Trends in waterbird numbers in the southern Rift Valley of Kenya

Bennun, L. & Nasirwa, O. 2000. Trends in waterbird numbers in the southern Rift Valley of Kenya. Ostrich 71 (1 & 2): 220–226.

Each January since 1991, volunteer teams have counted waterbirds at major wetlands in the southern Kenyan Rift Valley. There has been consistent coverage at Lakes Naivasha, Elmenteita, Nakuru and (since 1992) Bogoria. These lakes are shallow and, except for Bogoria, fluctuate greatly in extent; all but Naivasha are saline. Lake levels were moderately high in 1991–1993 but have been generally low since. Flamingo totals for the three saline lakes combined were more than one million from 1992–1994, but roughly halved each year since then. Greater Flamingos Phoenicopterus ruber made up between 0.7 and 4.1% of total flamingo numbers; other waterbirds made up between 2.7 and 10.2% of the overall total. Lakes Naivasha, Elmenteita and Nakuru together hold most of the non-flamingo waterbirds in the southern Rift; to compare trends for other species, we pooled totals for these sites. Significant, or near-significant, declines were evident for grebes, pelicans, cormorants, storks, gulls, rallids, kingfishers, terns and raptors. No group showed an overall increasing trend. At Dandora, a smaller site with stable water levels, these groups showed large annual fluctuations but no obvious declines. In most waterbird groups where numbers decreased, the probable cause was sustained low lake levels at Lake Nakuru; numbers at Lake Naivasha remained stable. Exceptions were rallids, kingfishers and raptors, where numbers steadily declined at Naivasha. There is a need to investigate local environmental causes of these changes for kingfishers and raptors, and to assess possible loss of breeding sites for rallids.     

Morphological Differences Between Mandan And Historic Arikara Crania

Abstract

Arikara cranial measurements are compared with Mandan data to define the nature and magnitude of differences remaining at the beginning of the Historic period. A discriminant function approach is followed. Special attention is given to determining uniqueness of the two sets of crania as estimated by rates of group misclassification. Three validation procedures are applied in estimating these rates: resubstitution, jackknife, and holdout.

Several variables show significant heterogeneity between Arikara and Mandan including nasal height, maximum cranial breadth, and auricular height. Mandan crania tend to be narrower, have less nasal height, and are lower in auricular height. Functions developed for Leavenworth Arikara and Mandan crania have an accuracy of about 84 percent. Data for the Leavenworth Site are expanded with addition of a sample excavated by William H. Over 60 years ago.     

Possible relationship of cranial traumatic injuries with violence in the south‐east Iberian Peninsula from the Neolithic to the Bronze Age

The main aim of this study was to analyze the presence and distribution of cranial trauma, as possible evidence of violence, in remains from the Neolithic to Bronze Age from the SE Iberian Peninsula. The sample contains skulls, crania, and cranial vaults belonging to 410 prehistoric individuals. We also studied 267 crania from medieval and modern times for comparative purposes. All lesions in the prehistoric crania are healed and none of them can be attributed to a specific weapon. In all studied populations, injuries were more frequent in adults than in subadults and also in males than in females, denoting a sexual division in the risk of suffering accidents or intentional violence. According to the archeological record, the development of societies in the SE Iberian Peninsula during these periods must have entailed an increase in conflict. However, a high frequency of cranial traumatic injuries was observed in the Neolithic series, theoretically a less conflictive time, and the lowest frequency was in crania from the 3rd millennium B.C. (Copper Age), which is characterized by the archeologists as a period of increasing violence. The relatively large size and the high rate of injuries in Neolithic crania and the practice of cannibalism are strongly suggestive of episodes of interpersonal or intergroup conflict. The number and distribution of injuries in Bronze Age is consistent with the increase in violence at that time described by most archeologists. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Intra- and interobserver error in craniometry: A cautionary tale

