Plants are multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae. Plants were treated as one of two kingdoms including all living things that were not animals, all algae and fungi were treated as plants. However, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotes. By one definition, plants form the clade Viridiplantae, a group that includes the flowering plants and other gymnosperms and their allies, liverworts and the green algae, but excludes the red and brown algae. Green plants obtain most of their energy from sunlight via photosynthesis by primary chloroplasts that are derived from endosymbiosis with cyanobacteria, their chloroplasts contain b, which gives them their green color. Some plants are parasitic or mycotrophic and have lost the ability to produce normal amounts of chlorophyll or to photosynthesize. Plants are characterized by sexual reproduction and alternation of generations, although asexual reproduction is common.
There are about 320 thousand species of plants, of which the great majority, some 260–290 thousand, are seed plants. Green plants provide a substantial proportion of the world's molecular oxygen and are the basis of most of Earth's ecosystems on land. Plants that produce grain and vegetables form humankind's basic foods, have been domesticated for millennia. Plants have many cultural and other uses, as ornaments, building materials, writing material and, in great variety, they have been the source of medicines and psychoactive drugs; the scientific study of plants is known as a branch of biology. All living things were traditionally placed into one of two groups and animals; this classification may date from Aristotle, who made the distincton between plants, which do not move, animals, which are mobile to catch their food. Much when Linnaeus created the basis of the modern system of scientific classification, these two groups became the kingdoms Vegetabilia and Animalia. Since it has become clear that the plant kingdom as defined included several unrelated groups, the fungi and several groups of algae were removed to new kingdoms.
However, these organisms are still considered plants in popular contexts. The term "plant" implies the possession of the following traits multicellularity, possession of cell walls containing cellulose and the ability to carry out photosynthesis with primary chloroplasts; when the name Plantae or plant is applied to a specific group of organisms or taxon, it refers to one of four concepts. From least to most inclusive, these four groupings are: Another way of looking at the relationships between the different groups that have been called "plants" is through a cladogram, which shows their evolutionary relationships; these are not yet settled, but one accepted relationship between the three groups described above is shown below. Those which have been called "plants" are in bold; the way in which the groups of green algae are combined and named varies between authors. Algae comprise several different groups of organisms which produce food by photosynthesis and thus have traditionally been included in the plant kingdom.
The seaweeds range from large multicellular algae to single-celled organisms and are classified into three groups, the green algae, red algae and brown algae. There is good evidence that the brown algae evolved independently from the others, from non-photosynthetic ancestors that formed endosymbiotic relationships with red algae rather than from cyanobacteria, they are no longer classified as plants as defined here; the Viridiplantae, the green plants – green algae and land plants – form a clade, a group consisting of all the descendants of a common ancestor. With a few exceptions, the green plants have the following features in common, they undergo closed mitosis without centrioles, have mitochondria with flat cristae. The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria. Two additional groups, the Rhodophyta and Glaucophyta have primary chloroplasts that appear to be derived directly from endosymbiotic cyanobacteria, although they differ from Viridiplantae in the pigments which are used in photosynthesis and so are different in colour.
