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25-790: Huaca Prieta was occupied as early as 14,500 BP , long before ceramics were introduced. It consists of a huge mound of ash, stones, textiles, plants and shells, with some burials and constructions. It was first excavated by Junius B. Bird in 1946–1947 who excavated three large test pits in or beside it. The remains, now at the American Museum of Natural History in New York City, include many examples of complex textiles made with twining techniques which incorporated intricate designs of mythological humans, condors, snakes and crabs. The many stone artifacts were not fancy—fish net weights, flakes and simple pebble tools; there were no projectile points. In

50-645: Is Tibitó , in the mountains of Colombia, which has been carbon dated to 11,740 BP. Monte Verde II in southern Chile, dating 14,000 cal BP or earlier, is also predominantly unifacial. In North America, early unifacial assemblages are quite commonly found along with bifacial assemblages. Such sites as Gault and the nearby Friedkin sites in Texas, Cactus Hill in Virginia, and Paisley Cave in Oregon are notable. All of them are also dated before 14,000 cal BP. Until recently, it

75-469: Is a time scale used mainly in archaeology , geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date (epoch) of the age scale, with 1950 being labelled as the "standard year". The abbreviation "BP" has been interpreted retrospectively as "Before Physics", which refers to

100-478: Is sometimes used for dates established by means other than radiocarbon dating, such as stratigraphy . This usage differs from the recommendation by van der Plicht & Hogg, followed by the Quaternary Science Reviews , both of which requested that publications should use the unit "a" (for "annum", Latin for "year") and reserve the term "BP" for radiocarbon estimations. Some archaeologists use

125-516: Is the earliest maize discovered so far in South America. According to archaeologist Tom D. Dillehay , several varieties of early corn have been discovered here. "Most notably, Dillehay’s team found the world’s earliest-known collection of corn macroremains (e.g., stalks and cobs), which included all early varieties of the plant—ceremonial popcorn, corn used for chicha beer, flour corn, and corn for foraging animals." This suggests that Huaca Prieta

150-818: The Universidad Austral de Chile and the University of Kentucky . Dillehay received his advanced degrees in anthropology from the University of Texas at Austin. He established anthropology departments at the Pontifical Catholic University of Chile in Temuco and at Austral University of Chile in Valdivia. In 1977, Dillehay became involved in the excavations at Monte Verde , a site in Chile where an early human settlement

175-681: The Guañape, Early Cupisnique and Cupisnique cultures. The last is linked to the highland Chavín culture . A large tsunami damaged both mounds leaving a thick layer of cobblestones just north of the preceramic mound, at about 850 BCE, between the two Cupisnique phases. The end of Huaca Prieta's occupation came gradually. It fell into disuse as the economy changed to being more agriculture-based, and its ceremonial significance diminished. Other nearby mounds supplanted Huaca Prieta in importance, such as Paredones and El Brujo. The earliest occupational levels of Huaca Prieta have been examined in 2017. These are

200-726: The Siches area (in north Peru, close to the Ecuador border), share similar developments as Huaca Prieta. The Itaparica tradition in central-northwestern Brazil, dated between 11,000 and 10,000 BP, is believed to be totally unifacial. It is associated with a rapid population density increase in Brazil at that time. The San Dieguito complex of Southern California, the Southwestern United States , and northwestern Mexico (as early as 10,200 BP) also featured predominantly unifaces. Also relevant

225-471: The exponential decay relation and the "Libby half-life" 5568 a. The ages are expressed in years before present (BP) where "present" is defined as AD 1950. The year 1950 was chosen because it was the standard astronomical epoch at that time. It also marked the publication of the first radiocarbon dates in December 1949, and 1950 also antedates large-scale atmospheric testing of nuclear weapons , which altered

250-495: The field of archaeology, but was ultimately accepted two decades later. Dillehay's work combines archaeology and ethnography. His excavations span eight countries, including the United States. Dillehay began excavating Huaca Prieta in 2007, where he found evidence that people had lived in that area between 13,300 and 14,200 years ago. In addition to his archaeological work, Dillehay has conducted ethnographic research among

275-480: The global ratio of carbon-14 to carbon-12 . Dates determined using radiocarbon dating come as two kinds: uncalibrated (also called Libby or raw ) and calibrated (also called Cambridge ) dates. Uncalibrated radiocarbon dates should be clearly noted as such by "uncalibrated years BP", because they are not identical to calendar dates. This has to do with the fact that the level of atmospheric radiocarbon ( carbon-14 or C) has not been strictly constant during

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300-477: The levels dated to 15,000-8000 BP. They indicate only an occasional and intermittent human presence before the ceremonial mound was built. The stone artifacts are characterised by minimally worked unifacial stone tools . Such tools are also characteristic of some other similarly dated sites in South America. The absence of fishhooks and harpoons has also been noted at these levels. It is likely that those early occupants engaged primarily in simple food gathering along

