Bay
A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is called a gulf, sound, or bight. A cove is a type of smaller bay with narrow entrance. A fjord is a steep bay shaped by glacial activity. A bay can be the estuary of a river, such as the Chesapeake Bay, an estuary of the Susquehanna River. Bays may be nested within each other; some large bays, such as the Bay of Bengal and Hudson Bay, have varied marine geology. The land surrounding a bay reduces the strength of winds and blocks waves. Bays were significant in the history of human settlement because they provided safe places for fishing, they were important in the development of sea trade as the safe anchorage they provide encouraged their selection as ports. The United Nations Convention on the Law of the Sea called the Law of the Sea, defines a bay as a well-marked indentation whose penetration is in such proportion to the width of its mouth as to contain land-locked waters and constitute more than a mere curvature of the coast.
An indentation shall not, however, be regarded as a bay unless its area is as large as, or larger than, that of the semi-circle whose diameter is a line drawn across the mouth of that indentation. There are various ways; the largest bays have developed through plate tectonics. As the super-continent Pangaea broke up along curved and indented fault lines, the continents moved apart and left large bays. Bays form through coastal erosion by rivers and glaciers. A bay formed by a glacier is a fjord. Rias are characterised by more gradual slopes. Deposits of softer rocks erode more forming bays, while harder rocks erode less leaving headlands. Bay platform Great capes Headlands and bays
Great Rann of Kutch
The Great Rann of Kutch is a salt marsh in the Thar Desert in the Kutch District of Gujarat, India. It is reputed to be one of the largest salt deserts in the world; this area has been inhabited by the Kutchi people. The Hindi word is derived from Sanskrit/Vedic word iriṇa attested in the Mahabharata; the Great Rann of Kutch, along with the Little Rann of Kutch and the Banni grasslands on its southern edge, is situated in the district of Kutch and comprises some 30,000 square kilometres between the Gulf of Kutch and the mouth of the Indus River in southern Pakistan. The marsh can be accessed from the village of Kharaghoda in Surendranagar District; the Great Rann of Kutch together with the Little Rann of Kutch is called Rann of Kutch. In India's summer monsoon, the flat desert of salty clay and mudflats, which average 15 meters above sea level, fills with standing water. In wet years, the wetland extends from the Gulf of Kutch on the west through to the Gulf of Cambay on the east; the area was a vast shallow of the Arabian Sea until continuing geological uplift closed off the connection with the sea, creating a vast lake, still navigable during the time of Alexander the Great.
The Ghaggar River, which presently empties into the desert of northern Rajasthan emptied into the Rann of Kutch, but the lower reaches of the river dried up as its upstream tributaries were captured by the Indus and Ganges thousands of years ago. Traces of the delta and its distributary channels on the northern boundary of the Rann of Kutch were documented by the Geological Survey of India in 2000; the Luni River, which originates in Rajasthan, drains into the desert in the northeast corner of the Rann. Other rivers feeding into the marsh include the Rupen from the east and the West Banas River from the northeast. Nara Canal or Puran river, a delta channel of Indus River empties during floods into Kori Creek located in the Great Rann of Kutch. There are sandy islets of thorny scrub, forming a wildlife sanctuary and a breeding ground for some of the largest flocks of greater and lesser flamingos. Wildlife, including the Indian wild ass, shelter on islands of higher ground, called bets, during the flooding.
This is one of the hottest areas of India – with summer temperatures averaging and peaking at 49.5 °C. Winter temperatures reduce and can go below 0 °C. Many religions are found here, including Hinduism, Jainism & Sikhism. Although most of the marsh is in protected areas, the habitats are vulnerable to cattle grazing, firewood collection and salt extraction operations, all of which may involve transportation that disturbs wildlife. There are several wildlife sanctuaries and protected reserves on the Indian side in the Rann of Kutch region. From the city of Bhuj, various ecologically rich and wildlife conservation areas of the Kutch/Kachchh district can be visited such as Indian Wild Ass Sanctuary, Kutch Desert Wildlife Sanctuary, Narayan Sarovar Sanctuary, Kutch Bustard Sanctuary, Banni Grasslands Reserve and Chari-Dhand Wetland Conservation Reserve. In India the northern boundary of the Greater Rann of Kutch forms the International Border between India and Pakistan, it is patrolled by India's Border Security Force and Indian Army conducts exercises here to acclimatize its troops to this harsh terrain.
