Understanding Fossil Phytolith Preservation: The Role of Partial Dissolution in Paleoecology and Archaeology

Opaline phytoliths are important microfossils used for paleoecological and archaeological reconstructions that are primarily based on relative ratios of specific morphotypes. Recent studies have shown that phytolith assemblages are prone to post-depositional alteration involving partial dissolution, however, the manner in which partial dissolution affects morphotype composition is poorly understood. Here we show that morphotype assemblages from four different plant species subjected to controlled partial dissolution are significantly different from the original assemblages, indicating that the stability of various morphotypes differs, mainly depending on their surface area to bulk ratios. This underlying mechanism produces distorted morphotype compositions in partially dissolved phytolith assemblages, bearing vast implications for morphotype-based paleoecological and archaeological interpretation. Together with analyses of phytolith assemblages from a variety of archaeological sites, our results establish criteria by which well-preserved phytolith assemblages can be selected for accurate paleoecological and archaeological reconstructions

The first Neanderthal remains from an open-air Middle Palaeolithic site in the Levant

The late Middle Palaeolithic (MP) settlement patterns in the Levant included the repeated use of caves and open landscape sites. The fossil record shows that two types of hominins occupied the region during this period - Neandertals and Homo sapiens. Until recently, diagnostic fossil remains were found only at cave sites. Because the two populations in this region left similar material cultural remains, it was impossible to attribute any open-air site to either species. In this study, we present newly discovered fossil remains from intact archaeological layers of the open-air site 'Ein Qashish, in northern Israel. The hominin remains represent three individuals: EQH1, a nondiagnostic skull fragment; EQH2, an upper right third molar (RM3); and EQH3, lower limb bones of a young Neandertal male. EQH2 and EQH3 constitute the first diagnostic anatomical remains of Neandertals at an open-air site in the Levant. The optically stimulated luminescence ages suggest that Neandertals repeatedly visited 'Ein Qashish between 70 and 60 ka. The discovery of Neandertals at open-air sites during the late MP reinforces the view that Neandertals were a resilient population in the Levant shortly before Upper Palaeolithic Homo sapiens populated the region

Understanding Fossil Phytolith Preservation: The Role of Partial Dissolution in Paleoecology and Archaeology

<div><p>Opaline phytoliths are important microfossils used for paleoecological and archaeological reconstructions that are primarily based on relative ratios of specific morphotypes. Recent studies have shown that phytolith assemblages are prone to post-depositional alteration involving partial dissolution, however, the manner in which partial dissolution affects morphotype composition is poorly understood. Here we show that morphotype assemblages from four different plant species subjected to controlled partial dissolution are significantly different from the original assemblages, indicating that the stability of various morphotypes differs, mainly depending on their surface area to bulk ratios. This underlying mechanism produces distorted morphotype compositions in partially dissolved phytolith assemblages, bearing vast implications for morphotype-based paleoecological and archaeological interpretation. Together with analyses of phytolith assemblages from a variety of archaeological sites, our results establish criteria by which well-preserved phytolith assemblages can be selected for accurate paleoecological and archaeological reconstructions.</p></div

Early Evidence for Northern Salmonid Fisheries Discovered using Novel Mineral Proxies

Salmonid resources currently foster socioeconomic prosperity in several nations, yet their importance to many ancient circumpolar societies is poorly understood due to insufficient fish bone preservation at archaeological sites. As a result, there are serious gaps in our knowledge concerning the antiquity of northern salmonid fisheries and their impacts on shaping biodiversity, hunter-gatherer adaptations, and human-ecological networks. The interdisciplinary study presented here demonstrates that calcium-magnesium phosphate minerals formed in burned salmonid bones can preserve at ancient northern sites, thus informing on the early utilization of these resources despite the absence of morphologically classifiable bones. The minerals whitlockite and beta magnesium tricalcium phosphate were identified in rare morphologically classifiable Atlantic salmonid bones from three Mid-Holocene sites in Finland. Large amounts of beta magnesium tricalcium phosphate were also experimentally formed by burning modern Atlantic salmonid and brown trout bones. Our results demonstrate the value of these minerals as proxies for ancient northern salmonid fishing. Specifically, the whitlockite mineral was discovered in hearth sediments from the 5,600 year old Yli-Ii Kierikinkangas site on the Iijoki River in northern Finland. Our fine sieving and mineralogical analyses of these sediments, along with zooarchaeological identification of recovered bone fragments, have confirmed for the first time that the people living at this village did incorporate salmonids into their economies, thus providing new evidence for early estuary/riverine fisheries in northern Finland.Peer reviewe

Black-Coloured Bones in Hayonim Cave, Israel: Differentiating Between Burning and Oxide Staining

Identification of fossil burned bones is commonly based on their black colour. While colour-based identification is applicable to recent burned bones, fossil bones may be black due to mineral staining, such as by black manganese oxides. We therefore developed an analytical method that purifies oxides from bones. The end product of the method was analysed by means of Fourier transform infra-red (FTIR) spectroscopy. The method can be used for differentiating between black fossil bones that are burned and unstained, burned and stained, and stained but not burned. A survey of 30 black bones from the Mousterian and Aurignacian deposits of Hayonim Cave (Israel) showed that the majority of the bones were indeed burned, of which a few were burned and stained. Several bones were stained and unburned. This method can be readily applied to other archaeological sites where the proportions of burned and stained bones may be quite different

The solubility of phytolith assemblages extracted by dry ashing from modern fresh plant samples.

