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130-493: The Broken Mammoth site was occupied at least three separate times in its history, the last occupation occurring approximately 2,500 years ago. The oldest occupation of the site occurred between 11,000 and 12,000 years ago according to radiocarbon dating , making this one of the oldest sites in Alaska. It is possible that the site was occupied at approximately the same time as other Nenana complex sites in Alaska. Features found at

260-413: A red squirrel and a porcupine date the process of forestation at slightly more than 9,500 years ago. Windier conditions reestablished at Broken Mammoth around 10,000 BP with loess accumulation accelerating until about 7800 B.P. After this time modern conditions stabilized after 5700 B.P. The stratigraphy at Broken Mammoth is well preserved and is one of the primary factors that have helped establish

390-422: A beta particle (an electron , e ) and an electron antineutrino ( ν e ), one of the neutrons in the C nucleus changes to a proton and the C nucleus reverts to the stable (non-radioactive) isotope N . During its life, a plant or animal is in equilibrium with its surroundings by exchanging carbon either with the atmosphere or through its diet. It will, therefore, have

520-400: A concave shaped base. Points found at Broken Mammoth of these two type date to approximately 12,100 B.P. Radiocarbon dating of charcoal from hearths found at the site date to approximately to 10,290 B.P. and 12,270 B.P. At other Tanana River Valley sites such as Swan Point and Healey Lake, microblades were also found with these sites but curiously enough not at Broken Mammoth. The reasons for

650-527: A decade. It was revised again in the early 1960s to 5,730 ± 40 years, which meant that many calculated dates in papers published prior to this were incorrect (the error in the half-life is about 3%). For consistency with these early papers, it was agreed at the 1962 Radiocarbon Conference in Cambridge (UK) to use the "Libby half-life" of 5568 years. Radiocarbon ages are still calculated using this half-life, and are known as "Conventional Radiocarbon Age". Since

780-423: A few years, but the surface waters also receive water from the deep ocean, which has more than 90% of the carbon in the reservoir. Water in the deep ocean takes about 1,000 years to circulate back through surface waters, and so the surface waters contain a combination of older water, with depleted C , and water recently at the surface, with C in equilibrium with the atmosphere. Creatures living at

910-442: A fragment of bone, provides information that can be used to calculate when the animal or plant died. The older a sample is, the less C there is to be detected, and because the half-life of C (the period of time after which half of a given sample will have decayed) is about 5,730 years, the oldest dates that can be reliably measured by this process date to approximately 50,000 years ago (in this interval about 99.8% of

1040-408: A given sample stopped exchanging carbon – the older the sample, the less C will be left. The equation governing the decay of a radioactive isotope is: N = N 0 e − λ t {\displaystyle N=N_{0}\,e^{-\lambda t}\,} where N 0 is the number of atoms of the isotope in the original sample (at time t = 0, when

1170-400: A higher δ C than one that eats food with lower δ C values. The animal's own biochemical processes can also impact the results: for example, both bone minerals and bone collagen typically have a higher concentration of C than is found in the animal's diet, though for different biochemical reasons. The enrichment of bone C also implies that excreted material

1300-413: A mass of less than 1% of those on land and are not shown in the diagram. Accumulated dead organic matter, of both plants and animals, exceeds the mass of the biosphere by a factor of nearly 3, and since this matter is no longer exchanging carbon with its environment, it has a C / C ratio lower than that of the biosphere. The variation in the C / C ratio in different parts of

1430-401: A month and requires a sample about ten times as large as would be needed otherwise, but it allows more precise measurement of the C / C ratio in old material and extends the maximum age that can be reliably reported. Ivory Ivory is a hard, white material from the tusks (traditionally from elephants ) and teeth of animals, that consists mainly of dentine , one of

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1560-869: A paper in Science in 1947, in which the authors commented that their results implied it would be possible to date materials containing carbon of organic origin. Libby and James Arnold proceeded to test the radiocarbon dating theory by analyzing samples with known ages. For example, two samples taken from the tombs of two Egyptian kings, Zoser and Sneferu , independently dated to 2625 BC plus or minus 75 years, were dated by radiocarbon measurement to an average of 2800 BC plus or minus 250 years. These results were published in Science in December 1949. Within 11 years of their announcement, more than 20 radiocarbon dating laboratories had been set up worldwide. In 1960, Libby

1690-401: A protective measure against predators. Alongside the use of protective measures, the tusks were used during the mating season to be used for dominance, as their antlers were smaller back then compared to now. Evolution made the antlers bigger and the use of their tusks diminished as antlers grew, making them nothing more than teeth in their mouths. These teeth have the same chemical compound as

1820-424: A quartz chopper/scraper/plane. Also found at this zone are several ivory tusk fragments with scratches that could have come from stone tools. One tusk fragment has a stone microchip embedded in one of the scratches bolstering this theory. A cache was also found with ivory artifacts, two points, and a possible handle. One of the ivory fragments from this cache was radiocarbon dated to approximately 15,800 B.P. The age of

1950-483: A range of items from ivory carvings to false teeth , piano keys , fans , and dominoes . Elephant ivory is the most important source, but ivory from mammoth , walrus , hippopotamus , sperm whale , orca , narwhal and warthog are used as well. Elk also have two ivory teeth, which are believed to be the remnants of tusks from their ancestors. The national and international trade in natural ivory of threatened species such as African and Asian elephants

2080-549: A rock crusher. The Wildlife Conservation Society has pointed out that the global ivory trade leads to the slaughter of up to 35,000 elephants a year in Africa. In June 2018, Conservative MEPs' Deputy Leader Jacqueline Foster MEP urged the EU to follow the UK's lead and introduce a tougher ivory ban across Europe. China was the biggest market for poached ivory but announced they would phase out

2210-629: A sample. More recently, accelerator mass spectrometry has become the method of choice; it counts all the C atoms in the sample and not just the few that happen to decay during the measurements; it can therefore be used with much smaller samples (as small as individual plant seeds), and gives results much more quickly. The development of radiocarbon dating has had a profound impact on archaeology . In addition to permitting more accurate dating within archaeological sites than previous methods, it allows comparison of dates of events across great distances. Histories of archaeology often refer to its impact as