This inhospitable salty lowland, rich in natural gas, was one scene of perennial border disputes between India and Pakistan that, in April 1965, contributed to the Indo-Pakistani War of 1965. The same year, Prime Minister of the United Kingdom Harold Wilson persuaded the combatants to end hostilities and establish a tribunal to resolve the dispute. A verdict was reached in 1968 which saw Pakistan getting 10% of its claim of 9,100 square kilometres. 90 % was awarded to India. Tensions spurted again in 1999 during the Atlantique incident; the Indus river had been flowing in to Rann of Kutch area and Rann of Kutch used to be its catchment area forming part of its delta. Indus river branch called Koree river, shifted its course after an earthquake in 1819 isolating Rann of Kutch from its delta. Pakistan has constructed Left Bank Outfall Drain project to bypass the saline and polluted water, not fit for agriculture use to reach sea via Rann of Kutch area without passing through the Indus delta; the 500 km long LBOD, begins from northern Ghotki district in Sindh province of Pakistan and joins Rann of Kutch in Badin district of Sindh.
Rann of Kutch is joint water body of Pakistan. Water released by the LBOD is enhancing the flooding in India and contaminating the quality of water bodies which are source of water to salt farms spread over vast area; the LBOD water is planned to join the sea via disputed Sir Creek but LBOD water is entering Indian territory due to many breaches in its left bank caused by floods At night, an unexplained strange dancing light phenomenon known locally as Chir Batti occurs in the Rann, the adjoining Banni grasslands, the seasonal wetlands. The Government of Gujarat hosts an annual 3 month long festival during winter called the Rann Utsav where tourists can see the various sights of the Rann. For 2017, the festival of Rann started on 1 November 2017. Rann Utsav gives visitors not only a chance to experience full moon on salt deserts but get a taste of the local culture and hospitality. Specially built local houses are used to house tourists to give them a taste of local traditions Many adventure clubs and travel clubs organize expeditions.
Some women and young girls make their living by selling different types of embroidered cloths. The embroidery is of various styles such as Rabari, Sindhi, Mutwa, Ari and So
United Kingdom
The United Kingdom the United Kingdom of Great Britain and Northern Ireland, sometimes referred to as Britain, is a sovereign country located off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland, many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state, the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world; the Irish Sea lies between Great Ireland. With an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world, it is the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017. The UK is constitutional monarchy; the current monarch is Queen Elizabeth II, who has reigned since 1952, making her the longest-serving current head of state.
The United Kingdom's capital and largest city is London, a global city and financial centre with an urban area population of 10.3 million. Other major urban areas in the UK include Greater Manchester, the West Midlands and West Yorkshire conurbations, Greater Glasgow and the Liverpool Built-up Area; the United Kingdom consists of four constituent countries: England, Scotland and Northern Ireland. Their capitals are London, Edinburgh and Belfast, respectively. Apart from England, the countries have their own devolved governments, each with varying powers, but such power is delegated by the Parliament of the United Kingdom, which may enact laws unilaterally altering or abolishing devolution; the nearby Isle of Man, Bailiwick of Guernsey and Bailiwick of Jersey are not part of the UK, being Crown dependencies with the British Government responsible for defence and international representation. The medieval conquest and subsequent annexation of Wales by the Kingdom of England, followed by the union between England and Scotland in 1707 to form the Kingdom of Great Britain, the union in 1801 of Great Britain with the Kingdom of Ireland created the United Kingdom of Great Britain and Ireland.
Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain and Northern Ireland. There are fourteen British Overseas Territories, the remnants of the British Empire which, at its height in the 1920s, encompassed a quarter of the world's land mass and was the largest empire in history. British influence can be observed in the language and political systems of many of its former colonies; the United Kingdom is a developed country and has the world's fifth-largest economy by nominal GDP and ninth-largest economy by purchasing power parity. It has a high-income economy and has a high Human Development Index rating, ranking 14th in the world, it was the world's first industrialised country and the world's foremost power during the 19th and early 20th centuries. The UK remains a great power, with considerable economic, military and political influence internationally, it is sixth in military expenditure in the world. It has been a permanent member of the United Nations Security Council since its first session in 1946.
