The Neolithic, the final division of the Stone Age, began about 12,000 years ago when the first development of farming appeared in the Epipalaeolithic Near East, in other parts of the world. The division lasted until the transitional period of the Chalcolithic from about 6,500 years ago, marked by the development of metallurgy, leading up to the Bronze Age and Iron Age. In Northern Europe, the Neolithic lasted until about 1700 BC, while in China it extended until 1200 BC. Other parts of the world remained broadly in the Neolithic stage of development, although this term may not be used, until European contact; the Neolithic comprises a progression of behavioral and cultural characteristics and changes, including the use of wild and domestic crops and of domesticated animals. The term Neolithic derives from the Greek νέος néos, "new" and λίθος líthos, "stone" meaning "New Stone Age"; the term was coined by Sir John Lubbock in 1865 as a refinement of the three-age system. Following the ASPRO chronology, the Neolithic started in around 10,200 BC in the Levant, arising from the Natufian culture, when pioneering use of wild cereals evolved into early farming.
The Natufian period or "proto-Neolithic" lasted from 12,500 to 9,500 BC, is taken to overlap with the Pre-Pottery Neolithic of 10,200–8800 BC. As the Natufians had become dependent on wild cereals in their diet, a sedentary way of life had begun among them, the climatic changes associated with the Younger Dryas are thought to have forced people to develop farming. By 10,200–8800 BC farming communities had arisen in the Levant and spread to Asia Minor, North Africa and North Mesopotamia. Mesopotamia is the site of the earliest developments of the Neolithic Revolution from around 10,000 BC. Early Neolithic farming was limited to a narrow range of plants, both wild and domesticated, which included einkorn wheat and spelt, the keeping of dogs and goats. By about 6900–6400 BC, it included domesticated cattle and pigs, the establishment of permanently or seasonally inhabited settlements, the use of pottery. Not all of these cultural elements characteristic of the Neolithic appeared everywhere in the same order: the earliest farming societies in the Near East did not use pottery.
In other parts of the world, such as Africa, South Asia and Southeast Asia, independent domestication events led to their own regionally distinctive Neolithic cultures, which arose independently of those in Europe and Southwest Asia. Early Japanese societies and other East Asian cultures used pottery before developing agriculture. In the Middle East, cultures identified as Neolithic began appearing in the 10th millennium BC. Early development occurred from there spread eastwards and westwards. Neolithic cultures are attested in southeastern Anatolia and northern Mesopotamia by around 8000 BC; the prehistoric Beifudi site near Yixian in Hebei Province, contains relics of a culture contemporaneous with the Cishan and Xinglongwa cultures of about 6000–5000 BC, neolithic cultures east of the Taihang Mountains, filling in an archaeological gap between the two Northern Chinese cultures. The total excavated area is more than 1,200 square yards, the collection of neolithic findings at the site encompasses two phases.
The Neolithic 1 period began around 10,000 BC in the Levant. A temple area in southeastern Turkey at Göbekli Tepe, dated to around 9500 BC, may be regarded as the beginning of the period; this site was developed by nomadic hunter-gatherer tribes, as evidenced by the lack of permanent housing in the vicinity, may be the oldest known human-made place of worship. At least seven stone circles, covering 25 acres, contain limestone pillars carved with animals and birds. Stone tools were used by as many as hundreds of people to create the pillars, which might have supported roofs. Other early PPNA sites dating to around 9500–9000 BC have been found in Jericho, West Bank, Gilgal in the Jordan Valley, Byblos, Lebanon; the start of Neolithic 1 overlaps the Heavy Neolithic periods to some degree. The major advance of Neolithic 1 was true farming. In the proto-Neolithic Natufian cultures, wild cereals were harvested, early seed selection and re-seeding occurred; the grain was ground into flour. Emmer wheat was domesticated, animals were herded and domesticated.
