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At least 469 records · Page 26Linked to original sources
PubMed2005

Haplotype trees and modern human origins.

A haplotype is a multisite haploid genotype at two or more polymorphic sites on the same chromosome in a defined DNA region. An evolutionary tree of the haplotypes can be estimated if the DNA region had little to no recombination. Haplotype trees can be used to reconstruct past human gene-flow patterns and historical events, but any single tree captures only a small portion of evolutionary history, and is subject to error. A fuller view of human evolution requires multiple DNA regions, and errors can be minimized by cross-validating inferences across loci. An analysis of 25 DNA regions reveals an out-of-Africa expansion event at 1.9 million years ago. Gene flow with isolation by distance was established between African and Eurasian populations by about 1.5 million years ago, with no detectable interruptions since. A second out-of-Africa expansion occurred about 700,000 years ago, and involved interbreeding with at least some Eurasian populations. A third out-of-Africa event occurred around 100,000 years ago, and was also characterized by interbreeding, with the hypothesis of a total Eurasian replacement strongly rejected (P < 10(-17)). This does not preclude the possibility that some Eurasian populations could have been replaced, and the status of Neanderthals is indecisive. Demographic inferences from haplotype trees have been inconsistent, so few definitive conclusions can be made at this time. Haplotype trees from human parasites offer additional insights into human evolution and raise the possibility of an Asian isolate of humanity, but once again not in a definitive fashion. Haplotype trees can also indicate which genes were subject to positive selection in the lineage leading to modern humans. Genetics provides many insights into human evolution, but those insights need to be integrated with fossil and archaeological data to yield a fuller picture of the origin of modern humans.

Emigration and Immigration↗
PubMed1990

Patterns of skeletal histologic change through time: comparison of an archaic native American population with modern populations.

This paper compares patterns of histologic change in an archaic Native American population with those in modern white populations. Histologic sections were removed from core biopsies taken from the anterior femoral cortex of an archeologic sample of Pecos Indians. The data demonstrate many microstructural similarities between the Pecos and modern populations, even though they were genetically and culturally distinct. Pecos women had small Haversian canals and large osteon mean wall thickness, with no clear evidence of an intracortical bone volume deficit even in the older age groups, although significant marrow cavity expansion occurred in both males and females with age. No striking relationships were found between bone tissue changes and gross geometric changes with age. The data suggest that a more active life-style is associated with greater osteon mean wall thickness or osteon population density, but that it alone does not protect against significant bone loss on the cortical-endosteal surface.

Adult↗
PubMed2004

Corrected TIMI frame count: applicability in modern digital catheter laboratories when different frame acquisition rates are used.

The original description of the TIMI frame count (TFC) method was based on angiograms acquired at 30 f/sec. Modern digital angiograms are acquired at lower frame rates (between 12.5 and 25 f/sec). Coronary angiography was acquired at 12.5 and 25 f/sec after 200 mug of intracoronary glyceryl trinitrate. Results of the corrected TIMI frame count (cTFC) at 12.5 and 25 f/sec for each vessel were: right coronary artery, 19.5 +/- 5.2 and 20.4 +/- 6.6 (P = 0.15); circumflex artery, 25.6 +/- 8.2 and 25.9 +/- 8.7 (P = 0.5); and left anterior descending artery, 22.5 +/- 8.1 and 23.8 +/- 10.4 (P = 0.15), respectively. The mean difference in the TFC between two injections by the same operator and by two operators was 0.4 (P = 0.7) and 0.4 (P = 0.2), respectively. The mean difference in the TFC for repeat measurements by the same observer and between two observers was 0.26 (P = 0.3) and 0.06 (P = 0.8), respectively. We confirm that the cTFC is a quantitative method to assess coronary flow that can be applied in a modern digital laboratory.

Aged↗
PubMed1997

Ancient and modern mitochondrial DNA sequences and the colonization of the Pacific.