This study investigates intra- and interobserver measurement error in craniometry. Data consists of 72 craniometric measurements taken on a series of 28 Sadlermuit Eskimo crania. Utermohle measured the series twice; Zegura measured it once. Statistical procedures used to demonstrate measurement imprecision include the mean difference, the method error statistic, two-way anova without replication, the t-test for paired comparisons, Fisher's distribution-free sign test, and the t-test for independent samples. The results indicate less intraobserver repeatability than expected as well as an alarming lack of interobserver reproducibility for many of these craniometric measurements. We hope these results will serve as a caution against the widespread belief that craniometric measurements are always produced with a high degree of precision by experienced craniometrists. In addition, these results suggest that investigators employing craniometric measurements to study population affinities, functional morphology, forensics, fossil primates, and human microevolution might profit from conducting a measurement error analysis as an important baseline for the interpretation of the biological significance of their results.     

Artificial cranial deformation and fossil Australians revisited

Based on cranial characters shared by Homo erectus in Java and Homo sapiens in Australia, Australasia is widely considered the strongest case for a regional origin of modern humans. However, artificial vault deformation has been suggested to be the cause of "archaic" characters such as frontal recession in key fossil Australian crania. We use log-log plots of cranial arc versus chord measurements and we score nonmetric traits often thought to be associated with artificial deformation to make systematic comparisons across groups and deformation types to identify universal consequences of artificial deformation. Based on our large comparative sample (n = 588) apparatus-deformed crania have flatter frontals and occipitals and usually more angulated parietals in the sagittal plane than undeformed crania, regardless of deformation type. Fossil Australian samples exhibit evidence of both undeformed and deformed individuals. The sample from Coobool Creek provides evidence that undeformed individuals had more rounded frontals than recent Australians. However, many individuals from Coobool Creek, Kow Swamp, and Nacurrie exhibit modification of one or more cranial contours. The Kow Swamp individuals in particular plot with deformed crania from all regions. In addition, the frequency of hyperostotic traits such as bregmatic eminence, metopic and sagittal keels in H. sapiens is influenced by both artificial deformation and pathological hypervascularity/hyperostosis. Thus it is unwise to use cranial contours and these nonmetric traits to infer genetic relatedness between Fossil Australians and Indonesian H. erectus.     

Fingerprints of Whites and Negroes from Southern Brazil

Studies on 1,115 individuals (451 Whites, 240 Light Mulattoes, 236 Dark Mulattoes and 188 Negroes) from Pôrto Alegre, Brazil are reported. The differences among those subgroups are not large and there is not a clear gradient when we consider samples with increasing Negro ancestry. The most marked difference between Whites and the total Negroid group occurred in the prevalence of radial loops. Comparison with Portuguese and African series indicates that no single factor can fully explain the observed distributions. But the values of Dankmeijer's index are exactly those expected on the assumption of 50% White admixture in the Pôrto Alegre Negro, in agreement with previous investigations.     

Anterior femoral curvature: Its probable basis and utility as a criterion of racial assessment

Stewart ('62) and Walensky ('65) indicated that while the metrical expression of anterior femoral curvature alone will not always differentiate between Whites, American Negroes, and North American Indians, it was very useful as a racial criterion in combination with observed traits such as torsion, pilastry, and cross-sectional shape. Seven additional North American Indian groups reported here, representing both pre-Columbian and post-contact times, upheld the observation that anterior femoral curvature is a useful feature of racial assessment for Negroes, Whites and North American Indians. However, two South American groups studied (Ecuador and Peru) were only slightly more curved than American Negroes, and were less curved than Whites and North American Indians. The metrical expression of anterior femoral curvature therefore is not a useful feature of racial assessment for separating these two South American Indian groups from Whites and American Negroes. Femora of American Negro and White individuals with low ponderal indices were found to be less bowed than the norms for their race; individuals with high ponderal indices were more bowed than the norm for their race. The assumed genetic basis for expression of anterior femoral curvature suggested by Stewart ('62) and Walensky ('65) seems to be a feature of human plastic response to body weight rather than to temporal, clinal, postural or equestrian influences.     