2340-503: A strong anisotropy to ivory's mechanical characteristics. Separate hardness measurements on three orthogonal tusk directions indicated that circumferential planes of tusk had up to 25% greater hardness than radial planes of the same specimen. During hardness testing, inelastic and elastic recovery was observed on circumferential planes while the radial planes displayed plastic deformation. This implies that ivory has directional viscoelasticity . These anisotropic properties can be explained by

2470-402: A well-preserved display of animal resources, most notably of large animals including mammoth , elk , caribou and bison . It appears that large animals, particularly bison and elk were important. It is possible inhabitants even hunted or scavenged mammoth, however they more than likely butchered any mammoth kills away from the site. No post cranial elements of mammoth remains have been found at

2600-620: Is a method for determining the age of an object containing organic material by using the properties of radiocarbon , a radioactive isotope of carbon . The method was developed in the late 1940s at the University of Chicago by Willard Libby , based on the constant creation of radiocarbon ( C ) in the Earth's atmosphere by the interaction of cosmic rays with atmospheric nitrogen . The resulting C combines with atmospheric oxygen to form radioactive carbon dioxide , which

2730-429: Is also referred to individually as a carbon exchange reservoir. The different elements of the carbon exchange reservoir vary in how much carbon they store, and in how long it takes for the C generated by cosmic rays to fully mix with them. This affects the ratio of C to C in the different reservoirs, and hence the radiocarbon ages of samples that originated in each reservoir. The atmosphere, which

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2860-414: Is assumed to have originally had the same C / C ratio as the ratio in the atmosphere, and since the size of the sample is known, the total number of atoms in the sample can be calculated, yielding N 0 , the number of C atoms in the original sample. Measurement of N , the number of C atoms currently in the sample, allows the calculation of t , the age of the sample, using

2990-440: Is contaminated so that 1% of the sample is modern carbon, it will appear to be 600 years younger; for a sample that is 34,000 years old, the same amount of contamination would cause an error of 4,000 years. Contamination with old carbon, with no remaining C , causes an error in the other direction independent of age – a sample contaminated with 1% old carbon will appear to be about 80 years older than it truly is, regardless of

3120-428: Is depleted in C because of the marine effect, C is removed from the southern atmosphere more quickly than in the north. The effect is strengthened by strong upwelling around Antarctica. If the carbon in freshwater is partly acquired from aged carbon, such as rocks, then the result will be a reduction in the C / C ratio in the water. For example, rivers that pass over limestone , which

3250-400: Is depleted in C relative to the diet. Since C makes up about 1% of the carbon in a sample, the C / C ratio can be accurately measured by mass spectrometry . Typical values of δ C have been found by experiment for many plants, as well as for different parts of animals such as bone collagen , but when dating a given sample it is better to determine

3380-426: Is done by calibration curves (discussed below), which convert a measurement of C in a sample into an estimated calendar age. The calculations involve several steps and include an intermediate value called the "radiocarbon age", which is the age in "radiocarbon years" of the sample: an age quoted in radiocarbon years means that no calibration curve has been used − the calculations for radiocarbon years assume that

3510-517: Is illegal. The word ivory ultimately derives from the ancient Egyptian âb, âbu ('elephant'), through the Latin ebor- or ebur . Both the Greek and Roman civilizations practiced ivory carving to make large quantities of high value works of art, precious religious objects, and decorative boxes for costly objects. Ivory was often used to form the white of the eyes of statues. There

3640-532: Is inadequately seen at the Broken Mammoth site; only a few flakes and bones are directly dated to within this time period with no microblades being found yet at this time. The Transitional Period followed the Beringian Period from 13,000 B.P. to 9,500 B.P. Two types of Chindadn points are associated with this time period, Chindadn point two being triangular shaped and Chindadn point three having

3770-409: Is incorporated into plants by photosynthesis ; animals then acquire C by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and thereafter the amount of C it contains begins to decrease as the C undergoes radioactive decay . Measuring the proportion of C in a sample from a dead plant or animal, such as a piece of wood or

3900-459: Is less CO 2 available for the photosynthetic reactions. Under these conditions, fractionation is reduced, and at temperatures above 14 °C (57 °F) the δ C values are correspondingly higher, while at lower temperatures, CO 2 becomes more soluble and hence more available to marine organisms. The δ C value for animals depends on their diet. An animal that eats food with high δ C values will have

4030-460: Is located on a bluff overlooking the Tanana River. Charles E. Holmes found the site in the summer of 1989 while he was conducting an archaeological survey in the area. Holmes named the site Broken Mammoth because of a piece of broken mammoth bone Holmes found on the slope at the front of the site. Preliminary excavations of the site began in 1990 by Holmes and David Yesner with excavations on

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4160-415: Is mostly composed of calcium carbonate , will acquire carbonate ions. Similarly, groundwater can contain carbon derived from the rocks through which it has passed. These rocks are usually so old that they no longer contain any measurable C , so this carbon lowers the C / C ratio of the water it enters, which can lead to apparent ages of thousands of years for both the affected water and

4290-450: Is no direct dating for B3. Unit C dates to sometime after 9,000 B.P with the final unit (Unit D) being an accumulation of silt deposits over the last 8,000 to 9,000 years. The resources of the region were diverse and plentiful, with large mammals; birds (mostly waterfowl) and the occupants of this region exploited some fish as well. Avian fauna is extremely diverse including mallard , teal , swan and geese . The Broken Mammoth site boasts

4420-419: Is now used to convert a given measurement of radiocarbon in a sample into an estimate of the sample's calendar age. Other corrections must be made to account for the proportion of C in different types of organisms (fractionation), and the varying levels of C throughout the biosphere (reservoir effects). Additional complications come from the burning of fossil fuels such as coal and oil, and from