It has been a leading member state of the European Union and its predecessor, the European Economic Community, since 1973. The United Kingdom is a member of the Commonwealth of Nations, the Council of Europe, the G7, the G20, NATO, the Organisation for Economic Co-operation and Development and the World Trade Organization; the 1707 Acts of Union declared that the kingdoms of England and Scotland were "United into One Kingdom by the Name of Great Britain". The term "United Kingdom" has been used as a description for the former kingdom of Great Britain, although its official name from 1707 to 1800 was "Great Britain"; the Acts of Union 1800 united the kingdom of Great Britain and the kingdom of Ireland in 1801, forming the United Kingdom of Great Britain and Ireland. Following the partition of Ireland and the independence of the Irish Free State in 1922, which left Northern Ireland as the only part of the island of Ireland within the United Kingdom, the name was changed to the "United Kingdom of Great Britain and Northern Ireland".
Although the United Kingdom is a sovereign country, Scotland and Northern Ireland are widely referred to as countries. The UK Prime Minister's website has used the phrase "countries within a country" to describe the United Kingdom; some statistical summaries, such as those for the twelve NUTS 1 regions of the United Kingdom refer to Scotland and Northern Ireland as "regions". Northern Ireland is referred to as a "province". With regard to Northern Ireland, the descriptive name used "can be controversial, with the choice revealing one's political preferences"; the term "Great Britain" conventionally refers to the island of Great Britain, or politically to England and Wales in combination. However, it is sometimes used as a loose synonym for the United Kingdom as a whole; the term "Britain" is used both as a synonym for Great Britain, as a synonym for the United Kingdom. Usage is mixed, with the BBC preferring to use Britain as shorthand only for Great Britain and the UK Government, while accepting that both terms refer to the United K
Estuary
An estuary is a enclosed coastal body of brackish water with one or more rivers or streams flowing into it, with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments, they are subject both to marine influences—such as tides and the influx of saline water—and to riverine influences—such as flows of fresh water and sediment. The mixing of sea water and fresh water provide high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world. Most existing estuaries formed during the Holocene epoch with the flooding of river-eroded or glacially scoured valleys when the sea level began to rise about 10,000–12,000 years ago. Estuaries are classified according to their geomorphological features or to water-circulation patterns, they can have many different names, such as bays, lagoons, inlets, or sounds, although some of these water bodies do not meet the above definition of an estuary and may be saline.
The banks of many estuaries are amongst the most populated areas of the world, with about 60% of the world's population living along estuaries and the coast. As a result, many estuaries suffer degradation from a variety of factors including: sedimentation from soil erosion from deforestation and other poor farming practices; the word "estuary" is derived from the Latin word aestuarium meaning tidal inlet of the sea, which in itself is derived from the term aestus, meaning tide. There have been many definitions proposed to describe an estuary; the most accepted definition is: "a semi-enclosed coastal body of water, which has a free connection with the open sea, within which sea water is measurably diluted with freshwater derived from land drainage". However, this definition excludes a number of coastal water bodies such as coastal lagoons and brackish seas. A more comprehensive definition of an estuary is "a semi-enclosed body of water connected to the sea as far as the tidal limit or the salt intrusion limit and receiving freshwater runoff.
This broad definition includes fjords, river mouths, tidal creeks. An estuary is a dynamic ecosystem having a connection to the open sea through which the sea water enters with the rhythm of the tides; the sea water entering the estuary streams. The pattern of dilution varies between different estuaries and depends on the volume of fresh water, the tidal range, the extent of evaporation of the water in the estuary. Drowned river valleys are known as coastal plain estuaries. In places where the sea level is rising relative to the land, sea water progressively penetrates into river valleys and the topography of the estuary remains similar to that of a river valley; this is the most common type of estuary in temperate climates. Well-studied estuaries include the Severn Estuary in the United Kingdom and the Ems Dollard along the Dutch-German border; the width-to-depth ratio of these estuaries is large, appearing wedge-shaped in the inner part and broadening and deepening seaward. Water depths exceed 30 m.
Examples of this type of estuary in the U. S. are the Hudson River, Chesapeake Bay, Delaware Bay along the Mid-Atlantic coast, Galveston Bay and Tampa Bay along the Gulf Coast. Bar-built estuaries are found in place where the deposition of sediment has kept pace with rising sea level so that the estuaries are shallow and separated from the sea by sand spits or barrier islands, they are common in tropical and subtropical locations. These estuaries are semi-isolated from ocean waters by barrier beaches. Formation of barrier beaches encloses the estuary, with only narrow inlets allowing contact with the ocean waters. Bar-built estuaries develop on sloping plains located along tectonically stable edges of continents and marginal sea coasts, they are extensive along the Atlantic and Gulf coasts of the U. S. in areas with active coastal deposition of sediments and where tidal ranges are less than 4 m. The barrier beaches that enclose bar-built estuaries have been developed in several ways: building up of offshore bars by wave action, in which sand from the sea floor is deposited in elongated bars parallel to the shoreline, reworking of sediment discharge from rivers by wave and wind action into beaches, overwash flats, dunes, engulfment of mainland beach ridges due to sea level rise and resulting in the breaching of the ridges and flooding of the coastal lowlands, forming shallow lagoons, elongation of barrier spits from the erosion of headlands due to the action of longshore currents, with the spits growing in the direction of the littoral drift.
