Excerpted From
"The Evolution of Cultural Behavior"
Richard B. Potts, B.A., Ph.D. (2002) for Encarta Enclopedia
Study Notes
1. Human cultural behavior depends on the social transfer of information from one generation to the next (enculturation), which itself depends on a sophisticated system of communication, such as language.
2. The term culture has often been used to distinguish the behavior of humans from that of other animals.
3. Modern humans differ from other animals, and probably many early human species, in that they actively teach each other and can pass on and accumulate unusually large amounts of knowledge.
4. People also have a uniquely long period of learning before adulthood, and the physical and mental capacity for language.
5. Language of all forms -- spoken, signed, and written -- provides a medium for communicating vast amounts of information, much more than any other animal appears to be able to transmit through gestures and vocalizations.
6. Scientists have traced the evolution of human cultural behavior through the study of archaeological artifacts... and related evidence. Artifacts show that throughout much of human evolution, culture has developed slowly.
7. During the Paleolithic, or early Stone Age, basic techniques for making stone tools changed very little for periods of well over a million years.
8. Over the past 30,000 years, the basic anatomy of humans has undergone only one prominent change: The bones of the average human skeleton have become much smaller and thinner.
9. Culture has played a prominent role in the evolution of Homo sapiens. Within the last 60,000 years, people have migrated to settle almost all unoccupied regions of the world, such as small island chains and the continents of Australia and the Americas.
10. These migrations depended on developments in transportation, hunting and fishing tools, shelter, and clothing.
11. Within the past 30,000 years, cultural evolution has sped up dramatically. This change shows up in the archaeological record as a rapid expansion of stone tool types and tool making techniques, and in works of art and indications of evolving religion, such as burials.
12. By 10,000 years ago, people first began to harvest and cultivate grains and to domesticate animals
13. The development of agriculture provided people with larger quantities and more stable supplies of food, which set the stage for the rise of the first civilizations.
14. Paleoanthropologists and archaeologists have studied the evolution of
Social Life
15. Most primate species, including the African apes, live in social groups of varying size and complexity. Within their groups, individuals often have multifaceted roles, based on age, sex, status, social skills, and personality.
16. The discovery in 1975 at Hadar, Ethiopia, of a group of several Australopithecus afarensis individuals who died together 3.2 million years ago appears to confirm that early humans lived in social groups. .
17. One of the first physical changes in the evolution of humans from apes-- a decrease in the size of male canine teeth-- also indicates a change in social relations.
18. Male apes sometimes use their large canines to threaten (or sometimes fight with) other males of their species, usually over access to females, territory, or food.
19. The evolution of small canines in australopiths implies that males had either developed other methods of threatening each other or become more cooperative.
20. Scientists believe that several of the most important changes from apelike to characteristically human social life occurred in species of the genus Homo...
21. These changes, which may have occurred at different times, included (1) prolonged maturation of infants, including an extended period during which they required intensive care from their parents; (2) special bonds of sharing and exclusive mating between particular males and females, called pair-bonding; and (3) the focus of social activity at a home base, a safe refuge in a special location known to family or group members.
Parental Care
22. Humans, who have a large brain, have a prolonged period of infant development and childhood because the brain takes a long time to mature.
23. Since the australopith brain was not much larger than that of a chimp, some scientists think that the earliest humans had a more apelike rate of growth, which is far more rapid than that of modern humans. This view is supported by studies of australopith fossils looking at tooth development-a good indicator of overall body development.
24. The human brain becomes very large as it develops, so a woman must give birth to a baby at an early stage of development in order for the infant's head to fit through her birth canal.
25. Thus, human babies require a long period of care to reach a stage of development at which they depend less on their parents.
26. In contrast with a modern female, a female australopith could give birth to a baby at an advanced stage of development because its brain would not be too large to pass through the birth canal.
27. The need to give birth early-- and therefore to provide more infant care-- may have evolved around the time of the middle Homo species Homo ergaster. This species had a brain significantly larger than that of the australopiths, but a narrow birth canal.
