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
The Neolithic Revolution, Neolithic Demographic Transition, Agricultural Revolution, or First Agricultural Revolution was the wide-scale transition of many human cultures during the Neolithic period from a lifestyle of hunting and gathering to one of agriculture and settlement, making an larger population possible. These settled communities permitted humans to observe and experiment with plants to learn how they grew and developed; this new knowledge led to the domestication of plants. Archaeological data indicates that the domestication of various types of plants and animals happened in separate locations worldwide, starting in the geological epoch of the Holocene around 12,500 years ago, it was the world's first verifiable revolution in agriculture. The Neolithic Revolution narrowed the diversity of foods available, resulting in a downturn in the quality of human nutrition; the Neolithic Revolution involved far more than the adoption of a limited set of food-producing techniques. During the next millennia it would transform the small and mobile groups of hunter-gatherers that had hitherto dominated human pre-history into sedentary societies based in built-up villages and towns.
These societies radically modified their natural environment by means of specialized food-crop cultivation, with activities such as irrigation and deforestation which allowed the production of surplus food. Other developments found widely are the domestication of animals, polished stone tools, rectangular houses; these developments, sometimes called the Neolithic package, provided the basis for centralized administrations and political structures, hierarchical ideologies, depersonalized systems of knowledge, densely populated settlements and division of labour, more trade, the development of non-portable art and architecture, property ownership. The earliest known civilization developed in Sumer in southern Mesopotamia; the relationship of the above-mentioned Neolithic characteristics to the onset of agriculture, their sequence of emergence, empirical relation to each other at various Neolithic sites remains the subject of academic debate, varies from place to place, rather than being the outcome of universal laws of social evolution.
The Levant saw the earliest developments of the Neolithic Revolution from around 10,000 BCE, followed by sites in the wider Fertile Crescent. The term Neolithic Revolution was coined in 1923 by V. Gordon Childe to describe the first in a series of agricultural revolutions in Middle Eastern history; the period is described as a "revolution" to denote its importance, the great significance and degree of change affecting the communities in which new agricultural practices were adopted and refined. The beginning of this process in different regions has been dated from 10,000 to 8,000 BC in the Fertile Crescent and 8000 BC in the Kuk Early Agricultural Site of Melanesia; this transition everywhere seems associated with a change from a nomadic hunter-gatherer way of life to a more settled, agrarian-based one, with the inception of the domestication of various plant and animal species—depending on the species locally available, also influenced by local culture. Recent archaeological research suggests that in some regions such as the Southeast Asian peninsula, the transition from hunter-gatherer to agriculturalist was not linear, but region-specific.
There are several competing theories as to the factors that drove populations to take up agriculture. The most prominent of these are: The Oasis Theory proposed by Raphael Pumpelly in 1908, popularized by V. Gordon Childe in 1928 and summarised in Childe's book Man Makes Himself; this theory maintains that as the climate got drier due to the Atlantic depressions shifting northward, communities contracted to oases where they were forced into close association with animals, which were domesticated together with planting of seeds. However, today this theory has little support amongst archaeologists because subsequent climate data suggests that the region was getting wetter rather than drier; the Hilly Flanks hypothesis, proposed by Robert Braidwood in 1948, suggests that agriculture began in the hilly flanks of the Taurus and Zagros mountains, where the climate was not drier as Childe had believed, fertile land supported a variety of plants and animals amenable to domestication. The Feasting model by Brian Hayden suggests that agriculture was driven by ostentatious displays of power, such as giving feasts, to exert dominance.
