Robert L. Kelly

Hunter-Gatherer Mobility Strategies

The nature of hunter-gatherer mobility strategies--the way in which hunter-gatherers move about a landscape over the course of a year--is discussed, using ethnographic data. Several mobility variables that measure residential and logistical mobility are defined; several environmental variables which measure resource accessibility and resource monitoring costs are also defined. Ethnographic data are used to demonstrate patterning between the nature of mobility strategies and the resource structure of an environment. The data show that the extent to which a group of hunter-gatherers emphasizes residential or logistical mobility is closely related to the structure of resources in their environment.

The Three Sides of a Biface

An attitude determining system for vehicles, such as spacecraft or for ground-based environments measures the angle between a reference and the line-of-sight to a star or other celestial object of known position or to aircraft and missiles. The system includes a rotating scanning telescopic sensor, and a fixed mirror positioned so that the sensor scans both the direct and the reflected line-of-sight of the celestial object in the course of each rotation. Associated transducers and electronic circuits determine the relative angular positions of the telescopic sensor at the instants it detects the direct and the reflected radiation from the celestial object. A computation based on the two angles gives the angular position of the celestial object relative to the vehicle reference. The system cancels or substantially reduces errors due to optical or electronic inaccuracies which identically affect the direct and the reflected angular position measurements.

A continuous climatic impact on Holocene human population in the Rocky Mountains.

Ancient cultural changes have often been linked to abrupt climatic events, but the potential that climate can exert a persistent influence on human populations has been debated. Here, independent population, temperature, and moisture history reconstructions from the Bighorn Basin in Wyoming (United States) show a clear quantitative relationship spanning 13 ka, which explains five major periods of population growth/decline and ∼45% of the population variance. A persistent ∼300-y lag in the human demographic response conforms with either slow (∼0.3%) intrinsic annual population growth rates or a lag in the environmental carrying capacity, but in either case, the population continuously adjusted to changing environmental conditions.

Projectile point shape and durability: the effect of thickness:length

We describe an experiment that tests the hypothesis that projectile points with high thickness: length ratios are more durable than points with low thickness: length ratios. Fifty obsidian projectile points were manufactured to specific lengths, widths, and thicknesses. These were then fired into a deer carcass with a bow repeatedly until each point broke. None of the points were resharpened. The hardness of the material struck was a significant predictor of a points durability. Controlling for this variable, however, we found that points with a high thickness: length ratio (>.121) were slightly albeit significantly more durable than those with a low ratio. No other attribute of size or shape was a significant predictor of durability.

Agriculture, population growth, and statistical analysis of the radiocarbon record

Significance We statistically analyze the radiocarbon record and show that early farming societies in Europe grew at the same rate as contemporaneous foraging societies in North America. Thus, our results challenge the commonly held view that the advent of agriculture was linked to accelerated growth of the human population. The same rates of prehistoric population growth measured worldwide suggest that the global climate and/or biological factors intrinsic to the species and not factors related to the regional environment or subsistence practices regulated the growth of the human population for most of the last 12,000 y. This study demonstrates that statistical analysis of the radiocarbon record is a robust quantitative approach for studying prehistoric human demography. The human population has grown significantly since the onset of the Holocene about 12,000 y ago. Despite decades of research, the factors determining prehistoric population growth remain uncertain. Here, we examine measurements of the rate of growth of the prehistoric human population based on statistical analysis of the radiocarbon record. We find that, during most of the Holocene, human populations worldwide grew at a long-term annual rate of 0.04%. Statistical analysis of the radiocarbon record shows that transitioning farming societies experienced the same rate of growth as contemporaneous foraging societies. The same rate of growth measured for populations dwelling in a range of environments and practicing a variety of subsistence strategies suggests that the global climate and/or endogenous biological factors, not adaptability to local environment or subsistence practices, regulated the long-term growth of the human population during most of the Holocene. Our results demonstrate that statistical analyses of large ensembles of radiocarbon dates are robust and valuable for quantitatively investigating the demography of prehistoric human populations worldwide.

Late Holocene Great Basin prehistory

Late Holocene Great Basin prehistory is a spatial and temporal mosaic of lifeways related to changing physical and social environments. Evidence shows changes in technology, subsistence, foraging tactics, and population density, though the causes of these changes are still under investigation. Current research has emphasized the role of wetlands and, related to this, the so-called Numic expansion, whose timing and nature are still poorly understood. Behavioral ecology applied to a macroregional scale probably offers the most useful approach to solving this and other issues, given the exigencies of hunter-gatherer archaeology in a desert environment.

Maybe we do know when people first came to North America; and what does it mean if we do?

Abstract The history of research in North America suggests that we already know when people arrived in the continental US: about 11,500 14 C yr BP. Research also suggests that people were in the southern cone of South America by a comparable age, if not earlier. If the New World was colonized by Late Pleistocene migrants from Asia via the Bering Strait, then the earliest sites should be in North not South America. Several possibilities might account for this apparent paradox: (a) the inability to locate pre-11,500 14 C yr BP sites in North America, (b) asynchroneity of late Pleistocene/early Holocene 14 C dates between North and South America, (c) inaccurate dating of South American sites, or (d) a coastal migration that by-passed interior North America. All these possibilities currently appear unlikely, and the paradox resists explanation at this date.