Artificial cranial deformation in Pleistocene Australians: the Coobool Creek sample

Several authors have suggested that some Pleistocene Australian crania have been altered by artificial cranial deformation. The large sample from Coobool Creek has featured prominently in this debate. The present study reevaluates the evidence for artificial cranial deformation in this population using both a larger cranial sample and a more comprehensive set of measurements than those used in earlier work on this subject. Additionally, random expectation statistics are used to calculate statistical significance for these examinations. The results of this study agree with prior work indicating that a portion of this sample shows evidence for artificial deformation of the cranial vault. Many Coobool Creek crania display strong shape similarities with a population of known deformed individuals from New Britain. Coobool Creek crania 1, 41, 65, and 66 show the strongest evidence for deformation, but several other individuals from this sample also show clear evidence for culturally manipulated changes in cranial shape. This project provides added support for the argument that at least some Pleistocene Australian groups were practicing artificial cranial deformation.     

Artificial cranial deformation in Kow Swamp 1 and 5: A response to

Recently, Curnoe (2007) tested the predictions of competing models of modern human origins using three crania from Australia: Kow Swamp 1 and 5 and Keilor. The Kow Swamp specimens have long been suspected of having been altered through artificial deformation of the skull. Though Curnoe (2007) provided assurances that no evidence of deformation is present in those specimens, the current study retests the hypothesis that these Australian specimens are artificially deformed. The Australian crania are compared to known deformed individuals from New Britian through canonical variates analysis, and the resulting Mahalanobis distances are examined for statistical significance with random expectation statistics. The results show that Kow Swamp 1 and 5 have strong shape similarities to known deformed individuals, and both crania are very different in shape from Keilor. Keilor is statistically significantly different in shape from both Kow Swamp specimens and all of the known deformed specimens. These findings cast doubt on Curnoe's (2007) conclusions of a shared Australian cranial morphology as well as the retention of an archaic suite of morphologies in the Australians.     

Craniometric Variation In The Northern And Central Plains

Abstract

Cranial measurements of 13 male and 12 female samples from the Central and Northern Plains region were subjected to canonical analysis. The samples include historic or protohistoric crania that can be ascribed to the Arikara, Mandan, Pawnee, Ponca and Omaha tribes. In addition, two samples belong to the archaeologically defined St. Helena Focus. Both sexes yielded five significant canonical variates, although only four were readily interpretable. The first canonical variate is clearly a Siouan-Caddoan discriminator and reflects variation in cranial vault height. St. Helena sites associate with the Arikara on this axis, supporting previous craniometric analyses which suggest a relationship between these two groups. Subsequent canonical variates deal with more particular aspects of craniometric variation among groups, but are still interpretable in historic or evolutionary terms. The classificatory analysis shows that the Arikara sites are closely related. A major exception to this is the Sully site, which frequently misclassifies with non-Arikara groups. This suggests that the Sully crania have little collective reality; and that there may be non-Arikara components represented at the Sully Site.     

Patterns of variation in waterbird numbers on four Rift Valley lakes in Kenya, 1991–1999