<p>Solubility was determined at pH 10 after the solutions reached saturation with respect to Si. The percentage of weight loss shows that the experimental conditions resulted in partial dissolution of the phytolith assemblages. Error bars indicate 1σ standard deviation between duplicates. Cross: sedge inflorescence; triangle: reed leaf; diamond: rice inflorescence; circle: palm leaf; square: rice leaf.</p

Calculated surface area to bulk (SA/V) ratios for selected morphotypes in the various modern plant assemblages.

<p>Error bars indicate 1σ standard deviation among several measured individual phytoliths of the same morphotype (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125532#pone.0125532.s006" target="_blank">S1 Table</a>). The relatively large variation reflects the natural variability in phytolith sizes. Values above 1 indicate relatively unstable morphotypes while values below 1 indicate relatively stable morphotypes. Note that the same morphotype (e.g., psilate parallelpipedal elongated, here denoted as P.E. psilate) may have very different SA/V ratio in different plant parts (or in different plant species, e.g., bilobate short cells from rice leaves vs. reed leaves), depending on their overall size—the larger the morphotype the lower its SA/V value and the higher its stability. This observation indicates that bulkiness, as affected by size, are important factors determining the stability of phytolith morphotypes.</p

Identification of pastoral sites using stable nitrogen and carbon isotopes from bulk sediment samples : a case study in modern and archaeological pastoral settlements in Kenya

The identification of pastoral sites in the East African archaeological record is problematic. Recently, a method for the identification of degraded livestock enclosure sediments had been developed that takes into account the geoarchaeological indicators of micromorphology, phytolith concentrations and the mineral assemblages. This suite of indicators may not always be present in degraded livestock enclosure sediments. This study presents an additional indicator by which degraded livestock enclosure sediments may be identified, namely the isotopic composition of organic nitrogen measured on bulk sediment samples. We studied a highly controlled ethnoarchaeological sequence of abandoned Maasai livestock enclosure sediments sampled in Rombo area, southern Kenya. The results were compared to archaeological sediments from the Elmenteitan Pastoral Neolithic site of Sugenya, southwestern Kenya, radiocarbon dated to ca. 2000 BP (uncalibrated). The sediments from both sites were studied using all four types of analyses, i.e., micromorphology, mineralogy, phytolith concentrations, and stable carbon and nitrogen isotopic compositions on bulk sediment samples. The results show that in abandoned livestock enclosure sediments of known ages a significant enrichment in the heavy nitrogen isotope (15N) occurs, and that carbon isotopic compositions may be useful for differentiating cattle from caprine enclosures following their dietary preferences (i.e., grazers vs. browsers). A similar pattern of 15N enrichment is observed in sediments sampled within the site of Sugenya while sediments sampled outside the site's perimeter are generally depleted in 15N. The micromorphological, mineralogical and phytolith analyses support the conclusion that the sediments from within the site of Sugenya represent degraded livestock enclosure sediments. The carbon isotopic composition from the degraded dung deposits strongly suggests that livestock kept at Sugenya were cattle. Overall, this study presents new empirical data that can be used for the identification of livestock enclosures, and shows that the isotopic signatures and geoarchaeological indicators can preserve for at least two millennia.8 page(s

Comparison of solubility at pH 10 among modern and ancient phytolith assemblages in relation to antiquity.

<p>Open diamonds: modern plants (this study and wheat from Cabanes <i>et al</i>.[<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125532#pone.0125532.ref027" target="_blank">27</a>]). Squares: 7^th century AD assemblages from the shallowly buried site of Wadi el-Mustayer, Negev desert, Israel [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125532#pone.0125532.ref040" target="_blank">40</a>]. Circles: 9^th century BCE assemblages from the deeply buried site of Tell es-Safi/Gath, southern Shephela, Israel. Triangle: 10^th century BCE assemblage from the deeply buried site of Tel Dor, northern coast, Israel [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125532#pone.0125532.ref027" target="_blank">27</a>]. Full diamonds: 11^th century BCE assemblages from the shallowly buried site of Izbet Sartah, western Samarian hills, Israel [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125532#pone.0125532.ref037" target="_blank">37</a>]. Star: 9^th-mid 8^th millennia BCE assemblages from the deeply buried site of Aşıklı Höyük, Anatolia, Turkey. Note that high solubility at pH 10 indicates better preservation as solubility is closer to that of modern plant assemblages. The lowest values, indicating poor preservation, were obtained from shallowly buried sites from humid Mediterranean environments. The highest values, indicating good preservation, were obtained from deeply buried sites in various environmental settings with no relation to antiquity. Exceptional good preservation is noticed in shallowly buried sites in arid environments.</p