Pair-Bonding
28. Pair-bonding, usually of a fairly short duration, occurs in a variety of primate species. Some scientists speculate that prolonged bonds developed in humans along with increased sharing of food.
29. Among primates, humans have a distinct type of food-sharing behavior. People will delay eating food until they have returned with it to the location of other members of their social group.
30. This type of food sharing may have arisen at the same time as the need for intensive infant care, probably by the time of H. ergaster. By devoting himself to a particular female and sharing food with her, a male could increase the chances of survival for his own offspring.
The Home Base
31. Humans have lived as foragers for millions of years. Foragers obtain food when and where it is available over a broad territory.
32. Modern-day foragers (also known as hunter-gatherers)-- such as the San people in the Kalahari Desert of southern Africa-- also set up central campsites, or home bases, and divide work duties among men and women.
33. Women gather readily available plant and animal foods, while men take on the often less successful task of hunting.
34. Female and male family members and relatives bring together their food to share at their home base.
35. The modern form of the home base-- which also serves as a haven for raising children and caring for the sick and elderly-- may have first developed with middle Homo after about 1.7 million years ago.
B. Subsistence
36. Human subsistence refers to the types of food humans eat, the technology used in and methods of obtaining or producing food, and the ways in which social groups or societies organize themselves for getting, making, and distributing food.
37, For millions of years, humans probably fed on-the-go, much as other primates do.
38. The lifestyle associated with this feeding strategy is generally organized around small, family-based social groups that take advantage of different food sources at different times of year.
39. The early human diet probably resembled that of closely related primate species.
40. The first humans probably also had a diet based mostly on plant foods. In addition, they undoubtedly ate some animal foods and might have done some hunting.
41. Human subsistence began to diverge from that of other primates with the production and use of the first stone tools.
42. With this development, the meat and marrow (the inner, fat-rich tissue of bones) of large mammals became a part of the human diet. Thus, with the advent of stone tools, the diet of early humans became distinguished in an important way from that of apes.
43. Scientists have found broken and butchered fossil bones of antelopes, zebras, and other comparably sized animals at the oldest archaeological sites, which date from about 2.5 million years ago.
44. With the evolution of late Homo, humans began to hunt even the largest animals on Earth, including mastodons and mammoths, members of the elephant family.
45. Agriculture and the domestication of animals arose only in the recent past, with H. sapiens.
Models of Subsistence in Early Homo
46. Paleoanthropologists have debated whether early members of the modern human genus were aggressive hunters, peaceful plant gatherers, or opportunistic scavengers. Many scientists once thought that predation and the eating of meat had strong effects on early human evolution.
47. This hunting hypothesis suggested that early humans in Africa survived particularly arid periods by aggressively hunting animals with primitive stone or bone tools.
48. Supporters of this hypothesis thought that hunting and competition with carnivores powerfully influenced the evolution of human social organization and behavior; tool-making; anatomy, such as the unique structure of the human hand; and intelligence.
49. Beginning in the 1960s, studies of apes cast doubt on the hunting hypothesis. Researchers discovered that chimpanzees cooperate in hunts of at least small animals, such as monkeys. Hunting did not, therefore, entirely distinguish early humans from apes, and therefore hunting alone may not have determined the path of early human evolution.
50. Some scientists instead argued in favor of the importance of food-sharing in early human life. According to a food-sharing hypothesis, cooperation and sharing within family groups-instead of aggressive hunting-- strongly influenced the path of human evolution.
51. Critique of the food-sharing hypothesis resulted from more careful study of animal bones from the early archaeological sites. Microscopic analysis of these bones revealed the marks of human tools and carnivore teeth, indicating that both humans and potential predators-such as hyenas, cats, and jackals-were active at these sites. This evidence suggested that what scientists had thought were home bases where early humans shared food were in fact food-processing sites that humans abandoned to predators. Thus, evidence did not clearly support the idea of food-sharing among early humans.
52. The new research also suggested a different view of early human subsistence--that early humans scavenged meat and bone marrow from dead animals and did little hunting. According to this scavenging hypothesis, early humans opportunistically took parts of animal carcasses left by predators, and then used stone tools to remove marrow from the bones.