95-GHz Polarimetric Radar Measurements of Orographic Cap Clouds

Abstract The use of millimeter-wavelength radars for cloud microphysical research was investigated in experiments at the Elk Mountain Observatory near Laramie, Wyoming, between April 1990 and March 1992. The 95-GHz polarimetric radar used in these experiments is a portable, high-power, dual-polarization radar capable of characterizing the complex scattering matrix in two pulses. The scatterers polarimetric response is characterized in terms of the Mueller matrix, a form that is seen to be convenient for computing the response of a scatterer for any arbitrary combination of transmit and receive antenna polarizations. This paper summarizes the results of recent experiments carried out at the Elk Mountain Observatory. Polarimetric data from orographic cap clouds are found to be sensitive to ice-particle orientation and composition. Comparison of radar-observed reflectivities with those computed from in situ images shows good agreement if the volume fraction of ice in ice-air mixtures is taken into account.

Bioarchaeology of the Stillwater Marsh: Prehistoric Human Adaptation in the Western Great Basin

This monograph reports on the recovery and study ofhuman remains from the Stillwater Marsh in the western American Great Basin (west-central Nevada). Analysis of these remains provides new details on health, lifeway, and population history of prehistoric native populations inhabiting the region. These results inform our understanding of how earlier societies used resources drawn from both lacustrine and uplands landscapes in this challenging setting. Between 1982 and 1986, record high winter precipitation resulted in massive flooding of several Great Basin wetlands, including the Stillwater Marsh, located in the Carson Sink in western Nevada. As the floodwaters receded in 1985 and 1986, dozens ofarchaeological sites and hundreds ofhuman skeletal remains were uncovered. Soon thereafter, the Nevada State Museum salvaged the disturbed remains representing, according to Brooks et al. (1988), 416 burials or individuals. Wind and wave erosion, however, continued to disturb burials in the region. In 1987, archaeological crews under our direction surveyed the most heavily impacted marsh shoreline in order to document scattered skeletal remains and burials in danger ofdestruction. This monograph reports on eight burials excavated in 1987, 557 isolated human cranial and postcranial elements, and 122 isolated teeth collected during the course ofthis shoreline survey. These remains represent a minimum of 85 people, including 50 adults and 35 juveniles. This monograph also presents various analyses ofthe combined samples of human remains collected by the Nevada State Museum and by us. These analyses include assessments ofdental health, evidence for iron deficiency anemia, the use of serum albumin and mitochondrial DNA as population markers, dental hypoplasia, bone chemistry, osteoarthritis, and longbone (femur and humerus) cross-sectional geometry. Results are used to test competing reconstructions of the prehistoric use of wetland resources and to characterize the human condition generally in this region of the Desert West. One reconstruction argues that wetland resources could consistently provide sufficient food for a hunter-gatherer population and would therefore have been used by a sedentary population. An alternative reconstruction argues that temporal fluctuations in wetland resources relative to resources available in other valleys or in the nearby uplands would have resulted in a residentially mobile lifeway, even where the wetlands could provide the necessary amount of food. The importance ofthe skeletal sample lies largely in its size: There is no comparable skeletal population in the Great Basin that has been analyzed 7 to date. Some ofthe analyses reported here are the first of their type to be conducted on prehistoric Great Basin peoples. Only six of the burials of the entire Stillwater series have been radiocarbon dated. These dates range from ca. 2300 to 300 B.P., with four of the dates falling within the Underdown phase (1250650 B.P.), the predominant period represented by projectile point types found in, and radiocarbon dates on, the archaeological sites exposed by high water. Consequently, the human remains here are treated as if they were a single population. The dates available do not indicate any obvious temporal trends, but better controls are needed to ascertain whether such trends exist. Overall, the Stillwater skeletal remains are extraordinarily robust. They reflect a population that was generally healthy, but people who lived physically demanding lives. The frequency ofdental caries is very low in the series. High rates of occlusal surface wear, a function of the introduction of grit to the diet through seed grinding on metates and the preparation of food in a sandy environment, may have contributed to low caries prevalence. However, given that most foods consumed were noncariogenic, it is likely that the low prevalence ofcaries in this sample is related to diet and not attrition. The burials also show a low frequency of cribra orbitalia and porotic hyperostosis suggesting low rates of iron deficiency anemia. A long-running debate in Great Basin archaeology concerns the origin and timing of the migration ofNumic-speaking peoples into this region ofthe Desert West. Linguistic data suggest an entry of these peoples sometime between 1000 and 700 B.P. Study of serum albumin revealed similarities between the Stillwater population and modern UtoAztecan or Yuman speakers. The most common allele among the indigenous peoples of North America is AIA. However, within some populations, including Numic speakers, another alleleA/me-occurs at low frequencies. This allele is present in four of the analyzed samples, a frequency nearly as high as that known for any living population. Because these burials were not dated, it is not known if individuals with this allele occur in early or late burials, or throughout the sequence. Thus, the timing of the Numic migration into the