Barrier beaches form in shallow water and are parallel to the shoreline, resulting in long, narrow estuaries. The average water depth is less than 5 m, exceeds 10 m. Examples of bar-built estuaries are Barnegat Bay, New Jersey. Fjords were formed where pleistocene glaciers deepened and widened existing river valleys so that they become U-shaped in cross s
Sea level rise
Since at least the start of the 20th century, the average global sea level has been rising. Between 1900 and 2016, the sea level rose by 16–21 cm. More precise data gathered from satellite radar measurements reveal an accelerating rise of 7.5 cm from 1993 to 2017, a trend of 30 cm per century. This acceleration is due to human-caused global warming, driving thermal expansion of seawater and the melting of land-based ice sheets and glaciers. Between 1993 and 2018, thermal expansion of the oceans contributed 42% to sea level rise. Climate scientists expect the rate to further accelerate during the 21st century. Projecting future sea level is challenging, due to the complexity of many aspects of the climate system; as climate research into past and present sea levels leads to improved computer models, projections have increased. For example, in 2007 the Intergovernmental Panel on Climate Change projected a high end estimate of 60 cm through 2099, but their 2014 report raised the high-end estimate to about 90 cm.
A number of studies have concluded that a global sea level rise of 200 to 270 cm this century is "physically plausible". A conservative estimate of the long-term projections is that each Celsius degree of temperature rise triggers a sea level rise of 2.3 metres over a period of two millennia: an example of climate inertia. The sea level will not rise uniformly everywhere on Earth, it will drop in some locations. Local factors include tectonic effects and subsidence of the land, tides and storms. Sea level rises can influence human populations in coastal and island regions. Widespread coastal flooding is expected with several degrees of warming sustained for millennia. Further effects are higher storm-surges and more dangerous tsunamis, displacement of populations and degradation of agricultural land and damage in cities. Natural environments like marine ecosystems are affected, with fish and plants losing parts of their habitat. Societies can respond to sea level rise in three different ways: to retreat, to accommodate and to protect.
Sometimes these adaptation strategies go hand in hand, but at other times choices have to be made among different strategies. Ecosystems that adapt to rising sea levels by moving inland might not always be able to do so, due to natural or man-made barriers. Understanding past sea level is important for the analysis of current and future changes. In the recent geological past, changes in land ice and thermal expansion from increased temperatures are the dominant reasons of sea level rise; the last time the Earth was 2 °C warmer than pre-industrial temperatures, sea levels were at least 5 metres higher than now: this was when warming because of changes in the amount of sunlight due to slow changes in the Earth's orbit caused the last interglacial. The warming was sustained over a period of thousands of years and the magnitude of the rise in sea level implies a large contribution from the Antarctic and Greenland ice sheets. Since the last glacial maximum about 20,000 years ago, the sea level has risen by more than 125 metres, with rates varying from less than a mm/year to 40+ mm/year, as a result of melting ice sheets over Canada and Eurasia.
Rapid disintegration of ice sheets led to so called'meltwater pulses', periods during which sea level rose rapidly. The rate of rise started to slow down about 8,200 years before present. Sea level changes can be driven either by variations in the amount of water in the oceans, the volume of the ocean or by changes of the land compared to the sea surface; the different techniques used to measure changes in sea level do not measure the same. Tide gauges can only measure relative sea level, whilst satellites can measure absolute sea level changes. To get precise measurements for sea level, researchers studying the ice and the oceans on our planet factor in ongoing deformations of the solid Earth, in particular due to landmasses still rising from past ice masses retreating, the Earth's gravity and rotation. Since the 1992 launch of TOPEX/Poseidon, altimetric satellites have been recording the change in sea level; those satellites can measure the hills and valleys in the sea caused by currents and detect trends in their height.
