| LEARNING OBJECTIVES 1. Explain the impact that brain and language evolution has had on the development of the human species. 2. Explain why Homo sapiens is referred to as a cultural species and how humans have come to populate the world. 3. Identify the factors that gave rise to religion and some the characteristics that defined early religion during the Paleolithic Era. View Timelines: Prehistory | Evolution |
BRAIN AND LANGUAGE EVOLUTION
What is it that makes the human species so different from all others on Earth? For centuries, scientists, historians, and philosophers have wrestled with this question, seeking to pinpoint the qualities that set humanity apart. The historian David Christian believes the answer lies in human pre-adaptations—traits that evolved over millions of years and, while initially serving one purpose, later became crucial to our species’ extraordinary success. These pre-adaptations, he argues, laid the foundation for the unique abilities that have allowed humans to transform their environments, create complex societies, and dominate the planet. What are these pre-adaptions?
- Sociability
- Linguistic skills
- Bipedalism
- Dexterous hands
- Meat-eating and hunting
- Large period of childhood learning
- Large forebrains
While not all pre-adaptations are unique to humans, two stand out as having played a critical role in our extraordinary success as a species: encephalization (the increase in brain size and complexity) and the evolution of language. Together, these traits revolutionized human cognition and communication, enabling us to solve complex problems, share knowledge across generations, and create the rich cultures that define our species. Christian emphasizes:
| “What makes us so different? The answer to that question will show why our evolution counts as a fundamental turning point in the modern creation story. Put simply, we are different because we keep adapting and finding new ways of extracting energy from the environment. Constant adaptation has allowed us to multiply and to create societies more complex than those of any other species on Earth.” |
THE ORIGIN OF HUMAN LANGUAGE
The human brain is an incredibly intricate and complex organ, central to the evolution of one of humanity’s defining traits: language. Recent advances in neuroscience have revealed the roles of specific brain regions—such as the olfactory bulb, cerebellum, visual cortex, temporal lobe, and the overall frontal cortex, including its primary motor, premotor, and prefrontal cortices—in shaping our cognitive and linguistic abilities. Because “the ability to speak and understand language requires the recruitment of several brain regions,” it is critical to understand the “anatomical and neural mechanisms underlying human spoken language.”
The origin of language, something uniquely human, must therefore be explored through the lens of brain evolution. But the brain does not act alone. Its organization is intricately linked to the human vocal apparatus—the lungs, tongue, teeth, nasal passages, and other structures that enable the production of speech. Together, these components make possible the extraordinary “transformation between acoustic waveform and thought,” allowing humans to convey abstract ideas, emotions, and complex information.
FOXP2
Another crucial factor in this evolutionary story is the FOXP2 gene. Sometimes referred to as the “language gene,” FOXP2 has been linked to speech and language development, providing a genetic basis for our ability to produce and comprehend spoken language. Its discovery has shed light on the intricate interplay between brain evolution, vocal anatomy, and genetics, offering new insights into how language came to define what it means to be human.
Why did language evolve so quickly in modern humans? Recent discoveries in genetics may hold the key to this question, particularly the role of a gene known as FOXP2. This gene provides instructions for making “a protein called forkhead box P2 . . . [which] . . . appears to be essential for the normal development of speech and language.” While FOXP2 is not unique to humans, molecular biologists have discovered two key differences in the human version of this gene compared to that of chimpanzees. The proteins encoded by human and chimpanzee FOXP2 differ by just two amino acid substitutions, but these small changes likely enhanced the gene’s function, fine-tuning humans’ ability to produce and process speech.
Additionally, patterns of variation in the FOXP2 gene in human populations suggest that these changes underwent Darwinian selection within the past 200,000 years—a period corresponding to the emergence of anatomically modern humans. This strong selective pressure implies that these genetic changes conferred a significant adaptive advantage, likely improving communication and social coordination. The discovery of FOXP2 offers an essential piece of the puzzle in understanding how language, one of humanity’s most defining traits, evolved so rapidly and shaped the success of our species.