These groups differ from green plants in that the storage polysaccharide is floridean starch and is stored in the cytoplasm rather than in the plastids. They appear to have had a common origin with Viridiplantae and the three groups form the clade Archaeplastida, whose name implies that their chloroplasts were derived from a single ancient endosymbiotic event; this is the broadest modern definition of the term'plant'. In contrast, most other algae not only have different pigments but have chloroplasts with three or four surrounding membranes, they are not close relatives of the Archaeplastida having acquired chloroplasts separately from ingested or symbiotic green and red algae. They are thus not included in the broadest modern definition of the plant kingdom, although they were in the past; the green plants or Viridiplantae were traditionally divided into the green algae (including
Calf Creek culture
Calf Creek Culture was a nomadic hunter-gatherer people who lived in the southcentral region of North America in the area of what is today Oklahoma and surrounding states, artifacts having been found in such places as Beard's Bluff and Sand Springs, Oklahoma. The Calf Creek culture was active during the early to middle Archaic period in the Americas 7,500 to 4,000 years ago; the Calf Creek people were noted for their use of heat-treated flint spearheads. The Calf Creek point was first named and described in an Arkansas amateur archaeological journal by Don Dickson in 1968, for examples found at Calf Creek cave in Searcy County Arkansas; the cave was named for a perennial stream that runs nearby. In 2003, a 5,120±25-year-old bison skull was found on the banks of the Arkansas River by Kim Holt; this find was featured on History Detectives. The skull had a Calf Creek culture spearhead embedded just over the orbital of the right eye socket; the size of the spearhead, the wound it inflicted further suggest that the Calf Creek used atlatls
A midden is an old dump for domestic waste which may consist of animal bone, human excrement, botanical material, mollusc shells, sherds and other artifacts and ecofacts associated with past human occupation. These features, provide a useful resource for archaeologists who wish to study the diet and habits of past societies. Middens with damp, anaerobic conditions can preserve organic remains in deposits as the debris of daily life are tossed on the pile; each individual toss will contribute a different mix of materials depending upon the activity associated with that particular toss. During the course of deposition sedimentary material is deposited as well. Different mechanisms, from wind and water to animal digs, create a matrix which can be analyzed to provide seasonal and climatic information. In some middens individual dumps of material can be analysed. A shell midden or shell mound is an archaeological feature consisting of mollusk shells; the Danish term køkkenmøddinger was first used by Japetus Steenstrup to describe shell heaps and continues to be used by some researchers.
A midden, by definition, contains the debris of human activity, should not be confused with wind or tide created beach mounds. Some shell middens are processing remains: areas where aquatic resources were processed directly after harvest and prior to use or storage in a distant location; some shell middens are directly associated as a designated village dump site. In other middens, the material is directly associated with a house in the village; each household would dump its garbage directly outside the house. In all cases, shell middens are complex and difficult to excavate and exactly; the fact that they contain a detailed record of what food was eaten or processed and many fragments of stone tools and household goods makes them invaluable objects of archaeological study. Shells have a high calcium carbonate content; this slows the normal rate of decay caused by soil acidity, leaving a high proportion of organic material available for archaeologists to find. Edward Sylvester Morse conducted one of the first archaeological excavations of shellmounds in Omori, Japan in 1877, which led to the discovery of a style of pottery described as "cord-marked", translated as "Jōmon", which came to be used to refer to the early period of Japanese history when this style of pottery was produced.
Shell middens were studied in Denmark in the latter half of the 19th century. The Danish word køkkenmødding is now used internationally; the English word "midden" derives from the same Old Norse word. Shell middens are found in lakeshore zones all over the world. Consisting of mollusc shells, they are interpreted as being the waste products of meals eaten by nomadic groups or hunting parties; some are small examples relating to meals had by a handful of individuals, others are many metres in length and width and represent centuries of shell deposition. In Brazil, they are known as sambaquis, having been created over a long period between the 6th millennium BC and the beginning of European colonisation. European shell middens are found along the Atlantic seaboard and in Denmark and date to the 5th millennium BC, containing the remains of the earliest Neolithisation process. Younger shell middens are found in Latvia, the Netherlands and Schleswig Holstein. All these are examples where communities practiced hunting/gathering economy.
