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69-415: Monte Verde II represents a campsite with wooden tent-like structures that was later covered by a bog, sealing the site under a layer of anerobic peat. The occupants of the site made rope and utilized animal skins, and consumed a variety of plant foods, including seaweed (despite the site being 60 kilometres (37 mi) from the ocean at the time), tubers, seeds, fruits and nuts. Remains at the site show that

138-694: A peat -filled bog formed that inhibited the bacterial decay of organic material and preserved many perishable artifacts and other items for millennia. Radiocarbon dating of bones and charcoal in 1982 gave the site an average age of 14,800 BP (calibrated), more than 1,000 years earlier than the oldest-known site of human habitation in the Americas at that time. In the initial excavation, two large hearths and many small ones were found. The remains of local animals were discovered, in addition to wooden posts from approximately twelve huts. Scraps of clothing made of hide were also found. This led archaeologists to estimate

207-421: A "winter kill". Oxygen depletion can result from a number of natural factors, but is most often a concern as a consequence of pollution and eutrophication in which plant nutrients enter a river, lake, or ocean, and phytoplankton blooms are encouraged. While phytoplankton, through photosynthesis , will raise DO saturation during daylight hours, the dense population of a bloom reduces DO saturation during

276-484: A 25-year span of tree ring (or similar) data for this match to be possible. Wiggle-matching can be used in places where there is a plateau on the calibration curve, and hence can provide a much more accurate date than the intercept or probability methods are able to produce. The technique is not restricted to tree rings; for example, a stratified tephra sequence in New Zealand, known to predate human colonization of

345-617: A Pre-Clovis site. Still, the early date for the site was not widely accepted until 1997. It had hitherto been generally agreed that ancient people had entered the Americas using the Bering Strait Land Bridge, which was about 13,000 kilometers (8,000 miles) north of the Monte Verde site. Though the Monte Verde site does not disprove the Bering Strait theory, it does support the theory that, instead of going down

414-437: A century, from 1080 BP to 1180 BP. The intercept method is based solely on the position of the intercepts on the graph. These are taken to be the boundaries of the 68% confidence range, or one standard deviation. However, this method does not make use of the assumption that the original radiocarbon age range is a normally distributed variable: not all dates in the radiocarbon age range are equally likely, and so not all dates in

483-413: A correction would need to be applied to radiocarbon ages to obtain calendar dates. Uncalibrated dates may be stated as "radiocarbon years ago", abbreviated " C ya". The term Before Present (BP) is established for reporting dates derived from radiocarbon analysis, where "present" is 1950. Uncalibrated dates are stated as "uncal BP", and calibrated (corrected) dates as "cal BP". Used alone,

552-405: A date range at one standard deviation confidence for the radiocarbon ages, select a calibration curve, and produce probabilistic output both as tabular data and in graphical form. In the example CALIB output shown at left, the input data is 1270 BP, with a standard deviation of 10 radiocarbon years. The curve selected is the northern hemisphere INTCAL13 curve, part of which is shown in the output;

621-437: A footprint, assumed to have been made by a child, stone tools, and cordage. Dr. Dillehay obtained the date for this site by radiocarbon dating charcoal and bone found within the site. At Monte Verde II, seven partial carcasses of Notiomastodon , alongside remains single individual of the extinct llama Palaeolama show evidence of butchery, with some of these carcasses having preserved meat tissue still adhered to them. In

690-420: A linear relationship between radiocarbon age and calendar age. In places where the calibration curve is steep, and does not change direction, as in example t 1 in blue on the graph to the right, the resulting calendar year range is quite narrow. Where the curve varies significantly both up and down, a single radiocarbon date range may produce two or more separate calendar year ranges. Example t 2 , in red on

759-430: A narrower probability distribution (i.e., greater accuracy) as a result of the combined measurements. Bayesian statistical techniques can be applied when there are several radiocarbon dates to be calibrated. For example, if a series of radiocarbon dates is taken from different levels in a given stratigraphic sequence, Bayesian analysis can help determine if some of the dates should be discarded as anomalies, and can use

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828-466: A process called calibration . Calibration is needed because the atmospheric C / C ratio, which is a key element in calculating radiocarbon ages, has not been constant historically. Willard Libby , the inventor of radiocarbon dating, pointed out as early as 1955 the possibility that the ratio might have varied over time. Discrepancies began to be noted between measured ages and known historical dates for artefacts, and it became clear that

