The origin of man.

Five characters separate man from other hominoids-a large neocortex, bipedality, reduced anterior dentition with molar dominance, material culture, and unique sexual and reproductive behavior. Evidence provided by the fossil record, primate behavior, and demographic analysis shows that the traditional view that early human evolution was a direct consequence of brain expansion and material culture is incorrect, and that the unique sexual and reproductive behavior of man may be the sine qua non of human origin.

Primate phylogeny and immunological distance.

Recalculation of the time of divergence of the Pongidae and Hominidae after correction of immunological distance by inclusion of generation length yields minimum dates of approximately 14 million years ago.

Paleodemography of the libben site, Ottawa county, ohio.

The Libben site, a Late Woodland ossuary and occupation site from the Great Black Swamp of northern Ohio has yielded a well-preserved skeletal sample of 1327 articulated individuals. The outstanding preservation and completeness of the site and the utilization of an exhaustive aging methodology make this the largest and most comprehensively censused North American prehistoric cemetery. Survivorship data indicate a robust, successful population. Life expectancy at birth was 20 years. Among adults, male mortality was consistently higher than female, a condition possibly related to high interpersonal and intergroup aggression. Infant mortality was generally low, and a general hypothesis concerning the elevation of infant mortality and the simultaneous depression of adult mortality among aboriginal peoples after European contact is suggested.

Collagen fiber orientation in the femoral necks of apes and humans: do their histological structures reflect differences in locomotor loading?

Human hip joint anatomy differs substantially from that in other primates. Humans modulate pelvic tilt during walking with a highly developed abductor apparatus, but other primates (such as chimpanzees) clearly lack such an apparatus (they exhibit a Trendelenburg gait during bipedal progression). Because the primate femoral neck is cantilevered whenever it supports body mass, it must be consistently subjected to substantial bending at the neck/shaft interface during stance phase in quadrupedal or bipedal locomotion. It has been argued, however, that the powerful abduction during the single support phase in humans results in almost entirely compressive stress on the human femoral neck. We examined collagen fiber orientation in human and chimpanzee femoral neck cortices using circularly polarized light, which has been shown to be a strong correlate of bone loading patterns. Chimpanzee superior femoral neck cortex was shown to be largely nonbirefringent (dark), but the inferior cortex was strongly birefringent. Human femoral necks showed strong birefringence both superiorly and inferiorly. These results are consistent with loading patterns suggested from anatomical structure, and provide corroborative evidence of bone's ability to preferentially orient collagen fibers during extracellular matrix deposition.

Femoral morphology and cross-sectional geometry of adult myostatin-deficient mice.

GDF-8, also known as myostatin, is a member of the transforming growth factor-beta (TGF-beta) superfamily of secreted growth and differentiation factors that is expressed in vertebrate skeletal muscle. Myostatin functions as a negative regulator of skeletal muscle growth and myostatin null mice show a doubling of muscle mass compared with normal mice. We examined femoral morphology of adult myostatin-deficient mice to assess the effects of muscle fiber hypertrophy and hyperplasia on bone shape and cross-sectional geometry. Femora of age- and weight-matched adult mice homozygous for the disrupted myostatin sequence were compared with those of wild-type controls (n = 8 per group). Results show that, as was the case in previous studies, myostatin null mice have hindlimb muscle masses that are approximately double those of controls. Myostatin-deficient mice exhibit third trochanters that are significantly larger than those of controls, whereas the femoral midshafts of the control and experimental mice do not differ significantly from one another in cortical area, bending moment of inertia, and polar moment of inertia. Our findings indicate that the increased muscle mass of myostatin-deficient mice primarily affects sites of muscle insertion, but does not induce additional cortical bone deposition in the diaphysis relative to controls. We therefore conclude that the expanded third trochanters of myostatin-deficient subjects result from tendon and Sharpey fiber expansion associated with muscle growth rather than cortical bone deposition in response to increased levels of mechanical stress.

Adaptationism and the anthropoid postcranium: selection does not govern the length of the radial neck.

The length of the radial neck has been assumed to vary in living and extinct primates in accordance with its role as a moment arm during flexion by the m. biceps brachii. We here use a simple developmental approach to investigate whether or not this trait does, in fact, vary in such a manner. We find, instead, that virtually all variation in radial neck length is explicable as a simple correlate of overall body size, and that there is no evidence to conclude that selection has separately modified radial neck length in response to differing locomotor patterns. Further implications for the interpretation of mammalian skeletal morphology are briefly discussed.