This required assembling large quantities of food. The Demographic theories proposed by Carl Sauer and adapted by Lewis Binford and Kent Flannery posit an sedentary population that expanded up to the carrying capacity of the local environment and required more food than could be gathered. Various social and economic factors helped drive the need for food; the evolutionary/intentionality theory, developed by David Rindos and others, views agriculture as an evolutionary adaptation of plants and humans. Starting with domestication by protection of wild plants, it led to specialization of location and full-fledged domestication. Peter Richerson, Robert Boyd, Robert Bettinger make a case for the development of agriculture coinciding with an stable climate at the beginning of the Holocene. Ronald Wright's book and Massey Lecture Series A Short History of Progress popularized this hypothesis; the postulated Younger Dryas impact event, claimed to be in part responsible for megafauna extinction and ending the last glacial period, could have provided circumstances that required the evolution
A basket is a container, traditionally constructed from stiff fibers, can be made from a range of materials, including wood splints and cane. While most baskets are made from plant materials, other materials such as horsehair, baleen, or metal wire can be used. Baskets are woven by hand; some baskets are fitted with a lid. Baskets serve utilitarian as well as aesthetic purposes; some baskets are ceremonial, religious, in nature. While baskets are used for harvesting and transport, specialized baskets are used as sieves for a variety of purposes, including cooking, processing seeds or grains, tossing gambling pieces, fans, fish traps, laundry. Prior to the invention of woven baskets, people used tree bark to make simple containers; these containers could be used to transport gathered food and other items, but crumbled after only a few uses. Weaving strips of bark or other plant material to support the bark containers would be the next step, followed by woven baskets; the last innovation appears to be baskets so woven that they could hold water.
Depending on soil conditions, baskets may not be preserved in the archaeological record. Sites in the Middle East show that weaving techniques were used to make mats and also baskets, circa 8000 BCE. Twined baskets date back to 7000 in Oasisamerica. Baskets made with interwoven techniques were common at 3000 BCE. Baskets were designed as multi-purpose vessels to carry and store materials and to keep stray items about the home; the plant life available in a region affects the choice of material, which in turn influences the weaving technique. Rattan and other members of the Arecaceae or palm tree family, the thin grasses of temperate regions, broad-leaved tropical bromeliads each require a different method of twisting and braiding to be made into a basket; the practice of basket making has evolved into an art. Artistic freedom allows basket makers a wide choice of colors, sizes and details; the carrying of a basket on the head by rural women, has long been practised. Representations of this in Ancient Greek art are called Canephorae.
The phrase "to hell in a handbasket" means to deteriorate. The origin of this use is unclear. "Basket" is sometimes used as an adjective towards a person, born out of wedlock. This occurs more in British English. "Basket" refers to a bulge in a man's crotch. Basket makers use a wide range of materials: Wicker Straw Plastic Metal Bamboo Palm Carbon fiber Zepeda, Ofelia. Ocean Power: Poems from the Desert. ISBN 0-8165-1541-7. "Basket". Encyclopædia Britannica. 3. 1911. Baskets, The Women's Committee of the Philadelphia Museum of Art
Outline of prehistoric technology
The following outline is provided as an overview of and topical guide to prehistoric technology. Prehistoric technology – technology that predates recorded history. History is the study of the past using written records. Anything prior to the first written accounts of history is prehistoric, including earlier technologies. About 2.5 million years before writing was developed, technology began with the earliest hominids who used stone tools, which they may have used to start fires, cut food, bury their dead. Prehistoric technology can be described as: Prehistoric – "before we had written records," from the Latin word for "before," præ. Prehistory is the span of time before recorded history, that is, before the invention of writing systems. Technology – making, modification and knowledge of tools, techniques, crafts and methods of organization, in order to solve a problem, improve a preexisting solution to a problem, achieve a goal, handle an applied input/output relation or perform a specific function.
Three-age system – in archaeology and physical anthropology, the periodization of human prehistory into three consecutive time periods, each named after the main material used in its respective tool-making technologies: the Stone Age, the Bronze Age, the Iron Age. Beginning of prehistoric technology – the earliest technology began before recorded history, that is, at the beginning of the Stone Age. Latest prehistoric technology – the level of technology reached before true writing was introduced differed by region... Latest prehistoric technology in the Near East – cultures in the Near East achieved the development of writing first, during their Bronze Age. Latest prehistoric technology in the rest of the Old World: Europe and China reached Iron Age technological development before the introduction of writing there. Stone Age – broad prehistoric period, lasting 2.5 million years, during which stone was used in the manufacture of implements with a sharp edge, a point, or a percussion surface.