In 2006, remains of figs were discovered in a house in Jericho dated to 9400 BC. The figs are of a mutant variety that cannot be pollinated by insects, therefore the trees can only reproduce from cuttings; this evidence suggests that figs were the first cultivated crop and mark the invention of the technology of farming. This occurred centuries before the first cultivation of grains. Settlements became more permanent, with circular houses, much like those of the Natufians, with single rooms. However, these houses were for the first time made of mudbrick; the settlement had a surrounding stone wall and a stone tower. The wall served as protection from nearby groups, as protection from floods, or to keep animals penned; some of the enclosures suggest grain and meat storage. The Neolithic 2 began around 8800 BC according to the ASPRO chronology in the Levant; as with the PPNA dates, there are two versions from the same laboratories noted above. This system of terminology, however, is not convenient for southeast Anatolia and settlements of the middle Anatolia basin.
A settlement of 3,000 inhabitants was found in th
In agriculture, a terrace is a piece of sloped plane, cut into a series of successively receding flat surfaces or platforms, which resemble steps, for the purposes of more effective farming. This type of landscaping is therefore called terracing. Graduated terrace steps are used to farm on hilly or mountainous terrain. Terraced fields decrease both erosion and surface runoff, may be used to support growing crops that require irrigation, such as rice; the Rice Terraces of the Philippine Cordilleras have been designated as a UNESCO World Heritage Site because of the significance of this technique. Terraced paddy fields are used in rice and barley farming in east and southeast Asia, as well as the Mediterranean and South America. Drier-climate terrace farming is common throughout the Mediterranean Basin, where they are used for vineyards, olive trees, cork oak, etc. In the South American Andes, farmers have used terraces, known as andenes, for over a thousand years to farm potatoes and other native crops.
Terraced farming was developed by the Wari culture and other peoples of the south-central Andes before 1000 AD, centuries before they were used by the Inca, who adopted them. The terraces were built to make the most efficient use of shallow soil and to enable irrigation of crops by allowing runoff to occur through the outlet; the Inca built on these, developing a system of canals and puquios to direct water through dry land and increase fertility levels and growth. These terraced farms are found, they provided the food necessary to support the populations of great Inca cities and religious centres such as Machu Picchu. Terracing is used for sloping terrain. At the seaside Villa of the Papyri in Herculaneum, the villa gardens of Julius Caesar's father-in-law were designed in terraces to give pleasant and varied views of the Bay of Naples. Terraced fields are common in islands with steep slopes; the Canary Islands present a complex system of terraces covering the landscape from the coastal irrigated plantations to the dry fields in the highlands.
These terraces, which are named cadenas, are built with stone walls of skillful design, which include attached stairs and channels. In Old English, a terrace was called a "lynch". An example of an ancient Lynch Mill is in Lyme Regis; the water is directed from a river by a duct along a terrace. This set-up was used in steep hilly areas in the UK. In Japan, some of the 100 Selected Terraced Rice Fields, from Iwate in the north to Kagoshima in the south, are disappearing, but volunteers are helping the farmers both to maintain their traditional methods and for sightseeing purposes. Anden Banaue Rice Terraces Rice Terraces of the Philippine Cordilleras Satoyama Terrace garden Terrace Fields around the World
Irrigation is the application of controlled amounts of water to plants at needed intervals. Irrigation helps to grow agricultural crops, maintain landscapes, revegetate disturbed soils in dry areas and during periods of less than average rainfall. Irrigation has other uses in crop production, including frost protection, suppressing weed growth in grain fields and preventing soil consolidation. In contrast, agriculture that relies only on direct rainfall is referred to as rain-fed or dry land farming. Irrigation systems are used for cooling livestock, dust suppression, disposal of sewage, in mining. Irrigation is studied together with drainage, the removal of surface and sub-surface water from a given area. Irrigation has been a central feature of agriculture for over 5,000 years and is the product of many cultures, it was the basis for economies and societies across the globe, from Asia to the Southwestern United States. Archaeological investigation has found evidence of irrigation in areas lacking sufficient natural rainfall to support crops for rainfed agriculture.
The earliest known use of the technology dates to the 6th millennium BCE in Khuzistan in the south-west of present-day Iran. Irrigation was used as a means of manipulation of water in the alluvial plains of the Indus valley civilization, the application of it is estimated to have begun around 4500 BC and drastically increased the size and prosperity of their agricultural settlements; the Indus Valley Civilization developed sophisticated irrigation and water-storage systems, including artificial reservoirs at Girnar dated to 3000 BCE, an early canal irrigation system from c. 2600 BCE. Large-scale agriculture was practiced, with an extensive network of canals used for the purpose of irrigation. Farmers in the Mesopotamian plain used irrigation from at least the third millennium BCE, they developed perennial irrigation watering crops throughout the growing season by coaxing water through a matrix of small channels formed in the field. Ancient Egyptians practiced basin irrigation using the flooding of the Nile to inundate land plots, surrounded by dykes.