On Canada's west coast, there are shell middens that run for more than a kilometer along the coast and are several meters deep. The midden in Namu, British Columbia is over 9 meters deep and spans over 10,000 years of continuous occupation. Shell middens created in coastal regions of Australia by indigenous Australians exist in Australia today. Middens provide evidence of prior occupation and are protected from mining and other developments. One must exercise caution in deciding whether one is examining a beach mound. There are good examples on the Freycinet Peninsula in Tasmania where wave action is combining charcoal from forest fire debris with a mix of shells into masses that storms deposit above high-water mark. Shell mounds near Weipa in far north Queensland that are less than 2 meters high and a few tens of meters long are claimed to be middens, but are in fact shell cheniers re-worked by nest mound-building birds. Shell mounds are credited with the creation of tropical hardwood hammocks, one example being the Otter mound preserve in Florida, where shell deposits from Calusa natives provided flood free high areas in otherwise large watered areas.
There are instances in which shell middens may have doubled as areas of ceremonial construction or ritual significance. The Woodland period Crystal River site provides an example of this phenomenon; some shell mounds, known as shell rings, are open arcs with a clear central area. Many are known from Japan and the southeastern United States, at least one from South America; the word is of Scandinavian via Middle English derivation.
The Adena culture was a Pre-Columbian Native American culture that existed from 1000 to 200 BC, in a time known as the Early Woodland period. The Adena culture refers to what were a number of related Native American societies sharing a burial complex and ceremonial system; the Adena lived in an area including parts of present-day Ohio, Wisconsin, West Virginia, New York and Maryland. The Adena Culture was named for the large mound on Thomas Worthington's early 19th-century estate located near Chillicothe, which he named "Adena", Adena sites are concentrated in a small area - maybe 200 sites in the central Ohio Valley, with another 200 scattered throughout Wisconsin, Kentucky, West Virginia and Maryland, although those in Ohio may once have numbered in the thousands; the importance of the Adena complex comes from its considerable influence on other contemporary and succeeding cultures. The Adena culture is seen as the precursor to the traditions of the Hopewell culture, which are sometimes thought as an elaboration, or zenith, of Adena traditions.
The Adena were notable for their agricultural practices, artistic works, extensive trading network, which supplied them with a variety of raw materials, ranging from copper from the Great Lakes to shells from the Gulf Coast. Lasting traces of Adena culture are still seen in the remains of their substantial earthworks. At one point, larger Adena mounds numbered in the hundreds, but only a small number of the remains of the larger Adena earthen monuments still survive today; these mounds ranged in size from 20 feet to 300 feet in diameter and served as burial structures, ceremonial sites, historical markers, gathering places. These earthen monuments were built using hundreds of thousands of baskets full of specially selected and graded earth. According to archaeological investigations, Adena earthworks were built as part of their burial rituals, in which the earth of the earthwork was piled atop a burned mortuary building; these mortuary buildings were intended to keep and maintain the dead until their final burial was performed.
Before the construction of the earthworks, some utilitarian and grave goods would be placed on the floor of the structure, burned with the goods and honored dead within. The earthwork would be constructed, a new mortuary structure would be placed atop the new earthwork. After a series of repetitions, mortuary/earthwork/mortuary/earthwork, a quite prominent earthwork would remain. In the Adena period, circular ridges of unknown function were sometimes constructed around the burial earthworks. Although the mounds are beautiful artistic achievements themselves, Adena artists created smaller, more personal pieces of art. Art motifs that became important to many Native Americans began with the Adena. Motifs such as the weeping eye and cross and circle design became mainstays in many succeeding cultures. Many pieces of art seemed to revolve around shamanic practices, the transformation of humans into animals—particularly birds, wolves and deer—and back to human form; this may indicate a belief that the practice imparted the animals' qualities to the wearer or holder of the objects.
Deer antlers, both real and constructed of copper, wolf and mountain lion jawbones, many other objects were fashioned into costumes and other forms of regalia by the Adena. Distinctive tubular smoking pipes, with either flattened or blocked-end mouthpieces, suggest the offering of smoke to the spirits; the objective of pipe smoking may have been altered states of consciousness, achieved through the use of the hallucinogenic plant Nicotiana rustica. All told, Adena was a manifestation of a broad regional increase in the number and kind of artifacts devoted to spiritual needs; the Adena carved small stone tablets 4 or 5 inches by 3 or 4 inches by.5 inches thick. On one or both flat sides were gracefully composed stylized zoomorphs or curvilinear geometric designs in deep relief. Paint has been found on some Adena tablets, leading archaeologists to propose that these stone tablets were used to stamp designs on cloth or animal hides, or onto their own bodies, it is possible. Unlike in other cultures, Adena pottery was not buried with the dead or the remains of the cremated, as were other artifacts.