The period ended between 6000 and 2000 BCE with the advent of metalworking. Paleolithic – prehistoric period of human history distinguished by the development of the most primitive stone tools discovered, covers 99% of human technological prehistory. Lower Paleolithic – earliest subdivision of the Paleolithic or Old Stone Age, it spans the time from around 2.5 million years ago when the first evidence of craft and use of stone tools by hominids appears in the current archaeological record, until around 300,000 years ago, spanning the Oldowan and Acheulean lithic technology. Stone tool use – early human use of stone tool technology, such as the hand axe, was similar to that of primates, found to be limited to the intelligence levels of modern children aged 3 to 5 years. Ancestors of homo sapiens used stone tools as follows: Homo habilis – first "homo" species, it lived from 2.3 to 1.4 million years ago in Africa and created stone tools called Oldowan tools. Homo ergaster – in eastern and southern Africa about 2.5 to 1.7 million years ago, it refined Oldowan tools and developed the first Acheulean bifacial axes.
Homo erectus – lived about 1.8 to 1.3 million years ago in West Asia and Africa and is thought to be the first hominid to hunt in coordinated groups, use complex tools, care for infirm or weaker companions. Homo antecessor – earliest hominid in Northern Europe, it used stone tools. Homo heidelbergensis – lived between 600,000 and 400,000 years ago and used stone tool technology similar to the Acheulean tools used by Homo erectus. Control of fire by early humans – European and Asian sites dating back 1.5 million years ago seem to indicate controlled use of fire by H. erectus. A northern Israel site from about 690,000 to 790,000 years ago suggests controlled use of fire in a hearth from pre-existing natural fires or embers. Burial – the act of placing a deceased person into the ground. Homo heidelbergensis – may have been the first species to bury their dead about 500,000 years ago. Middle Paleolithic period – in Europe and the Near East during which the Neanderthals lived, their technology is the Mousterian.
The earliest evidence of settlement in Australia dates to around 55,000 years ago when modern humans crossed from Asia by island-hopping. The Bhimbetka rock shelters exhibit the earliest traces of human life in India, some of which are 30,000 years old. Homo neanderthalensis Stone tools – homo neanderthalensis used Mousterian stone tools that date back to around 300,000 years ago and include smaller, knife-like and scraper tools. Burials – homo neanderthalensis buried their dead, doing so in shallow graves along with stone tools and animal bones, although the reasons and significance of the burials are disputed. Homo sapiens – the only living species in the genus Homo originated in Africa about 200,000 years ago. Greater mental capability and ability to walk erect provided freed hands for manipulating objects, which allowed for far greater use of tools. Art of the Middle Paleolithic Burial – intentional burial with grave goods, may be one of the earliest detectable forms of religious practice since it may signify a "concern for the dead that transcends daily life."
The earliest undisputed human burial so far dates back 130,000 years. Human skeletal remains stained with red ochre were discovered in the Skhul cave at Qafzeh, Israel with a variety of grave goods. Upper Paleolithic Revolution – theoretical occurrence betw
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
Prehistoric technology is technology that predates recorded history. History is the study of the past using written records. Anything prior to the first written accounts of history is prehistoric, including earlier technologies. About 2.5 million years before writing was developed, technology began with the earliest hominids who used stone tools, which they may have used to start fires and bury their dead. There are several factors that made the evolution of prehistoric technology necessary. One of the key factors is behavioral modernity of the developed brain of Homo sapiens capable of abstract reasoning, language and problem solving; the advent of agriculture resulted in lifestyle changes from nomadic lifestyles to ones lived in homes, with domesticated animals, land farmed using more varied and sophisticated tools. Art, architecture and religion evolved over the course of the prehistoric periods; the Stone Age is a broad prehistoric period during which stone was used in the manufacture of implements with a sharp edge, a point, or a percussion surface.
