “domesticator” and the plants and/or animals were the “domesticate.” An external observer might reasonably conclude that wheat domesticated humans—wheat has become a very successful plant as a result of its devious domestication of humans. It certainly is more abundant than it would be without human assistance and it occupies a much larger fraction of the earth’s surface than humans do.

A similar argument could be made about the co-evolution of humans and wolves. Wolf domestication is not a settled subject by any means. One hypothesis is that wolves were attracted to food scraps left around human encampments. This idea suggests that the scavenger wolves self-domesticated and humans had little agency in the process. Other theories suggest that the process was more cooperative between wolves and humans and that humans learned hunting techniques from wolves and perhaps engaged in cooperative behaviors with wolves (Pierotti & Fogg, 2017). In any case, there is little disagreement that the wolf was the first animal domesticated by humans somewhere between 13,000 and 30,000 years ago. The domestication of wolves resulted in what we now know as dogs (aka “man’s best friend”). Wolves and dogs are essentially the same species—notwithstanding aforementioned difficulties and issues with actually defining what the term “species” means (Video 1.6). The domestication of cats is traced back to 7,500 BCE (in Cyprus), although early cat domestication is typically associated with Ancient Egyptian culture. Domestication of animals for food is another matter entirely.

It is believed that sheep were the first animals to be domesticated for food between 11,000 and 9,000 BCE. This took place in the Fertile Crescent and Goats were domesticated a little bit later on (~8,000 BCE). Nomadic communities used these animals for milk, meat, and skins. Sheep and goats were a mobile food source that could survive on lands that were not particularly fertile (grasslands and shrublands). This was a particularly valuable biological exploitation or technological development.

There are many ideas as to what drives or enables humans to domesticate particular animals. Jared Diamond’s Pulitzer Prize winning book, Guns, Germs, and Steel: The Fates of Human Societies, suggests that some regions of the world were simply endowed with animals that were docile enough to be domesticated, while others were not (Diamond, 1997). Ross Tellam suggests that the evolution of lactose tolerance in humans was a profound advantage enabling the consumption of energy-rich milk from sheep, cows, horses, and goats (Lear, 2012). Horses were initially domesticated for food rather than transportation. The earliest evidence for actually riding horses only dates back to the Eurasian steppe around 3,000–4,000 years ago. As with plants, the pattern, or geographic distribution of animals that were ultimately domesticated by humans is not uniform throughout the world (Figure 1.5). Humans did more than domesticate animals for food. Sometimes they hunted them to extinction (Smith et al., 2018).

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1.4 Homo sapiens: Agents of Global Change

The archaeological record in North America, South America, and Australia suggests that when humans arrive most large mammal species go extinct. Where did they go? We hunted many of them to extinction and ate them. We still have many wild mammals on the planet. But the pattern is clear: 11,000 years ago, the average mass of a non-human wild mammal in North America was about 200 pounds. Now it is about 15 pounds. This trend is continuing (excluding of course the billions of domesticated sheep, cows, goats, and pigs; Figure 1.6). The story of the growth of the human population to the present is clearly one of global domination. Renowned biologist, E.O. Wilson, stated:

Human beings—mammals of the 50 kilogram weight class and members of a group, the primates, otherwise noted for scarcity—have become a hundred times more numerous than any other land animal of comparable size in the history of life. By every conceivable measure, humanity is ecologically abnormal. Our species appropriates between 20 and 40 per cent of the solar energy captured in organic material by land plants. There is no way that we can draw upon the resources of the planet to such a degree without drastically reducing the state of most other species. (from “The Diversity of Life”)

This ascent of H. sapiens has profoundly changed many natural patterns on the planet including land use patterns, plant distribution patterns, and biodiversity patterns (Figure 1.7). There is growing concern that we are even changing climatic patterns and fundamental biogeochemical cycles in ways that threaten our continued survival. Some describe the ideology that causes human domination of the planet as “human supremacy.” Human supremacy, the belief in the inherent dominance of humans over the natural world, has profound implications for the environment. It is argued that this perspective leads to exploitative practices, deforestation, overconsumption, and pollution. This is justified when humans perceive themselves as separate from and superior to the ecosystems on which they actually depend. The relentless pursuit of economic growth without due consideration for ecological balance has resulted in habitat destruction, loss of biodiversity, and climate change. Recognizing the interconnectedness of all life forms and adopting a more harmonious approach are crucial to mitigate the adverse impacts of human supremacy on the environment and secure a sustainable future for our planet. The specific processes that drive these changing patterns will be explored in Unit II of this book.

[figure number=Figure 1.6 caption=Distribution of Earths Mammals filename=Fig_1.6.jpg]

It took 200,000 years for our human population to reach 1 billion—and only 200 more years to reach almost 8 billion. Our growth has begun slowing, as women have fewer babies on average. When will the global population peak? Can we minimize our impact on Earth’s resources, even as we approach 10 or 12 billion? This video animates the reality described in the “J-Curve” of the first figure of the next chapter (Figure 2.1) (Video 1.7). Major events of human history are denoted with circular symbols along the timeline (e.g., Bubonic Plague, Peak Mayan Civilization, Birth of Islam). The video may seem a bit slow; however, try to realize that it is collapsing roughly 200,000 years of history into 6 min. That is roughly 5,000 or 6,000 human generations. Very little biological evolution of H. sapiens has taken place over that time in the sense that we believe that a H. sapiens infant from 200,000 years ago time-warped into a crib in the world today would be indistinguishable from the rest of us. This video frames the concepts covered in Chapter 2.

