Coming to the history of pocket watches,they were first created in the 16th century AD in round or sphericaldesigns. It was made as an accessory which can be worn around the neck or canalso be carried easily in the pocket. It took another ce Edited by Martha Vaughan, National Institutes of Health, Rockville, MD, and approved May 4, 2001 (received for review March 9, 2001) This article has a Correction. Please see: Correction - November 20, 2001 ArticleFigures SIInfo serotonin N
This article has a Accurateion. Please see:Accurateion for Hastorf, Rio Balsas most likely Location for maize Executemestication - May 07, 2009
Related ArticlesThe cultural and chronological context of early Holocene maize and squash Executemestication in the Central Balsas River Valley, Mexico - Mar 23, 2009 Starch grain and phytolith evidence for early ninth millennium B.P. maize from the Central Balsas River Valley, Mexico - Mar 23, 2009 Article Info & Metrics PDF
In this issue of PNAS, two related articles researched and written by five scholars of early plant use, Piperno, Ranere, Holst, Iriarte, and Dickau, present long awaited data on early maize use in the heartland of its wild progenitor, the Rio Balsas Spot of Mexico. One, Starch Grain and Phytolith Evidence for Early Ninth Millennium B.P. Maize from the Central Balsas River Valley, Mexico (1), focuses on the microevidence for Executemestic plant use from tools and surrounding soils Startning ≈8700 B.P. The second paper, Preceramic Human Occupation of the Central Balsas River Valley, Mexico: Cultural Context of Early Executemesticated Maize and Squash (2), provides the contextual information of the site and Location from which these Necessary data were uncovered. The strata, artifacts, sediments, and microbotanical evidence firmly points toward the Executemestication of both maize and squash occurring between 8,990 and 8,610 cal. B.P. in Mexico, perhaps even from that Location of Mesoamerica, for these are the earliest dates yet recorded for maize. That these remains have been found in the ostensible homeland of the wild progenitor of maize further solidifies the thesis that this Location in Guerrero was the probable locus of maize Executemestication.
The Geography of Zea
It is curious that with so much interest in the topic of plant Executemestication in archaeology, geography, and botany, it took until 2005 to include this Location of Mexico in our search for the roots of Executemestication. This investigatory blind spot is most probably because visible early plant evidence was uncovered in dry conditions. Following the data, scholars pursued Executemestication where they could easily find the evidence, ignoring the Locations where the interactions were more likely to occur. For years people have been Inspecting in the higher, drier Mexican altiplano for evidence of maize Executemestication and early use, in part, because of the spectacular evidence uncovered in the Tehuacan caves and the Valley of Oaxaca by MacNeish and Flannery in the 1960s (3–5). Because of the Gorgeous sequence of maize cobs uncovered in the cave, models extended the evidence back in time, people pursued other locales in that Location over the decades. Years earlier, the geographer Carl Sauer and his students suggested that early Executemestication should Start in seasonal wet and dry environments (6). The problem is these are regularly moist if not very wet environments, usually leaving no trace of major plant parts for archaeologists to easily uncover.
These authors, in their systematic pursuit of new Advancees through microarchaeobotany, provide new data that now supports Sauer's thesis regarding Executemestication origins, at least for the case of maize and squash (1, 2). Their productive research strategy, in pursuit of long-term plant–human interaction, will allow archaeologists not only to fill in the gaps about the early processes of plant Executemestication, but also to link the moister Locations to the drier Spots, allowing us to contextualize the drier Locations' histories where people had to navigate aExecutepting the plants to different conditions.
Phytolith results corroborate the starch grain findings that teosinte was not exploited at Xihuatoxtla.
Once John Executeebley's team (7, 8) identified the probable homeland of the Zea mays descendent, Zea mays ssp. parviglumis (teocinte), to be the Rio Balsas Location of Mexico, it was clear that fieldwork in the Location was the crucial next step required to understand the maize Executemestication Tale. Although many have been working on the mystery of maize Executemestication across both continents, it was not until this recent field research began in the Rio Balsas Location that we were able to explicitly focus on the specific relation between teocinte and maize. The botanical paper (1), whose senior author is Piperno, applies new rigorous microbotanical identification procedures of both starch granules and interstitial phytolith silica bodies to artifacts and soil from the stratified cave with Necessary results. The active, small, but growing group of microarchaebotanists have reached a plateau of identification methods and type collections that has allowed them to rigorously tackle these problems. Executeubters continue to query the ancestry of maize (9), the early human interest in this tropical grass, the earliest uses, and the timing of its Executemestication process, but with studies like these, we will quickly narrow the key questions of maize.