The period lasted 2.5 million years, from the time of early hominids to Homo sapiens in the Pleistocene era, ended between 6000 and 2000 BCE with the advent of metalworking. The Stone Age lifestyle was that of hunter-gatherers who traveled to hunt game and gather wild plants, with minimal changes in technology; as the last glacial period of the current ice age neared its end, large animals like the mammoth and bison antiquus became extinct and the climate changed. Humans adapted by maximizing the resources in local environments and eating a wider range of wild plants and hunting or catching smaller game. Domestication of plants and animals with early stages in the Old World Mesolithic and New World Archaic periods led to significant changes and reliance on agriculture in the Old World Neolithic and New World Formative stage; the agricultural life led to significant technological advancements. Although Paleolithic cultures left no written records, the shift from nomadic life to settlement and agriculture can be inferred from a range of archaeological evidence.
Such evidence includes ancient tools, cave paintings, other prehistoric art, such as the Venus of Willendorf. Human remains provide direct evidence, both through the examination of bones, the study of mummies. Though concrete evidence is limited and historians have been able to form significant inferences about the lifestyle and culture of various prehistoric peoples, the role technology played in their lives; the Lower Paleolithic period was the earliest subdivision of the Old Stone Age. It spans the time from around 2.5 million years ago when the first evidence of craft and use of stone tools by hominids appears in the current archaeological record, until around 300,000 years ago, spanning the Oldowan and Acheulean lithic technology. Early human used stone tool technology, such as a hand axe, similar to that used by primates, which are found to have intelligence levels of modern children aged 3 to 5 years. Intelligence and use of technology did not change much for millions of years; the first "Homo" species began with Homo habilis about 2.4 to 1.5 million years ago.
Homo habilis created. Homo ergaster lived in eastern and southern Africa about 2.5 to 1.7 million years ago and used more diverse and sophisticated stone tools than its predecessor, Homo habilis, including having refined the inherited Oldowan tools and developed the first Acheulean bifacial axes. Homo erectus lived about 1.8 to 1.3 million years ago in West Asia and Africa and is thought to be the first hominid to hunt in coordinated groups, use complex tools, care for infirm or weaker companions. Homo antecessor the earliest hominid in Northern Europe lived from 1.2 million to 800,000 years ago and used stone tools. Homo heidelbergensis lived between 600,000 and 400,000 years ago and used stone tool technology similar the Acheulean tools used by Homo erectus. European and Asian sites dating back 1.5 million years ago seem to indicate controlled use of fire by Homo erectus. A northern Israel site from about 690,000 to 790,000 years ago suggests. Homo heidelbergensis may have been the first species to bury their dead about 500,000 years ago.
The Middle Paleolithic period occurred in Europe and the Near East, during which the Neanderthals lived. The earliest evidence of settlement in Australia dates to around 40,000 years ago when modern humans crossed from Asia by island-hopping; the Bhimbetka rock shelters exhibit the earliest traces of human life in India, some of which are 30,000 years old. Homo neanderthalensis used Mousterian Stone tools that date back to around 300,000 years ago and include smaller, knife-like and scraper tools, they buried their dead in shallow graves along with stone tools and animal bones, although the reasons and significance of the burials are disputed. Homo sapiens, the only living species in the genus Homo, originated in Africa about 200,000 years ago; as compared to their predecessors, Homo sapiens had greater mental capability and ability to walk erect, which provided freed hands for manipulating objects and far greater use of tools. There was art created during this period. Intentional burial with grave goods, may be one of the earliest detectable forms of religious practice since it may signify a "concern for the dead that transcends daily life."