Adena pottery was tempered with grit or crushed limestone and was thick. The vessel shapes were flat-bottomed jars, sometimes with small foot-like supports; the large and elaborate mound sites served a nearby scattering of people. The population was dispersed in small settlements of one to two structures. A typical house was built in a circle form from 15 to 45 feet in diameter; the walls were made of paired posts tilted outward, that were joined to other pieces of wood to form a cone shaped roof. The roof was covered with bark and the walls may have been bark and/or wickerwork, their sustenance was acquired through the cultivation of native plants. Hunted deer, black bear, beaver, turkey, trumpeter swan, ruffed grouse. Gathered several edible seed and nuts. Cultivated pumpkin, squash and goosefoot; the Adena ground stone axes. Somewhat rougher slab-like stones with chipped edges were used as hoes. Bone and antler were used in small tools, but more prominently in ornamental objects such as beads and worked animal-jaw gorgets or paraphernalia.
Spoons and other implements were made fro
Archaic period (North America)
In the classification of the archaeological cultures of North America, the Archaic period or "Meso-Indian period" in North America, taken to last from around 8000 to 1000 BC in the sequence of North American pre-Columbian cultural stages, is a period defined by the archaic stage of cultural development. The Archaic stage is characterized by subsistence economies supported through the exploitation of nuts and shellfish; as its ending is defined by the adoption of sedentary farming, this date can vary across the Americas. The rest of the Americas have an Archaic Period; this classification system was first proposed by Gordon Willey and Philip Phillips in the accepted 1958 book Method and Theory in American Archaeology. In the organization of the system, the Archaic period followed the Lithic stage and is superseded by the Formative stage; the Lithic stage The Archaic stage The Formative stage The Classic stage The Post-Classic stageNumerous local variations have been identified within the cultural rankings.
The period has been subdivided by region and time. For instance, the Archaic Southwest tradition is subdivided into the Dieguito-Pinto, Oshara and Chihuahua cultures. Since the 1990s, secure dating of multiple Middle Archaic sites in northern Louisiana and Florida has challenged traditional models of development. In these areas, hunter-gatherer societies in the Lower Mississippi Valley organized to build monumental earthwork mound complexes as early as 3500 BC, with building continuing over a period of 500 years; such early mound sites as Frenchman's Bend and Hedgepeth were of this time period. Watson Brake is now considered to be the oldest mound complex in the Americas, it precedes. More than 100 sites have been identified as associated with the regional Poverty Point culture of the Late Archaic period, it was part of a regional trading network across the Southeast. Across what is now the Southeastern United States, starting around 4000 BC, people exploited wetland resources, creating large shell middens.
Middens developed where the people lived along rivers, but there is limited evidence of Archaic peoples along the coastlines prior to 3000 BC. Archaic sites on the coast may have been inundated by rising sea levels. Starting around 3000 BC, evidence of large-scale exploitation of oysters appears. During the period 3000 BC to 1000 BC, shell rings, large shell middens that more or less surround open centers, were developed along the coast of the Southeastern United States; these shell rings are numerous in South Carolina and Georgia, but are found scattered around the Florida Peninsula and along the Gulf of Mexico coast as far west as the Pearl River. In some places, such as Horr's Island in Southwest Florida, resources were rich enough to support sizable mound-building communities year-round. Four shell or sand mounds on Horr's Island have been dated to between 4,870 and 4,270 Before Present. Early Archaic8000 BC: The last glacial ends, causing sea levels to rise and flood the Beringia land bridge, closing the primary migration route from Siberia.