EVOLUTION AND CULTURAL INVENTION
However, it is important to recognize that “evolution did not create symbols or grammar . . . [but] . . . human creativity and intelligence did.” For this reason, the quest for the origins of human language must account for both the cognitive capacities provided by evolution and the cultural invention of language. Evolution equipped the human brain with the ability to think abstractly, solve problems, and innovate, but it was humans who transformed those capacities into realities. So, what exactly is language? According to linguist Daniel Everett, “Language is the interaction of meaning (semantics), sentence structure (syntax), sound properties (phonetics and phonology), cultural conditions on usage (pragmatics and discourse), and gestures.” While all animals communicate, Everett’s definition highlights the extraordinary complexity and cultural foundation of human language.
Language is believed to have evolved from culturally invented symbols. Everett argues that “Language gradually emerged from a culture, formed by people who communicated with one another via human brains.” This process relied on what Everett describes as a synergy between grammar, symbols, and culture—each shaping and reinforcing the other. Language became the mechanism for transmitting knowledge and facilitating collective learning, allowing humans to preserve, refine, and share their accumulated knowledge across generations. This extraordinary ability enabled humans not only to adapt to new environments but also to innovate and thrive in ways no other species could. Language, then, is more than a means of communication—it is the foundation of human civilization and the key to our success as a species. Terrence Deacon and Ursula Goodenough explain:
| “Most organisms communicate, but humans are unique in communicating via symbolic language. This entails relationships between signifiers (e.g. words) and what’s signified (e.g. objects or ideas), where what’s special is the construction of a system of relationships among the signifiers themselves, generating a seemingly unlimited web of associations, organized by semantic regularities and constraints, retrieved in narrative form, and enabled by complex memory systems.” |
In the following excerpt, evolutionary biologist Mark Pagel—renowned for his work on the evolution of communication—explores the extraordinary nature of human language. He delves into what language is, how it shapes our lives, and when it might have originated. By examining the roots of this uniquely human trait, Pagel provides valuable insight into the defining features of our species and the pivotal role language plays in our success. He explains:
| “Human language is distinct from all other known animal forms of communication in being compositional. Human language allows speakers to express thoughts in sentences comprising subjects, verbs and objects—such as ‘I kicked the ball’—and recognizing past, present and future tenses. Compositionality gives human language an endless capacity for generating new sentences as speakers combine and recombine sets of words into their subject, verb and object roles. For instance, with just 25 different words for each role, it is already possible to generate over 15,000 distinct sentences. Human language is also referential, meaning speakers use it to exchange specific information with each other about people or objects and their locations or actions. No one knows for sure when language evolved, but fossil and genetic data suggest that humanity can probably trace its ancestry back to populations of anatomically modern Homo sapiens (people who would have looked like you and me) who lived around 150,000 to 200,000 years ago in eastern or perhaps southern Africa [4,5,6]. Because all human groups have language, language itself, or at least the capacity for it, is probably at least 150,000 to 200,000 years old. This conclusion is backed up by evidence of abstract and symbolic behaviour in these early modern humans, taking the form of engravings on red-ochre.” |
The evolution of the human brain and the development of language “enabled humans to store considerable amounts of information on an unprecedented scale with great adaptive potential,” transforming our species into exceptional problem-solvers. This combination of cognitive abilities and cultural innovation allowed humans to adapt to new environments far more quickly than adaptation by natural selection, which relies on genetic changes over vast timescales. Equipped with these unique traits, humans were no longer bound by the slow pace of genetic evolution. Instead, language and culture became the tools through which they could share knowledge, solve problems, and innovate, enabling rapid adaptation to diverse ecosystems.
This ability had profound implications for human history. It allowed humans to spread across the globe, from the grasslands of Africa to the frozen tundras of Siberia and beyond—a process known as extensification. Unlike other species, humans didn’t just survive in new environments; they thrived by shaping their surroundings to meet their needs. This adaptability laid the foundation for agriculture, urban societies, trade networks, and the transmission of knowledge across generations. By combining biological evolution with cultural creativity, humans transcended the limitations of other species, becoming not just survivors but world-builders.
HUMAN CULTURE
What is culture? Culture is the information that is shared and acquired from other individuals through social transmission. Alex Mesoudi notes that humans are a cultural species in that “we acquire a multitude of beliefs, attitudes, preferences, knowledge, skills, customs, and norms from other members of our species culturally, through social learning processes such as imitation, teaching, and language.” Similarly, Steven J. Mithen emphasizes that “Cultural behavior derives from our capacity for learning, decision making, and problem-solving.” Culture shapes how humans interact with one another and the world, providing the framework for social structures, traditions, and innovations. Importantly, language is what makes humans a cultural species, as it allows us to transmit knowledge, beliefs, and practices across generations, fostering collective learning.