The earliest undisputed human burial so far dates back 130,000 years. Human skeletal remains stained with red ochre w
The common hippopotamus, or hippo, is a large herbivorous, semiaquatic mammal native to sub-Saharan Africa. It is one of only two extant species in the family Hippopotamidae, the other being the pygmy hippopotamus; the name comes from the ancient Greek for "river horse". After the elephant and rhinoceros, the common hippopotamus is the third-largest type of land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, the closest living relatives of the Hippopotamidae are cetaceans from which they diverged about 55 million years ago. Common hippos are recognisable by their barrel-shaped torsos, wide-opening mouths revealing large canine tusks, nearly hairless bodies, columnar legs and large size. Despite its stocky shape and short legs, it is capable of running 30 km/h over short distances; the common hippopotamus inhabits rivers and mangrove swamps, where territorial bulls preside over a stretch of river and groups of five to thirty females and young.
During the day, they remain cool by staying in the mud. They emerge at dusk to graze on grasses. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land; the hippopotamus is among the most dangerous animals in the world as it is aggressive and unpredictable. They are poaching for their meat and ivory canine teeth; the Latin word "hippopotamus" is derived from the ancient Greek ἱπποπόταμος, from ἵππος, hippos, "horse", ποταμός, potamos, "river", meaning "horse of the river". In English, the plural is "hippopotamuses", but "hippopotami" is used. Hippopotamuses are gregarious. A group is called a pod, dale, or bloat; the hippopotamus is the type genus of the family Hippopotamidae. The pygmy hippopotamus belongs to a different genus in Hippopotamidae, either Choeropsis or Hexaprotodon. Hippopotamidae are sometimes known as hippopotamids. Sometimes, the subfamily Hippopotaminae is used. Further, some taxonomists group hippopotamuses and anthracotheres in the superfamily Anthracotheroidea.
Hippopotamidae are classified along with other even-toed ungulates in the order Artiodactyla. Other artiodactyls include camels, cattle and pigs, although hippopotamuses are not related to these groups. Five subspecies of hippos have been described based on morphological differences in their skulls and geographical differences: Great northern hippopotamus or Nile hippopotamus H. a. amphibius – which stretched from Egypt, where they are now extinct, south up the Nile River to Tanzania and Mozambique East African hippopotamus H. a. kiboko – in Kenya in the African Great Lakes region, in Somalia in the Horn of Africa. Broader nasals and more hollowed interorbital region Cape hippopotamus or South African hippopotamus H. a. capensis – from Zambia to South Africa, most flattened skull of the subspecies West African hippopotamus or Tchad hippopotamus H. a. tschadensis – throughout Western Africa to, as the name suggests, Chad shorter and wider face, with prominent orbits Angola hippopotamus H. a. constrictus – in Angola, the southern Democratic Republic of Congo and Namibia, named for its deeper preorbital constrictionThe suggested subspecies were never used or validated by field biologists.
Genetic analyses have tested the existence of three of these putative subspecies. A study examining mitochondrial DNA from skin biopsies taken from 13 sampling locations, considered genetic diversity and structure among hippo populations across the continent; the authors found low, but significant, genetic differentiation among H. a. amphibius, H. a. capensis, H. a. kiboko. Neither H. a. tschadensis nor H. a. constrictus has been tested. Until 1909, naturalists grouped hippos with pigs, based on molar patterns. Several lines of evidence, first from blood proteins from molecular systematics and DNA and the fossil record, show that their closest living relatives are cetaceans – whales and porpoises; the common ancestor of hippos and whales branched off from Ruminantia and the rest of the even-toed ungulates. The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semiaquatic ancestor that branched off from other artiodactyls around 60 million years ago.
This hypothesized ancestral group split into two branches around 54 million years ago. One branch would evolve into cetaceans beginning about 52 million years ago, with the protowhale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which underwent aquatic adaptation into the aquatic cetaceans; the other branch became the anthracotheres, a large family of four-legged beasts, the earliest of which in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants. A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene species Merycopotamus and Libycosaurus and the latest anthracotheres in the Pliocene. Meryco