8000 BC: Sufficient rain falls on the American Southwest to support many large mammal species--mammoth, a bison species-—that soon go extinct. 8000 BC: Hunters in the American Southwest use the atlatl. 7500 BC: Early basketry. 7560—7370 BC: Kennewick Man dies along the shore of the Columbia River in Washington State, leaving one of the most complete early Native American skeletons. 7000 BC: Northeastern peoples depend on deer and wild grains as the climate warms. 7000 BC: Native Americans in Lahontan Basin, Nevada mummify their dead to give them honor and respect, evidencing deep concern about their treatment and condition. Middle Archaic6500 BC–200 AD: The San Dieguito-Pinto tradition and Chihuahua Tradition flourish in southern California, the Southwest, northwestern Mexico. 6000 BC: Ancestors of Penutian-speaking peoples settle in the Northwestern Plateau. 6000 BC: Nomadic hunting bands roam Subarctic Alaska following herds of caribou and other game animals. 6000 BC: Aleuts begin to arrive in the Aleutian Islands.
5700 BC: Cataclysmic eruption of Mount Mazama in Oregon. 5500 BC–500 AD Oshara Tradition, a Southwestern Archaic Tradition, arises in north-central New Mexico, the San Juan Basin, the Rio Grande Valley, southern Colorado, southeastern Utah. Natives of the Northwestern Plateau begin to rely on salmon runs. 5000 BC: Early cultivation of food crops began in Mesoamerica. 5000 BC: Native Americans in the Pacific Northwest from Alaska to California develop a fishing economy, with salmon as a staple. 5000 BC: The Old Copper Culture of the Great Lakes area hammers the metal into various tools and ornaments, such as knives, awls, bracelets and pendants. 5000 BC–200 AD: The Cochise Tradition arises in the American Southwest. Native Americans in the northern Great Lakes produce copper tools and utensils traded throughout the Great Plains and Ohio Valley. Shell ornaments and copper items at Indian Knoll in Kentucky evidence an extensive trade system over several millennia. 4000 BC: Inhabitants of Mesoamerica cultivate maize while Peruvian natives cultivate beans and squash.
4000–1000 BC: Old Copper Complex emerges in the Great Lakes region 3500 BC: The largest, oldest drive site at Head-Smashed-In Buffalo Jump, Canada. 3500–3000 BC: Construction of extensive mound complex built at Watson Brake in the floodplain of the Ouachita River near Monroe in northern Louisiana. Shell ornaments and copper items at Indian Knoll, Kentucky evi
Fort Ancient is a name for a Native American culture that flourished from Ca. 1000-1750 CE and predominantly inhabited land near the Ohio River valley in the areas of modern-day southern Ohio, northern Kentucky, southeastern Indiana and western West Virginia. Although a contemporary of the Mississippian Culture, they are considered a "sister culture" and distinguished from the Mississippian Culture. Although far from agreed upon, there is evidence to suggest that the Fort Ancient Culture were not the direct descendants of the Hopewellian Culture], it is suspected. The Fort Ancient Culture were most the builders of the Great Serpent Mound; the name of the culture originates from the Fort Ohio archeological site. However, the Fort Ancient Site is now thought to have been built by Ohio Hopewellian people, it was occupied by the succeeding Fort Ancient culture. The site is located on a hill above the Little Miami River, close to Ohio. Despite its name, most archaeologists do not believe that Fort Ancient was used as a fortress by either the Ohio Hopewell culture or the Fort Ancient culture.