The flood water remained until the fertile sediment had settled before the engineers returned the surplus to the watercourse. There is evidence of the ancient Egyptian pharaoh Amenemhet III in the twelfth dynasty using the natural lake of the Faiyum Oasis as a reservoir to store surpluses of water for use during dry seasons; the lake swelled annually from the flooding of the Nile. The Ancient Nubians developed a form of irrigation by using a waterwheel-like device called a sakia. Irrigation began in Nubia some time between the third and second millennia BCE, it depended upon the flood waters that would flow through the Nile River and other rivers in what is now the Sudan. In sub-Saharan Africa irrigation reached the Niger River region cultures and civilizations by the first or second millennium BCE and was based on wet-season flooding and water harvesting. Evidence of terrace irrigation occurs in pre-Columbian America, early Syria and China. In the Zana Valley of the Andes Mountains in Peru, archaeologists have found remains of three irrigation canals radiocarbon-dated from the 4th millennium BCE, the 3rd millennium BCE and the 9th century CE.
These canals provide the earliest record of irrigation in the New World. Traces of a canal dating from the 5th millennium BCE were found under the 4th-millennium canal. Ancient Persia used irrigation as far back as the 6th millennium BCE to grow barley in areas with insufficient natural rainfall; the Qanats, developed in ancient Persia about 800 BCE, are among the oldest known irrigation methods still in use today. They are now found in the Middle East and North Africa; the system comprises a network of vertical wells and sloping tunnels driven into the sides of cliffs and of steep hills to tap groundwater. The noria, a water wheel with clay pots around the rim powered by the flow of the stream, first came into use at about this time among Roman settlers in North Africa. By 150 BCE the pots were fitted with valves to allow smoother filling as they were forced into the water; the irrigation works of ancient Sri Lanka, the earliest dating from about 300 BCE in the reign of King Pandukabhaya, under continuous development for the next thousand years, were one of the most complex irrigation systems of the ancient world.
In addition to underground canals, the Sinhalese were the first to build artificial reservoirs to store water. These reservoirs and canal systems were used to irrigate paddy fields, which require a lot of water to cultivate. Most of these irrigation systems still exist undamaged up to now, in Anuradhapura and Polonnaruwa, because of the advanced and precise engineering; the system was further extended during the reign of King Parakrama Bahu. The oldest known hydraulic engineers of China were Sunshu Ao of the Spring and Autumn period and Ximen Bao of the Warring States period, both of whom worked on large irrigation projects. In the Sichuan region belonging to the state of Qin of ancient China, the Dujiangyan Irrigation System devised by the Qin Chinese hydrologist and irrigation engineer Li Bing was built in 256 BCE to irrigate a vast area of farmland that today still supplies water. By the 2nd century AD, during the Han Dynasty, the Chinese used chain pumps which lifted water from a lower elevation to a higher one.
These were powered by manual foot-pedal, hydraulic waterwheels, or rotating mechanical wheels pulled by oxen. The water was used for public works, providing water for urban residential quarters and palace gardens, bu
The three-age system is the categorization of history into time periods divisible by three. In history and physical anthropology, the three-age system is a methodological concept adopted during the 19th century by which artifacts and events of late prehistory and early history could be ordered into a recognizable chronology, it was developed by C. J. Thomsen, director of the Royal Museum of Nordic Antiquities, Copenhagen, as a means to classify the museum’s collections according to whether the artifacts were made of stone, bronze, or iron; the system first appealed to British researchers working in the science of ethnology who adopted it to establish race sequences for Britain's past based on cranial types. Although the craniological ethnology that formed its first scholarly context holds no scientific value, the relative chronology of the Stone Age, the Bronze Age and the Iron Age is still in use in a general public context, the three ages remain the underpinning of prehistoric chronology for Europe, the Mediterranean world and the Near East.
