Alejandro Pérez-Pérez

Non-occlusal dental microwear variability in a sample of Middle and Late Pleistocene human populations from Europe and the Near East.

Non-occlusal, buccal tooth microwear variability has been studied in 68 fossil humans from Europe and the Near East. The microwear patterns observed suggest that a major shift in human dietary habits and food processing techniques might have taken place in the transition from the Middle to the Late Pleistocene populations. Differences in microwear density, average length, and orientation of striations indicate that Middle Pleistocene humans had more abrasive dietary habits than Late Pleistocene populations. Both dietary and cultural factors might be responsible for the differences observed. In addition, the Middle Paleolithic Neanderthal specimens studied show a highly heterogeneous pattern of microwear when compared to the other samples considered, which is inconsistent with a hypothesis of all Neanderthals having a strictly carnivorous diet. The high density of striations observed in the buccal surfaces of several Neanderthal teeth might be indicative of the inclusion of plant foods in their diet. The buccal microwear variability observed in the Neanderthals is compatible with an overall exploitation of both plant and meat foods on the basis of food availability. A preliminary analysis of the relationship between buccal microwear density and climatic conditions prevailing in Europe during the Late Pleistocene has been attempted. Cold climatic conditions, as indicated by oxygen isotope stage data, seem to be responsible for higher densities of microwear features, whereas warmer periods could correspond to a reduced pattern of scratch density. Such a relationship would be indicative of less abrasive dietary habits, perhaps more meat dependent, during warmer periods.

Dietary inferences through buccal microwear analysis of Middle and Upper Pleistocene human fossils

Buccal microwear has been studied in a sample of 153 molar teeth from different modern hunter-gatherer, pastoralist, and agriculturalist groups, with different diets (Inuit, Fueguians, Bushmen, Australian aborigines, Andamanese, Indians from Vancouver, Veddahs, Tasmanians, Lapps, and Hindus), preserved at museum collections. Molds of an area of the buccal surface have been obtained and observed at 100x magnification in a scanning electron microscope (SEM). The length and orientation of each striation have been determined with a semiautomatic program of an image analyzer system (IBAS). Results show that intergroup variability is significantly higher than the intragroup variability. There exists a tendency toward fewer striations and a higher proportion of vertical striations in the carnivorous groups than in the vegetarian ones. This microwear pattern is concordant with biomechanics (predominantly vertical mandible movements in meat eaters) and phytolith content in plants (more abrasive particles in vegetarian diets). The variability found has been used in a multivariate analysis as a base to compare the microwear pattern of a sample of 20 Middle and Upper Pleistocene fossils, mainly from Europe, analyzed with the same methodology. The sample includes specimens usually classified as archaic H. sapiens (Broken Hill, Banyoles, Montmaurin, La Chaise-Suard, La Chaise-Bourgeios et Delaunay), Neanderthal (La Quina V, Gibraltar 2, Tabun 1 and 2, Amud 1, Malarnaud, St. Cesaire, Marillac), and anatomically modern H. sapiens (Skhül 4, Qafzeh 9, Cro-Magnon 4, Abri-Pataud, Veyrier, La Madelaine, Rond-du-Barry). Results indicate that some of the Neanderthal specimens have a microwear pattern close to that of the carnivorous groups (such as Inuit and Fueguians), suggesting that these individuals follow a hunter strategy. In contrast, archaic H. sapiens and H. sapiens sapiens seem to have a more abrasive diet, probably more depending on vegetable materials, than the Neanderthals.

Late neandertals in southeastern Iberia: Sima de las Palomas del Cabezo Gordo, Murcia, Spain.

Middle Paleolithic fossil human remains from the Sima de las Palomas in southeastern Iberia (dated to ≤43,000–40,000 calendar years before present) present a suite of derived Neandertal and/or retained ancestral morphological features in the mandibular symphysis, mandibular ramus, dental occlusal morphology, and distal hand phalanx. These traits are combined with variation in the mandibular corpus, discrete dental morphology, tooth root lengths, and anterior dental size that indicate a frequency difference with earlier Iberian and more northern European Neandertals. The Palomas Neandertals therefore confirm the late presence of Neandertals associated with the Iberian persistence of the Middle Paleolithic, but suggest microevolutionary processes and/or population contact with contemporaneous modern humans to the north.

A review of interproximal wear grooves on fossil hominin teeth with new evidence from Olduvai Gorge.

Interproximal (approximal) grooves at the cementum-enamel junction of premolar and molar teeth have been observed in a broad range of human ancestors and related extinct species from 1.84 million years ago to the present. Many hypotheses have been presented to explain the aetiology of these grooves, though their form and positioning are most consistent with tooth-picking behaviours. This paper reviews occurrences of interproximal grooves in the cheek teeth of modern and fossil humans, evaluates hypotheses on their cause, and reports on a previously undescribed groove found in OH 60, a molar tooth from Olduvai Gorge. This specimen is among the earliest to show such grooving, and is most likely attributable to Homo erectus. It is concluded that, because interproximal grooves have been observed only on Homo teeth, they probably reflect a behaviour or behaviours unique to that genus.