Starting in about 1000 CE, terminal Late Woodland groups in the Middle Ohio Valley adopted maize agriculture. They began settling in small, year-round nuclear family households and settlements of no more than 40 to 50 individuals; these small scattered settlements, located along terraces that overlooked rivers and sometimes on flood plains, would be occupied for short periods before the groups moved on to new locations. By 1200 the small villages began to coalesce into larger settlements of up to 300 people, they were occupied for longer periods up to 25 years. During the Early and Middle Fort Ancient period, the houses were designed as single-family dwellings. Fort Ancient buildings are larger multi-family dwellings. Settlements were permanent, as the people moved to a new location after one or two generations, when the natural resources surrounding the old village were exhausted; the people laid out the villages around an open oval central plaza, surrounded by circular and/or rectangular domestic structures facing the plaza.
The arrangement of buildings in Fort Ancient settlements is thought to have served as a sort of solar calendar, marking the positions of the solstices and other significant dates. The people began to build low platform mounds for ceremonial purposes, many villages added defensive palisades to their boundaries; the plaza was the center of village life: the place where ceremonies and other social events were held. The Late Fort Ancient period from 1400 to 1750 is the protohistoric era in the Middle Ohio Valley. During this era, the dispersed populations began to coalesce; the Gist-phase villages became much larger than during the preceding period, with populations as high as 500. Archaeologists have speculated that the larger villages and palisades are evidence that after 1450, warfare and intergroup strife increased, leading the people to consolidate their villages for better protection; this era showed increased contact with Mississippian peoples. The Madisonville horizon of artifacts after 1400 includes high proportions of bowls, salt pans, triangular strap handles, negative painted pottery and beaded rims, some effigies, all items and styles that are associated with the Mississippian cultures of the Lower Ohio Valley, at sites such as Angel Mounds and Kincaid Mounds.
These sites were abandoned during this time period. During the Montour phase, the people inhabited their villages year-round, although less densely in the winter than in the summer months; this may indicate that during the winter, family groups and hunting parties may have returned to the regions occupied by their ancestors. Such a pattern was observed for example, among the Miami and Potawatomi. By their trading, the Fort Ancient people had access to European trade items, such as glass, iron and copper, which have been found as grave goods at sites such as Lower Shawneetown and Hardin Village; such artifacts appeared and were used in the area before the arrival of European explorers or settlers. Although the Fort Ancient peoples did not encounter Europeans at this time, like other groups in the interior of the continent, may have suffered high fatalities from their diseases, transmitted among Native Americans by trade contacts; the next-known inhabitants of the area, who were encountered by French and English explorers, were the historic Shawnee tribe.
Scholars believe that the Fort Ancient society, like the Mississippian cultures to the south and west, may have been disrupted by waves of infectious disease epidemics from the first Spanish explorers in the mid-16th century. After 1525 at the Madisonville Site, the type site for the Madisonville Phase, dwellings were built on a smaller scale and in fewer number; this change indicated the culture was less attached to a sedentary life. Scholars believe that similarities in material culture, art and Shawnee oral history link the historic tribe to the Fort Ancient people; the Fort Ancient culture can be divided into Early, Middle & Late Phases. It is not believed that they merged into a singular society until close to the end of the Middle Phase. At this time, Fort Ancients were poor sedentary societies, they lived. The locals farmed corn, beans & sunflower-- the last of which being a plant
The Clovis culture is a prehistoric Paleo-Indian culture, named for distinct stone tools found in close association with Pleistocene fauna at Blackwater Locality No. 1 near Clovis, New Mexico, in the 1920s and 1930s. It appears around 11,500–11,000 uncalibrated radiocarbon years before present at the end of the last glacial period, is characterized by the manufacture of "Clovis points" and distinctive bone and ivory tools. Archaeologists' most precise determinations at present suggest this radiocarbon age is equal to 13,200 to 12,900 calendar years ago. Clovis people are considered to be the ancestors of most of the indigenous cultures of the Americas; the only human burial, directly associated with tools from the Clovis culture included the remains of an infant boy researchers named Anzick-1. Paleogenetic analyses of Anzick-1's ancient nuclear, Y-chromosome DNA reveal that Anzick-1 is related to modern Native American populations, which lends support to the Beringia hypothesis for the settlement of the Americas.