53.Observations that many animals, such as antelope, often die off in the dry season make the scavenging hypothesis quite plausible. Early toolmakers would have had plenty of opportunity to scavenge animal fat and meat during dry times of the year. However, other archaeological studies--and a better appreciation of the importance of hunting among chimpanzees--suggest that the scavenging hypothesis is too narrow.
54. Many scientists now believe that early humans both scavenged and hunted. Evidence of carnivore tooth marks on bones cut by early human toolmakers suggests that the humans scavenged at least the larger of the animals they ate. They also ate a variety of plant foods. Some disagreement remains, however, as to how much early humans relied on hunting, especially the hunting of smaller animals.
The Rise of Hunting
55. Scientists debate about when humans first began hunting on a regular basis. For instance, elephant fossils found with tools made by middle Homo once led researchers to the idea that members of this species were hunters of big game. However, the simple association of animal bones and tools at the same site does not necessarily mean that early humans had killed the animals or eaten their meat. Animals may die in many ways, and natural forces can accidentally place fossils next to tools.
56. Recent excavations at Olorgesailie, Kenya, show that H. erectus cut meat from elephant carcasses but do not reveal whether these humans were regular or specialized hunters.
57. Humans who lived outside of Africa-especially in colder temperate climates-- almost certainly needed to eat more meat than their African counterparts.
58. Humans in temperate Eurasia would have had to learn about which plants they could safely eat, and the number of available plant foods would drop significantly during the winter. Still, although scientists have found very few fossils of edible or eaten plants at early human sites, early inhabitants of Europe and Asia probably did eat plant foods in addition to meat.
59.Sites that provide the clearest evidence of early hunting include Boxgrove, England, where about 500,000 years ago people trapped a great number of large game animals between a watering hole and the side of a cliff and then slaughtered them.
60.At Schöningen, Germany, a site about 400,000 years old, scientists have found wooden spears with sharp ends that were well designed for throwing and probably used in hunting large animals.
61. Neandertals and other archaic humans seem to have eaten whatever animals were available at a particular time and place. So, for example, in European Neandertal sites, the number of bones of reindeer (a cold-weather animal) and red deer (a warm-weather animal) changed depending on what the climate had been like. Neandertals probably also combined hunting and scavenging to obtain animal protein and fat.
62. For at least the past 100,000 years, various human groups have eaten foods from the ocean or coast, such as shellfish and some sea mammals and birds.
63. Others began fishing in interior rivers and lakes. Between probably 90,000 and 80,000 years ago people in Katanda, in what is now the Democratic Republic of the Congo, caught large catfish using a set of barbed bone points, the oldest known specialized fishing implements.
64. The oldest stone tips for arrows or spears date from about 50,000 to 40,000 years ago. These technological advances, probably first developed by early modern humans, indicate an expansion in the kinds of foods humans could obtain.
65. Beginning 40,000 years ago humans began making even more significant advances in hunting dangerous animals and large herds, and in exploiting ocean resources.
66. People cooperated in large hunting expeditions in which they killed great numbers of reindeer, bison, horses, and other animals of the expansive grasslands that existed at that time.
67. In some regions, people became specialists in hunting certain kinds of animals. The familiarity these people had with the animals they hunted appears in sketches and paintings on cave walls, dating from as much as 32,000 years ago.
68 Hunters also used the bones, ivory, and antlers of their prey to create art and beautiful tools. In some areas, such as the central plains of North America that once teemed with a now-extinct type of large bison (Bison occidentalis), hunting may have contributed to the extinction of entire species.
Tools
69. The making and use of tools alone probably did not distinguish early humans from their ape predecessors.
70. Instead, humans made the important breakthrough of using one tool to make another. Specifically, they developed the technique of precisely hitting one stone against another, known as knapping.
71. Stone tool-making characterized the period sometimes referred to as the Stone Age, which began at least 2.5 million years ago in Africa and lasted until the development of metal tools within the last 7,000 years (at different times in different parts of the world).
72. Although early humans may have made stone tools before 2.5 million years ago, toolmakers may not have remained long enough in one spot to leave clusters of tools that an archaeologist would notice today.