897-440: A river into the sea is less dense than salt water, stratification in the water column can result. Vertical mixing between the water bodies is therefore reduced, restricting the supply of oxygen from the surface waters to the more saline bottom waters. The oxygen concentration in the bottom layer may then become low enough for hypoxia to occur. Areas particularly prone to this include shallow waters of semi-enclosed water bodies such as

966-487: Is Pilauco Bajo , dated to 12,500–11,000 BP. Researchers postulated that the two sites were complementary – Monte Verde would be a habitation site, and Pilauco Bajo would be a hunting and scavenging site. Further south lies the Pali Aike Crater lava tube, dated to 14,000–10,000 BP. The Chinchorro culture , which was mostly a coastal culture of northern Chile and southern Peru, originated ca. 9,000 years BP, and

1035-475: Is formed, removing even more oxygen from the environment in the forms of carbon dioxide, bicarbonate ions, and carbonate. Dissolved inorganic carbon is made at a rate of 2.3–6.5 mg/(m ⋅day). As phytoplankton breakdown, free phosphorus and nitrogen become available in the environment, which also fosters hypoxic conditions. As the breakdown of this phytoplankton takes place, the more phosphorus turns into phosphates, and nitrogens turn into nitrates. This depletes

1104-450: Is found at the boundary of anoxic and hypoxic zones. Hypoxia can occur throughout the water column and also at high altitudes as well as near sediments on the bottom. It usually extends throughout 20–50% of the water column, but depends on the water depth and location of pycnoclines (rapid changes in water density with depth). It can occur in 10–80% of the water column. For example, in a 10-meter water column, it can reach up to 2 meters below

1173-444: Is known as a "summer kill". The same phenomena can occur in the winter, but for different reasons. During winter, ice and snow cover can attenuate light, and therefore reduce rates of photosynthesis. The freezing over of a lake also prevents air-water interactions that allow the exchange of oxygen. This creates a lack of oxygen while respiration continues. When the oxygen becomes badly depleted, anaerobic organisms can die, resulting in

1242-454: Is less well understood. It was more ephemeral, having come from ancient river sediments. Dillehay found charcoal scatters which may have been the remains of fireplaces next to stone and wood artifacts. These were dated to at least 33,000BP. He acknowledges MV-I has issues, such as uncertain artifacts, doubtful radiocarbon dates, and unreliable contexts. He hesistates to accept this level without additional evidence, including sites of similar age in

1311-608: Is poisonous to anaerobic bacteria for example. Oxygen depletion is typically expressed as a percentage of the oxygen that would dissolve in the water at the prevailing temperature and salinity. A system with low concentration—in the range between 1 and 30% saturation—is called hypoxic or dysoxic . Most fish cannot live below 30% saturation since they rely on oxygen to derive energy from their nutrients. Hypoxia leads to impaired reproduction of remaining fish via endocrine disruption . A "healthy" aquatic environment should seldom experience less than 80% saturation. The exaerobic zone

1380-525: Is situated on the banks of Chinchihuapi Creek, a tributary of the Maullín River located 36 miles (58 km) from the Pacific Ocean . One of the rare open-air prehistoric sites found so far in the Americas, Monte Verde was well preserved because it was located in an anaerobic bog environment near the creek. A short time after the site was originally occupied, the waters of the creek rose and

1449-415: Is suggested to have been occupied by about twenty to thirty people. A twenty-foot-long tent-like structure of wood and animal hides was erected on the banks of the creek and was framed with logs and planks staked in the ground, making walls of poles covered with animal hides. Using ropes made of local reeds, the hides were tied to the poles creating separate living quarters within the main structure. Outside

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1518-495: Is the amount of particulate organic carbon (POC) overall at a given time, t. G(0) is the concentration of POC before breakdown takes place. k is a rate constant in year-1, and t is time in years. For most POC of phytoplankton, the k is around 12.8 years-1, or about 28 days for nearly 96% of carbon to be broken down in these systems. Whereas for anoxic systems, POC breakdown takes 125 days, over four times longer. It takes approximately 1 mg of oxygen to break down 1 mg of POC in

1587-411: Is the coastal migration hypothesis, which argues that people migrated from Asia down along the western coasts of North and South America. Monte Verde is located 8,000 miles south of the Bering Strait. Such a considerable distance was probably unreasonable to trek by foot, especially on ice. Furthermore, remains of 22 varieties of seaweed are referenced in regards to this theory. Modern native inhabitants of