Major Mitochondrial DNA Haplotype Heterogeneity in Highland and Lowland Amerindian Populations from Bolivia

This study provides the frequencies of four mitochondrial DNA (mtDNA) haplogroups of 233 native South Amerindians in eight populations living in the Beni Department of Bolivia, including six populations not previously studied. Linguistically, these populations belong to the three principal South Amerindian language stocks, Andean, Equatorial-Tucanoan, and Ge-Pano-Carib. Frequency analyses under geographic, historic, linguistic, and genetic configurations using the statistic of Weir (Weir 1990) and analysis of molecular variance (AMOVA) show similar results. Results are also similar when phenetic cluster is used. Aymara belongs almost exclusively to haplogroup B, Quechua- and Moseten-speaking tribes belong to haplogroups A and B, but the first tribe presents high frequencies of haplogroup B. Yuracare, Trinitario, and Ignaciano exhibit high frequencies of A, B, and C haplogroups, and the Movima present a large proportion of haplogroup C. There is some correspondence between mtDNA haplogroup frequencies and language affiliation and historical connections, but less so with geographic aspects. The present study provides a context for understanding the relationship between different Amerindian populations living in a multiethnic area of Bolivia.

Mitochondrial DNA diversity in the Llanos de Moxos: Moxo, Movima and Yuracare Amerindian populations from Bolivia lowlands

Background: Movima, Yuracare, Ignaciano and Trinitario are Amerindian populations living in the Bolivian lowlands of the Amazonian basin. The cultural and genetic affinity of the peoples living in this area is poorly known, despite many archaeological studies demonstrating its importance in pre-Columbian times. Densely populated Amerindian groups occupied the region, both in the Llanos and along the river streams of the Amazonian basin, practising intense agricultural activities and exchange of goods. The historical and linguistic records indicate that the land was occupied through successive migrations that gave rise to complex socio-economic communities. Genetic information suggests that the colonization of the American continent was fairly simple from a emigrational point of view, but other evolutionary processes, such as genetic drift or natural selection, could have also shaped the genetic background of present day populations in the Beni region. Aim: The objective of this study is to characterize the genetic diversity of these populations by analysing the sequence variability of the HVR-I control region in the mitochondrial DNA (mtDNA). The Amerindian origin of these populations suggests that close genetic similarities should be evident between the Beni samples studied here and other Amerindian groups. However, complex processes of population interactions and/or isolation in the Beni region might result in non-expected genetic affinities. Subjects and methods: DNA was extracted from pulled-out hairs obtained in situ from non-closely related individuals living in the Beni Department in Bolivia. DNA was extracted using a standard Chelex™ 100 method and a 401 bp DNA fragment of the HVR-I region was amplified using specific primers (L-15978 and H-16412). DNA amplicons were purified by centrifugation using Microspin™ S-300 HR columns and both SNA strands were sequenced after asymmetric PCR using direct Dye-Terminator 2 sequencing kit (Perkin-Elmer). Two independent 401 and 328 bp DNA fragments were sequenced separately for each sample. The sequence analyses includes mismatch distributions and mean pairwise differences, median network analysis, and neighbour joining, maximum likelihood phylogenetic comparisons. Genetic diversity of DNA sequences was also measured in various ways for the sample studied and UPGMA trees were drawn, including a large number of South Amerindian sequences. Results: The genetic diversity of 401 nucleotide long mtDNA sequences in the hypervariable control region, from positions 16 000–16 400, was characterized in a sample of 54 Amerindians living in the Llanos de Moxos. A total of 34 distinct lineages were observed, defined by 41 variable nucleotide positions, and 70.6% of all lineages were single sequences. All four major Amerindian haplogroups were detected (A 18.5%, n=10 ; B 24.1%, n=13, C 50.0% n=27 ; and D 5.6%, n=3). The median network analysis observed suggests that processes of population expansion took place in the Beni region. However, no clear haplotype differentiation by population could be detected. High levels of molecular variability and a bimodal pair-wise mismatch distribution were seen within the sample. The analyses of molecular variance (AMOVA) showed that most of the variance observed was due to intrapopulation variability, and that the highest among-groups variance was obtained when a linguistic classification criteria was used. The phylogenetic comparison revealed unique lineages in the Beni areas, not reported for other Amerindian populations. Conclusions: The genetic diversity observed in the Beni area is higher than that observed in other American populations living in much larger areas and with a long, known evolutionary history, despite the reduced area of Moxos. This could result from processes of reproductive isolation between groups, followed by population expansions and migration, where genetic drift might have be a major evolutionary force in population differentiation.