Part Two: The role of constitutional factors, diet, and infectious disease in the etiology of porotic hyperostosis and periosteal reactions in prehistoric infants and children.

Abstract A model of analysis incorporating methodological improvements and epidemiological refinements has been employed to investigate the etiology of porotic hyperostosis and periosteal reactions in infants and children from the Libben Site, a Late Woodland ossuary and occupation site from Ottawa County, Ohio. Results of the age-specific intrapopulational analysis of porotic hyperostosis demonstrate that the skeletal lesion strongly fits the age-specific distribution of hypochromic microcytic iron-deficiency anemia in infants and children. The data indicate that the lesion is a response to nutritional stress. Similarly, our findings show that the age-specific distribution of periosteal reactions strongly coincides with, and appears to be a response to, infectious disease as it occurs in infants and children. More importantly, survivorship and growth data indicate that porotic hyperostosis and periosteal reactions are strongly associated with patterns of infant and child morbidity and mortality, and therefore appear to play an important role in selection and fitness at Libben. Based upon the age-specific patterns and associations observed for porotic hyperostosis and periosteal reactions in the Libben infants and children, it is suggested that: 1. the current methodological procedure of partitioning skeletal populations into broad age categories can significantly distort important age-specific pathophysiological relationships; 2. skeletal lesions should be classified according to their physical quality (i.e., remodeled and unremodeled) to provide an estimate of both the morbidity and mortality associated with the age-specific distribution of a particular skeletal lesion; 3. porotic hyperostosis may be a valuable indicator of nutritional stress which can be employed to evaluate the nutritional status of prehistoric human populations; 4. the pathogenesis of porotic hyperostosis can best be understood in terms of the synergistic interactions between constitutional factors, diet, and infectious disease.

Dental wear in the Libben population: its functional pattern and role in the determination of adult skeletal age at death.

Modal patterns of occlusal attrition are presented for the Libben population based on a sample of 332 adult dentitions. Maxillas and mandibles were reviewed independently by seriation prior to assessment of complete dentitions. The Spearman rank order coefficient for upper and lower dentitions was .96. Wear patterns are very similar to those reported by Murphy (1959a: Am. J. Phys. Anthropol. 17:167-178) for Australian aborigines. There were no significant sexual differences in wear rate. Dental wear is concluded to be a highly reliable and important indicator of adult age at death for skeletal populations if seriation procedures are employed.

AL 288-1--Lucy or Lucifer: gender confusion in the Pliocene.

Häusler & Schmid (1995) challenged the long held opinion that AL 288-1 (Australopithecus afarensis), popularly known as "Lucy", was female. They concluded that AL 288-1 was most probably male ("Lucifer") and, by extension, the hypodigm for A. afarensis consists of two species which differ from one another in body size; in their opinion, AL 288-1 was most probably a male of the smaller of the two species. Häusler & Schmid based their conclusion on an obstetric analysis of AL 288-1 and Sts 14 (A. africanus) and on a comparison of the two australopithecine pelves with those of modern humans. This study evaluates the pelvic anatomy and probable sex of AL 288-1 by both assessing the obstetric adequacy of its pelvis and critically reviewing Häusler & Schmid's (1995, 1997) analyses of australopithecine pelvic dimorphism and relative body size of AL 288-1. Three results are shown. First, using Häusler & Schmid's own data, AL-288-1's and Sts 14's pelves are seen not to be dimorphic with respect to each other, as are human males and females, but they are in fact comparable in both size and shape. Second, AL 288-1's pelvis would have been obstetrically adequate, even with an inferred newborn brain size (as suggested by Häusler & Schmid) for A. afarensis that is likely overestimated. Third, AL 288-1 is shown to be one of the smallest adult individuals in A. afarensis. We conclude that AL 288-1 and Sts 14 were the same sex, and that the name "Lucy" correctly identifies AL 288-1's gender as female.

Hallucal tarsometatarsal joint in Australopithecus afarensis.

Hallucal tarsometatarsal joints from African pongids, modern humans, and Australopithecus afarensis are compared to investigate the anatomical and mechanical changes that accompanied the transition to terrestrial bipedality. Features analyzed include the articular orientation of the medial cuneiform, curvature of the distal articular surface of the medial cuneiform, and the articular configuration of the hallucal metatarsal proximal joint surface. Morphological characteristics of the hallucal tarsometatarsal joint unequivocally segregate quadrupedal pongids and bipedal hominids.

Metatarsophalangeal joints of Australopithecus afarensis.

