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 Stone Age was a broad prehistoric period during which stone was used to make implements with an edge, a point, or a percussion surface. The period lasted 3.4 million years and ended between 8700 BCE and 2000 BCE with the advent of metalworking. Stone Age artifacts include tools used by modern humans and by their predecessor species in the genus Homo, by the earlier contemporaneous genera Australopithecus and Paranthropus. Bone tools were used during this period as well but are preserved in the archaeological record; the Stone Age is further subdivided by the types of stone tools in use. The Stone Age is the first period in the three-age system of archaeology, which divides human technological prehistory into three periods: The Stone Age The Bronze Age The Iron Age The Stone Age is contemporaneous with the evolution of the genus Homo, the only exception being the early Stone Age, when species prior to Homo may have manufactured tools. According to the age and location of the current evidence, the cradle of the genus is the East African Rift System toward the north in Ethiopia, where it is bordered by grasslands.
The closest relative among the other living primates, the genus Pan, represents a branch that continued on in the deep forest, where the primates evolved. The rift served as a conduit for movement into southern Africa and north down the Nile into North Africa and through the continuation of the rift in the Levant to the vast grasslands of Asia. Starting from about 4 million years ago a single biome established itself from South Africa through the rift, North Africa, across Asia to modern China, called "transcontinental'savannahstan'" recently. Starting in the grasslands of the rift, Homo erectus, the predecessor of modern humans, found an ecological niche as a tool-maker and developed a dependence on it, becoming a "tool equipped savanna dweller"; the oldest indirect evidence found of stone tool use is fossilised animal bones with tool marks. Archaeological discoveries in Kenya in 2015, identifying the oldest known evidence of hominin use of tools to date, have indicated that Kenyanthropus platyops may have been the earliest tool-users known.
The oldest stone tools were excavated from the site of Lomekwi 3 in West Turkana, northwestern Kenya, date to 3.3 million years old. Prior to the discovery of these "Lomekwian" tools, the oldest known stone tools had been found at several sites at Gona, Ethiopia, on the sediments of the paleo-Awash River, which serve to date them. All the tools come from the Busidama Formation, which lies above a disconformity, or missing layer, which would have been from 2.9 to 2.7 mya. The oldest sites containing tools are dated to 2.6–2.55 mya. One of the most striking circumstances about these sites is that they are from the Late Pliocene, where previous to their discovery tools were thought to have evolved only in the Pleistocene. Excavators at the locality point out that: "...the earliest stone tool makers were skilled flintknappers.... The possible reasons behind this seeming abrupt transition from the absence of stone tools to the presence thereof include... gaps in the geological record."The species who made the Pliocene tools remains unknown.
Fragments of Australopithecus garhi, Australopithecus aethiopicus and Homo Homo habilis, have been found in sites near the age of the Gona tools. In July 2018, scientists reported the discovery in China of the oldest stone tools outside Africa, estimated at 2.12 million years old. Innovation of the technique of smelting ore began the Bronze Age; the first most significant metal manufactured was bronze, an alloy of copper and tin, each of, smelted separately. The transition from the Stone Age to the Bronze Age was a period during which modern people could smelt copper, but did not yet manufacture bronze, a time known as the Copper Age, or more technically the Chalcolithic, "copper-stone" age; the Chalcolithic by convention is the initial period of the Bronze Age. The Bronze Age was followed by the Iron Age; the transition out of the Stone Age occurred between 6000 BCE and 2500 BCE for much of humanity living in North Africa and Eurasia. The first evidence of human metallurgy dates to between the 5th and 6th millennium BCE in the archaeological sites of Majdanpek and Pločnik in modern-day Serbia, though not conventionally considered part of the Chalcolithic or "Copper Age", this provides the earliest known example of copper metallurgy.
Note the Rudna Glava mine in Serbia. Ötzi the Iceman, a mummy from about 3300 BCE carried with him a flint knife. In regions such as Sub-Saharan Africa, the Stone Age was followed directly by the Iron Age; the Middle East and southeastern Asian regions progressed past Stone Age technology around 6000 BCE. Europe, the rest of Asia became post-Stone Age societies by about 4000 BCE; the proto-Inca cultures of South America continued at a Stone Age level until around 2000 BCE, when gold and silver made their entrance. The Americas notably did not develop a widespread behavior of smelting Bronze or Iron after the Stone Age period, although the technology existed. Stone tool manufacture continued after the Stone Age ended in a given area. In Europe and North America, millstones were in use until well into the 20th century, still are in many parts of the world; the terms "Stone Age", "Bronze Age", "Iron Age" were never meant to suggest that advancement and time periods in prehistory are only measured by the type of tool material, rather than, for
In archaeology, in particular of the Stone Age, lithic reduction is the process of fashioning stones or rocks from their natural state into tools or weapons by removing some parts. It has been intensely studied and many archaeological industries are identified entirely by the lithic analysis of the precise style of their tools and the chaîne opératoire of the reduction techniques they used; the starting point is the selection of a piece of tool stone, detached by natural geological processes, is an appropriate size and shape. In some cases solid rock or larger boulders may be quarried and broken into suitable smaller pieces, in others the starting point may be a piece of the debitage, a flake removed from a previous operation to make a larger tool; the selected piece is called the lithic core. A basic distinction is that between flaked or chipped stone, the main subject here, ground stone objects made by grinding. Flaked stone reduction involves the use of a hard hammer percussor, such as a hammerstone, a soft hammer fabricator, or a wood or antler punch to detach lithic flakes from the lithic core.