4550-641: Is some evidence of either whale or walrus ivory used by the ancient Irish. Solinus , a Roman writer in the 3rd century claimed that the Celtic peoples in Ireland would decorate their sword-hilts with the 'teeth of beasts that swim in the sea'. Adomnan of Iona wrote a story about St Columba giving a sword decorated with carved ivory as a gift that a penitent would bring to his master so he could redeem himself from slavery. The Syrian and North African elephant populations were reduced to extinction, probably due to

4680-456: Is sometimes called) percolates into the rest of the reservoir. Photosynthesis is the primary process by which carbon moves from the atmosphere into living things. In photosynthetic pathways C is absorbed slightly more easily than C , which in turn is more easily absorbed than C . The differential uptake of the three carbon isotopes leads to C / C and C / C ratios in plants that differ from

4810-453: Is the main pathway by which C is created: n + 7 N → 6 C + p where n represents a neutron and p represents a proton . Once produced, the C quickly combines with the oxygen ( O ) in the atmosphere to form first carbon monoxide ( CO ), and ultimately carbon dioxide ( CO 2 ). C + O 2 → CO + O CO + OH → CO 2 + H Carbon dioxide produced in this way diffuses in

4940-702: Is used today to make handcrafted knives and similar implements. Mammoth ivory is rare and costly because mammoths have been extinct for millennia, and scientists are hesitant to sell museum-worthy specimens in pieces. Some estimates suggest that 10 or more million mammoths are still buried in Siberia. Fossil walrus ivory from animals that died before 1972 is legal to buy and sell in the United States, unlike many other types of ivory. The ancestors of elk had teeth, also known as elk ivory, that protruded outwards, similar to animals that have tusks, they were used as

5070-565: Is usually needed to determine the size of the offset, for example by comparing the radiocarbon age of deposited freshwater shells with associated organic material. Volcanic eruptions eject large amounts of carbon into the air. The carbon is of geological origin and has no detectable C , so the C / C ratio in the vicinity of the volcano is depressed relative to surrounding areas. Dormant volcanoes can also emit aged carbon. Plants that photosynthesize this carbon also have lower C / C ratios: for example, plants in

5200-399: Is where C is generated, contains about 1.9% of the total carbon in the reservoirs, and the C it contains mixes in less than seven years. The ratio of C to C in the atmosphere is taken as the baseline for the other reservoirs: if another reservoir has a lower ratio of C to C , it indicates that the carbon is older and hence that either some of

5330-402: The C has decayed, or the reservoir is receiving carbon that is not at the atmospheric baseline. The ocean surface is an example: it contains 2.4% of the carbon in the exchange reservoir, but there is only about 95% as much C as would be expected if the ratio were the same as in the atmosphere. The time it takes for carbon from the atmosphere to mix with the surface ocean is only

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5460-526: The C will have decayed), although special preparation methods occasionally make an accurate analysis of older samples possible. In 1960, Libby received the Nobel Prize in Chemistry for his work. Research has been ongoing since the 1960s to determine what the proportion of C in the atmosphere has been over the past 50,000 years. The resulting data, in the form of a calibration curve ,

5590-489: The C / C ratio in the atmosphere. This increase in C concentration almost exactly cancels out the decrease caused by the upwelling of water (containing old, and hence C -depleted, carbon) from the deep ocean, so that direct measurements of C radiation are similar to measurements for the rest of the biosphere. Correcting for isotopic fractionation, as is done for all radiocarbon dates to allow comparison between results from different parts of

5720-404: The δ C value for that sample directly than to rely on the published values. The carbon exchange between atmospheric CO 2 and carbonate at the ocean surface is also subject to fractionation, with C in the atmosphere more likely than C to dissolve in the ocean. The result is an overall increase in the C / C ratio in the ocean of 1.5%, relative to

5850-555: The "Accra Declaration" calling for a total ivory trade ban, and twenty range states attended a meeting in Kenya calling for a 20-year moratorium in 2007. Methods of obtaining ivory can be divided into: The use and trade of elephant ivory have become controversial because they have contributed to seriously declining elephant populations in many countries. It is estimated that consumption in Great Britain alone in 1831 amounted to

5980-677: The "radiocarbon revolution". Radiocarbon dating has allowed key transitions in prehistory to be dated, such as the end of the last ice age , and the beginning of the Neolithic and Bronze Age in different regions. In 1939, Martin Kamen and Samuel Ruben of the Radiation Laboratory at Berkeley began experiments to determine if any of the elements common in organic matter had isotopes with half-lives long enough to be of value in biomedical research. They synthesized C using

6110-449: The Broken Mammoth site establishes that human occupation of central Alaska began sometime before 11,000 B.P. There is evidence to suggest that humans occupied parts of central Alaska before 13,500 B.P. with the possibility that people lived in the region even earlier. The artifacts discovered at Broken Mammoth suggest earlier occupation in northwest and east Alaska as evident by the presence of obsidian materials. The absence of microblades in

6240-410: The Broken Mammoth site however the obvious use of mammoth tusks as tools make it clear that the inhabitants of the area had access to such remains. Radiocarbon dates some of the fossilized ivory from 20,000 B.P. to 18,000 B.P. clearly indicating that it was collected for use as tools. However ivory from the oldest levels at Broken Mammoth dates to approximately 13, 525 B.P. and coincides with the dating of

6370-523: The Indian elephant in their annual tribute caravans to China. Chinese craftsmen carved ivory to make everything from images of deities to the pipe stems and end pieces of opium pipes . In Japan, ivory carvings became popular in the 17th century during the Edo period , and many netsuke and kiseru , on which animals and legendary creatures were carved, and inro , on which ivory was inlaid, were made. From

6500-893: The Origins of the First Americans. Albuquerque: University of New Mexico, 1993. ISBN   0-8263-1480-5 Hoffecker, John F. A Prehistory of the North: Human Settlement of the Higher Latitudes. New Brunswick, NJ: Rutgers UP, 2005. ISBN   0-8135-3468-2 West, Frederick Hadleigh., and Constance F. West. American Beginnings: the Prehistory and Palaeoecology of Beringia. Chicago: University of Chicago, 1996 ISBN   0-226-89399-5 Radiocarbon dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating )

6630-689: The Philippines, ivory was also used to craft the faces and hands of Catholic icons and images of saints prevalent in the Santero culture. Tooth and tusk ivory can be carved into a vast variety of shapes and objects. Examples of modern carved ivory objects are okimono , netsukes , jewelry, flatware handles, furniture inlays, and piano keys. Additionally, warthog tusks, and teeth from sperm whales , orcas and hippos can also be scrimshawed or superficially carved, thus retaining their morphologically recognizable shapes. As trade with Africa expanded during

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6760-549: The Tanana River Valley have reliably dated to this period, Swan Point , Mead site, and Broken Mammoth. The Broken Mammoth site can be considered a part of the Nenana complex of tool manufacturing and techniques. The Chindadn complex dates to 13,500 B.P. to 13,000 B.P. The lithics from this period are small triangular or teardrop-shaped bifaces, usually made of thin flake and often poorly flaked. The Chindadn complex

6890-399: The above-ground nuclear tests performed in the 1950s and 1960s. Because the time it takes to convert biological materials to fossil fuels is substantially longer than the time it takes for its C to decay below detectable levels, fossil fuels contain almost no C . As a result, beginning in the late 19th century, there was a noticeable drop in the proportion of C in

7020-454: The absence of microblade technology of this time period at Broken Mammoth remain unclear. The remains of several hearths have been found at Broken Mammoth with the radiocarbon dating of the charcoal providing sound evidence for the age of the site. A shallow pit hearth feature was excavated with a radiocarbon date of approximately 4524 years ago and is associated with several flakes and obsidian microblades. This hearth demonstrates that there

7150-399: The actual calendar date, both because it uses the wrong value for the half-life of C , and because no correction (calibration) has been applied for the historical variation of C in the atmosphere over time. Carbon is distributed throughout the atmosphere, the biosphere, and the oceans; these are referred to collectively as the carbon exchange reservoir, and each component

7280-566: The age of the site. The site consists of Aeolian sediments (sand and loess) overlying weathered bedrock of the Yukon-Tanana crystalline terrace. The deposits are divided in four units: A, B, C and D with the oldest layer being unit A. Unit A is composed of fine sand dating to approximately 12,000 B.P. Units B, C, and D are made up of Aeolian silt or loess. Unit B contains three different palaeosol complexes with B1 dating to 11,800 B.P. to 11,200 B.P, B2 dates to 10,300 B.P. to 9,300 B.P while there

7410-418: The appropriate correction for the location of their samples. The effect also applies to marine organisms such as shells, and marine mammals such as whales and seals, which have radiocarbon ages that appear to be hundreds of years old. The northern and southern hemispheres have atmospheric circulation systems that are sufficiently independent of each other that there is a noticeable time lag in mixing between

7540-554: The artifacts originated from Batza Tena in northwest Alaska and from the Wrangell–St. Elias National Park and Preserve area in east Alaska. This implies that older sites must exist because the raw materials must have been obtained and then distributed to other regions through trade and interaction. Until these sites are discovered we will not know when the occupation of the Beringian straits began, until then Broken Mammoth establishes

7670-457: The atmosphere as the carbon dioxide generated from burning fossil fuels began to accumulate. Conversely, nuclear testing increased the amount of C in the atmosphere, which reached a maximum in about 1965 of almost double the amount present in the atmosphere prior to nuclear testing. Measurement of radiocarbon was originally done with beta-counting devices, which counted the amount of beta radiation emitted by decaying C atoms in

7800-438: The atmosphere might be expected to decrease over thousands of years, but C is constantly being produced in the lower stratosphere and upper troposphere , primarily by galactic cosmic rays , and to a lesser degree by solar cosmic rays. These cosmic rays generate neutrons as they travel through the atmosphere which can strike nitrogen-14 ( N ) atoms and turn them into C . The following nuclear reaction

7930-547: The atmosphere, is dissolved in the ocean, and is taken up by plants via photosynthesis . Animals eat the plants, and ultimately the radiocarbon is distributed throughout the biosphere . The ratio of C to C is approximately 1.25 parts of C to 10 parts of C . In addition, about 1% of the carbon atoms are of the stable isotope C . The equation for the radioactive decay of C is: 6 C → 7 N + e + ν e By emitting

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8060-421: The atmospheric C / C ratio has not changed over time. Calculating radiocarbon ages also requires the value of the half-life for C . In Libby's 1949 paper he used a value of 5720 ± 47 years, based on research by Engelkemeir et al. This was remarkably close to the modern value, but shortly afterwards the accepted value was revised to 5568 ± 30 years, and this value was in use for more than

8190-492: The ban, disallowing any sales of ivory on eBay. A more recent sale in 2008 of 108 tonnes from the three countries and South Africa took place to Japan and China. The inclusion of China as an "approved" importing country created enormous controversy, despite being supported by CITES, the World Wide Fund for Nature and Traffic . They argued that China had controls in place and the sale might depress prices. However,

8320-425: The biosphere, gives an apparent age of about 400 years for ocean surface water. Libby's original exchange reservoir hypothesis assumed that the C / C ratio in the exchange reservoir is constant all over the world, but it has since been discovered that there are several causes of variation in the ratio across the reservoir. The CO 2 in the atmosphere transfers to the ocean by dissolving in

8450-454: The calibration curve (IntCal) also reports past atmospheric C concentration using this conventional age, any conventional ages calibrated against the IntCal curve will produce a correct calibrated age. When a date is quoted, the reader should be aware that if it is an uncalibrated date (a term used for dates given in radiocarbon years) it may differ substantially from the best estimate of

8580-435: The carbon exchange reservoir means that a straightforward calculation of the age of a sample based on the amount of C it contains will often give an incorrect result. There are several other possible sources of error that need to be considered. The errors are of four general types: In the early years of using the technique, it was understood that it depended on the atmospheric C / C ratio having remained

8710-500: The carbon exchange reservoir, but because of the long delay in mixing with the deep ocean, the actual effect is a 3% reduction. A much larger effect comes from above-ground nuclear testing, which released large numbers of neutrons into the atmosphere, resulting in the creation of C . From about 1950 until 1963, when atmospheric nuclear testing was banned , it is estimated that several tonnes of C were created. If all this extra C had immediately been spread across