73. The earliest simple form of stone tool-making involved breaking and shaping an angular rock by hitting it with a palm-sized round rock known as a hammerstone.
74. Scientists refer to tools made in this way as Oldowan, after Olduvai Gorge in Tanzania, a site from which many such tools have come. The Oldowan tradition lasted for about 1 million years.
75. Oldowan tools include large stones with a chopping edge, and small, sharp flakes that could be used to scrape and slice. Sometimes Oldowan toolmakers used anvil stones (flat rocks found or placed on the ground) on which hard fruits or nuts could be broken open.
76. Learning the skill of Oldowan toolmaking certainly required observation, but not necessarily instruction or language. Thus, Oldowan tools were simple, and their makers used them for such purposes as cutting up animal carcasses, breaking bones to obtain marrow, cleaning hides, and sharpening sticks for digging up edible roots and tubers.
77. The Acheulean toolmaking tradition, which began sometime between 1.7 million and 1.5 million years ago, consisted of increasingly symmetrical tools, most of which scientists refer to as handaxes and cleavers.
78. Acheulean toolmakers, such as Homo erectus, also worked with much larger pieces of stone than did Oldowan toolmakers. The symmetry and size of later Acheulean tools shows increased planning and design--and thus probably increased intelligence--on the part of the toolmakers. The Acheulean tradition continued for over 1.35 million years.
79. The next significant advances in stone toolmaking were made by at least 200,000 years ago.
80.One of these methods of toolmaking, known as the prepared core technique (and Levallois in Europe), involved carefully and exactingly knocking off small flakes around one surface of a stone and then striking it from the side to produce a preformed tool blank, which could then be worked further.
81. Within the past 40,000 years, modern humans developed the most advanced stone toolmaking techniques. The so-called prismatic-blade core tool-making technique involved removing the top from a stone, leaving a flat platform, and then breaking off multiple blades down the sides of the stone. Each blade had a triangular cross-section, giving it excellent strength. Using these blades as blanks, people made exquisitely shaped spearheads, knives, and numerous other kinds of tools.
Environmental Adaptation
82. Early humans experienced dramatic shifts in their environments over time. Fossilized plant pollen and animal bones, along with the chemistry of soils and sediments, reveal much about the environmental conditions to which humans had to adapt.
83.By 8 million years ago, the continents of the world, which move over very long periods, had come to the positions they now occupy.
84. But the crust of the Earth has continued to move since that time. These movements have dramatically altered landscapes around the world.
85. Important geological changes that affected the course of human evolution include those in southern Asia that formed the Himalayan mountain chain and the Tibetan Plateau, and those in eastern Africa that formed the Great Rift Valley.
86. The formation of major mountain ranges and valleys led to changes in wind and rainfall patterns. In many areas dry seasons became more pronounced, and in Africa conditions became generally cooler and drier.
87. By 5 million years ago, the amount of fluctuation in global climate had increased. Temperature fluctuations became quite pronounced during the Pliocene Epoch (5 million to 1.6 million years ago).
88. During this time the world entered a period of intense cooling called an ice age, which began around 2.8 million years ago.
89. Between 5 million and 2 million years ago, a mixture of forests, woodlands, and grassy habitats covered most of Africa.
90. Eastern Africa entered a significant drying period around 1.7 million years ago, and after 1 million years ago large parts of the African landscape turned to grassland.
91. So the early australopiths and early Homo lived in relatively wooded places, whereas Homo ergaster and H. erectus lived in areas of Africa that were more open.
92. Early human populations encountered many new and different environments when they spread beyond Africa, including colder temperatures in the Near East and bamboo forests in Southeast Asia.
93. By at least 1 million years ago, populations had moved into the temperate climates of Europe and Asia, where they encountered long seasons of very cold weather.
94. All of these changes-dramatic shifts in the landscape, changing rainfall and drying patterns, and temperature fluctuations--posed challenges to the immediate and long-term survival of early human populations.
95. Populations in different environments evolved different adaptations, which in part explains why more than one species existed at the same time during much of human evolution.