As flakes are detached in sequence, the original mass of stone is reduced. Lithic reduction may be performed in order to obtain sharp flakes, of which a variety of tools can be made, or to rough out a blank for refinement into a projectile point, knife, or other object. Flakes of regular size that are at least twice as long as they are broad are called blades. Lithic tools produced this way may be unifacial. Cryptocrystalline or amorphous stone such as chert, flint and chalcedony, as well as other fine-grained stone material, such as rhyolite and quartzite, were used as a source material for producing stone tools; as these materials lack natural planes of separation, conchoidal fractures occur when they are struck with sufficient force. The propagation of force through the material takes the form of a Hertzian cone that originates from the point of impact and results in the separation of material from the objective piece in the form of a partial cone known as a lithic flake; this process is predictable, allows the flintknapper to control and direct the application of force so as to shape the material being worked.
Controlled experiments may be performed using glass cores and consistent applied force in order to determine how varying factors affect core reduction. It has been shown that stages in the lithic reduction sequence may be misleading and that a better way to assess the data is by looking at it as a continuum; the assumptions that archaeologists sometimes make regarding the reduction sequence based on the placement of a flake into a stage can be unfounded. For example, a significant amount of cortex can be present on a flake taken off near the end of the reduction sequence. Removed flakes exhibit features characteristic of conchoidal fracturing, including striking platforms, bulbs of force, eraillures. Flakes are quite sharp, with distal edges only a few molecules thick when they have a feather termination; these flakes can be used directly as tools or modified into other utilitarian implements, such as spokeshaves and scrapers. By understanding the complex processes of lithic reduction, archaeologists recognize that the pattern and amount of reduction contribute tremendous effect to lithic assemblage compositions.
One of the measurements is the geometric index of reduction. There are two elements in this index:'t' and'T'. The'T' is the'height' of maximum blank thickness and the't' is the height of retouched scar from the ventral surface; the ratio between t and T is the geometric index of reduction. In theory this ratio shall range between 0 and 1; the bigger the number is the larger amount of lost weight from lithic flake. By using a logarithmic scale, a linear relationship between the geometric index and the percentage of original flake weight lost through retouch is confirmed. In choosing a reduction index, it is important to understand the strengths and weaknesses of each method, how they fit to the intended research question, as different indices provide different levels of information. For example, Kuhn's geometric index of unifacial reduction, which describes the ratio of scar height relative to the flake thickness, is influenced by the morphology of the flake blank which limits the applicability of this reduction index.
Alongside the various percussion and manipulation techniques described below, there is evidence that heat was at least sometimes used. Experimental archaeology has demonstrated that heated stones are sometimes much easier to flake, with larger flakes being produced in flint, for example. In some cases the heating changes the colour of the stone. Percussion reduction, or percussion flaking, refers to removal of flakes by impact. A core or other objective piece, such as a formed tool, is held in one hand, struck with a hammer or percussor. Alternatively, the objective piece can be struck between a stationary anvil-stone, known as bipolar percussion. Percussion can be done by throwing the objective piece at an anvil stone; this is sometimes called projectile percussion. Percussors are traditionally either a stone cobble or pebble referred to as a hammerstone, or a billet made of bone, antler, or wood. Flakes are struck from a core using a punch, in which case the percussor never makes contact with the objective piece.