The structure reflects the cultural and historical background of Mediterranean Europe and the Middle East and soon underwent further subdivisions, including the 1865 partitioning of the Stone Age into Paleolithic and Neolithic periods by John Lubbock. It is, however, of little or no use for the establishment of chronological frameworks in sub-Saharan Africa, much of Asia, the Americas and some other areas and has little importance in contemporary archaeological or anthropological discussion for these regions; the concept of dividing pre-historical ages into systems based on metals extends far back in European history originated by Lucretius in the first century BC. But the present archaeological system of the three main ages—stone and iron—originates with the Danish archaeologist Christian Jürgensen Thomsen, who placed the system on a more scientific basis by typological and chronological studies, at first, of tools and other artifacts present in the Museum of Northern Antiquities in Copenhagen.
He used artifacts and the excavation reports published or sent to him by Danish archaeologists who were doing controlled excavations. His position as curator of the museum gave him enough visibility to become influential on Danish archaeology. A well-known and well-liked figure, he explained his system in person to visitors at the museum, many of them professional archaeologists. In his poem and Days, the ancient Greek poet Hesiod between 750 and 650 BC, defined five successive Ages of Man: 1. Golden, 2. Silver, 3. Bronze, 4. Heroic and 5. Iron. Only the Bronze Age and the Iron Age are based on the use of metal:... Zeus the father created the third generation of mortals, the age of bronze... They were terrible and strong, the ghastly action of Ares was theirs, violence.... The weapons of these men were bronze, of bronze their houses, they worked as bronzesmiths. There was not yet any black iron. Hesiod knew from the traditional poetry, such as the Iliad, the heirloom bronze artifacts that abounded in Greek society, that before the use of iron to make tools and weapons, bronze had been the preferred material and iron was not smelted at all.
He did not continue the manufacturing metaphor, but mixed his metaphors, switching over to the market value of each metal. Iron was cheaper than bronze, so there must have been a silver age, he portrays a sequence of metallic ages. Each age has less of a moral value than the preceding. Of his own age he says: "And I wish that I were not any part of the fifth generation of men, but had died before it came, or had been born afterward." The moral metaphor of the ages of metals continued. Lucretius, replaced moral degradation with the concept of progress, which he conceived to be like the growth of an individual human being; the concept is evolutionary:. Everything must pass through successive phases. Nothing remains. Everything is on the move. Everything is transformed by nature and forced into new paths... The Earth passes through successive phases, so that it can no longer bear what it could, it can now what it could not before; the Romans believed that the species of animals, including humans, were spontaneously generated from the materials of the Earth, because of which the Latin word mater, "mother", descends to English-speakers as matter and material.
In Lucretius the Earth is Venus, to whom the poem is dedicated in the first few lines. She brought forth humankind by spontaneous generation. Having been given birth as a species, humans must grow to maturity by analogy with the individual; the different phases of their collective life are marked by the accumulation of customs to form material civilization: The earliest weapons were hands and teeth. Next came stones and branches wrenched from trees, fire and flame as soon as these were discovered. Men learnt to use tough iron and copper. With copper they tilled the soil. With copper they whipped up the clashing waves of war... By slow degrees the iron sword came to the fore. Lucretius envisioned a pre-technological human, "far tougher than the men of today... They lived out their lives in the fashion of wild beasts roaming at large." The next stage was the use of huts, clothing and the family. City-states and citadels followed them. Lucretius supposes that the initial
A metate or metlatl is a type or variety of quern, a ground stone tool used for processing grain and seeds. In traditional Mesoamerican culture, metates were used by women who would grind lime-treated maize and other organic materials during food preparation. Similar artifacts are found all over the world, including China. While varying in specific morphology, metates adhere to a common shape, they consist of large stones with a smooth depression or bowl worn into the upper surface. The bowl is formed by the continual and long-term grinding of materials using a smooth hand-held stone; this action consists of a horizontal grinding motion that differs from the vertical crushing motion used in a mortar and pestle. The depth of the bowl varies, though they are not deeper than those of a mortar; the specific angles of the metate body allow for a proficient method of turning grains into flour. Another type of metate called a grinding slab may be found among boulder or exposed bedrock outcroppings; the upper face of the stone is used for grinding materials, such as acorns, that results in the smoothing of the stone's face and the creation of pocked dimples.