96. Some early human adaptations to new climates involved changes in physical (anatomical) form.
97. For example, the physical adaptation of having a tall, lean body such as that of H. ergaster-- with lots of skin exposed to cooling winds-would have dissipated heat very well.
98. This adaptation probably helped the species to survive in the hotter, more open environments of Africa around 1.7 million years ago.
99. Conversely, the short, wide bodies of the Neandertals would have conserved heat, helping them to survive in the ice age climates of Europe and western Asia.
100. Increases in the size and complexity of the brain, however, made early humans progressively better at adapting through changes in cultural behavior.
101. Humans have always adapted to their environments by adjusting their behavior.
102. For instance, early australopiths moved both in the trees and on the ground, which probably helped them survive environmental fluctuations between wooded and more open habitats.
103. Early Homo adapted by making stone tools and transporting their food over long distances, thereby increasing the variety and quantities of different foods they could eat. An expanded and flexible diet would have helped these toolmakers survive unexpected changes in their environment and food supply.
104. When populations of H. erectus moved into the temperate regions of Eurasia, they faced new challenges to survival. During the colder seasons they had to either move away or seek shelter, such as in caves.
105. Some of the earliest definitive evidence of cave dwellers dates from around 800,000 years ago at the site of Atapuerca in northern Spain. This site may have been home to early H. heidelbergensis populations. H. erectus also used caves for shelter.
106. Eventually, early humans learned to control fire and to use it to create warmth, cook food, and protect themselves from other animals. The oldest known fire hearths date from between 450,000 and 300,000 years ago, at sites such as Bilzingsleben, Germany; Verteszöllös, Hungary; and Zhoukoudian (Chou-k'ou-tien), China.
107. African sites as old as 1.6 million to 1.2 million years contain burned bones and reddened sediments, but many scientists find such evidence too ambiguous to prove that humans controlled fire.
108. Early populations in Europe and Asia may also have worn animal hides for warmth during glacial periods. The oldest known bone needles, which indicate the development of sewing and tailored clothing, date from about 30,000 to 26,000 years ago.
E. Symbolic Thought-Language, Art, and Religion
The evolution of cultural behavior relates directly to the development of the human brain, and particularly the cerebral cortex, the part of the brain that allows abstract thought, beliefs, and expression through language. Humans communicate through the use of symbols-ways of referring to things, ideas, and feelings that communicate meaning from one individual to another but that need not have any direct connection to what they identify. For instance, a word-one type of symbol-does not usually relate directly to the thing or idea it represents; it is abstract. English-speaking people use the word lion to describe a lion, not because a dangerous feline looks like the letters l-i-o-n, but because these letters together have a meaning created and understood by people.
People can also paint abstract pictures or play pieces of music that evoke emotions or ideas, even though emotions and ideas have no form or sound. In addition, people can conceive of and believe in supernatural beings and powers-abstract concepts that symbolize real-world events such as the creation of Earth and the universe, the weather, and the healing of the sick. Thus, symbolic thought lies at the heart of three hallmarks of modern human culture: language, art, and religion.
Language
In language, people creatively join words together in an endless variety of sentences-each with a distinct meaning-according to a set of mental rules, or grammar. Language provides the ability to communicate complex concepts. It also allows people to exchange information about both past and future events, about objects that are not present, and about complex philosophical or technical concepts.
Language gives people many adaptive advantages, including the ability to plan for the future, to communicate the location of food or dangers to other members of a social group, and to tell stories that unify a group, such as mythologies and histories. However, words, sentences, and languages cannot be preserved like bones or tools, so the evolution of language is one of the most difficult topics to investigate through scientific study.
It appears that modern humans have an inborn instinct for language. Under normal conditions it is almost impossible for a person not to develop language, and people everywhere go through the same stages of increasing language skill at about the same ages. While people appear to have inborn genetic information for developing language, they learn specific languages based on the cultures from which they come and the experiences they have in life.
The ability of humans to have language depends on the complex structure of the modern brain, which has many interconnected, specific areas dedicated to the development and control of language. The complexity of the brain structures necessary for language suggests that it probably took a long time to evolve. While paleoanthropologists would like to know when these important parts of the brain evolved, endocasts (inside impressions) of early human skulls do not provide enough detail to show this.