But is there a relationship between culture and human evolution? And when do the earliest examples of culture appear in human history? These are challenging questions, but some scholars believe the answers lie in a series of caves on the southern tip of Africa. One of the most fascinating examples comes from Blombos Cave, where artifacts dating back to approximately 70,000 B.C.E. provide some of the earliest evidence of material culture. Among these artifacts are engraved ochre pieces and shell beads, which suggest the presence of symbolic thought, social behaviors, and creativity. These tangible creations—what anthropologists call “material culture”—represent the earliest known attempts to create and share meaning within a community, offering a glimpse into the origins of human culture itself.
Culture “is a compendium of useful innovations that are preserved because individuals appreciate their value.” This ability to create, share, and adapt innovations to different environments is what has made our species so successful. But an intriguing question arises: Did human language and intelligence evolve primarily to enhance our foraging skills, or were they shaped by the need to build social networks that fostered collaboration and innovation? For archaeologist John Gowlett, the answer lies in both. He emphasizes what he calls the “eternal triangle” of human evolution, with its three points being diet change, detailed environmental knowledge, and social collaboration. These factors, Gowlett argues, are deeply interconnected: shifts in diet required knowledge of the environment to locate resources, while social collaboration allowed humans to hunt, gather, and share food in ways no other species could match.
This interplay of biology, culture, and environment raises another critical question: should we focus solely on evolution to explain humanity’s ecological success? In the following excerpt, Robert Boyd challenges this perspective, inviting us to consider how culture and social learning shaped our unique trajectory:
| “Most accounts of human evolution explain our ecological success as the result of superior cognitive abilities. While it is probable that individual humans are smarter than other animals, we do not think this is the most important cause of our success. Think about what people have to know to survive and prosper in just one habitat where human foragers have flourished, the North American Arctic. They have to know how to make dozens of essential tools—kayaks, warm clothing, toggle harpoons, oil lamps, shelters built of skin and snow, goggles to prevent snow blindness, dog sleds and the tools to make these tools. They also have to know how to use all of this stuff, where and when to hunt and gather, what to seek, how to process it if you succeed, and so on and on. Then they have to decide how to organize their society: how to regulate exchange of resources, how to organize marriage, resolve conflicts and so on and on. If individual intelligence were the key, individuals could create all of this knowledge on their own.” |
HUMAN EXTENSIFICATION
Early human migration and the population of the world, a process referred to as extensification, was made possible by humans’ extraordinary cognitive abilities, language, and collective learning (culture). Extensification allowed humans to spread across the globe at a startling rate, adapting to new environments without relying solely on the slow mechanisms of evolutionary change. This topic has been explored by the historian and environmentalist Kirkpatrick Sale through a fascinating hypothesis. Sale contends that around 70,000 years ago, humans developed a hunting and gathering culture that was shaped by climatic changes and the resulting scarcity of food. The quest for resources necessary for survival fueled new patterns of migration, as groups sought out environments where they could thrive. Sale argues that this migration, combined with the hunting and gathering culture, fundamentally altered humanity’s relationship with the biosphere. Humans evolved into what he describes as a species of domination—one that “allowed it to stand distanced from the world so that it was able to expand its control and dominion in a totally unprecedented way, justified in the name of survival.”
While cultural and environmental pressures helped shape the patterns of human migration, scientists have developed hypotheses to explain how humans physically spread across the globe. One such hypothesis is the multiregional continuity model, developed by Milford Wolpoff and Alan Thorne. This model proposes that humans evolved over the last million years in multiple regions of the Afro-Eurasian landmass from Homo ergaster, with populations in different regions contributing to the development of modern humans. According to Wolpoff and Thorne, this mode of development helps explain the regional variations we see among human populations today. Fossil records and morphological studies provide the primary evidence for this model, offering a glimpse into the complex web of interactions and adaptations that shaped the human species as it expanded its reach across the world.