Great Basin based on this analysis is inconclusive. The analysis ofmitochondrial DNA reveals a very low frequency of the 9-basepair deletion, a deletion observed in some prehistoric and extant Native American populations. The study suggests that the Stillwater population is probably not ancestral to any group that has a much higher deletion frequency (e.g., California Penutian, Zuni, Yuman, ANTHROPOLOGICAL PAPERS AMERICAN MUSEUM OF NATURAL HISTORY Washo, or Southern Uto-Aztecan language groups). This finding is in part consistent with Smith et al. (this volume), who were able to exclude California Penutian and Washo as descendants. However, it also suggests that the Yuman and Southern UtoAztecan groups are probably not direct descendants of the Stillwater population. Several possibilities remain as to the identification ofancestraldescendant relationships in this region. Dental hypoplasias are nonspecific growth arrest markers in teeth; as such, they provide evidence on periodicity and intensity of stress in a population. These features may be a product of either dietary or disease-related stress during tooth development. The low rate of nonspecific infections in the population suggests that dietary stress may have been a major cause of dental hypoplasias. Many diseases do not leave impressions on skeletal tissues, which limits understanding ofspecific causes of hypoplasias. Regardless, dental hypoplasias within the Stillwater sample suggest that this population underwent less frequent and less intense physiological stress than Georgia coastal hunter-gatherers or agriculturalists. The stress events occurred at 3-4 years of age. Data on carbon and nitrogen isotopes were collected from human bone collagen, archaeological faunal remains, and modern plant specimens in order to reconstruct diet. The data show significant variation in diet compared to boreal forest huntergatherers and southwestern U.S. agriculturalists. However, this variation does not exhibit patterning by bone element, age group, or sex. The control specimens indicate that the diet could have been derived from the marsh, with variation representing either periodic movement out of the Stillwater Marsh and the use of other resources or changes in the range of resources available within the marsh itself. Significantly, the data suggest that pinion seeds, an important element of diet elsewhere in the Great Basin, may not have been a large part of the Stillwater diet. Although data from dental hypoplasias and bone chemistry indicate a comparatively healthy population that ate a range of food items, the prevalence of osteoarthritis and the nature oflong-bone cross sections indicate a physically demanding lifestyle. Osteoarthritis was found to have afflicted 75 percent of Stillwater individuals, with highest frequencies on lumbar vertebrae, cervical vertebrae, and the elbow. Controlling for age, there are several differences between males and females. Overall, osteoarthritis is less prevalent among females than males with the exception of lumbar vertebrae. This suggests that women carried heavy loads daily, perhaps children (as well as food, water, firewood, and other burdens), while foraging. Males have significantly higher frequencies of osteoarthritis in the hip and ankle, and possibly in the shoulder. Based on this and especially the observed differences between male and female femur cross-sectional geometry, it appears that males did more walking and more strenuous walking than females. Comparisons of the Stillwater population to Georgia coastal hunter-gatherers and agriculturalists, as well as southwestern Anasazi agriculturalists, show a tendency for the femora of huntergatherer males to exhibit higher bending and torsional strength than males in agricultural populations. The shape of the female femur, on the other hand, shows no change with the mode of subsistence, but instead correlates with the overall terrain inhabited by the different populations. Finally, the Stillwater adults show a relatively low amount of cortical bone in the cross sections analyzed. Although the relatively old age distribution for the series may account for recorded bone loss, periodic suboptimal nutrition likely played an important role. This study casts light on current reconstructions of prehistoric lifeways in the Carson Sink. It does not provide evidence of a sedentary lifestyle, but instead points to considerable mobility and heavy workloads for both males and females. Males may have been more mobile than females, which appears to be reflected in Great Basin ethnographic data, and cross-culturally as well, where males generally walk longer daily distances in hunting forays than women do in plant-gathering trips. Moreover, analysis of cross-sectional geometry of the femur reveals that travel over difficult terrain (uplands) was an important feature of the Stillwater adaptation, especially for males. On the other hand, the study suggests that the diet could have been comprised of only those resourc

Detection of Ice Hydrometeor Alignment Using an Airborne W-band Polarimetric Radar

Abstract This paper presents airborne W-band polarimetric radar measurements at horizontal and vertical incidence on ice clouds using a 95-GHz radar on the University of Wyoming King Air research aircraft. Coincident, in situ measurements from probes on the King Air make it possible to interpret polarimetric results in terms of hydrometeor composition, phase, and orientation. One of the key polarimetric measurements recently added to those possible with the W-band radar data system is the copolar correlation coefficient ρHV. A discussion of the relation between cloud scattering properties and ρHV covers a test for isotropy of the distribution of observed hydrometeors in the plane of polarization and qualitative evaluation of the possible impact of Mie (resonant) scattering on ρHV measurements made at W band. Prior measurements of ρHV at S band and Ku band are compared with the W-band results. The technique used to measure ρHV, including the real-time and postprocessing steps required, is explained, with a...