Mitochondrial DNA (mtDNA) is a valuable tool for the study of recent human evolution because it is easy to analyse, is inherited uniparentally and has a relatively rapid rate of evolution. mtDNA analysis has been used extensively for the elucidation of the pattern of migrations of human populations. Several studies have focused on the Pacific because Polynesia was settled by humans for the first time relatively recently and there is a wealth of archaeological and linguistic data to complement genetic data on the region. Results of mtDNA analyses on modern-day Pacific populations indicate reduced genetic variability, and suggest that the Polynesians descend from people who migrated relatively recently from island Southeast Asia and that a population bottleneck occurred during the settlement of the central Pacific. Several informative polymorphisms have been identified in the hypervariable control region of mtDNA in modern-day Pacific populations that are helpful in tracing the ancestral affinities of these people. Studies of these mtDNA polymorphisms in ancient bones of prehistoric Pacific islanders indicate that the proto-Polynesian colonizers may have descended from the early settlers of island Melanesia. Although fraught with technical difficulties, studies of ancient DNA can provide valuable evidence on the genetic affinities of past peoples.

Asia↗
PubMed1983

Aroma retention in modern bread production.

In highly industrialized countries bread consumption rate decreases in favour of flavour-intensive foods like meat, sweets, cocoa products or alcoholic beverages. This trend which is unfavourable from the nutritional point of view may be forced by flavour losses in modern bread technology itself. Sensory profile studies indicate 4 points which may change the traditional bread flavour, i.e. reduction of flour extraction rate, changes within bread formula, shortening of the dough procedures or of baking time. Possible ways for improving bread flavour in modern technology are discussed. The use of precursor systems as well as of biotechnical procedures deliver chances for future bread production with improved flavour quality.

Bread↗
PubMed1991

Modern immunoassays in meat-product analysis.

The increased regulation of foodstuffs in modern society requires analytical methods which are easy to perform, sensitive, specific and relatively inexpensive. The basic antigen-antibody reaction provides means for very specific analytical procedures. Immunoassays are powerful analytical tools that permit the specific and rapid detection or measurement of antigens and haptens to which antibodies can be produced. Sensitive recognition of the interaction is made possible by labelling the analyte or antibody, mainly with radioisotope (RIA) and enzyme (ELISA). Wide applications of these modern immunoassays to food analysis began about 1980. The paper reviews investigations, where various types of RIA and ELISA were developed for the use in meat product analysis. Detection and determination of various meat species, non-meat proteins, microorganisms and bacterial toxins, drugs, anabolic hormones, pesticides, mycotoxins, and other contaminants in meat and meat products by the means of immunoassays is described. Now, the commercial kits are available for most of these compounds. They make possible to perform analysis in different laboratories under standard conditions. The reason of an enthusiasmic acceptance of this technology is related to its inherent specificity, high sensitivity, and the facility of application. In fact, immunoassays compete with other analytical technics. They have the advantage of economy when screening large numbers of samples.

Animals↗
PubMed2005

Blockheads, roundheads, pointy heads: intellectual disability and the brain before modern medicine.

Recent work on the conceptual history of intellectual disability has pointed to a discontinuity in the seventeenth century, identifying the concept as essentially modern in a more radical sense than mental illness or physical disability. However, Galenist accounts of intellectual impairment were clearly connected (via anatomy) to neurology, which could be taken as prima facie evidence that Galenism shares with modern medicine one of its basic explanatory approaches to intellectual disability. Close textual examination does not bear out this counter-claim, at least as far as the conceptual apparatus itself is concerned. However, it does reveal a degree of continuity in the medical mind-set as discourses of monstrosity were transposed from the domain of anatomy to that of post-Cartesian psychology.

Anatomy↗
PubMed2002

Stable isotope (13C, 15N and 34S) analysis of the hair of modern humans and their domestic animals.