A second hypothesis is the Out-of-Africa model, which argues that all modern humans descended from a few common ancestors who lived approximately 250,000 years ago in Africa. This hypothesis is strongly supported by genetic evidence: comparisons of present-day human DNA reveal less genetic diversity in populations outside Africa, suggesting they originated from a smaller group of migrants who left the continent. However, a lingering mystery is why humans migrated out of Africa around 60,000 years ago. Scholars propose several possible factors, including drought caused by climatic changes, the development of new technologies, improved nutrition, or even a genetic mutation that enhanced cognitive or physical abilities.
More recently, some researchers have turned to the catastrophic eruption of Mount Toba around 71,000 B.C.E. for potential clues. This volcanic event—1,000 times more powerful than Mount Saint Helens—sent debris into the atmosphere, causing global temperatures to plummet by as much as 25 degrees. The resulting environmental upheaval may have created resource shortages in Africa, forcing populations to migrate in search of more hospitable regions. Whether prompted by environmental pressures or human innovation, this migration marks a pivotal moment in human history, showcasing the adaptability and resilience that have defined our species.
David Reich explains that “Each of us has two genomes: one from our mother, one from our father. Some segments are more alike than others. The more differences—or mutations—in a given segment, the longer it’s been since the gene copies bequeathed to us by our parents shared a common ancestor. These mutations tell us how closely related two people are and record exquisitely precise information about the past.” Mutations, small changes in DNA that accumulate over generations, serve as a kind of molecular clock, allowing scientists to trace relationships between individuals and populations. This genetic record offers a powerful tool for reconstructing the movements and interactions of ancient human populations, helping to illuminate the story of human evolution with remarkable precision.
More recently, the application of genetics to the study of the deep human past has revolutionized our understanding of human origins, migration, and diversity. The sequencing of the human genome has revealed that 99.9% of DNA in all humans is identical, while the remaining 0.1% contains the mutations that allow geneticists to trace ancestry and relatedness. These variations act as molecular markers, enabling scientists to reconstruct ancient migration routes and connections between populations. Genetic evidence now confirms that all modern humans share a common ancestry originating in Africa, with genetic branches diverging approximately 200,000 years ago. This discovery has provided robust support for the Out-of-Africa Model, complementing fossil and archaeological evidence to paint a comprehensive picture of human extensification.
Through genetics, we not only gain insight into the origins of our species but also into the shared biological heritage that unites us all. This transformative field has underscored the extraordinary adaptability and diversity of humans while reminding us of the common thread that links all of humanity to a single African origin.
HUMANS IN THE PALEOLITHIC ERA
As humans migrated out of Africa, their ingenuity and adaptability allowed them to thrive in new and often challenging environments. This phase of human globalization took place during the Paleolithic Age (2.5 million years ago–12,000 B.C.E.), the first and longest era in human history. Reconstructing human life during the Paleolithic Era is a challenging task, as writing had not yet been developed. However, scholars have drawn valuable insights by studying the archaeological record and present-day hunting and foraging societies. For example, excavations of Paleolithic sites have uncovered stone tools, which played a crucial role in human survival. These tools allowed early humans to process a wide range of foods, including plants, nuts, and meat, and provided a critical advantage in adapting to diverse environments.
From these findings, scholars have inferred that Paleolithic humans lived in small, mobile bands, relying on cooperative hunting and foraging to subsist. Their technological innovations, combined with accumulated knowledge about local ecosystems, enabled them to spread across the globe and establish a foundation for the development of human culture.
From about 35,000 B.C.E., technological innovations continued to drive human survival and expand their colonization efforts. Early humans began crafting tools from materials other than stone, such as bones, ivory, and antlers, using them to create harpoons, fish hooks, and other specialized implements. The advent of projectile technology, including the bow and arrow, spear, and spear thrower, revolutionized hunting practices and increased the efficiency of resource acquisition. These advancements not only ensured human survival but also created opportunities for reflective thinking—the capacity to contemplate existence, the environment, and the unseen forces shaping life.
Evidence of this reflective thought can be found in the remarkable cave paintings of Altamira (Spain), Chauvet-Pont-d’Arc, and Lascaux (France), where early humans depicted animals and symbols with stunning artistry and precision. These paintings likely held spiritual or symbolic significance, serving as a means of communication or ritual. Reflective thinking is also evident in burial practices, which suggest a belief in an afterlife or reverence for the dead, and in objects of worship such as Venus figurines. These figurines, often depicting exaggerated female forms, are thought to represent fertility goddesses, highlighting an early awareness of reproduction’s role in human survival. Together, these artifacts provide a glimpse into the developing symbolic and spiritual life of early humans, marking the Paleolithic period as a transformative era in human history.