1656-528: The Cordilleran Glacier (which covered much of present-day Canada) had not yet melted enough to reveal an ice-free corridor for people to reasonably journey by foot. The Monte Verde radiocarbon dates precede 13,000 BP, despite the fact that before the glacial melt, the vast, desolate, icy landscape of much of the Americas could not possibly have permitted enough vegetation to sustain traveling people or herded animals. The most prevalent theory today

1725-487: The Last Glacial Maximum , archaeologists are increasingly willing to accept the possibility that the initial settlement of the Americas occurred via coastlines. The site was discovered in late 1975 when a veterinary student visited the area of Monte Verde, where severe erosion was occurring due to logging. Prior to the logging, the site itself had been preserved well due to the favorable conditions created by

1794-700: The Waddenzee or the Gulf of Mexico , where land run-off is substantial. In these areas a so-called " dead zone " can be created. Low dissolved oxygen conditions are often seasonal, as is the case in Hood Canal and areas of Puget Sound , in Washington State. The World Resources Institute has identified 375 hypoxic coastal zones around the world, concentrated in coastal areas in Western Europe,

1863-449: The Americas. Monte Verde I is located under an outwash plain , which formed during the last glaciation. It is not directly below MV-II. It was first concluded to be a site of human occupation because of three clay-lined burned areas and 26 stones, 13 of which may have been modified by humans. In 2013, Dillehay and his team returned to perform another excavation at Monte Verde due to the inadequate previous excavations. In 2015, Monte Verde I

1932-548: The Chinchihuapi creek banks. The student was shown a strange "cow bone" collected by nearby farmers who had found it exposed in the eroded Chinchihuapi Creek. The bone later proved to be from Notiomastodon , a gomphothere related to modern elephants. Tom Dillehay , an American anthropologist and professor at the Universidad Austral de Chile at the time, started excavating Monte Verde in 1977. The site

2001-491: The Clovis. Therefore, it is feasible that they traveled along the coast by boat or along the shoreline, and could survive on marine resources throughout the voyage south. The presence of non-local items at Monte Verde, such as plants, beach-rolled pebbles, quartz, and tar, indicates possible trade networks and other sites of human habitation of similar age. Awareness about Monte Verde among the international archaeology community

2070-777: The Eastern and Southern coasts of the US, and East Asia, particularly in Japan. Hypoxia may also be the explanation for periodic phenomena such as the Mobile Bay jubilee , where aquatic life suddenly rushes to the shallows, perhaps trying to escape oxygen-depleted water. Recent widespread shellfish kills near the coasts of Oregon and Washington are also blamed on cyclic dead zone ecology. Phytoplankton are mostly made up of lignin and cellulose, which are broken down by oxidative mechanism, which consume oxygen. The breakdown of phytoplankton in

2139-466: The INTCAL series of curves, beginning with INTCAL98, published in 1998, and updated in 2004, 2009, 2013 and 2020. The improvements to these curves are based on new data gathered from tree rings, varves , coral, and other studies. Significant additions to the datasets used for INTCAL13 include non-varved marine foraminifera data, and U-Th dated speleothems . The INTCAL13 data includes separate curves for

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2208-633: The May 9, 2008 issue of Science , a team reported that they identified nine species of seaweed and marine algae recovered from hearths and other areas in the ancient settlement. The seaweed samples were directly dated between 14,220 and 13,980 years ago. These sites, located approximately 500 meters upstream from the Monte Verde sites along the same river, have been dated to about 14,500 BP. Similar materials, including burned areas and fragmentary scorched animal bones, along with small rock flakes, have been recovered. Dillehay and his team conducted excavations between

2277-698: The Northern and Southern Hemispheres, as they differ systematically because of the hemisphere effect; there is also a separate marine calibration curve. The calibration curve for the southern hemisphere is known as the SHCal as opposed to the IntCal for the northern hemisphere. The most recent version being published in 2020. There is also a different curve for the period post 1955 due to atomic bomb testing creating higher levels of radiocarbon which vary based on latitude, known as bomb cal. Modern methods of calibration take

2346-409: The amount of rainfall in a given year. Those factors affect all trees in an area and so examining tree-ring sequences from old wood allows the identification of overlapping sequences. In that way, an uninterrupted sequence of tree rings can be extended far into the past. The first such published sequence, based on bristlecone pine tree rings, was created in the 1960s by Wesley Ferguson . Hans Suess used

2415-411: The atmosphere and natural waters. Atmospheric hypoxia occurs naturally at high altitudes . Total atmospheric pressure decreases as altitude increases, causing a lower partial pressure of oxygen, which is defined as hypobaric hypoxia. Oxygen remains at 20.9% of the total gas mixture, differing from hypoxic hypoxia , where the percentage of oxygen in the air (or blood) is decreased. This is common in