To measure the distance to the sea surface, the satellite sends a microwave pulse to the ocean's surface and records the time it takes to return. A microwave radiometer corrects any delay. Combining this data with the precise location of the spacecraft makes it possible to determine sea-surface height to within a few centimeters. Current rates of sea level rise from satellite altimetry have been estimated to be 3.0 ± 0.4 millimetres per year for the period 1993–2017. Earlier satellite measurements were at odds with tide gauge measurements. A small calibration error for the Topex/Poseidon satellite discovered in 2015 was identified as the cause of this mismatch, it had caused a slight overestimation of the 1992–2005 sea levels, which masked the ongoing sea level rise acceleration. Satellites are useful for measuring regional variations in sea level, such as the substantial rise between 1993 and 2012 in the western tropical Pacific; this sharp rise has been linked to increasing trade winds, which occur when the Pacific Decadal Oscillation and the El Niño–Southern Oscillation change from one state to t
Fish
Fish are gill-bearing aquatic craniate animals that lack limbs with digits. They form a sister group to the tunicates. Included in this definition are the living hagfish and cartilaginous and bony fish as well as various extinct related groups. Tetrapods emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish are rendered paraphyletic by excluding the tetrapods; because in this manner the term "fish" is defined negatively as a paraphyletic group, it is not considered a formal taxonomic grouping in systematic biology, unless it is used in the cladistic sense, including tetrapods. The traditional term pisces is considered a typological, but not a phylogenetic classification; the earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era.
Many fish of the Paleozoic developed external armor. The first fish with jaws appeared in the Silurian period, after which many became formidable marine predators rather than just the prey of arthropods. Most fish are ectothermic, allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. Fish can communicate in their underwater environments through the use of acoustic communication. Acoustic communication in fish involves the transmission of acoustic signals from one individual of a species to another; the production of sounds as a means of communication among fish is most used in the context of feeding, aggression or courtship behaviour. The sounds emitted by fish can vary depending on the stimulus involved, they can produce either stridulatory sounds by moving components of the skeletal system, or can produce non-stridulatory sounds by manipulating specialized organs such as the swimbladder.
Fish are abundant in most bodies of water. They can be found in nearly all aquatic environments, from high mountain streams to the abyssal and hadal depths of the deepest oceans, although no species has yet been documented in the deepest 25% of the ocean. With 33,600 described species, fish exhibit greater species diversity than any other group of vertebrates. Fish are an important resource for humans worldwide as food. Commercial and subsistence fishers hunt fish in wild fisheries or farm them in ponds or in cages in the ocean, they are caught by recreational fishers, kept as pets, raised by fishkeepers, exhibited in public aquaria. Fish have had a role in culture through the ages, serving as deities, religious symbols, as the subjects of art and movies. Fish do not represent a monophyletic group, therefore the "evolution of fish" is not studied as a single event. Early fish from the fossil record are represented by a group of small, armored fish known as ostracoderms. Jawless fish lineages are extinct.
An extant clade, the lampreys may approximate ancient pre-jawed fish. The first jaws are found in Placodermi fossils; the diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. It is unclear if the advantage of a hinged jaw is greater biting force, improved respiration, or a combination of factors. Fish may have evolved from a creature similar to a coral-like sea squirt, whose larvae resemble primitive fish in important ways; the first ancestors of fish may have kept the larval form into adulthood, although the reverse is the case. Fish are a paraphyletic group: that is, any clade containing all fish contains the tetrapods, which are not fish. For this reason, groups such as the "Class Pisces" seen in older reference works are no longer used in formal classifications. Traditional classification divides fish into three extant classes, with extinct forms sometimes classified within the tree, sometimes as their own classes: Class Agnatha Subclass Cyclostomata Subclass Ostracodermi † Class Chondrichthyes Subclass Elasmobranchii Subclass Holocephali Class Placodermi † Class Acanthodii † Class Osteichthyes Subclass Actinopterygii Subclass Sarcopterygii The above scheme is the one most encountered in non-specialist and general works.
Many of the above groups are paraphyletic, in that they have given rise to successive groups: Agnathans are ancestral to Chondrichthyes, who again have given rise to Acanthodiians, the ancestors of Osteichthyes. With the arrival of phylogenetic nomenclature, the fishes has been split up into a more detailed scheme, with the following major groups: Class Myxini Class Pteraspidomorphi † Class Thelodonti † Class Anaspida † Class Petromyzontida or Hyperoartia Petromyzontidae Class Conodonta † Class Cephalaspidomorphi † Galeaspida † Pituriaspida † Osteostraci † Infraphylum Gnathostomata Class Placodermi † Class Chondrichthyes Class Acanthodii † Superclass Osteichthy
Agriculture
Agriculture is the science and art of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to live in cities; the history of agriculture began thousands of years ago. After gathering wild grains beginning at least 105,000 years ago, nascent farmers began to plant them around 11,500 years ago. Pigs and cattle were domesticated over 10,000 years ago. Plants were independently cultivated in at least 11 regions of the world. Industrial agriculture based on large-scale monoculture in the twentieth century came to dominate agricultural output, though about 2 billion people still depended on subsistence agriculture into the twenty-first. Modern agronomy, plant breeding, agrochemicals such as pesticides and fertilizers, technological developments have increased yields, while causing widespread ecological and environmental damage. Selective breeding and modern practices in animal husbandry have increased the output of meat, but have raised concerns about animal welfare and environmental damage.