Relationships between dietary status and recent migration were examined by delta(13)C, delta(15)N and delta(34)S analysis of hair samples from 43 modern humans living in a rural community in SW England. The isotopic content of 38 'local' hair samples was compared with that of five recently arrived individuals (from Canada, Chile, Germany and the USA). Hair samples from domestic animals (i.e. mainly cats, dogs, cows and horses) were analysed to examine the difference in delta(13)C, delta(15)N and delta(34)S values between herbivores and carnivores. Generally, modern human hair data from the triple stable isotope (delta(13)C, delta(15)N and delta(34)S) provided enough information to confirm the dietary status and origin of the individual subjects. The dietary intake was generally reflected in the animal hair delta(15)N and delta(13)C values, i.e. highest in the carnivores (cats). However, a non-local origin of food sources given to domesticated omnivores (i.e. dogs) was suggested by their hair delta(34)S values.

Adult↗
PubMed1997

Body proportions in Late Pleistocene Europe and modern human origins.

Body proportions covary with climate, apparently as the result of climatic selection. Ontogenic research and migrant studies have demonstrated that body proportions are largely genetically controlled and are under low selective rates; thus studies of body form can provide evidence for evolutionarily short-term dispersals and/or gene flow. Following these observations, competing models of modern human origins yield different predictions concerning body proportion shifts in Late Pleistocene Europe. Replacement predicts that the earliest modern Europeans will possess "tropical" body proportions (assuming Africa is the center of origin), while Regional Continuity permits only minor shifts in body shape, due to climatic change and/or improved cultural buffering. This study tests these predictions via analyses of osteometric data reflective of trunk height and breadth, limb proportions and relative body mass for samples of Early Upper Paleolithic (EUP), Late Upper Paleolithic (LUP) and Mesolithic (MES) humans and 13 recent African and European populations. Results reveal a clear tendency for the EUP sample to cluster with recent Africans, while LUP and MES samples cluster with recent Europeans. These results refute the hypothesis of local continuity in Europe, and are consistent with an interpretation of elevated gene flow (and population dispersal?) from Africa, followed by subsequent climatic adaptation to colder conditions. These data do not, however, preclude the possibility of some (albeit small) contribution of genes from Neandertals to succeeding populations, as is postulated in Bräuer's "Afro-European Sapiens" model.

Bone and Bones↗
PubMed1997

Using distance matrices to choose between competing theories and an application to the origin of modern humans.

This paper examines competing theories for cases in which both the data and the hypotheses can be represented as distance matrices. A test due to Dow & Cheverud has been used for such comparisons in anthropology, but when data are spatially, temporally, or phylogenetically autocorrelated, this test may be far too liberal. We examine a classification procedure based on ratios of probabilities obtained from Mantel tests of the competing hypotheses and find that design matrices describing only lag-one connections and those eliminating common connections of competing hypotheses are the most informative. We apply this method to simulated gene-frequency data in a 7 x 7 chessboard representing a stepping-stone model and discriminate between alternative theories with a 7% misclassification rate. We also apply these techniques to the current controversy concerning the origin of anatomically modern humans by testing design matrices representing regional continuity and single African origins. The outcome for lag-one matrices and those showing only unique lag-one differences indicate that the single African origin of anatomically modern humans fits the distance matrix based on 165 characters of 83 fossil crania better than the competing theory. However, we also tested a design matrix describing single origin out of southwest Asia. This design matrix was clearly most similar to the data in all tested cases. These results make the regional-continuity theory a less likely explanation for the observed cranial differences than the two single-origin theories. Of these, single southwest Asian origins seems the more likely interpretation of the data.

Biological Evolution↗
PubMed1998

The Middle/Upper Paleolithic interface and the relationship of Neanderthals and early modern humans in the Hrvatsko Zagorje, Croatia.

