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The article is a review of the chemical elements which are used in Anthropology to indicate about a life history of an individual or population. <p> Bone = 70% mineral, 20% collagen, 8% water, and 2% noncollagenous components. <p> The mineral phase is principally composed of calcium phosphate, which is present in both crystalline and amorphous forms. The dominant form is crystalline hydroxyapatite. <p> For normal adults the tunrover rate of trabecular bone is estimated to be three to ten times faster than for cortical bone. Although there are variations, the annual turnover rate for trabecular bone averages 10% and that for cortical bone 2.5%. <p> There is a great deal that we do not know about the distribution of trace elements in the skeleton. Further, most researchers are using inferential statistics to compare populations have assumed a normal distribution. This may not be true since many physiological variables follow a log-normal or Poisson distribution. <p> <b>Strontium</b><p> Strontium is just below calcium in the periodic table and as a result shares many of its chemical properties, including the ability to replace calcium in the metabolic process of plants and animals. In general, plants do not discriminate between calcium and strontium, so the proportion of these elements in platns reflects the proportion in their environmnet. By contrast, the intestinal epithelium of mammals has the ability to discriminate against strontium in favor of calcium. As a result, mammaliam tissues have lower Sr/Ca ratios than the foods ingested by the animals. Thus, herbivores have lower Sr/Ca ratios than the plants on whihc they feed. In turn, carnivores have an even lower ratio because the herbivores on which they prey have less strontium than plants. Omnivores are intermediate. Specifically, an increased proportion of meat and plant foods would increase the Sr/Ca ratio
an increased proportion of meat would lower it. <p> Questions that have been asked:<p> 1) estimation of the proportion of meat and vegetable foods in the diet by comparing human and animal bon from the same site<br/> 2) comparisons of the dietary proportions of meat and vegetables between sties, with and without animal controls<br/> 3) estimation of dietary change at a site or region over time<br/> 4) inference of status differentiation within a site or temporal changes in social distinctions<br/> 5) investigation of possible correlates between dietary and morphological change<br/> <p> All of these studies have focused on the terrestrial plant versus terrestrial animal dichotomy. Aquatic and marine resource may strongly influence the skeletal strontium content. <p> pg 78<br/> Mollusks and marine fish bone accumulate strontium, and the latter may be significant when the entire fish is consumed, as in the case of anchovies. <p> In animals, the strontium content of the enamel reflect the level of circulating strontium in youth, when the enamel is fomed. Bone strontium, by contrast, reflects levels circulating in adult animals. <p> pg 79<br/>As a possible control for diagenesis in strontrium, Sillen suggests that determination be made on both herbivore and carnivore from the same stratum as human bones. Tough to do however. <p> Status difference detection is the most difficult of those 5 listed above. This is because diets vary over time and meat intake varied as well. There could have been high and low status meats culturally but that does not discriminate physiologically. <p> pg 80<br/> Barium<br/> <p> Magnesium<br/> <p> pg 81<br/> Transition elements of manganese, iron, copper, and zinc. <p> <u>Iron</u> <p> Heme iron is derived primarily from hemoglobin and myoglobin, whereas nonheme iron comes largely from plant sources. <p> pg 84<br/> Carbon Isotopes<p> Almost 99% of the earth's carbon is the stable carbon <sup>12</sup>C, and just over 1% is the other, <sup>13</sup>C
the unstable C<sup>14</sup> comprises only a tiny fraction. <p> <i>Canopy Effect</i> <p> Leaves near the floor are isotopically lighter than the same variety near the top of the canopy. Rotting vegetation on the forest floor releases isotopically light carbon dioxide, and the forest canopy traps the air so that it does not mix freely with the atmosphere <p> pg 86<br/> In coastal areas where neight C\-4\- plants nore seafood can be excluded from the subsistance base, interpretation of collagen delta<sup>13</sup>C values become much more equivocal. <p> pg 90<br/> Nitrogen<p> The distinction between leguminous and non-leguminous plants is pertinent because nitrogen-fixing platns (primarily legumes) have a nitrogen isotope ratio similar to that of the atmosphere, whereas plants that cannot fix nitrogen have an isotopic composition similar to the soil in which they are grown. <p> The usually higher delta<sup>15</sup>N values of marine nitrogen compounds are a result of dentification with a high fractionation factor than the continuous input of isotopically enriched organic matter. Nitrogen enrichment increaes with each food chain. Thus, there is an isotopic enrichment with tropic levels in both terrestrial and marine food chains, but marine organisms have significantly higher <sup>15</sup>N content than their terrestrial counterparts. <p> Coastal fisher-gatherers produced higher delta<sup>15</sup>N values than the agriculturalists, and the value ranges were non-overlapping. <p> Carbon isotopes alone cannot distinguish between marine and C\-4\- plant components of the diet, should both be present, but nitrogen isotopes or barium may resolve the marine contribution.
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