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Chapter Summary/Key Takeaways

This chapter provided a brief history of human origins from australopithecus (~4 million years ago) to the arrival of H. sapiens (~200,000 years ago). The changes in our bodies, brains, and diet over time were likely driven primarily by the selective pressures of biological evolution; however, increasingly cultural and technological evolution has been shown to have a greater influence on how human beings experience their own existence.

In Chapter 2, we will take a closer look at the history of the human population growth and how we characterize it mathematically. We will also explore contemporary spatial patterns of the human population. Where do most of us live? How many children do we have? How long do we live? What do we eat? What gods do we believe in? What languages do we speak? What are our migration patterns? What is the distribution of wealth and income? In other words—Where and who are we now?

Comprehensive Questions

• When and where was the first human? Why is this a tricky question?
• What is the “obstetrical dilemma” and how might it relate to the development of cooperation in humans?
• When did bipedalism evolve and why?
• Compare and contrast “The Three-Age System” with Harari’s “Three Revolutions.”
• How did the advent of agriculture change human history?
• It seems you can buy bananas in any supermarket. Where did they come from originally? What plants and animals originally came from South America?
• What is the relative global biomass of humans, cows, sheep, and elephants in the world today? Where would the global biomass of humans have been at the dawn of the agricultural revolution?
• How could it be argued that wolves domesticated humans rather than the other way around? What do you think makes the most sense?
• What does Yuval Noah Harari mean by “The Cognitive Revolution”?
• What is the “Boserup Hypothesis”?
• What part of today’s world is dominated by intensive subsistence rice agriculture?

References

Agusti, J. (2018). Evolution of the genus ‘Homo’: New mysteries and perspectives. Mètode Revista de difusió de la investigació, 8. https://doi.org/10.7203/metode.8.9308. https://metode.cat/wp-content/uploads/2017/09/2018-B1-agusti-evolution-Homo-genus.pdf

Barr W. A., Pobiner B., Rowan J., Du A., & Faith J. T. (2022).Proceedings of the National Academy of Sciences of the United States of America, 119(5). https://doi.org/10.1073/pnas.2115540119

Diamond, J. (1997). Guns, germs, and steel: The fates of human societies. Norton.

Felisa, A. S., Elliott Smith, R. E., Lyons, S. Kathleen, & Payne, Jonathan L. (2018). Body size downgrading of mammals over the late Quaternary. Science, 360, 310–313 https://science.sciencemag.org/content/360/6386/310

Harari, Y. (2015). Sapiens: A brief history of humankind. Harper.

Historical Estimates of the World Population. (n.d.). In U.S. Census Bureau. https://www.census.gov/data/tables/time-series/demo/international-programs/historical-est-worldpop.html

History of Agriculture. (n.d.). In Wikipedia https://en.wikipedia.org/wiki/History_of_agriculture

Jaynes, J. (1976). The origin of consciousness in the breakdown of the bicameral mind. Houghton Mifflin.

Key, C. A. (1998). Cooperation, paternal care, and the evolution of hominid social groups, University College London (PhD thesis) https://discovery.ucl.ac.uk/id/eprint/1383487/1/407310.pdf

Kurlansky, M. (1997). Cod: A biography of the fish that changed the world. Walker and Co.

Lear, J. (2012). Our furry friends: The history of animal domestication. Journal of Young Investigators, 23(2). https://www.jyi.org/2012-february/2017/9/17/our-furry-friends-the-history-of-animal-domestication

Leroy, F., & Praet, I. (2015). Meat traditions. The co-evolution of humans and meat. Appetite, 90, 200–211.

Obstetrical Dilemma. (n.d.). In Wikipedia. https://en.wikipedia.org/wiki/Obstetrical_dilemma

Pierotti, R., & Fogg, B. R. (2017). The first domestication: How wolves and humans coevolved. https://www.amazon.com/First-Domestication-Wolves-Humans-Coevolved/dp/0300226160

Pobiner, B. (2013). Evidence for meat-eating by early humans. Nature Education Knowledge, 4(6):1Reader, J. (2009). Potato: A history of the Propitious Esculent. Yale University Press.

Robinson J. (2014). The first hunter–Gatherers. https://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780199551224.001.0001/oxfordhb-9780199551224-e-029

Than, K. (2010). Neanderthals, humans interbred – First solid DNA evidence. National Geographic. https://www.nationalgeographic.com/news/2010/5/100506-science-neanderthals-humans-mated-interbred-dna-gene/

Than, K. (2013). Neanderthal burials confirmed as ancient ritual. National Geographic. https://www.nationalgeographic.com/news/2013/12/131216-la-chapelle-neanderthal-burials-graves/#close

Understanding Evolution: Your one-stop source for information on evolution https://evolution.berkeley.edu/evolibrary/article/evo_41

Wayman, E. (2012). Becoming human: The evolution of walking upright. Smithsonian Magazine. https://www.smithsonianmag.com/science-nature/becoming-human-the-evolution-of-walking-upright-13837658/

Wrangham, R. (2009). Catching fire: How cooking made us human. Basic Books.Zink, K., Lieberman, D. (2016). Impact of meat and Lower Palaeolithic food processing techniques on chewing in humans. Nature, 531, 500–503 (2016). https://doi.org/10.1038/nature16990

Zohar, I., Alperson-Afil, N., Goren-Inbar, N. et al.., Prévost, M., Tütken, T., Sisma-Ventura, G., Hershkovitz, I., & Najorka J. (2022). Evidence for the cooking of fish 780,000 years ago at Gesher Benot Ya’aqovYa”aqov, Israel. Nature Ecology and Evolution, 6, 2016–2028. https://doi.org/10.1038/s41559-022-01910-z