Some scientists think that even the early australopiths had some ability to understand and use symbols. Support for this view comes from studies with chimpanzees. A few chimps and other apes have been taught to use picture symbols or American Sign Language for simple communication. Nevertheless, it appears that language-as well as art and religious ritual-became vital aspects of human life only during the past 100,000 years, primarily within our own species.
Art
Humans also express symbolic thought through many forms of art, including painting, sculpture, and music. The oldest known object of possible symbolic and artistic value dates from about 250,000 years ago and comes from the site of Berekhat Ram, Israel. Scientists have interpreted this object, a figure carved into a small piece of volcanic rock, as a representation of the outline of a female body. Only a few other possible art objects are known from between 200,000 and 50,000 years ago. These items, from western Europe and usually attributed to Neandertals, include two simple pendants-a tooth and a bone with bored holes-and several grooved or polished fragments of tooth and bone.
Sites dating from at least 400,000 years ago contain fragments of red and black pigment. Humans might have used these pigments to decorate bodies or perishable items, such as wooden tools or clothing of animal hides, but this evidence would not have survived to today. Solid evidence of the sophisticated use of pigments for symbolic purposes-such as in religious rituals-comes only from after 40,000 years ago. From early in this period, researchers have found carefully made types of crayons used in painting and evidence that humans burned pigments to create a range of colors.
People began to create and use advanced types of symbolic objects between about 50,000 and 30,000 years ago. Much of this art appears to have been used in rituals-possibly ceremonies to ask spirit beings for a successful hunt. The archaeological record shows a tremendous blossoming of art between 30,000 and 15,000 years ago. During this period people adorned themselves with intricate jewelry of ivory, bone, and stone. They carved beautiful figurines representing animals and human forms. Many carvings, sculptures, and paintings depict stylized images of the female body. Some scientists think such female figurines represent fertility.
Early wall paintings made sophisticated use of texture and color. The area of what is now southern France contains many famous sites of such paintings. These include the caves of Chauvet, which contain art over 30,000 years old, and Lascaux, in which paintings date from as much as 18,000 years ago. In some cases, artists painted on walls that can be reached only with special effort, such as by crawling. The act of getting to these paintings gives them a sense of mystery and ritual, as it must have to the people who originally viewed them, and archaeologists refer to some of the most extraordinary painted chambers as sanctuaries. Yet no one knows for sure what meanings these early paintings and engravings had for the people who made them. See also Paleolithic Art.
3. Religion
Graves from Europe and western Asia indicate that the Neandertals were the first humans to bury their dead. Some sites contain very shallow graves, which group or family members may have dug simply to remove corpses from sight. In other cases it appears that groups may have observed rituals of grieving for the dead or communicating with spirits. Some researchers have claimed that grave goods, such as meaty animal bones or flowers, had been placed with buried bodies, suggesting that some Neandertal groups might have believed in an afterlife. In a large proportion of Neandertal burials, the corpse had its legs and arms drawn in close to its chest, which could indicate a ritual burial position.
Other researchers have challenged these interpretations, however. They suggest that perhaps the Neandertals had practical rather than religious reasons for positioning dead bodies. For instance, a body manipulated into a fetal position would need only a small hole for burial, making the job of digging a grave easier. In addition, the animal bones and flower pollen near corpses could have been deposited by accident or without religious intention.
Many scientists once thought that fossilized bones of cave bears (a now-extinct species of large bear) found in Neandertal caves indicated that these people had what has been referred to as a cave bear cult, in which they worshiped the bears as powerful spirits. However, after careful study researchers concluded that the cave bears probably died while hibernating and that Neandertals did not collect their bones or worship them. Considering current evidence, the case for religion among Neandertals remains controversial. See also Religion: Rituals and Symbols.