2484-487: The bottom axis; it is a trimodal graph, with peaks at around 710 AD, 740 AD, and 760 AD. Again, the 1σ confidence ranges are in dark grey, and the 2σ confidence ranges are in light grey. Before the widespread availability of personal computers made probabilistic calibration practical, a simpler "intercept" method was used. Once testing has produced a sample age in radiocarbon years with an associated error range of plus or minus one standard deviation (usually written as ±σ),

2553-466: The calibration curve can be used to derive a range of calendar ages for the sample. The calibration curve itself has an associated error term, which can be seen on the graph labelled "Calibration error and measurement error". This graph shows INTCAL13 data for the calendar years 3100 BP to 3500 BP. The solid line is the INTCAL13 calibration curve, and the dotted lines show the standard error range, as with

2622-420: The data to publish the first calibration curve for radiocarbon dating in 1967. The curve showed two types of variation from the straight line: a long-term fluctuation with a period of about 9,000 years, and a shorter-term variation, often referred to as "wiggles", with a period of decades. Suess said that he drew the line showing the wiggles by "cosmic schwung ", or freehand. It was unclear for some time whether

2691-405: The dates do derive from the same object. This is done by calculating a combined error term for the radiocarbon dates for the samples in question, and then calculating a pooled mean age. It is then possible to apply a T test to determine if the samples have the same true mean. Once this is done the error for the pooled mean age can be calculated, giving a final answer of a single date and range, with

2760-542: The environment depends on the presence of oxygen, and once oxygen is no longer in the bodies of water, ligninperoxidases cannot continue to break down the lignin. When oxygen is not present in the water, the time required for breakdown of phytoplankton changes from 10.7 days to a total of 160 days. The rate of phytoplankton breakdown can be represented using this equation: G ( t ) = G ( 0 ) e − k t {\displaystyle G(t)=G(0)e^{-kt}} In this equation, G(t)

2829-601: The environment, and therefore, hypoxia takes place quickly as oxygen is used up quickly to digest POC. About 9% of POC in phytoplankton can be broken down in a single day at 18 °C. Therefore, it takes about eleven days to completely break down phytoplankton. After POC is broken down, this particulate matter can be turned into other dissolved carbon, such as carbon dioxide, bicarbonate ions, and carbonate. As much as 30% of phytoplankton can be broken down into dissolved carbon. When this particulate organic carbon interacts with 350 nm ultraviolet light, dissolved inorganic carbon

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2898-399: The graph, shows this situation: a radiocarbon age range of about 1260 BP to 1280 BP converts to three separate ranges between about 1190 BP and 1260 BP. A third possibility is that the curve is flat for some range of calendar dates; in this case, illustrated by t 3 , in green on the graph, a range of about 30 radiocarbon years, from 1180 BP to 1210 BP, results in a calendar year range of about

2967-430: The ice free corridor as previously hypothesized, people may have populated the Americas through a coastal route. A group of 12 respected archaeologists revisited the site in 1997 and concluded that Monte Verde was an inhabited site and predated the Clovis culture. One of Dillehay's colleagues, Dr. Mario Pino , claimed a lower layer of the site is 33,200 years old, based on the discovery of burned wood several hundred feet to

3036-436: The islands, has been dated to 1314 AD ± 12 years by wiggle-matching. When several radiocarbon dates are obtained for samples which are known or suspected to be from the same object, it may be possible to combine the measurements to get a more accurate date. Unless the samples are definitely of the same age (for example, if they were both physically taken from a single item) a statistical test must be applied to determine if

3105-518: The nature of the preservation of Monte Verde, it was one of the first Pre-Clovis sites to be accepted by the academic community. Dillehay, himself, doubted his dates due to the strong hold the Clovis First hypothesis had on the academic community. Monte Verde was one of the most accepted Pre-Clovis sites, according to a survey done by Amber Wheat in 2012. Out of 132 respondents (mainly archaeologists), approximately 65% of them confirmed Monte Verde as

3174-435: The night by respiration . When phytoplankton cells die, they sink towards the bottom and are decomposed by bacteria , a process that further reduces DO in the water column. If oxygen depletion progresses to hypoxia, fish kills can occur and invertebrates like worms and clams on the bottom may be killed as well. Hypoxia may also occur in the absence of pollutants. In estuaries, for example, because freshwater flowing from