Paleolithic societies exploited a diverse array of plants and animals to meet their dietary needs. Specialists like Marshall Sahlins, in his work The Original Affluent Society, argue that these societies more than adequately met their daily caloric requirements through varied and sustainable diets. Hunting and foraging allowed these communities to maintain a strategic and systematic pattern of movement, following animal migrations and plant cycles with precision. This mobility discouraged the accumulation of private property, as constant movement made it impractical, and instead fostered semi-egalitarian social structures. Both men and women contributed equally to the survival of the community, with men often focusing on hunting and women specializing in foraging, though roles likely overlapped depending on the environment and group needs.
Knowledge sharing was central to these societies, as collective survival relied on passing down information about resources, seasonal cycles, and environmental conditions. This shared knowledge reinforced the sense of communal responsibility and cooperation that defined Paleolithic life. The semi-egalitarian nature of these communities—rooted in shared resources and a lack of wealth accumulation—stood in stark contrast to the hierarchical structures that would later emerge with the rise of agriculture and sedentary life.
Wherever humans went, they left a lasting impact on the environment they encountered. One striking example is the extinction of large animals, such as mammoths and giant ground sloths, which coincided with human colonization. These extinctions are believed to have resulted from overhunting or habitat changes caused by human activity, though climatic shifts may have also contributed. Humans also used fire-stick farming, a technique that involved setting controlled fires to clear vegetation, encourage the growth of fresh plants, and attract grazing animals. This practice not only reshaped local ecosystems but also ensured a steady supply of resources for hunting and foraging.
The subsistence strategies of Paleolithic societies, rooted in hunting and foraging, profoundly influenced their social organization and population density. Small, mobile bands of 15 to 50 members were the norm, allowing groups to adapt to seasonal resource availability and maintain ecological balance. Kinship, or blood relationships, served as the primary organizing principle in these bands, fostering cooperation and shared responsibility for survival. Together, these practices highlight the dynamic relationship between humans and their environment, where ecological changes and social structures were deeply intertwined.
THE ORIGINS OF RELIGION
Religion, a vital facet of culture, has played an instrumental role in shaping the course of human history. It has guided human behavior, provided meaning and purpose, and influenced the development of social and political systems across civilizations. For this reason, religion is one of the central themes we will focus on throughout this course. As we begin to explore the origins of religion, I would like you to reflect on the following two quotes. These insights will help frame our discussion, offering contrasting perspectives on the nature and purpose of religion and its role in shaping humanity.
| “Most people have a clear idea of what they mean by religion and can usually identify religious behavior when they see it. Nevertheless, when we have to define religion, we soon discover that the task is quite difficult, because religion is manifested in many different ways in our world.” – Irving Hexam “If we want to go on talking about ancient Mesopotamian religion, ancient Greek religion, or any other ancient religion, we should always bear in mind that we are talking about something modern when we do so. We are not naming something any ancient person would recognize. In our current context, we organize our contemporary world using the concepts of religious and secular.” – Brent Nongbri |
Rather than attempting to define religion, it may be more insightful to explore the characteristics that make up this complex and multifaceted concept. Religion takes many forms across cultures, and focusing on its characteristics allows us to identify commonalities while appreciating its diversity. To begin this exploration, consider the two models below. Take a moment to examine their characteristics, noting where they overlap and where they diverge. This exercise will help illuminate the universal elements of religion as well as the unique perspectives each model offers on this enduring human phenomenon.
Currently, no single persuasive general theory exists to explain the origins of religion. Earlier efforts proposed that religion arose because it comforts humans or serves social purposes, such as fostering cohesion and order. More recently, cognitive theories have reframed religion as a product of mental processes like perception, memory, and reasoning. This perspective suggests that religion helps humans interpret and influence the world by projecting humanlike qualities onto the unknown—a strategy known as anthropomorphism. Because humans understand humanity best, they attribute human characteristics to animals, gods, or objects to make sense of the unfamiliar and unpredictable.