Carved, volcanic-stone ceremonial metates represent one of the most unusual and complex traditions of pre-Columbian artifacts from Costa Rica. They come in many different forms, morphological variation corresponds to different regions and time periods, they can be rectangular, flat, or curved. They may not have rims and between three and four legs; some exhibits show signs of use-wear while others show no signs of wear and appear to have been made for use as burial goods. Some examples characterized as metate might have been a type of throne for sitting on – not a metate at all; some examples are known as effigy-headed metate, which feature an animal’s head at one end, with the metate itself making up the body of the creature. Animals depicted are jaguar, crocodile or birds; the most complex type of ceremonial metate is the class referred to as “flying-panel” metate. This style comes from the Atlantic watershed region, including the City of Guayabo and represents a high level of craftsmanship and complexity.
Carved from a single piece of stone, these metates contain multiple figures, both underneath the plate and on the legs. Trophy heads, jaguar and saurian figures are the most common themes; the “flying panel” metate is believed to be the precursor to free standing sculptural figures more common in the Atlantic watershed region. The earliest traditions of stone sculpture in Costa Rica, including ceremonial metate, began in late Period IV. Metate rimless plates; those from the Atlantic Watershed have a plate, horizontally flat and rimmed. Both are associated with mortuary goods, suggesting differential social status existed within these communities; the three main types of Costa Rican stone sculpture at this time—tripod-metate, mace heads and jade “axe-god” pendants—peaked and declined in use during Period V. Stone sculpture was never popular again in the Nicoya/Guanacaste region, but in the Atlantic Watershed by Period VI, freestanding figural sculpture and new forms of ceremonial metate came into use.
These new metate types might be rectangular with four legs like the jaguar effigy-head examples or might be round in shape with a pedestal base. These latter types have carved human heads around the rim implying a relationship with ritual trophy-head taking; this particular form of metate seems to have been influenced by the stone sculptures of the Panamanian site of Barriles. At the site of Las Huacas, fifteen metates were excavated from sixteen graves. None of these metates had manos, suggesting that the carved metate as a mortuary object had a deeper symbolic meaning than just the processing of foodstuffs; the metate's basic mechanical purpose is a platform. This transformation of grain to flour has symbolic implications relating to life and rebirth, it is still not clear if maize was a main source of sustenance, it is possible that maize was reserved for making chicha, for use in ritual feasting activities. Given their role as a burial good, it seems that metate held a strong meaning for human life and the hope for a rebirth or transformation of some kind.
The three most popular iconographic elements of ceremonial metate seem to be saurian and jaguar creatures. Monkeys are common. A unique feature of ceremonial metate is the lack of human figures. Disembodied heads are the sole exception. While human figures become the main subject of the free standing sculptures, which depict nude females or male warriors with trophy heads and bound male captives, these do not seem to have been depicted on metate. Flying-panel metates have anthropomorphic figures, but these always have animal heads. In both the Nicoya and Atlantic-Watershed regions, metates are made with saurian imagery, it is thought that the saurian represents the surface of the earth, which relates to agricultural fertility. One of the oldest and most prominent themes in Chibcha art is that of the Crocodile god. Depicted as an anthropomorphic being with a crocodile head, he has been carved into fly-panel metates, sometimes shown standing on a double-headed saurian and other times on a jaguar.
As a symbol, the do
An earth oven, ground oven or cooking pit is one of the most simple and ancient cooking structures. At its most basic, an earth oven is a pit in the ground used to trap heat and bake, smoke, or steam food. Earth ovens have been used in many places and cultures in the past, the presence of such cooking pits is a key sign of human settlement sought by archaeologists. Earth ovens remain a common tool for cooking large quantities of food where no equipment is available, they have been used in various civilizations around the world and are still found in the Pacific region to date. To bake food, the fire is built allowed to burn down to a smoulder; the food is placed in the oven and covered. This covered area can be used to bake other various items. Steaming food in an earth oven covers a similar process. Fire-heated rocks are put into a pit and are covered with green vegetation to add moisture and large quantities of food. More green vegetation and sometimes water are added, if more moisture is needed.