Waterbird populations were censused each January from 1991 to 1999 at Lakes Naivasha, Elmenteita and Nakuru and from 1992 at Lake Bogoria. These shallow lakes in the Kenyan Rift Valley fluctuate greatly in water level and alkalinity. All but Naivasha are usually saline; Nakuru and Elmenteita at times support fish, while Bogoria is fishless. A standardized logarithmic index of relative abundance (value 1.0 for the mean) was calculated for each major waterbird group at each lake, and for Naivasha, Elmenteita and Nakuru combined (combined lakes). Its variance was used to compare levels of variation within and across lakes. For the combined lakes, there was high variance in large piscivores (whether combined or separated into groups), grebes, rallids and flamingos. There was low variance in Palaearctic waders (combined or separated into groups), ibises and spoonbills and birds of prey. However, the lakes generally showed idiosyncratic patterns of variation across the different groups. Variance in the indices for birds of prey and kingfishers were consistently low (max. 0.036 and 0.042, respectively), but no group had consistently high variance across all sites. The variance for all birds (other than flamingos) combined was low (0.018 – 0.085) and similar across all lakes and for combined lakes (0.018). For the combined lakes, the variance for flamingos was five times higher than for all other birds (p<0.05), though the two variances were almost equal for Bogoria. Flamingos were the most variable at Naivasha (variance 0.281) followed by Elmenteita (0.177), Nakuru (0.101) and Bogoria (0.024, and significantly lower than all the rest, p<0.05). This was opposite in order to the mean numbers of flamingos recorded at each site. Large piscivores were relatively stable at Naivasha (variance 0.005) but much more variable at Elmenteita (0.199) and Nakuru (0.269). Patterns of variation within lakes were correlated for some groups, such as waders at Naivasha and large piscivores at Nakuru. These correlations could be related to local ecological conditions. However, there were few large correlations across sites, and these were mainly direct. There was, therefore, no evidence that a fixed population of waterbirds was distributing itself across sites according to conditions. Each lake thus seems to represent and independent entity, while the waterbirds they host evidently move much more widely afield than this portion of the Rift Valley.     

An evaluation of race and sex identification from cranial measurements

A total of 104 adult human crania (95 American Indian and 9 Labrador Eskimo) are used in this evaluation of a discriminant functional analysis for determining race and sex from eight cranial measurements. The methods used are those given by Giles and Elliot ('62). The study shows that non-deformed American Indian crania are racially misclassified as American White and Negro in 35.6% of the cases when using this metrical method. Deformed Indian crania are racially misclassified 60.0% and 4.4% of the time as White and Negro respectively. The determination of sex on male crania, regardless of deformation, is as accurate as, or better than, the visual method of identification. The female crania, however, are shown to be incorrectly sexed in nearly 50% of the cases, with one non-deformed group (Palus) running as high as 80.0%. This evaluation suggests, therefore, that discriminant functional analyses for race and / or sex determinations are not applicable to problems of human identification unless the crania are from that population on which these functions were established.     

Brief communication: Artificial cranial modification in Kow Swamp and Cohuna

The crania from Kow Swamp and Cohuna have been important for a number of debates in Australian paleoanthropology. These crania typically have long, flat foreheads that many workers have cited as evidence of genetic continuity with archaic Indonesian populations, particularly the Ngandong sample. Other scientists have alleged that at least some of the crania from Kow Swamp and the Cohuna skull have been altered through artificial modification, and that the flat foreheads possessed by these individuals are not phylogenetically informative. In this study, several Kow Swamp crania and Cohuna are compared to known modified and unmodified comparative samples. Canonical variates analyses and Mahalanobis distances are generated, and random expectation statistics are used to calculate statistical significance for these tests. The results of this study agree with prior work indicating that a portion of this sample shows evidence for artificial modification of the cranial vault. Many Kow Swamp crania and Cohuna display shape similarities with a population of known modified individuals from New Britain. Kow Swamp 1, 5, and Cohuna show the strongest evidence for modification, but other individuals from this sample also show evidence of culturally manipulated changes in cranial shape. This project provides added support for the argument that at least some Pleistocene Australian groups were practicing artificial cranial modification, and suggests that caution should be used when including these individuals in phylogenetic studies. Am J Phys Anthropol 155:173–178, 2014. © 2014 Wiley Periodicals, Inc.     

Assessing land cover change in Kenya's Mau Forest region using remotely sensed data

Kenya's Rift Valley has been undergoing rapid land cover change for the past two decades, which has resulted in ecological and hydrological changes. An effort is under way to quantify the timing and rate of these changes in and around the River Njoro watershed located near the towns of Njoro and Nakuru using remote sensing and geographic information system (GIS) methods. Three Landsat TM images, representing a 17‐year period from 1986 to 2003 in which the area underwent a significant land cover transition, were classified and compared with one another. Vegetation diversity and temporal variability, common to tropical and sub‐tropical areas, posed several challenges in disaggregating classified data into sub‐classes. An iterative approach for the resolving challenges is presented that incorporates unsupervised and supervised classification routines in coordination with knowledge‐based spatial analyses. Changes are analysed at three spatial scales ranging from the highly impacted and deforested uplands to the watershed and landscape scales. Land cover transitions primarily occurred after 1995, and included large forest losses coupled with increases in mixed small‐scale agriculture and managed pastures and degraded areas. These changes in cover type are highly spatially variable and are theorized to have significant impacts on ecological and hydrologic systems with implications for environmental sustainability.     