Although we will likely never pinpoint the birth of the first religious idea, a substantial body of evidence suggests that cultural artifacts, art, and burial practices of the Upper Paleolithic (c. 50,000–10,000 B.C.E.) reflect early religious sentiments. Upper Paleolithic Homo sapiens, being anatomically and cognitively modern, had the capacity to create religion, making it plausible that religious systems emerged during this period. Early religions likely linked symbolic environmental information to social behaviors, guiding group actions and fostering cohesion. However, given the egalitarian and mobile nature of hunter-gatherer societies, religious beliefs were fewer in number and transmitted through ritual performances rather than scripture. Rituals played a central role in these early religions, as they reinforced social bonds, fostered solidarity, and strengthened group cohesion without centralized authority. Consequently, ritual-based religions likely dominated this transformative period in human history.
The model below identifies the factors that make it possible to create a religion/religious beliefs and the factors that moves humans to create religion/religious beliefs.
Recent reconstructions of early religion by scholars suggest a rich tapestry of beliefs, including animism, ancestor worship, shamanism, and concepts of an afterlife. Animism, the belief that objects, animals, and natural phenomena possess spiritual essence, likely shaped early humans’ connection to the world around them. Ancestor worship emphasized reverence for the dead, linking communities to their past and fostering social cohesion. Shamanism involved individuals acting as mediators between the human and spiritual realms, guiding rituals and practices. Finally, the concept of an afterlife reflects early beliefs about existence beyond death, providing meaning and comfort in the face of mortality.
It is generally agreed that “the oldest trait of religion was animism . . . which enables people to attribute intent and lifelike qualities to inanimate objects and would have prompted belief in beings or forces in an unseen realm of spirits.” In small-scale societies, animism provided a framework for understanding the natural world and addressing the unknown. However, as humans transitioned from small-scale to large-scale societies, religion also evolved to meet new social challenges. With the aid of the written record, it becomes clear that “supernatural agents become increasingly morally concerned, more effective at monitoring norm violations (omniscience) and better equipped to provide punishment and rewards (heaven and hell) according to prescribed behavior.”
- Animism: “the belief that all “natural” things, such as plants, animals, and even such phenomena as thunder, have intentionality (or a vital force) and can have influence on human lives.”
- Shamanism: “the presence in a society of a “shaman” (male or female), a socially recognized part-time ritual intercessor, healer, and problem solver. Shamans often use their power over spirit helpers during performances involving altered states of consciousness to benefit individuals and the group as a whole . . . who mediate between the earthly and spirit worlds to promote cohesion and physical and mental well-being in the society.”
- Ancestor Worship: “is defined as belief that the spirits of dead kin remain active in another realm where they may influence the living, and can be influenced by the living.”
This shift reflects the growing need for mechanisms to maintain social cohesion and enforce norms in larger, more complex societies where interpersonal relationships and kinship ties were no longer sufficient. Religions became more structured, with a greater focus on moral codes and divine accountability. The emphasis shifted from ritual-based religions to scripture-based systems, where religious texts codified teachings and prescribed behavior, allowing religion to standardize norms and extend its influence across generations. In large-scale societies, religion emerged as a critical institution for organizing social behavior, ensuring order, and reinforcing cultural values through the promise of divine rewards and punishments. This evolution highlights how religion adapted to address the changing needs of human societies, becoming a central force in shaping social, moral, and political systems.
IN CLOSING
“Cognition and Language Creates a Cultural Species” delves into the evolution of the human brain and language, emphasizing their pivotal roles in making Homo sapiens a uniquely cultural species. It highlights how encephalization, or the significant growth of the human brain relative to body size, enabled advanced cognitive functions, allowing humans to adapt to diverse environments through cumulative cultural knowledge rather than relying solely on biological evolution. Language, emerging as a transformative tool, facilitated the sharing, preservation, and expansion of knowledge across generations, enabling complex communication, problem-solving, and the formation of intricate societies. Additionally, this topic underscores the importance of pre-adaptations such as sociability, linguistic skills, bipedalism, dexterous hands, meat-eating and hunting, extended childhood learning periods, and large forebrains, which collectively contributed to human adaptability and ecological success. Together, these traits allowed humans to harness advanced cognition and language, fostering the development of culture, global settlement, and complex societies. The interplay of these factors underscores the central role cognition and language have played in human evolution and cultural development.
Great job! You have just completed the third topic in our quest to learn about ourselves. Our next topic, The Consequence of Cultivation, will explore the impact that plant domestication had on the course of human history.
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