Metatarsophalangeal joints from African pongids, modern humans, and Australopithecus afarensis are compared to investigate the anatomical and mechanical changes that accompanied the transition to terrestrial bipedality. Features analyzed include the shape and orientation of the metatarsal heads, excursion of the metatarsophalangeal joints, and orientation of the basal articular surface of the proximal phalanges. These features unequivocally segregate quadrupedal pongids and bipedal hominids and demonstrate a clear adaptation to terrestrial bipedality in the Hadar pedal skeleton.

The calcaneus of Australopithecus afarensis and its implications for the evolution of bipedality.

Calcanei from African apes, modern humans, and Australopithecus afarensis are compared to investigate the anatomical and mechanical changes that occurred in this bone as a result of the transition to terrestrial bipedality. Features analyzed include the cross-sectional area and volume of the calcaneal tuber, the geometry and orientation of the articular surfaces, and the surface topography of the calcaneal corpus. Calcaneal morphology is unequivocal in its partitioning of quadrupedal pongids and bipedal hominids.

Ectocranial suture closure: a revised method for the determination of skeletal age at death based on the lateral-anterior sutures.

A new method for estimation of age-at-death based on the degree of suture closure is presented. The method employs simple ectocranial scoring of specific sites on the external table. Composite scores for two groups of sutures, lateral-anterior and vault systems, which are used to provide estimates of age-at-death, have been developed from a sample of 236 crania from the Hamann-Todd Collection. A variety of tests show that the lateral-anterior sutures are superior to the sutures of the vault, that ectocranial is superior to endocranial observation, and that age estimates are independent of race and sex. It is concluded that suture closure can provide valuable estimates of age-at-death in both archaeological and forensic contexts when used in conjunction with other skeletal age indicators.

Radiographic changes in the clavicle and proximal femur and their use in the determination of skeletal age at death.

Visually seriated radiographs of the proximal femur, proximal humerus, clavicle, and calcaneus from 130 individuals from the Hamann-Todd collection were examined as indicators of skeletal age at death. The clavicle demonstrated the most consistent relationship to age in both sexes. The same radiographs were also seriated by size-normalized optical density as a means of establishing relative radiolucency. In this context, visual seriation proved superior. The four sites studied showed strong divergence in response to age. Since each was sampling bone response from the same individual, it is concluded that bone loss is highly site specific. This demonstrates the individual character of specific skeletal sites. Visual inspection of clavicular radiographs, seriated on a populational basis, provides age estimates that are comparable to anatomical age indicators and provides independent estimates of skeletal age when included in the summary age method (1985: Am. J. Phys. Anthropol. 68:1-14).

Anatomical, physiological, and epidemiological correlates of the aging process: a confirmation of multifactorial age determination in the Libben skeletal population.

Paleodemographic analyses based on estimates of skeletal age at death consistently report high levels of young adult mortality with few individuals living in excess of 50 years. Critics assert these data indicate systematic underaging of adults and justifiably remark that criteria for estimating skeletal age at death may be unreliable, age determinations are too frequently based on one or two criteria alone, and adult paleodemographic age profiles often mimic the age distribution of the modern population from which an age indicator's standards were originally derived. This study reports a series of tests based on well-documented biological aging phenomena that can be used to investigate potential effects of systematic underaging in adults, assuming the skeletal population is of sufficient size to permit such tests. These include patterns of third decade sternal clavicular epiphyseal fusion, multiple age and sex criteria associated with cortical bone dynamics, and fractures known to occur throughout the entire adult ages range. These phenomena are examined here for the Libben site skeletal population where adult age at death was determined by the multifactorial summary age technique. None of the biological criteria reported here were used in the Libben summary age analysis and thus serve as an independent test of accuracy in age determination. In addition, the summary age method has recently been applied to a series of modern skeletons of known age (Todd samples 1 and 2). Age standards for criteria employed with Libben and Todd 1 were identical. Since Todd 1 displayed underaging in older adults, a second Libben age distribution adjusted for Todd 1 bias was generated for comparison. A third Libben adult survivorship profile based on a Coale and Demeny West level 3 mortality experience, considered by some to be a more realistic model for skeletal populations, was produced for comparison. For all criteria examined, original Libben summary ages provided superior concordance with known patterns of biological aging in human populations. While Libben ages adjusted for Todd 1 bias were slightly better in the third decade, both Todd 1 adjusted and Coale and Demeny West level 3 age distributions produced unrealistic patterns of biological aging for individuals greater than 35 years. Implications of these results are discussed.