This paper presents the first detailed analysis of the artefacts from the Mousterian level G3 at Vindija Cave and a revision of the artefact analysis for the early Upper Paleolithic levels (j, i) at Velika Pećina, both in Croatia. Combined with an assessment of the artefacts from the crucial G1 level at Vindija, results of these analyses are used to argue that the combination of Middle and Upper Paleolithic elements in the upper G complex at Vindija is not necessarily the result of geological mixing but may well represent a natural cultural assemblage. Some Upper Paleolithic elements are possibly derived from the local Mousterian, while others result from extraneous cultural influences into this region. Interestingly, currently available radiocarbon dates indicate that Neanderthals (Vindija level G1) and early modern humans (Velika Pećina) were penecontemporaneous in this region at ca. 33 ka, or perhaps somewhat earlier if the radiocarbon dates are taken as minimum age estimates. Therefore some Upper Paleolithic tools associated with the Vindija G1 Neanderthals, such as bone points, may result from imitation of or trade with early modern people. While there is external influence on the development of the early Upper Paleolithic in this region, it exhibits a unique character which does not conform to that of classic Western or Central European Aurignacian.

Animals↗
PubMed1998

A critique of the evidence for scavenging by Neanderthals and early modern humans: new data from Kobeh Cave (Zagros Mountains, Iran) and Die Kelders Cave 1 layer 10 (South Africa).

The primary mode of faunal exploitation by Neandertals and early modern humans remains a debated topic. Binford (1981, 1984, 1985, 1988) has argued for an obligate scavenging mode, Stiner (1991a, 1991b, 1991c, 1993, 1994) for a more opportunistic scavenging mode, while other researchers (Chase, 1986, 1988, 1989; Klein, 1989, 1994, 1995; Klein & Cruz-Uribe, 1996) deny the importance of scavenging as a faunal exploitation tactic. The scavenging interpretations rely primarily on several patterns in the faunal remains: the presence of a skeletal element pattern dominated by heads or head and foot parts, the presence of carnivore tooth marks on bone fragments, and infrequent cut marks that typically are not located on shaft regions of long bones or on fleshy bones. Five sites have been used to argue for scavenging: Klasies River Mouth, Combe Grenal, Grotta Guattari, Grotta dei Moscerini, and Grotte Vaufrey. The former four of the five sites are biased samples in that long bone shafts and other difficult to identify fragments were discarded at excavation. The analysis of Grotte Vaufrey included only those shafts identifiable to species or genus, thus excluding the vast majority of shaft specimens. This bias systematically shapes the skeletal element and surface modification patterning in ways that make the assemblages appear to fit a model of scavenging, when in fact the main determinant of the pattern is the bias in the flawed samples. This problem is illustrated with two unbiased faunal assemblages (Kobeh Cave and Die Kelders Layer 10). Skeletal element abundance is calculated in a way that mimics the bias in the sites listed above by excluding the shafts. Using this procedure, both Kobeh and Die Kelders have a head and foot skeletal element pattern and thus appear scavenged. Both assemblages are then analyzed in their entirety and a new pattern, consistent with hunting, is revealed. Taphonomic data on bone survival and destruction provide an explanation for this result. Excluding shaft fragments from the analysis also biases the surface modification patterning in such a way as to produce a pattern more consistent with scavenging. The conclusion is that there is no reliable evidence for scavenging by Neandertals or early modern humans.

Animals↗
PubMed1999

The premaxilla in Neandertal and early modern children: ontogeny and morphology.