A covering of earth is added over everything. The food in the pit can take up to several hours to a full day to cook, regardless of the dry or wet method used. Today, many communities still use cooking pits for ceremonial or celebratory occasions, including the indigenous Fijian lovo, the Hawaiian imu, the Māori hāngi, the Mexican barbacoa, the New England clam bake; the central Asian tandoor use the method for uncovered, live-fire baking, a transitional design between the earth oven and the horizontal-plan masonry oven. This method is a permanent earth oven made out of clay or firebrick with a burning hot fire in the bottom. In many areas, archaeologists recognize "pit-hearths" as being used in the past. In Central Texas, there are large "burned-rock middens" speculated to be used for large-scale cooking of plants of various sorts the bulbs of sotol; the Mayan pib and Andean watia are other examples. In Mesoamerica and the Caribbean nations, barbacoa is a common practice. Barbacoa a Taino word referring to the pit itself, consists of slow-roasted meat in a maguey-lined pit, popular in Mexico alongside birria and salsa.
The clam bake, invented by Native Americans on the Atlantic seaboard and considered a traditional element of New England cuisine, traditionally uses a type of ad hoc earth oven. A large enough hole is dug into the sand and heated rocks are added to the bottom of the hole. A layer of seaweed is laid on top to create moisture and steam, followed by the food. Lastly, another layer of seaweed is added to trap in the steam and cook the food, which consists of shellfish and vegetables; the Curanto of the Chiloé Archipelago consists of shellfish, potatoes, milcao chapaleles, vegetables traditionally prepared in an earth oven. It has spread to the southern areas of Chile. Earth oven cooking is sometimes used for celebratory cooking in North Africa Morocco: a whole lamb is cooked in an earth oven in a manner similar to the Hawaiian kalua. Among Bedouin and Tuareg nomads, a simple earth oven is used – when men travel without family or kitchen equipment in the desert; the oven is used to bake bread but is used to cook venison and waran.
When baking bread, the wheat or barley flour is mixed with water and some salt and placed directly into the hot sands beneath the camp fire. It is covered again by hot coal and left to bake; this kind of bread is eaten with black tea. The sand has to be knocked off before consuming the bread. Sometimes this type of bread is made when the family is together, because people like the taste of it; the bread is mixed with molten fat and labneh and formed into a dough before eating. This bread may be known under other local names. Earth oven cooking was common in the past and continues into the present – for special occasions, since the earth oven process is labor-intensive. In some part-Melanesian and other related languages, the general term is "umu," from the Proto-Oceanic root *qumun. In some non-Polynesian, part-Polynesian, Micronesian parts of the Pacific, which some islands use the similar word umu, but not all Micronesian islands having many different languages use that base word umu, other words are used instead of umu - in Fiji it is a lovo and in Rotuman it is a koua.
In Papua New Guinea, "mumu" is used by Tok Pisin and English speakers, but each of the other hundreds of local languages has its own word. In the Solomon Islands the word in Pidgin is Toku. Despite the similarities, there are many differences in the details of preparation, their cultural significance, current usage. Earth ovens are said to have originated in Papua New Guinea and have been adopted by the arriving Polynesians; the Samoan umu uses the same method of cooking as many other earth ovens and is related to the Hawaiian earth oven, the imu, made underground by digging a pit. It is a common day-to-day method of preparing roasted foods, with modern ovens being restricted to western-style houses. In the traditional village house, gas burners will be used inside the house to cook some food in pots; the umu is sheltered by a roof in case of rain, it is separate from the house. There are no walls; the Samoan u
History of agriculture
The history of agriculture records the domestication of plants and animals and the development and dissemination of techniques for raising them productively. Agriculture began independently in different parts of the globe, included a diverse range of taxa. At least eleven separate regions of the Old and New World were involved as independent centers of origin. Wild grains were collected and eaten from at least 20,000 BC. From around 9500 BC, the eight Neolithic founder crops – emmer wheat, einkorn wheat, hulled barley, lentils, bitter vetch, chick peas, flax – were cultivated in the Levant. Rye may have been cultivated earlier but this remains controversial. Rice was domesticated in China by 6200 BC with earliest known cultivation from 5700 BC, followed by mung and azuki beans. Pigs were domesticated in Mesopotamia around 11,000 BC, followed by sheep between 11,000 BC and 9000 BC. Cattle were domesticated from the wild aurochs in the areas of modern Turkey and Pakistan around 8500 BC. Sugarcane and some root vegetables were domesticated in New Guinea around 7000 BC.