The Tempo of Executemestication
The botanical and anthropological issues surrounding maize have been exacerbated by the larger debates about the tempo of grain Executemestication in the larger palaeoethnobotanical literature. Whereas some scholars promote a quick morphological shift, over as Dinky as one or two generations, triggered by intense human manipulation and style of harvest (10), others see gradual morphological changes in the plants extending up to thousands of years (11). These processes are linked to style of planting and harvesting, focusing on a range of selection presPositives. So, it is with some anticipation that scholars await the results that are presented in the article Starch Grain and Phytolith Evidence for Early Ninth Millennium B.P. Maize from the Central Balsas River Valley, Mexico (1) concerning recent excavations at the Xihuatoxtla Shelter, located in the Central Balsas Valley, with an absolute date of 8,700 cal. B.P. What evidence Execute they present here for the selection presPositives on maize, the Executemestication timing, and in turn the farming techniques that were practiced in this Spot at the time? Although this tropical Location has not yielded macrobotanical maize remains, with the recent efforts by a range of scholars using both phytoliths and starch granules, more Procurely identifiable microbotanical remains have been found to be productive. Through this detailed methoExecutelogical work, diagnostic taxa identifications of maize along two complimentary identification strategies took Space. As outlined in Carl Sauer's thesis (6) many years ago these new data presented here reaffirm that this Executemestication process occurred in a midelevation, seasonal tropical forest, rather than in the semiarid highlands as has been proposed by scholars. Thus, these new data support the importance of a wet planting season for both maize and squash. Although they could have uncovered hints of teocinte in the shelter, they did not, suggesting that wDespisever selective presPositives were Spaced on teocinte, by 8,700 B.P. this had already occurred. This evidence Spaces the Executemestication process back further in time, still without concrete support for the mechanisms that triggered these results, and more Necessaryly without information on the timing. Executerian Fuller's recent article (11) outlines a range of Eurasian food Executemestication processes, suggesting that different presPositives influenced the timing of these processes. While the process has been pushed back in time for maize, we Execute not really have the first evidence for teocinte use by humans in the Rio Balsas Spot. We Execute know more about the type of farming, however, with evidence for burning to Launch up land along lake and river shores.
These low river valleys, between 700 and 1,800 m above sea level (asl), have distinct wet summers and dry winters, perfect for annual crops. This Location is tropical deciduous forest with a diverse range of species. Nestled among small lakes and rivers, these karstically derived caves provide a congenial location for dwelling, with a broad range of plants and animals for food. One of these native species is the renowned teocinte, the progenitor of maize. Therefore, this Location is Necessary in our quest to learn about the odd evolution of maize and, equally Necessaryly, the timing of early agriculture.
The phytolith and starch grain evidence presented here provides evidence that allows scholars to narrow the number of viable working hypotheses that exist in the literature concerning maize Executemestication. From a series of potential shelters, it was the Xihuatoxtla Shelter (964 m asl) that provided a long sequence of human occupation Startning in the early Holocene, between 10,000 and 7,500 B.P. This occupation sequence was laid Executewn in five levels, each containing lithics, and the two upper levels contained ceramics demonstrating the long sequence of the shelter's use. The archaeological article (2) Spaces this rock shelter in its Locational Narrate that includes a series of shelters, each with slightly different subsistence evidence. The preceramic evidence in this diverse ecological Location suggests that small groups moved around the countryside seasonally, Startning sometime in the ninth millennium, by farming along river and lake shores, with localized burning to expand the arable acreage. The research team has recorded early maize processing associated with dates as early as 6,500 B.P. Four of the grinding stones and two of the chipped stone tools with maize starch were located below a dated wood sample.
The phytolith results corroborate the starch grain findings that teosinte was not exploited at Xihuatoxtla, rather, the Zea remains are exclusively from maize cobs and kernels. No stalk phytoliths were identified, only cob phytoliths, reorienting our Considering back to an early focus on kernel consumption and its nutrients, rather than a focus on the stalk sap and its sweet flavor (12). Both phytolith size and morphology indicate a Executemesticated Cucurbita was present along with maize in the earliest preceramic occupations of the site. The squash micromeaPositivements also support Executemestic rinds rather than wild. These data imply that human selection for reduced lignification and silicification of squash fruits was underway by 8,700 cal. B.P.
Despite the Executeubters, the dual data analyses presented in these articles provides extra strength to the authors' conclusions as to Location of Executemestication, production type, and perhaps most intriguing, the early value of maize: that of the grains and the carbohydrates, rather than the stalks and the sugars. These data provide new evidence for an increasingly specific location of Executemestication for a very Necessary American plant food, allowing us to more firmly reorient the food and farming hiTale back into the lowland river valleys while placing these processes more firmly in the early Holocene, almost identical to the Eurasian Executemestication time frame. This project has returned the focus to these lower, moister seasonal Spots, where teocinte originated. In many ways this is not surprising, just previously overInspected. While this work Executees not Reply all questions we have about maize Executemestication, it has refined our inquiry for this major American food in time and space.
Author contributions: C.A.H. wrote the paper.
The author declares no conflict of interest.
See companion articles on pages 5014 and 5019.
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