8840-435: The date of the sample. Samples for dating need to be converted into a form suitable for measuring the C content; this can mean conversion to gaseous, liquid, or solid form, depending on the measurement technique to be used. Before this can be done, the sample must be treated to remove any contamination and any unwanted constituents. This includes removing visible contaminants, such as rootlets that may have penetrated

8970-686: The deaths of nearly 4,000 elephants. In 1975, the Asian elephant was placed on Appendix I of the Convention on International Trade in Endangered Species ( CITES ), which prevents international trade between member states of species that are threatened by trade. The African elephant was placed on Appendix I in January 1990. Since then, some southern African countries have had their populations of elephants "downlisted" to Appendix II, allowing

9100-669: The demand for ivory in the Classical world . The Chinese have long valued ivory for both art and utilitarian objects. Early reference to the Chinese export of ivory is recorded after the Chinese explorer Zhang Qian ventured to the west to form alliances to enable the eventual free movement of Chinese goods to the west; as early as the first century BC, ivory was moved along the Northern Silk Road for consumption by western nations. Southeast Asian kingdoms included tusks of

9230-514: The desired form. Other applications, such as ivory piano keys, introduce repeated wear and surface handling of the material. It is therefore essential to consider the mechanical properties of ivory when designing alternatives. Elephant tusks are the animal's incisors, so the composition of ivory is unsurprisingly similar to that of teeth in several other mammals. It is composed of dentine, a biomineral composite constructed from collagen fibers mineralized with hydroxyapatite . This composite lends ivory

9360-603: The domestic trade of non-ivory items; there have also been two "one off" sales of ivory stockpiles. In June 2015, more than a ton of confiscated ivory was crushed in New York City 's Times Square by the Wildlife Conservation Society to send a message that the illegal trade will not be tolerated. The ivory, confiscated in New York and Philadelphia , was sent up a conveyor belt into

9490-524: The earliest date between 11,000 B.P. and 12,000 B.P. Other artifacts from Cultural Zone 1 include a nearly complete lanceolate point. Cultural Zone 2 has only produced a few flakes, fire-broken rocks and hearthstones though there is the possibility that microblades could be excavated closer to the bluff edge. Excavations at Cultural Zone 3 at the site have yielded many tiny flakes, retouched flakes, larger biface fragments, points and point fragment, hammers made of quartz , and anvils. A small-eyed bone needle

9620-494: The early 20th century hence gives an apparent date older than the true date. For the same reason, C concentrations in the neighbourhood of large cities are lower than the atmospheric average. This fossil fuel effect (also known as the Suess effect, after Hans Suess, who first reported it in 1955) would only amount to a reduction of 0.2% in C activity if the additional carbon from fossil fuels were distributed throughout

9750-401: The entire carbon exchange reservoir, it would have led to an increase in the C / C ratio of only a few per cent, but the immediate effect was to almost double the amount of C in the atmosphere, with the peak level occurring in 1964 for the northern hemisphere, and in 1966 for the southern hemisphere. The level has since dropped, as this bomb pulse or "bomb carbon" (as it

9880-424: The equation above. The half-life of a radioactive isotope (usually denoted by t 1/2 ) is a more familiar concept than the mean-life, so although the equations above are expressed in terms of the mean-life, it is more usual to quote the value of C 's half-life than its mean-life. The currently accepted value for the half-life of C is 5,700 ± 30 years. This means that after 5,700 years, only half of

10010-471: The errors caused by the variation over time in the C / C ratio. These curves are described in more detail below . Coal and oil began to be burned in large quantities during the 19th century. Both are sufficiently old that they contain little or no detectable C and, as a result, the CO 2 released substantially diluted the atmospheric C / C ratio. Dating an object from

10140-586: The first half of the 20th century, Kenyan elephant herds were devastated because of demand for ivory, to be used for piano keys. During the Art Deco era from 1912 to 1940, dozens (if not hundreds) of European artists used ivory in the production of chryselephantine statues. Two of the most frequent users of ivory in their sculptured artworks were Ferdinand Preiss and Claire Colinet . While many uses of ivory are purely ornamental in nature, it often must be carved and manipulated into different shapes to achieve

10270-535: The first part of the 1800s, ivory became readily available. Up to 90 percent of the ivory imported into the United States was processed, at one time, in Connecticut where Deep River and Ivoryton in 1860s became the centers of ivory milling, in particular, due to the demand for ivory piano keys. Ivory usage in the last thirty years has moved towards mass production of souvenirs and jewelry. In Japan,

10400-908: The former is much easier to measure, and the latter can be easily derived: the depletion of C relative to C is proportional to the difference in the atomic masses of the two isotopes, so the depletion for C is twice the depletion of C . The fractionation of C , known as δ C , is calculated as follows: δ C 13 = ( ( C 13 C 12 ) sample ( C 13 C 12 ) standard − 1 ) × 1000 {\displaystyle \delta {\ce {^{13}C}}=\left({\frac {\left({\frac {{\ce {^{13}C}}}{{\ce {^{12}C}}}}\right)_{\text{sample}}}{\left({\frac {{\ce {^{13}C}}}{{\ce {^{12}C}}}}\right)_{\text{standard}}}}-1\right)\times 1000} ‰ where

10530-415: The hearth charcoal at the site that falls within that time period suggesting that the people of the region had contact with living mammoths. The evidence of this site suggests highly mobile groups who moved seasonally over the landscapes. The people exploited the various resources and wildlife by intercepting the various migratory routes of the herd animals (bison and elk) and migratory birds . The people of

10660-466: The hunting methods and food resources utilized by the early peoples in North America. . "Stratigraphy and Chronology." Broken Mammoth Archaeological Project . Alaska Department of Natural Resources, Division of Parks and Outdoor Rec., 08/Nov/2011. Web. 13 Apr 2012. < https://web.archive.org/web/20120630010133/http://dnr.alaska.gov/parks/oha/mammoth/mammoth4.htm%3E . Dixon, E. James. Quest for