Sorghum was domesticated in the Sahel region of Africa by 5000 BC. In the Andes of South America, the potato was domesticated between 8000 BC and 5000 BC, along with beans, llamas and guinea pigs. Bananas were hybridized in the same period in Papua New Guinea. In Mesoamerica, wild teosinte was domesticated to maize by 4000 BC. Cotton was domesticated in Peru by 3600 BC. Camels were domesticated late around 3000 BC; the Bronze Age, from c. 3300 BC, witnessed the intensification of agriculture in civilizations such as Mesopotamian Sumer, ancient Egypt, the Indus Valley Civilisation of South Asia, ancient China, ancient Greece. During the Iron Age and era of classical antiquity, the expansion of ancient Rome, both the Republic and the Empire, throughout the ancient Mediterranean and Western Europe built upon existing systems of agriculture while establishing the manorial system that became a bedrock of medieval agriculture. In the Middle Ages, both in the Islamic world and in Europe, agriculture was transformed with improved techniques and the diffusion of crop plants, including the introduction of sugar, rice and fruit trees such as the orange to Europe by way of Al-Andalus.
After the voyages of Christopher Columbus in 1492, the Columbian exchange brought New World crops such as maize, sweet potatoes, manioc to Europe, Old World crops such as wheat, barley and turnips, livestock including horses, cattle and goats to the Americas. Irrigation, crop rotation, fertilizers were introduced soon after the Neolithic Revolution and developed much further in the past 200 years, starting with the British Agricultural Revolution. Since 1900, agriculture in the developed nations, to a lesser extent in the developing world, has seen large rises in productivity as human labour has been replaced by mechanization, assisted by synthetic fertilizers and selective breeding; the Haber-Bosch process allowed the synthesis of ammonium nitrate fertilizer on an industrial scale increasing crop yields. Modern agriculture has raised social and environmental issues including water pollution, genetically modified organisms and farm subsidies. In response, organic farming developed in the twentieth century as an alternative to the use of synthetic pesticides.
Scholars have developed a number of hypotheses to explain the historical origins of agriculture. Studies of the transition from hunter-gatherer to agricultural societies indicate an antecedent period of intensification and increasing sedentism. Current models indicate that wild stands, harvested started to be planted, but were not domesticated. Localised climate change is the favoured explanation for the origins of agriculture in the Levant; when major climate change took place after the last ice age, much of the earth became subject to long dry seasons. These conditions favoured annual plants which die off in the long dry season, leaving a dormant seed or tuber. An abundance of storable wild grains and pulses enabled hunter-gatherers in some areas to form the first settled villages at this time. Early people began altering communities of flora and fauna for their own benefit through means such as fire-stick farming and forest gardening early. Exact dates are hard to determine, as people collected and ate seeds before domesticating them, plant characteristics may have changed during this period without human selection.
An example is the semi-tough rachis and larger seeds of cereals from just after the Younger Dryas in the early Holocene in the Levant region of the Fertile Crescent. Monophyletic characteristics were attained without any human intervention, implying that apparent domestication of the cereal rachis could have occurred quite naturally. Agriculture began independently in different parts of the globe, included a diverse range of taxa. At least 11 separate regions of the Old and New World were involved as independent centers of origin; some of the earliest known domestications were of animals. Domestic pigs had multiple centres of origin in Eurasia, including Europe, East Asia and Southwest Asia, where wild boar were first domesticated about 10,500 years ago. Sheep were domesticated in Mesopotamia between 11,000 BC and 9000 BC. Cattle were domesticated from the wild aurochs in the areas of modern Turkey and Pakistan around 8500 BC. Camels were domesticated late around 3000 BC, it was not until after 9500 BC that the eight so-called founder crops of agriculture appear: first emmer and einkorn wheat hulled barley, lenti