This comparative study of maxillae in Neandertals, Qafzeh, and extant children examines two specific traits: the premaxillary suture (sutura incisiva) and the interincisive sinuses, proposing a new hypothesis about some features of the Neandertal mid-face. Morphologic study of the premaxillary suture at its different borders (i.e. the nasal aspect of the frontal process, nasal and palatal aspects of the palatal process of the maxilla) indicates a persistence of the suture among very young Neandertal children in comparison to the condition in extant ones. This suggests a longer independence of some parts of the premaxilla in Neandertals. To further examine this possibility, CT scans of two Neandertal children were analyzed: Roc de Marsal, estimated to be about 3 years, and Engis 2, estimated to be about 5-6 years. The results are quite different between the fossils. In the older, the premaxillary suture is represented only by a deep groove. In the younger it extends deep to the surface of the nasal process reaching the Parinaud's canal. Synostosis of the premaxillary suture was found to occur later in Neandertal children than in modern ones. Moreover, we observed the existence of two interincisive sinuses in the fossil children, whereas this is rare in modern children (present on only 2% of our sample of 0-6 year-old infants, n = 247). Persistence of an open premaxillary suture represents the potential for an extended period of growth of the Neandertal mid-face. Although no trace of the premaxillary suture remains in adult Neandertals, Neandertals present many features classically considered as consequences of this persistence. The two interincisive sinuses could be a consequence of the labio-lingual diameter of the incisors. The results presented here can be further investigated by additional studies on the cranial sutural system and by precise morphologic observations and CT scans of the mid-face of a larger sample of fossil children.

Adult↗
PubMed2000

Body size, body shape, and long bone strength in modern humans.

To identify behaviorally significant differences in bone structure it is first necessary to control for the effects of body size and body shape. Here the scaling of cross-sectional geometric properties of long bone diaphyses with different "size" measures (bone length, body mass, and the product of bone length and body mass) are compared in two modern human populations with very different body proportions: Pecos Pueblo Amerindians and East Africans. All five major long bones (excluding the fibula) were examined. Mechanical predictions are that cortical area (axial strength) should scale with body mass, while section modulus (bending/torsional strength) should scale with the product of body mass and moment arm length. These predictions are borne out for section moduli, when moment arm length is taken to be proportional to bone length, except in the proximal femoral diaphysis, where moment arm length is proportional to mediolateral body breadth (as would be expected given the predominance of M-L bending loads in this region). Mechanical scaling of long bone bending/torsional strength is similar in the upper and lower limbs despite the fact that the upper limb is not weight-bearing. Results for cortical area are more variable, possibly due to a less direct dependence on mechanical factors. Use of unadjusted bone length alone as a "size" measure produces misleading results when body shape varies significantly, as is the case between many modern and fossil hominid samples. In such cases a correction factor for body shape should be incorporated into any "size" standardization.

Adult↗
PubMed2000

Postcranial functional morphology of Morotopithecus bishopi, with implications for the evolution of modern ape locomotion.

The large-bodied hominoid from Moroto, Uganda has until recently been known only from proconsulid like craniodental remains and some vertebrae with modern ape like features. The discovery of two partial femora and the glenoid portion of a scapula demonstrates that the functional anatomy of Morotopithecus differed markedly from other early and middle Miocene hominoids. Previous studies have consistently associated the vertebral remains with a short, stiff back and with orthograde postures. Although the proximal femur more closely resembles the femora of monkeys than of apes and suggests a moderate degree of hip abduction, the distal femur resembles those of extant large bodied apes and suggests a varied loading regime and an arboreal repertoire that may have included substantial vertical climbing. The femoral shaft displays uniformly thick cortical bone, beyond the range of thickness seen in extant primates, and signifies higher axial loading than is typical of most extant primates. The glenoid fossa is broad and uniformly curved as in extant suspensory primates. Overall, Morotopithecus is reconstructed as an arboreal species that probably relied on forelimb-dominated, deliberate and vertical climbing, suspension and quadrupedalism. Morotopithecus thus marks the first appearance of certain aspects of the modern hominoid body plan by at least 20 Ma. If the suspensory and orthograde adaptations linking Morotopithecus to extant apes are synapomorphies, Morotopithecus may be the only well-documented African Miocene hominoid with a close relationship to living apes and humans.

Animals↗
PubMed2002

The angular distribution of vertebral trabeculae in modern humans, chimpanzees and the Kebara 2 Neanderthal.