F. Domestication, Agriculture, and the Rise of Civilizations
One of the most important developments in human cultural behavior occurred when people began to domesticate (control the breeding of) plants and animals. Domestication and the advent of agriculture led to the development of dozens of staple crops (foods that form the basis of an entire diet) in temperate and tropical regions around the world. Almost the entire population of the world today depends on just four of these major crops: wheat, rice, corn, and potatoes. S
Human Manipulation of the Environment
The growth of farming and animal herding initiated one of the most remarkable changes ever in the relationship between humans and the natural environment. The change first began just 10,000 years ago in the Near East and has accelerated very rapidly since then. It also occurred independently in other places, including areas of Mexico, China, and South America. Since the first domestication of plants and animals, many species over large areas of the planet have come under human control. The overall number of plant and animal species has decreased, while the populations of a few species needed to support large human populations have grown immensely. In areas dominated by people, interactions among plants and animals usually fall under the control of a single species-Homo sapiens.
By the time of the initial transition to plant and animal domestication, the cold, glacial landscapes of 18,000 years ago had long since given way to warmer and wetter environments. At first, people adapted to these changes by using a wider range of natural resources. Later they began to focus on a few of the most abundant and hardy types of plants and animals. The plants people began to use in large quantities included cereal grains, such as wheat in western Asia; wild varieties of rice in eastern Asia; and maize, of which corn is one variety, in what is now Mexico. Some of the animals people first began to herd included wild goats in western Asia, wild ancestors of chickens in eastern Asia, and llamas in South America.
By carefully collecting plants and controlling wild herd animals, people encouraged the development of species with characteristics favorable for growing, herding, and eating. This process of selecting certain species and controlling their breeding eventually created new species of plants, such as oats, barley, and potatoes; and animals, including cattle, sheep, and pigs. From these domesticated plant and animal species, people obtained important products, such as flour, milk, and wool.
Effects of Food Production on Human Society
By harvesting and herding domesticated species, people could store large quantities of plant foods, such as seeds and tubers, and have a ready supply of meat and milk. These readily available supplies gave people some long-term food security. In contrast, the foraging lifestyle of earlier human populations never provided them with a significant store of food. With increased food supplies, agricultural peoples could settle into villages and have more children. The new reliance on agriculture and change to settled village life also had some negative effects. As the average diet became more dependent on large quantities of one or a few staple crops, people became more susceptible to diseases brought on by a lack of certain nutrients. A settled lifestyle also increased contact among people and between people and their refuse and waste matter, both of which acted to increase the incidence and transmission of disease.
People responded to the increasing population density-and a resulting overuse of farming and grazing lands-in several ways. Some people moved to settle entirely new regions. Others devised ways of producing food in larger quantities and more quickly. The simplest way was to expand onto new fields for planting and new pastures to support growing herds of livestock. Many populations also developed systems of irrigation and fertilization that allowed them to reuse cropland and to produce greater amounts of food on existing fields.
The Rise of Civilizations
The rise of civilizations-the large and complex types of societies in which most people still live today-developed along with surplus food production. People of high status eventually used food surpluses as a way to pay for labor and to create alliances among groups, often against other groups. In this way, large villages could grow into city-states (urban centers that governed themselves) and eventually empires covering vast territories. With surplus food production, many people could work exclusively in political, religious, or military positions; or in artistic and various skilled vocations. Command of food surpluses also enabled rulers to control laborers, such as in slavery. All civilizations developed based on such hierarchical divisions of status and vocation.
All early civilizations had some common features. Some of these included a bureaucratic political body, a military, a body of religious leadership, large urban centers, monumental buildings and other works of architecture, networks of trade, and food surpluses created through extensive systems of farming. Many early civilizations also had systems of writing, numbers and mathematics, and astronomy (with calendars); road systems; a formalized body of law; and facilities for education and the punishment of crimes.
With the rise of civilizations, human evolution entered a phase vastly different from all that came before. Prior to this time, humans had lived in small, family-centered groups essentially exposed to and controlled by forces of nature. Several thousand years after the rise of the first civilizations, most people now live in societies of millions of unrelated people, all separated from the natural environment by houses, buildings, automobiles, and numerous other inventions and technologies. Culture will continue to evolve quickly and in unforeseen directions, and these changes will, in turn, influence the physical evolution of Homo sapiens and any other human species to come.