This technique is referred to
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
In archaeology, a celt is a long, prehistoric, stone or bronze tool similar to an adze, a hoe or axe-like tool. The term "celt" came about from what was probably a copyist's error in many medieval manuscript copies of Job 19:24 in the Latin Vulgate Bible, which became enshrined in the authoritative Sixto-Clementine printed edition of 1592. While this is now considered to be the case by most scholars, some are still prepared to consider the existence of a real Latin word. A "celt" was thus wrongly assumed to be a type of ancient chisel. Early eighteenth century antiquarians, such as Lorenz Beger adopted the word for the stone and bronze tools they were finding at prehistoric sites. A shoe-last celt was a polished stone tool used during the early European Neolithic for felling trees and woodworking. Palstave "Celt, a word in common use among British and French archaeologists to describe the hatchets, adzes or chisels of chipped or shaped stone used by primitive man". Encyclopædia Britannica. 1911
Quern-stones are stone tools for hand-grinding a wide variety of materials. They are used in pairs; the lower, stone is called a quern, while the upper mobile stone is called a handstone. The central hole is called a handle slot enables the handstone to be rotated, they were first used in the Neolithic era to grind cereals into flour. An old Gaelic proverb is "The quern performs best when the grindstone has been pitted." The upper stones were concave whilst the lower was convex and sometimes a rind was present as a piece of wood etc that allowed the cereal etc to be added but still acted as a centering device. The upper stone sometimes had a cup shaped area around the hopper hole with a raised edge. Most handstones have a handle hole on the upper surface, however one class of quern-stones have a slot handle which indicates that a piece of wood was placed horizontally and protruded out from the edge so that the operator could turn the stone by standing and using a rod vertically. One class of upper quern-stones has from two to three sockets for the rod used to turn them and this is thought to reflect the need to reduce wear and tear by having alternative points of contact when in active use.
Quern-stones have been used by numerous civilizations throughout the world to grind materials, the most important of, grain to make flour for bread-making. They were replaced by millstones once mechanised forms of milling appeared the water mill and the windmill, although animals were used to operate the millstones. However, in many non-Westernised, non-mechanised cultures they are still manufactured and used and have only been replaced in many parts of the world in the last century or so. In early Maya civilizations the process of nixtamalization was distinctive in that hard, ripe kernels of maize were boiled in water and lime, thus producing nixtamal, made into unleavened dough for flat cakes by grinding with a handstone on a quern. Quern stones were used in China at least 10,000 years ago to grind wheat into flour; the production of flour by rubbing wheat by hand took several hours. Due to their form and the nature of the treatment of the surfaces, they reproduce the most ancient implements used for grinding cereal grain into flour.
Saddle querns were known in China during the Neolithic Age but rotary stone mills did not appear until the Warring States Period. A prehistoric quern dating back to 23,000 BCE was found at the Longwangchan archaeological site, in Hukou, Shaanxi in 2007; the site is located in the heartland of the northern Chinese loess plateau near the Yellow River. As well as grain, ethnographic evidence and Mesopotamian texts show that a wide range of foodstuffs and inorganic materials were processed using stone querns or mortars, including nuts, fruit, herbs, meat, pigments and clay. Moreover, one study analysing quern-stones noted that a number of querns had traces of arsenic and bismuth, unlike their source rocks, had levels of antimony which were ten times higher than those of the rocks; the authors concluded that this was due to the use of these querns in the preparation of medicines, dyes or in the manufacture of alloys. Querns were used in grinding metals ores after mining extraction; the aim was to liberate fine ore particles which could be separated by washing for example, prior to smelting.
They were thus used in gold mining in antiquity. In the Shetlands tobacco was not smoked when first introduced, but instead was ground up into snuff, inhaled up the nose. Snuff-querns consisted of an lower stone, fixed together by a central iron pivot; the quern was held on the user's lap, the eye of the quern was filled with dried tobacco leaves, the upper-stone was turned using the handle. The friction caused by the turning ground the leaves into a fine powder that built up around the edge of the lower-stone. Many snuff-querns had a small hole or cut made near the edge of the upper-stone, into which a pointed end of a lamb's horn was placed in order to turn the stone. There are, more surprising recorded uses of quern-stones. For example, DeBoer, in his review of the traditional gambling games of North American tribes, reports that one of the games involved bouncing a group of split canes off a quern. Violence is recorded in the Book of Judges: “But a certain woman threw an upper-millstone on Abimelech’s head, crushed his skull.”
The best type of stone from which to manufacture quern-stones are igneous rocks such as basalt. These have rough surfaces, but grains do not detach so the material being ground does not become gritty. However, such rocks are not always available, meaning that quern-stones have been manufactured from a wide variety of rocks, including sandstone and limestone. Quernmore Crag near Lancaster in England is named after the quarrying of millstone grit used to make quern stones in these parts. Rutter was able to show, for the southern Levant, that basalt quern-stones were preferred to those manufactured from other rock types. Basalt quern-stones were therefore transported over long-distances, leading him to argue that, despite their every-day, utilitarian function, they were used as a status symbol. Research in Scotland has indicated. Knocking stones were used in the preparation of small quantities of cereal however the earliest forms of quern were the saddle and trough querns; the earliest quern so far was found at Abu Hureyra, Syria.
A development was the rotary quern, which takes several forms. The saddle quern is produced by rocking or rolling
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