Bone is known to remodel to optimize its structure according to its mechanical environment. In particular trabecular arcades are thought to align with the orientations of components of principal strain. This paper presents the application of a novel method for quantifying trabecular orientation to test the hypothesis that hominoid posture and locomotion are reflected in trabecular architecture. Lateral radiographs were taken of vertebrae from the entire thoracolumbar spines of eight modern humans, seven Pan troglodytes and one Neanderthal. The radiographs were digitized and a square region of interest located at the centre of each vertebral body selected. Fourier transforms of the regions of interest were performed and the relative magnitude of the transform in each of 16 angular segments calculated. The simple indices of external vertebral body morphology, wedge angle and aspect ratio, were also calculated from the radiographs. All three species exhibit the same pattern, with the majority of trabeculae oriented either axially or dorsoventrally. This suggests that vertebral mechanical loading is similar in chimpanzees and humans, despite their apparent postural and locomotor differences. Significant differences between the magnitudes of the Fourier transform in the 78.75 degrees and 135 degrees orientations of chimpanzee and human vertebrae were observed in all but the upper thoracic spine. As the magnitudes at these orientations in the Neanderthal correspond more closely to that in the human and the orientational features were unrelated to the external vertebral morphology, the difference between the two magnitudes may well prove to be a useful parameter in future phylogenetic analysis. Modern human spines were found to show a greater variation in the proportions of axial and dorsoventral trabeculae with spinal level than chimpanzees, with the greatest differences observed in the upper thoracic spine and thoracolumbar junction, suggesting an association with postural spinal curves.

Animals↗
PubMed1999

Tendency for local repetitiveness in amino acid usages in modern proteins.

Systematic analyses of human proteins show that neural and immune system-specific, and therefore, relatively "modern" proteins have a tendency for repetitive use of amino acids at a local scale ( approximately 1-20 residues), while ancient proteins (human homologues of Escherichia coli proteins) do not. Those protein subsegments which are unique based on homology search account for the repetitiveness. Simulation shows that such repetitiveness can be maintained by frequent duplication on a very short scale (one to two codons) in the presence of substitutive point mutation, while the latter tends to mitigate the repetitiveness. DNA analyses also show the presence of cryptic (i.e. "out of the codon frame") repetitiveness, which cannot fully be explained by features in protein sequences. Simulative modification of the amino acid sequences of immune system-specific proteins estimate that 2.4 duplication events occur during the period equivalent to ten events of substitution mutation. It is also suggested that the repetitiveness leads to longitudinal unevenness within a given peptide domain. Those peptide motifs which contain similarly charged residues are likely to be generated more frequently in the presence of the tendency for repetitiveness than in its absence. Therefore, the neutral propensity of DNA for duplication, which can also tend to generate repetitiveness in amino acid sequences, seems to be manifested primarily when the constraints on amino acid sequences are relatively weak, and yet may be positively contributing to generation of unevenness in modern proteins.

Algorithms↗
PubMedDate not supplied

Demonstration of the glycocalyces associated with three oral gram-negative bacterial species using a modern acrylic resin technique.

The complex highly hydrated chemical composition of the bacterial glycocalyx renders it difficult to preserve and visualize at the ultrastructural level. Polyanionic stains such as ruthenium red help to maintain some structural integrity, and other more modern approaches include antibody stabilization, lectins, and the addition of lysine to the primary fixative. It has been suggested that the glycocalyx of certain disease-associated organisms may play a role in the pathogenesis of some microbially based diseases such as periodontitis. New, more adequate, modern methodologies are therefore required for the further study of this structure. In the present study a cold dehydration process in conjunction with LR white acrylic resin has been employed to study the glycocalyces of three oral gram-negative bacterial species reported to be periodontopathogens. When compared with organisms processed conventionally and with ruthenium red, the organisms processed by the cold dehydration and LR white method demonstrated a fibrous matrix that was not seen in the other specimens. These results indicate that a combination of reduced dehydration temperature and cold acrylic resin embedding provides the best methodology for the visualization of the fine structure of the bacterial glycocalyx. This approach may be particularly useful in the study of organisms within specific disease-associated environments such as the periodontal pocket.

Acrylic Resins↗