325-728: The lowercase letters bp , bc and ad as terminology for uncalibrated dates for these eras. The Centre for Ice and Climate at the University of Copenhagen instead uses the unambiguous "b2k", for "years before 2000 AD", often in combination with the Greenland Ice Core Chronology 2005 (GICC05) time scale. Some authors who use the YBP dating format also use "YAP" ("years after present") to denote years after 1950. SI prefix multipliers may be used to express larger periods of time, e.g. ka BP (thousand years BP), Ma BP (million years BP) and many others . Radiocarbon dating

350-508: The name (standard codes are used) of the laboratory concerned, and other information such as confidence levels, because of differences between the methods used by different laboratories and changes in calibrating methods. Conversion from Gregorian calendar years to Before Present years is by starting with the 1950-01-01 epoch of the Gregorian calendar and increasing the BP year count with each year into

375-596: The past from that Gregorian date. For example, 1000 BP corresponds to 950 AD, 1949 BP corresponds to 1 AD, 1950 BP corresponds to 1 BC, 2000 BP corresponds to 51 BC. Tom D. Dillehay Tom Dalton Dillehay (born 1948/1949) is an American anthropologist currently serving as the Rebecca Webb Wilson University Distinguished Professor of Anthropology, Religion, and Culture, as well as a Professor of Anthropology at Vanderbilt University . He has previously held teaching positions at

400-535: The shoreline, as well as in trapping and clubbing abundant local species of animals. Bifacial stone tools or projectile points were absent in those levels. According to the authors, Several other sites in the Americas featuring only unifacial stone tools at early occupational levels are also known. In particular, the Amotape complex of the northern coast of Peru (9,000-7,100 BCE) is notable. This cultural complex, as well as

425-596: The span of time that can be radiocarbon-dated. Uncalibrated radiocarbon ages can be converted to calendar dates by calibration curves based on comparison of raw radiocarbon dates of samples independently dated by other methods, such as dendrochronology (dating based on tree growth-rings) and stratigraphy (dating based on sediment layers in mud or sedimentary rock). Such calibrated dates are expressed as cal BP, where "cal" indicates "calibrated years", or "calendar years", before 1950. Many scholarly and scientific journals require that published calibrated results be accompanied by

450-399: The time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, which scientists must account for. In a convention that is not always observed, many sources restrict the use of BP dates to those produced with radiocarbon dating; the alternative notation "RCYBP" stands for the explicit "radio carbon years before present". The BP scale

475-477: The upper part of the mound there were many underground structures of unknown function, some with burials. They were made of cobblestones cemented with an ash-water mixture. The inhabitants fished, gathered shellfish, and grew fruit, gourds, squash, peppers, beans, tubers and, importantly, cotton. There is a low mound 70–170 m to the north (now called Monticulo Cupisnique) where Bird excavated three test pits. He found many ruins and much refuse, including ceramics of

500-418: Was an important hub in a large trading network reaching all the way to Mexico, where domesticated corn originated. A team of scientists excavating Huaca Prieta between 2007 and 2013 also discovered evidence of the avocado dating back perhaps 15,000 years. It had been thought previously that the avocado originated in the area of Puebla, Mexico, some 8,000 years ago. In 2016, 6000-year-old dyed cotton fabric

525-520: Was believed that maize was introduced to the region rather late, after the tsunami. In 2012, it was reported that corncobs found at two ancient sites in Peru (Paredones and Huaca Prieta) may date from as early as 4700   BCE. This suggests that people living along the coast of northern Peru were already eating corn by that time. These results were reported by Dolores Piperno , and other scientists from Washington's National Museum of Natural History . This

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550-696: Was discovered at the Preceramic site of Huaca Prieta. This marks the earliest recorded use of cotton worldwide. Gossypium barbadense may have been domesticated in the region. Analysis of the pigment used on the cloth identified it as indigotin, an indigoid dye. This marks the earliest recorded use of indigo dye to date, predating the use of indigo in Egypt's Fifth Dynasty by about 1,500 years. 7°55′26″S 79°18′25″W  /  7.924°S 79.307°W  / -7.924; -79.307 Before Present Before Present ( BP ) or " years before present ( YBP )"

575-464: Was discovered in 1975. Based on calibrated carbon 14 dates, Dillehay proposed that the remains found at Monte Verde are approximately 14,800 years old. This evidence, which suggests that the first humans arrived in the Americas around 15,000 years ago, challenges the "Clovis first" paradigm by indicating the possibility of an earlier human presence in South America. This proposal based on his research at Monte Verde met with virulent resistance within

600-446: Was first used in 1949. Beginning in 1954, metrologists established 1950 as the origin year for the BP scale for use with radiocarbon dating, using a 1950-based reference sample of oxalic acid . According to scientist A. Currie Lloyd: The problem was tackled by the international radiocarbon community in the late 1950s, in cooperation with the U.S. National Bureau of Standards . A large quantity of contemporary oxalic acid dihydrate

625-525: Was prepared as NBS Standard Reference Material (SRM) 4990B. Its C concentration was about 5% above what was believed to be the natural level, so the standard for radiocarbon dating was defined as 0.95 times the C concentration of this material, adjusted to a C reference value of −19 per mil (PDB). This value is defined as "modern carbon" referenced to AD 1950. Radiocarbon measurements are compared to this modern carbon value, and expressed as "fraction of modern" (fM). "Radiocarbon ages" are calculated from fM using

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