3243-503: The occupants also butchered now extinct megafauna , including the gomphothere (elephant-relative) Notiomastodon and the llama Palaeolama . Paleoecological evidence of the coastal landscape's ability to sustain human life further supports a " coastal migration " model. Dating of rock surfaces and animal bones suggests the coastal corridor was deglaciated and became habitable after 17,000 years BP. Although testing coastal migration theories can be difficult due to sea level rise since

3312-538: The oldest on record for any species of potato, wild or cultivated, suggest that southern Chile was one of the two main centres for the evolution of Solanum tuberosum tuberosum , the common potato. Remains of forty-five different edible plant species were found within the site, over a fifth of them originating from up to 150 miles (240 km) away. This suggested that the people of Monte Verde either had traded on or traveled regularly in this extended network. Other important finds from this site include human coprolites ,

3381-402: The original normal distribution of radiocarbon age ranges and use it to generate a histogram showing the relative probabilities for calendar ages. This has to be done by numerical methods rather than by a formula because the calibration curve is not describable as a formula. Programs to perform these calculations include OxCal and CALIB. These can be accessed online; they allow the user to enter

3450-435: The oxygen even more so in the environment, further creating hypoxic zones in higher quantities. As more minerals such as phosphorus and nitrogen are displaced into these aquatic systems, the growth of phytoplankton greatly increases, and after their death, hypoxic zones are formed. Radiocarbon calibration Radiocarbon dating measurements produce ages in "radiocarbon years", which must be converted to calendar ages by

3519-461: The population was around 20–30 inhabitants. A human footprint was also observed in the clay, probably from a 70 kg (150 lb) adult. The area consists of four distinct sites, Monte Verde I, Monte Verde II, Chinchihuapi I, and Chinchihuapi II. The Monte Verde site has two distinct levels. The upper level, MV-II, has been extensively characterized. Its occupation is reliably dated to sometime between 14,800 – 13,800 BP. The lower level, MV-I,

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3588-610: The presence of lithic tools and flakes, as well as burned features associated with burned animal and plant remains in CH-I. Material evidence gathered at Monte Verde has reshaped the way archaeologists think about the earliest inhabitants of the Americas. Radiocarbon dating has provided a date of 14,000 BP and possibly 14,800-33,000 BP. Previously, the earliest accepted site had been determined to be near Clovis, New Mexico, dating between 13,500 and 13,000 BP, over 1,000 years later than Monte Verde. The new dates supplied by Monte Verde have made

3657-411: The range suggested by the radiocarbon dates, the wiggles in the calibration curve best match the wiggles in the curve of sample dates. This "wiggle-matching" technique can lead to more precise dating than is possible with individual radiocarbon dates. Since the data points on the calibration curve are five years or more apart, and since at least five points are required for a match, there must be at least

3726-440: The range, and this range is used to read the result directly from the graph itself without reference to the lines showing the calibration error. Variations in the calibration curve can lead to very different resulting calendar year ranges for samples with different radiocarbon ages. The graph to the right shows the part of the INTCAL13 calibration curve from 1000 BP to 1400 BP, a range in which there are significant departures from

3795-440: The regions use these particular local seaweed varieties for medicinal purposes. Using an ethnographic analogy, this suggests that the Monte Verde residents used these varieties for similar purposes, which further suggests an extensive knowledge of marine resources. Together with a relative lack of stone tools, it appears that these first settlers were maritime-adapted hunter-gatherer-fishermen, and not necessarily big-game hunters like

3864-415: The resulting calendar year age are equally likely. Deriving a calendar year range by means of intercepts does not take this into account. For a set of samples with a known sequence and separation in time such as a sequence of tree rings, the samples' radiocarbon ages form a small subset of the calibration curve. The resulting curve can then be matched to the actual calibration curve by identifying where, in

3933-399: The sample error, this is one standard deviation. Simply reading off the range of radiocarbon years against the dotted lines, as is shown for sample t 2 , in red, gives too large a range of calendar years. The error term should be the root of the sum of the squares of the two errors: Example t 1 , in green on the graph, shows this procedure—the resulting error term, σ total , is used for

4002-522: The sealed burrows of some subterranean animals, such as blesmols . Atmospheric hypoxia is also the basis of altitude training , which is a standard part of training for elite athletes. Several companies mimic hypoxia using normobaric artificial atmosphere . An aquatic system lacking dissolved oxygen (0% saturation) is termed anaerobic, reducing , or anoxic . In water, oxygen levels are approximately 7 ppm or 0.0007% in good quality water, but fluctuate. Many organisms require hypoxic conditions. Oxygen