NONOCCLUSAL DENTAL MICROWEAR ANALYSIS OF 300,000-YEAR-OLD HOMO HEILDERBERGENSIS TEETH FROM SIMA DE LOS HUESOS (SIERRA DE ATAPUERCA, SPAIN)

Casts of nonocclusal enamel surfaces of 190 teeth from the Middle Pleistocene site of Sima de los Huesos have been micrographed by scanning electron microscopy. Microscopic analyses of striation density and length by orientation show distinct patterns of intrapopulation variability. Significant differences in the number and length of the striations by orientation are found between maxillary and mandibular teeth. This probably reflects differences in the mechanical forces involved in the process of chewing food. Significant differences are present between isolated and in situ teeth that could be caused by postdepositional processes differentially affecting the isolated teeth. In addition, a distinct and very unusual striation pattern is observed in a sample of teeth that can be explained only by a strong nondietary, most probably postmortem abrasion of the enamel surfaces. These teeth have a very high density of scratches, shorter in length than those found on other teeth, that are not indicative of dietary habits. No known depositional process may account for the presence of such postmortem wear since heavy transportation of materials within the clayish sediments has been discarded for the site. Despite this, a characteristic dietary striation pattern can be observed in most of the teeth analyzed. Most likely the diet of the Homo heidelbergensis hominids from Sima de los Huesos was highly abrasive, probably with a large dependence on hard, poorly processed plant foods, such as roots, stems, and seeds. A highly significant sex-related difference in the striation pattern can also be observed in the teeth analyzed, suggesting a differential consistency in the foods eaten by females and males.

Age and Individual Foraging Behavior Predict Tooth Wear in Amboseli Baboons

Teeth represent an essential component of the foraging apparatus for any mammal, and tooth wear can have significant implications for survival and reproduction. This study focuses on tooth wear in wild baboons in Amboseli, southern Kenya. We obtained mandibular and maxillary tooth impressions from 95 baboons and analyzed digital images of replicas made from these impressions. We measured tooth wear as the percent dentine exposure (PDE, the percent of the occlusal surface on which dentine was exposed), and we examined the relationship of PDE to age, behavior, and life history variables. We found that PDE increased significantly with age for both sexes in all three molar types. In females, we also tested the hypotheses that long-term patterns of feeding behavior, social dominance rank, and one measure of maternal investment (the cumulative number of months that a female had dependent infants during her lifetime) would predict tooth wear when we controlled for age. The hypothesis that feeding behavior predicted tooth wear was supported. The percent of feeding time spent consuming grass corms predicted PDE when controlling for age. However, PDE was not associated with social dominance rank or maternal investment.

Amplifying dinucleotide microsatellite loci from bone and tooth samples of up to 5000 years of age: more inconsistency than usefulness

We have studied the feasibility of using dinucleotide-repeat microsatellites in the analysis of DNA from ancient bones and teeth. We have used three microsatellites (IVS8CA, IVS17BTA, and IVS17BCA) within the cystic fibrosis transmembrane conductance regulator gene in 28 DNA samples from bones and teeth of up to 5000 years of age. PCR amplification was successful in 71.4% of cases. The repeated analysis of each marker produced different genotypes in 97% of samples, and the same individual genotype was reproduced at least once in 45.5% of cases. Alleles differing from the originals consisted of additions or deletions of 1–39 dinucleotides. The mechanism by which alleles differing from the originals were amplified can be related to the marked degradation of the DNA, with repeat sequences of different length interacting with the partially degraded repeats of the amplified loci. The repeated analysis of each sample allowed us to produce data with some anthropological interest. Among the haplotypes detected in samples from Easter Island, two (16-32-13 and 23-32-13) were found in more than one sample. Similarly, three haplotypes (16-7-17, 16-7-13, and 16-24-13) were detected more than once in samples from the Basque Country. Although haplotypes in the Basque Country are amongst the commonest in European chromosomes, most of those detected in the Easter Island samples are not frequent in Europeans. Thus, the repeated typing of microsatellites allowed us to postulate the genotypes that might be present in the samples but dinucleotide markers do not seem to be reliable enough for genotyping ancient bone and teeth samples.

Cutmarks and post-mortem striations in fossil human teeth

A sample of 24 teeth from 10 human fossils have been examined by Scanning Electron Microscope. Large striations attributable to feeding behavior (dental cutmarks) and/or topost-mortem damage have been found in five of the specimens (Broken Hill, Tabun I, Skhul 4, La Quina 5 and Malarnaud). At high magnification, it is possible to observe differences between the internal morphology of these structures andpost-mortem striations that were probably inadvertently made during the process of study and cleaning the fossil remains. Cutmarks can be related to the behavior of placing meat or other matter between the anterior teeth while cutting pieces of it with a stone tool. The presence of this type of scratching on the enamel surface of teeth might be indirectly used as indicative of meat consumption.