10790-612: The impressive mechanical properties—high stiffness, strength, hardness, and toughness—required for its use in the animal's day-to-day activities. Ivory has a measured hardness of 35 on the Vickers scale , exceeding that of bone. It also has a flexural modulus of 14 GPa, a flexural strength of 378 MPa a fracture toughness of 2.05 MPam . These measured values indicate that ivory mechanically outperforms most of its most common alternatives, including celluloid plastic and polyethylene terephthalate . Ivory's mechanical properties result from

10920-527: The increase in wealth sparked consumption of solid ivory hanko – name seals – which before this time had been made of wood. These hanko can be carved out in a matter of seconds using machinery and were partly responsible for massive African elephant decline in the 1980s, when the African elephant population went from 1.3 million to around 600,000 in ten years. Before plastics were introduced, ivory had many ornamental and practical uses, mainly because of

11050-454: The initial C will remain; a quarter will remain after 11,400 years; an eighth after 17,100 years; and so on. The above calculations make several assumptions, such as that the level of C in the atmosphere has remained constant over time. In fact, the level of C in the atmosphere has varied significantly and as a result, the values provided by the equation above have to be corrected by using data from other sources. This

11180-404: The inner tree rings do not get their C replenished and instead only lose C through radioactive decay. Hence each ring preserves a record of the atmospheric C / C ratio of the year it grew in. Carbon-dating the wood from the tree rings themselves provides the check needed on the atmospheric C / C ratio: with a sample of known date, and a measurement of

11310-423: The ivory found in the highly used and poached elephant tusks, making it another good alternative when it comes to taking ivory as the teeth can be possibly removed without harming the elk themselves. Among Indian tribes, elk teeth has major significance when it comes to jewelry. Among women, men wore them as well. Either through bracelets, earrings, and chokers, there was deeper meaning for both men and women within

11440-505: The ivory suggests that it was scavenged by the occupants from a much older kill site as opposed to the inhabitants killing and processing the mammoth themselves. The obsidian that was used at this site came from Wiki Peak source, and it was dated as early as 13,400 cal BP. Such obsidian was also used at the Walker Road, Alaska site, and Moose Creek, Alaska site in the same area—all dating to before 13,000 cal BP. The discovery of

11570-673: The laboratory's cyclotron accelerator and soon discovered that the atom's half-life was far longer than had been previously thought. This was followed by a prediction by Serge A. Korff , then employed at the Franklin Institute in Philadelphia , that the interaction of thermal neutrons with N in the upper atmosphere would create C . It had previously been thought that C would be more likely to be created by deuterons interacting with C . At some time during World War II, Willard Libby , who

11700-490: The legal domestic manufacture and sale of ivory products in May 2015. In September of the same year, China and the U.S. announced they would "enact a nearly complete ban on the import and export of ivory." The Chinese market has a high degree of influence on the elephant population. Trade in the ivory from the tusks of dead woolly mammoths frozen in the tundra has occurred for 300 years and continues to be legal . Mammoth ivory

11830-400: The lower loess levels at the site suggests that occupants of the site predated microblade technology. However Holmes argues that the absence of the technology at the site does not prove it did not exist during that time period as comparable sites do suggest such technology. Until The Broken Mammoth site offers excellent preservation of remains of the animals, providing archaeologists insight into

11960-541: The microstructure of the dentine tissue. It is thought that the structural arrangement of mineralized collagen fibers could contribute to the checkerboard-like Schreger pattern observed in polished ivory samples. This is often used as an attribute in ivory identification. As well as being an optical feature, the Schreger pattern could point towards a micropattern well-designed to prevent crack propagation by dispersing stresses. Additionally, this intricate microstructure lends

12090-553: The mid-1800s, the new Meiji government's policy of promoting and exporting arts and crafts led to the frequent display of elaborate ivory crafts at World's fair . Among them, the best works were admired because they were purchased by Western museums, wealthy people, and the Japanese Imperial Family . The Buddhist cultures of Southeast Asia , including Myanmar , Thailand , Laos and Cambodia , traditionally harvested ivory from their domesticated elephants. Ivory

12220-510: The neighbourhood of the Furnas caldera in the Azores were found to have apparent ages that ranged from 250 years to 3320 years. Any addition of carbon to a sample of a different age will cause the measured date to be inaccurate. Contamination with modern carbon causes a sample to appear to be younger than it really is: the effect is greater for older samples. If a sample that is 17,000 years old

12350-554: The occupation of the Tanana River Valley. Artifacts found at the Broken Mammoth site in Cultural Zone 1 include retouched flakes, end and side scrapers, points and point fragments, flake burins, burin spalls, microblades and microblade cores. The materials that these artifacts were made from include rhyolite , chalcedony , chert , basalt and obsidian (the latter providing even more evidence towards an even earlier peopling of North America.) The obsidian that comprised some of

12480-420: The ocean surface have the same C ratios as the water they live in, and as a result of the reduced C / C ratio, the radiocarbon age of marine life is typically about 400 years. Organisms on land are in closer equilibrium with the atmosphere and have the same C / C ratio as the atmosphere. These organisms contain about 1.3% of the carbon in the reservoir; sea organisms have

12610-635: The organism from which the sample was taken died), and N is the number of atoms left after time t . λ is a constant that depends on the particular isotope; for a given isotope it is equal to the reciprocal of the mean-life – i.e. the average or expected time a given atom will survive before undergoing radioactive decay. The mean-life, denoted by τ , of C is 8,267 years, so the equation above can be rewritten as: t = ln ⁡ ( N 0 / N ) ⋅ 8267 years {\displaystyle t=\ln(N_{0}/N)\cdot {\text{8267 years}}} The sample

12740-578: The physical structures of teeth and tusks. The chemical structure of the teeth and tusks of mammals is the same, regardless of the species of origin, but ivory contains structures of mineralised collagen . The trade in certain teeth and tusks other than elephant is well established and widespread; therefore, "ivory" can correctly be used to describe any mammalian teeth or tusks of commercial interest which are large enough to be carved or scrimshawed . Besides natural ivory, ivory can also be produced synthetically, hence (unlike natural ivory) not requiring