Within-group human variation in the Asian Pleistocene: the three Upper Cave crania

Numerous studies on Pleistocene samples have shown that within-group cranial variation was greater than that seen today. The three anatomically modern Upper Cave crania (UC 101, UC 102, and UC 103) from Zhoukoudian, China provide one of the best samples available for addressing the issue of the antiquity of the modern pattern of within-group cranial variability because archaeological evidence indicates that they are spatially and temporally restricted. Research on the Upper Cave fossils usually only includes UC 101 and UC 103 because of postmortem damage to UC 102's cranial vault. However, the face of UC 102 is undamaged, allowing for most facial measurements to be performed accurately. In this study we use facial dimensions to compare all three Upper Cave specimens, and we evaluate whether the variation seen among them is larger than that observed in extant populations.Using a worldwide sample of modern populations to establish a baseline, the three Upper Cave crania were compared to each other. Since there is disagreement over the sex of UC 102, this specimen is treated alternately as a female and as a male. Results show that the Upper Cave specimens exhibit significantly more variation than do individuals within more recent human populations, especially if UC 102 is considered male. Furthermore, results indicate that the fossils never fall into the same modern human group, and that each specimen is significantly atypical of its nearest modern neighbor in multivariate space.We conclude that the three Upper Cave crania do not represent a family group but are representative of the larger contemporaneous heterogeneous Asian Pleistocene population. Our results support the contention that today's within-group homogeneity is a relatively recent phenomenon, and is likely the result of a Neolithic population expansion and its many effects.     

颜面扁平度的变异和山顶洞人类化石的颜面扁平度

扁平的颜面这一蒙古人种的颅骨特征可上溯到直立人时代。在新石器时代,颜面扁平度总的来看华北地区的要比华南的稍大些,但这种南北差别并无严格的地理界线;在现代,这种地理上的差别更不明显。山顶洞人类头骨化石的过小的颜面扁平度很可能是受外来“基因流”的影响的结果。     

Were neandertal and modern human cranial differences produced by natural selection or genetic drift?

Most evolutionary explanations for cranial differences between Neandertals and modern humans emphasize adaptation by natural selection. Features of the crania of Neandertals could be adaptations to the glacial climate of Pleistocene Europe or to the high mechanical strains produced by habitually using the front teeth as tools, while those of modern humans could be adaptations for articulate speech production. A few researchers have proposed non-adaptive explanations. These stress that isolation between Neandertal and modern human populations would have lead to cranial diversification by genetic drift (chance changes in the frequencies of alleles at genetic loci contributing to variation in cranial morphology). Here we use a variety of statistical tests founded on explicit predictions from quantitative- and population-genetic theory to show that genetic drift can explain cranial differences between Neandertals and modern humans. These tests are based on thirty-seven standard cranial measurements from a sample of 2524 modern humans from 30 populations and 20 Neandertal fossils. As a further test, we compare our results for modern human cranial measurements with those for a genetic dataset consisting of 377 microsatellites typed for a sample of 1056 modern humans from 52 populations. We conclude that rather than requiring special adaptive accounts, Neandertal and modern human crania may simply represent two outcomes from a vast space of random evolutionary possibilities.     

Stereometric craniometry

A method is described whereby three-dimensional co-ordinates of points on a cranium can be recorded in terms of azimuth, elevation and radial distance from a selected point. These co-ordinates can be used to create two-dimensional representations of single crania, the differences between many crania or growth stages of individuals or series of individuals. The co-ordinates can be used in more conventional analytic ways in the same way as cartesian co-ordinates.