Environmental issues include contributions to global warming, depletion of aquifers, antibiotic resistance, growth hormones in industrial meat production. Genetically modified organisms are used, although some are banned in certain countries; the major agricultural products can be broadly grouped into foods, fibers and raw materials. Food classes include cereals, fruits, meat, milk and eggs. Over one-third of the world's workers are employed in agriculture, second only to the service sector, although the number of agricultural workers in developed countries has decreased over the centuries; the word agriculture is a late Middle English adaptation of Latin agricultūra, from ager, "field", which in its turn came from Greek αγρός, cultūra, "cultivation" or "growing". While agriculture refers to human activities, certain species of ant and ambrosia beetle cultivate crops. Agriculture is defined with varying scopes, in its broadest sense using natural resources to "produce commodities which maintain life, including food, forest products, horticultural crops, their related services".
Thus defined, it includes arable farming, animal husbandry and forestry, but horticulture and forestry are in practice excluded. The development of agriculture enabled the human population to grow many times larger than could be sustained by hunting and gathering. Agriculture began independently in different parts of the globe, included a diverse range of taxa, in at least 11 separate centres of origin. Wild grains were eaten from at least 105,000 years ago. From around 11,500 years ago, the eight Neolithic founder crops and einkorn wheat, hulled barley, lentils, bitter vetch, chick peas and flax were cultivated in the Levant. Rice was domesticated in China between 11,500 and 6,200 BC with the earliest known cultivation from 5,700 BC, followed by mung and azuki beans. Sheep were domesticated in Mesopotamia between 11,000 years ago. Cattle were domesticated from the wild aurochs in the areas of modern Turkey and Pakistan some 10,500 years ago. Pig production emerged in Eurasia, including Europe, East Asia and Southwest Asia, where wild boar were first domesticated about 10,500 years ago.
In the Andes of South America, the potato was domesticated between 10,000 and 7,000 years ago, along with beans, llamas and guinea pigs. Sugarcane and some root vegetables were domesticated in New Guinea around 9,000 years ago. Sorghum was domesticated in the Sahel region of Africa by 7,000 years ago. Cotton was domesticated in Peru by 5,600 years ago, was independently domesticated in Eurasia. In Mesoamerica, wild teosinte was bred into maize by 6,000 years ago. Scholars have offered multiple hypotheses to explain the historical origins of agriculture. Studies of the transition from hunter-gatherer to agricultural societies indicate an initial period of intensification and increasing sedentism. Wild stands, harvested started to be planted, came to be domesticated. In Eurasia, the Sumerians started to live in villages from about 8,000 BC, relying on the Tigris and Euphrates rivers and a canal system for irrigation. Ploughs appear in pictographs around 3,000 BC. Farmers grew wheat, vegetables such as lentils and onions, fruits including dates and figs.
Ancient Egyptian agriculture relied on its seasonal flooding. Farming started in the predynastic period at the end of the Paleolithic, after 10,000 BC. Staple food crops were grains such as wheat and barley, alongside industrial crops such as flax and papyrus. In India, wheat and jujube were domesticated by 9,000 BC, soon followed by sheep and goats. Cattle and goats were domesticated in Mehrgarh culture by 8,000–6,000 BC. Cotton was cultivated by the 5th-4th millennium BC. Archeological evidence indicates an animal-drawn plough from 2,500 BC in the Indus Valley Civilisation. In China, from the 5th century BC there was a nationwide granary system and widespread silk farming. Water-powered grain mills were in use followed by irrigation. By the late 2nd century, heavy ploughs had been developed with iron mouldboards; these spread westwards across Eurasia. Asian rice was domesticated 8,200–13,500 years ago – depending on the molecular clock estimate, used – on the Pearl River in southern China with a single genetic origin from the wild rice Oryza rufipogon