12870-454: The piano industry abandoned ivory as a key covering material in the 1970s. Ivory can be taken from dead animals – however, most ivory came from elephants that were killed for their tusks. For example, in 1930 to acquire 40 tons of ivory required the killing of approximately 700 elephants. Other animals which are now endangered were also preyed upon, for example, hippos, which have very hard white ivory prized for making artificial teeth. In

13000-440: The plants and freshwater organisms that live in it. This is known as the hard water effect because it is often associated with calcium ions, which are characteristic of hard water; other sources of carbon such as humus can produce similar results, and can also reduce the apparent age if they are of more recent origin than the sample. The effect varies greatly and there is no general offset that can be applied; additional research

13130-413: The pre-existing Egyptian chronology nor the new radiocarbon dating method could be assumed to be accurate, but a third possibility was that the C / C ratio had changed over time. The question was resolved by the study of tree rings : comparison of overlapping series of tree rings allowed the construction of a continuous sequence of tree-ring data that spanned 8,000 years. (Since that time

13260-567: The price of ivory in China has skyrocketed. Some believe this may be due to deliberate price fixing by those who bought the stockpile, echoing the warnings from the Japan Wildlife Conservation Society on price-fixing after sales to Japan in 1997, and monopoly given to traders who bought stockpiles from Burundi and Singapore in the 1980s. A 2019 peer-reviewed study reported that the rate of African elephant poaching

13390-405: The ratios in the atmosphere. This effect is known as isotopic fractionation. To determine the degree of fractionation that takes place in a given plant, the amounts of both C and C isotopes are measured, and the resulting C / C ratio is then compared to a standard ratio known as PDB. The C / C ratio is used instead of C / C because

13520-411: The region were hunters of large game such as bison but there is very little evidence that suggests they hunted mammoths. It can be theorized that the technology they had could allow for the opportunistic hunting on mammoths but it is highly unlikely that mammoth was a key resource for these people. It is much more likely that the ivory tools made from mammoth tusks were scavenged. The Broken Mammon site

13650-449: The reinforcement of collagen fibers in the composite oriented along the circumference. Owing to the rapid decline in the populations of the animals that produce it, the importation and sale of ivory in many countries is banned or severely restricted. In the ten years preceding a decision in 1989 by CITES to ban international trade in African elephant ivory, the population of African elephants declined from 1.3 million to around 600,000. It

13780-410: The remains of a bone needle) Early occupation of the Broken Mammoth had a setting similar to the lowland tundra with low vegetation, mostly shrubs and few trees. The regional pollen record provides evidence of shrubland with plant life including dwarf birch and willow . After approximately 9,000 years this shrubland became woodland which supporter spruce and alder trees . The faunal remains of

13910-403: The remains of fauna excavated around them. This indicates the occupants stayed at this site for some time, long enough to use the hearths multiple times. As at other Tanana River Valley sites such as Swan Point, Mead and Healey Lake, artifacts and stone tools found at Broken Mammoth are relatively infrequent. However the artifacts that have been found have provided keen insight into the history of

14040-652: The retrieval of the material from animals. Tagua nuts can also be carved like ivory. The trade of finished goods of ivory products has its origins in the Indus Valley . Ivory is a main product that is seen in abundance and was used for trading in Harappan civilization . Finished ivory products that were seen in Harappan sites include kohl sticks, pins , awls, hooks , toggles, combs , game pieces, dice , inlay and other personal ornaments. Ivory has been valued since ancient times in art or manufacturing for making

14170-654: The sale of 49 tonnes of ivory from Zimbabwe, Namibia and Botswana in 1997 to Japan. In 2007, under pressure from the International Fund for Animal Welfare , eBay banned all international sales of elephant-ivory products. The decision came after several mass slaughters of African elephants, most notably the 2006 Zakouma elephant slaughter in Chad . The IFAW found that up to 90% of the elephant-ivory transactions on eBay violated their own wildlife policies and could potentially be illegal. In October 2008, eBay expanded

14300-415: The same over the preceding few thousand years. To verify the accuracy of the method, several artefacts that were datable by other techniques were tested; the results of the testing were in reasonable agreement with the true ages of the objects. Over time, however, discrepancies began to appear between the known chronology for the oldest Egyptian dynasties and the radiocarbon dates of Egyptian artefacts. Neither

14430-456: The same proportion of C as the atmosphere, or in the case of marine animals or plants, with the ocean. Once it dies, it ceases to acquire C , but the C within its biological material at that time will continue to decay, and so the ratio of C to C in its remains will gradually decrease. Because C decays at a known rate, the proportion of radiocarbon can be used to determine how long it has been since

14560-412: The sample since its burial. Alkali and acid washes can be used to remove humic acid and carbonate contamination, but care has to be taken to avoid removing the part of the sample that contains the carbon to be tested. Particularly for older samples, it may be useful to enrich the amount of C in the sample before testing. This can be done with a thermal diffusion column. The process takes about

14690-622: The site continuing to this day. According to C.E. Holmes, the Beringian Period was the oldest in the Tanana River Valley. This was the period prior to 13,000 B.P., when a land bridge connecting Alaska and Siberia still remained. In turn, the Beringian Period is subdivided into the older part, dating prior to 13,500 B.P., and the more recent part, called the Chindadn complex, falling between 13,500 B.P. and 13,000 B.P. The lithics ( Stone tools ) dated prior to 13,500 B.P. include bifacial tools, blade and microblade technology . Only three sites in

14820-662: The site include hearths with charcoal dating to approximately 12,200 BP implying that some form of temporary occupation occurred which could include using the site as a temporary base. A small bone needle found at one of these hearths supports this theory. According to the Alaska Department of Natural Resources the evidence points to small camps, which served as headquarters for small hunting groups to operate seasonally. Activities that would have most likely occurred here include: manufacturing of tools and maintenance as well as food processing and skin working (as evident by

