湖北“郧县人”化石地层的ESR测年研究

本报道用电子自旋共振法测定与郧县人颅骨同层的９个哺乳动物牙釉质化石年龄的结果。其平均值为５８．１±９．３万年,对被测样检验了其对铀的封闭性,采用指数函数拟合与铀早期加入模型计算年龄,讨论了测年中可能存在的系统误差。     

On the fallacy of using orthogenetic models of rectilinear change in arvicolid teeth for estimating the age of the first human settlements in Western Europe

Lozano-Fernández et al. (Lozano-Fernández I, Blain HA, López-García JM, Agustí J. 2014. Biochronology of the first hominid remains in Europe using the vole Mimomys savini: Fuente Nueva 3 and Barranco León D, Guadix-Baza Basin, south-eastern Spain. Hist Biol: Int J Paleobiol. doi:10.1080/08912963.2014.920015) recently published age estimates for two Late Villafranchian sites of Orce (Guadix-Baza basin, SE Spain), BL-D and FN-3, which provide some of the earliest evidence of human presence in Western Europe. The estimates were obtained from mean Lm1 values of the water vole Mimomys savini preserved in the sites and a couple of rectilinear equations derived in the Atapuerca TD section for site age on tooth length. However, this chronometric tool has problems that discourage its use in biostratigraphy, including: (1) the assumption of an orthogenetic trend of Lm1 increase during the evolution of the M. savini/Arvicola lineage; (2) the use of a chronology for the TD section not supported by original ESR data; (3) the discrepancies between the mean Lm1 values published for the TD levels and (4) the chronological ranges predicted when the standard deviations are used, which are exceedingly large as to be of value for biostratigraphic purposes. As a result, the pseudo numerical ages estimated for the Orce sites only add noise to the timing of the first human dispersal in Europe, which is based on a combination of results from well-established techniques such as palaeomagnetism, biostratigraphy and ESR.     

Differing shades of colour: online dating preferences of biracial individuals

The racial and ethnic makeup of the United States has become increasingly diverse over the past few decades. Growing rates of interracial dating and marriage have led to an increasing number of biracial individuals. Despite increasing rates of biracial individuals, research on this population specifically in relation to dating preferences, remains limited in scope. In order to assess biracial individuals' romantic partner preferences, the present research examines 1,203 Internet dating profiles drawn from Match.com. This study utilizes logistic regression to examine the willingness of biracial individuals to cross the colour line when seeking a potential romantic partner. The findings suggest that there are distinct racial dating preferences that reflect the presence of a triracial hierarchy. These results are examined in relation to how identity formation and racial stratification may play a part in shaping the racial/ethnic dating preferences of biracial individuals.     

Inferences from tip‐calibrated phylogenies: a review and a practical guide

Molecular dating of phylogenetic trees is a growing discipline using sequence data to co‐estimate the timing of evolutionary events and rates of molecular evolution. All molecular‐dating methods require converting genetic divergence between sequences into absolute time. Historically, this could only be achieved by associating externally derived dates obtained from fossil or biogeographical evidence to internal nodes of the tree. In some cases, notably for fast‐evolving genomes such as viruses and some bacteria, the time span over which samples were collected may cover a significant proportion of the time since they last shared a common ancestor. This situation allows phylogenetic trees to be calibrated by associating sampling dates directly to the sequences representing the tips (terminal nodes) of the tree. The increasing availability of genomic data from ancient DNA extends the applicability of such tip‐based calibration to a variety of taxa including humans, extinct megafauna and various microorganisms which typically have a scarce fossil record. The development of statistical models accounting for heterogeneity in different aspects of the evolutionary process while accommodating very large data sets (e.g. whole genomes) has allowed using tip‐dating methods to reach inferences on divergence times, substitution rates, past demography or the age of specific mutations on a variety of spatiotemporal scales. In this review, we summarize the current state of the art of tip dating, discuss some recent applications, highlight common pitfalls and provide a ‘how to’ guide to thoroughly perform such analyses.     

The presence of the brown bear Ursus arctos in Holocene Britain: a review of the evidence

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Uptake of organic matter by the roots of sweet potato: Analysis of the δ14C value of plants

Summary To determine whether sweet potato (Ipomoea batatas (L.) Poir.) takes up organic matter through the roots from the medium, the concentrations of natural¹⁴C (¹⁴C) in plant organic matter, atmospheric CO₂ and compost applied to media were examined under soil and sand culture conditions. In these experiments, three kinds of composts of different ¹⁴C were used. CO₂ derived from the mineralization of compost was continuously pumped out from the pots and its direct uptake by the leaves was prevented.¹⁴C of plant parts harvested after the 43 days experimental period were affected by the ¹⁴C of the compost in the treatments where the compost of rice straw was applied, and which suggested that a significant amount of plant carbon was derived from the compost.     

Using chromosomal data in the phylogenetic and molecular dating framework: karyotype evolution and diversification in Nierembergia (Solanaceae) influenced by historical changes in sea level

Karyotype data within a phylogenetic framework and molecular dating were used to examine chromosome evolution in Nierembergia and to infer how geological or climatic processes have influenced in the diversification of this solanaceous genus native to South America and Mexico. Despite the numerous studies comparing karyotype features across species, including the use of molecular phylogenies, to date relatively few studies have used formal comparative methods to elucidate chromosomal evolution, especially to reconstruct the whole ancestral karyotypes. Here, we mapped on the Nierembergia phylogeny one complete set of chromosomal data obtained by conventional staining, AgNOR‐, C‐ and fluorescent chromosome banding, and fluorescent in situ hybridisation. In addition, we used a Bayesian molecular relaxed clock to estimate divergence times between species. Nierembergia showed two major divergent clades: a mountainous species group with symmetrical karyotypes, large chromosomes, only one nucleolar organising region (NOR) and without centromeric heterochromatin, and a lowland species group with asymmetrical karyotypes, small chromosomes, two chromosomes pairs with NORs and centromeric heterochromatin bands. Molecular dating on the DNA phylogeny revealed that both groups diverged during Late Miocene, when Atlantic marine ingressions, called the ‘Paranense Sea’, probably forced the ancestors of these species to find refuge in unflooded areas for about 2 Myr. This split agrees with an increased asymmetry and heterochromatin amount, and decrease in karyotype length and chromosome size. Thus, when the two Nierembergia ancestral lineages were isolated, major divergences occurred in chromosomal evolution, and then each lineage underwent speciation separately, with relatively minor changes in chromosomal characteristics.     

Combined dendrochronological and radiocarbon dating of three Russian icons from the 15th–17th century

Dendrochronology is usually the only method of precise dating of unsigned art objects made on or of wood. It has a long history of application in Europe, however in Russia such an approach is still at an infant stage, despite its cultural importance. Here we present the results of dendrochronological and radiocarbon accelerated mass spectrometry (AMS) dating of three medieval icons from the 15th–17th century that originate from the North of European Russia and are painted on wooden panels made from Scots pines. For each icon the wooden panels were dendrochronologically studied and five to six AMS dates were made. Two icons were successfully dendro-dated whereas one failed to be reliably cross-dated with the existing master tree-ring chronologies, but was dated by radiocarbon wiggle-matching. Wiggle-matching of radiocarbon dates is the most promising method for dating Russian icons in the absence of a dense dendrochronological network. However, for this case uncertainties connected with the radiocarbon method have to be taken into account and further studies of these uncertainties must be undertaken by comparing dendro-dated and radiocarbon-dated wooden works of art. Our results, moreover, showed that in two cases art-historical dates were by five to ten decades older than the earliest possible time of the creation of the icons, based on dendrochronology.