4071-505: The site a key factor in the debate over the first migration route from Asia to North America. Before the discovery of Monte Verde, the most popular and widely accepted theory was the overland route, which speculates that the first American inhabitants migrated from Asia across the Bering Strait and then spread throughout North America. However, the early dates associated with Monte Verde appear to weaken this theory. Prior to 13,000 BP,

4140-426: The sites, using test pits and core drillings. They discovered 12 small burned features directly associated with both burned and unburned animal remains, manuport stones, and anthropologically modified flakes, which were dated between 18,500 BP and 14,500 BP. These findings likely indicate seasonal activities in the area. Up until 2019, Dillehay has conducted two additional excavations at the Chinchihuapi site, revealing

4209-754: The south of Monte Verde. Radiocarbon dating established the wood as 33,000 years old. Dillehay was cautious of this earlier date, and as of 2007 it has not been verified or accepted by the scientific community. MV-I has been radiocarbon dated to 33,000 BP. As with other sites that suggest extremely early dates, such as the Topper site in South Carolina and Pedra Furada in Brazil, this deeper layer remains controversial. The only other archaeological site in Southern Chile comparable in age to Monte Verde

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4278-419: The surface. In a 20-meter water column, it can extend up to 8 meters below the surface. Hypolimnetic oxygen depletion can lead to both summer and winter "kills". During summer stratification , inputs or organic matter and sedimentation of primary producers can increase rates of respiration in the hypolimnion . If oxygen depletion becomes extreme, aerobic organisms, like fish, may die, resulting in what

4347-400: The tent-like structure, two large hearths had been built for community usage, most probably for tool making and craftwork. Each of the living quarters had a brazier pit lined with clay. Around those hearths, many stone tools and remnants of spilled seeds, nuts, and berries were found. A 13,000-year-old specimen of the wild potato , Solanum maglia , was also found at the site; these remains,

4416-435: The term BP is ambiguous. To produce a curve that can be used to relate calendar years to radiocarbon years, a sequence of securely-dated samples is needed, which can be tested to determine their radiocarbon age. Dendrochronology , or the study of tree rings, led to the first such sequence: tree rings from individual pieces of wood show characteristic sequences of rings that vary in thickness due to environmental factors such as

4485-407: The vertical width of the curve corresponds to the width of the standard error in the calibration curve at that point. A normal distribution is shown at left; this is the input data, in radiocarbon years. The central darker part of the normal curve is the range within one standard deviation of the mean; the lighter grey area shows the range within two standard deviations of the mean. The output is along

4554-449: The wiggles were real or not, but they are now well-established. The calibration method also assumes that the temporal variation in C level is global, such that a small number of samples from a specific year are sufficient for calibration, which was experimentally verified in the 1980s. Over the next 30 years, many calibration curves were published by using a variety of methods and statistical approaches. They were superseded by

4623-725: Was greatly increased in 1989 when Dillehay delivered a presentation on Monte Verde at a conference on settlement of the Americas at the University of Maine . Archaeologist David J. Meltzer notes on that presentation: The images Tom Dillehay was showing of the well-preserved remains at Monte Verde—wooden artifacts and house planks, fruits, berries, seeds, leaves, and stems, as well as marine algae, crayfish, chunks of animal hide, and what appeared to be several human coprolites found in three small pits—were unlike anything most of us, who long ago had learned to be used to stone tools and grateful for occasional bits of bone, had ever seen. Because of

4692-563: Was long lasting. Other sites on the coast, such as the Quebrada Jaguay, and Quebrada Tacahuay of Peru, seem to go back to ca. 13,000-12,000 BP. Huaca Prieta in northern Peru was occupied as early as 15,000 BP. Hypoxia (environmental) Hypoxia ( hypo : "below", oxia : "oxygenated") refers to low oxygen conditions. Hypoxia is problematic for air-breathing organisms, yet it is essential for many anaerobic organisms. Hypoxia applies to many situations, but usually refers to

4761-510: Was re-dated to around 18,500 to 14,500 BP. Charcoal remains, charred animal bone fragments and several lithic artifacts, about 34% of which were derived from non-local sources, were discovered. The older end of this range is controversial, however, as it is based on putative lithic tools which some have suggested are instead naturally occurring objects. According to the most recent studies by Dillehay and Pino, Monte Verde II has been dated to around 14,550 calibrated years Before Present. The site

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