14950-401: The surface water as carbonate and bicarbonate ions; at the same time the carbonate ions in the water are returning to the air as CO 2 . This exchange process brings C from the atmosphere into the surface waters of the ocean, but the C thus introduced takes a long time to percolate through the entire volume of the ocean. The deepest parts of the ocean mix very slowly with

15080-590: The surface waters, and as a result water from some deep ocean areas has an apparent radiocarbon age of several thousand years. Upwelling mixes this "old" water with the surface water, giving the surface water an apparent age of about several hundred years (after correcting for fractionation). This effect is not uniform – the average effect is about 400 years, but there are local deviations of several hundred years for areas that are geographically close to each other. These deviations can be accounted for in calibration, and users of software such as CALIB can provide as an input

15210-422: The surface waters, and the mixing is uneven. The main mechanism that brings deep water to the surface is upwelling, which is more common in regions closer to the equator. Upwelling is also influenced by factors such as the topography of the local ocean bottom and coastlines, the climate, and wind patterns. Overall, the mixing of deep and surface waters takes far longer than the mixing of atmospheric CO 2 with

15340-478: The tree-ring data series has been extended to 13,900 years.) In the 1960s, Hans Suess was able to use the tree-ring sequence to show that the dates derived from radiocarbon were consistent with the dates assigned by Egyptologists. This was possible because although annual plants, such as corn, have a C / C ratio that reflects the atmospheric ratio at the time they were growing, trees only add material to their outermost tree ring in any given year, while

15470-399: The tribes. For the women, it was believed that it would bring in good luck and good health. As for the men, it was seen that they were a good hunter. Ivory can also be produced synthetically. A species of hard nut is gaining popularity as a replacement for ivory, although its size limits its usability. It is sometimes called vegetable ivory , or tagua, and is the seed endosperm of

15600-404: The two. The atmospheric C / C ratio is lower in the southern hemisphere, with an apparent additional age of about 40 years for radiocarbon results from the south as compared to the north. This is because the greater surface area of ocean in the southern hemisphere means that there is more carbon exchanged between the ocean and the atmosphere than in the north. Since the surface ocean

15730-434: The value of N (the number of atoms of C remaining in the sample), the carbon-dating equation allows the calculation of N 0 – the number of atoms of C in the sample at the time the tree ring was formed – and hence the C / C ratio in the atmosphere at that time. Equipped with the results of carbon-dating the tree rings, it became possible to construct calibration curves designed to correct

15860-402: The white color it presents when processed. It was formerly used to make cutlery handles, billiard balls , piano keys , Scottish bagpipes , buttons and a wide range of ornamental items. Synthetic substitutes for ivory in the use of most of these items have been developed since 1800: the billiard industry challenged inventors to come up with an alternative material that could be manufactured ;

15990-497: The ‰ sign indicates parts per thousand . Because the PDB standard contains an unusually high proportion of C , most measured δ C values are negative. For marine organisms, the details of the photosynthesis reactions are less well understood, and the δ C values for marine photosynthetic organisms are dependent on temperature. At higher temperatures, CO 2 has poor solubility in water, which means there

16120-411: Was awarded the Nobel Prize in Chemistry for this work. In nature, carbon exists as three isotopes . Carbon-12 ( C ) and carbon-13 ( C ) are stable and nonradioactive; carbon-14 ( C ), also known as "radiocarbon", is radioactive. The half-life of C (the time it takes for half of a given amount of C to decay ) is about 5,730 years, so its concentration in

16250-530: Was found associated with a hearth that radiocarbon dates to approximately 10,300 B.P. The bone needle suggests that the occupants used this site to process resources, using skins to make clothing. Debris from the making of tools has been found at Cultural Zone 4. The debris is composed of rhyolite, basalt, obsidian, chert and quartzite, implying that the occupants of the site carried out some manufacturing and or repair of tools. Artifacts at this zone are largely incomplete but include retouched flakes, scrapers, large

16380-857: Was found by investigators from the Environmental Investigation Agency (EIA) that CITES sales of stockpiles from Singapore and Burundi (270 tonnes and 89.5 tonnes respectively) had created a system that increased the value of ivory on the international market, thus rewarding international smugglers and giving them the ability to control the trade and continue smuggling new ivory. Since the ivory ban, some Southern African countries have claimed their elephant populations are stable or increasing, and argued that ivory sales would support their conservation efforts. Other African countries oppose this position, stating that renewed ivory trading puts their own elephant populations under greater threat from poachers reacting to demand. CITES allowed

16510-595: Was in decline, with the annual poaching mortality rate peaking at over 10% in 2011 and falling to below 4% by 2017. The study found that the "annual poaching rates in 53 sites strongly correlate with proxies of ivory demand in the main Chinese markets, whereas between-country and between-site variation is strongly associated with indicators of corruption and poverty." Based on these findings, the study authors recommended action to both reduce demand for ivory in China and other main markets and to decrease corruption and poverty in Africa. In 2006, nineteen African countries signed

16640-482: Was prized for containers due to its ability to keep an airtight seal. It was also commonly carved into elaborate seals utilized by officials to "sign" documents and decrees by stamping them with their unique official seal. In Southeast Asian countries, where Muslim Malay peoples live, such as Malaysia , Indonesia and the Philippines , ivory was the material of choice for making the handles of kris daggers. In

16770-416: Was some occupation near the bluff's edge at the site. A second hearth radiocarbon dated to about 7,600 years ago has evidence of hearthstones , suggesting occupation for an extended period of time. Two more and (possibly a third) hearths, radio carbon dated from 9,690 years ago; 10,270 years ago; and 10,790 years ago respectively, have been found at the site clearly associated with hearthstones with lithics and

16900-785: Was then at Berkeley, learned of Korff's research and conceived the idea that it might be possible to use radiocarbon for dating. In 1945, Libby moved to the University of Chicago , where he began his work on radiocarbon dating. He published a paper in 1946 in which he proposed that the carbon in living matter might include C as well as non-radioactive carbon. Libby and several collaborators proceeded to experiment with methane collected from sewage works in Baltimore, and after isotopically enriching their samples they were able to demonstrate that they contained C . By contrast, methane created from petroleum showed no radiocarbon activity because of its age. The results were summarized in

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