The Clovis culture was replaced by several more localized regional societies from the Younger Dryas cold-climate period onward. Post-Clovis cultures include the Folsom tradition, Suwannee-Simpson, Plainview-Goshen and Redstone; each of these is thought to derive directly from Clovis, in some cases differing only in the length of the fluting on their projectile points. Although this is held to be the result of normal cultural change through time, numerous other reasons have been suggested as driving forces to explain changes in the archaeological record, such as the Younger Dryas postglacial climate change which exhibited numerous faunal extinctions. After the discovery of several Clovis sites in eastern North America in the 1930s, the Clovis people came to be regarded as the first human inhabitants who created a widespread culture in the New World. However, this theory has been challenged, in the opinion of many archaeologists, by several archaeological discoveries, including sites such as Cactus Hill in Virginia, Paisley Caves in the Summer Lake Basin of Oregon, the Topper site in Allendale County, South Carolina, Meadowcroft Rockshelter in Pennsylvania, the Friedkin site in Texas, Cueva Fell in Chile, Monte Verde in Chile.
The oldest claimed human archaeological site in the Americas is the Pedra Furada hearths, a site in Brazil that precedes the Clovis culture and the other sites mentioned by 19,000 to 30,000 years. This claim has become an issue of contention between North American archaeologists and their South American and European counterparts, who disagree on whether it is conclusively proven to be an older human site. A hallmark of the toolkit associated with the Clovis culture is the distinctively shaped, fluted-stone spear point, known as the Clovis point; the Clovis point is bifacial and fluted on both sides. Archaeologists do not agree on whether the widespread presence of these artifacts indicates the proliferation of a single people, or the adoption of a superior technology by diverse population groups; the culture is named after artifacts found between 1936 at Blackwater Locality No. 1, an archaeological site between the towns of Clovis and Portales, New Mexico. These finds were deemed important due to their direct association with mammoth species and the extinct Bison antiquus.
The in situ finds of 1936 and 1937 included most of four stone Clovis points, two long bone points with impact damage, stone blades, a portion of a Clovis blade core, several cutting tools made on stone flakes. Clovis sites have since been identified throughout much of the contiguous United States, as well as Mexico and Central America, into northern South America. Clovis people are accepted to have hunted mammoths, as well as extinct bison, gomphotheres, tapir, camelops and other smaller animals. More than 125 species of plants and animals are known to have been used by Clovis people in the portion of the Western Hemisphere they inhabited; the oldest Clovis site in North America is believed to be El Fin del Mundo in northwestern Sonora, discovered during a 2007 survey. It features occupation dating around 13,390 calibrated years BP. In 2011, remains of gomphotheres were found; the Aubrey site in Denton County, produced an identical radiocarbon date. The most held perspective on the end of the Clovis culture is that a decline in the availability of megafauna, combined with an overall increase in a less mobile population, led to local differentiation of lithic and cultural traditions across the Americas.
After this time, Clovis-style fluted points were replaced by other fluted-point traditions with an uninterrupted sequence across North and Central America. An continuous cultural adaptation proceeds from the Clovis period through the ensuing Middle and Late Paleoindian periods. Whether the Clovis culture drove the mammoth, other species, to extinction via overhunting – the so-called Pleistocene overkill hypothesis – is still an open, controversial, question, it has been hypothesized that the Clovis culture had its decline in the wake of the Younger Dryas cold phase. This'cold shock', lasting 1500 years, affected many parts of the world, including North America; this appears to have been triggered by a vast amount of meltwater – from Lake Agassiz – emptying into the North Atlantic, disrupting the thermohaline circulation. The Younger Dryas impact hypothesis, or Clovis comet hypothesis proposed that a large air burst or earth impact of a comet or comets from outer space initiated the Younger Drya