Showing papers in "American Journal of Physical Anthropology in 1966"

An evaluation of race and sex identification from cranial measurements.

Abstract: 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.

Sex determination of Finnish crania by discriminant function analysis.

Abstract: Using multivariant discriminant function analysis, the sex of 232 Finnish crania of known sex was determined. Eight measurements were used to form two discriminant functions. In 80% of cases the sex determination by means of the discriminant functions was identical with the original information. The applicability of the sex discriminant function of Giles and Elliot ('63) for American white and Negro crania was also tested on the Finnish crania. An accuracy of only 65% was attained.

Wolff's law and the problem of muscle attachment on resorptive surfaces of bone.

Abstract: During the growth of a bone, outer (periosteal) surfaces in many areas undergo normal remodeling processes involving resorptive removal. Attachments of muscles commonly occur on such outer resorptive surfaces. The cortex in these regions grows in an inward direction by bone deposition on endosteal surfaces. In some areas of a bone, a portion of a muscle can be inserted onto a depository surface, but other parts of the same muscle may be attached onto an adjacent resorptive surface. It has been generally assumed that the pull of a muscle acts to directly stimulate deposition of new bone, and that attachments of muscle are thereby responsible for determining the gross morphology of a whole bone. In view of the foregoing considerations, a re-evaluation and an expansion of this concept is now needed. Muscle pull, in many regions of a bone, can be associated with normal cortical recession (involving surface resorption) as well as with outward bone deposition.

A comparative study of facial growth in Homo and Macaca

Abstract: Sections were prepared throughout all areas of the various facial bones in young, growing Rhesus monkeys. The detailed distribution of resorptive and depository surfaces and the distribution of endosteal and periosteal bone tissue types were determined. From this information, the sequence of remodeling changes associated with the growth of the facial skeleton was then interpreted. This study is a sequal to previous reports in which growth and remodeling processes in the human face were described using similar procedures. In the present report, growth changes in the monkey and human facial skeleton are compared and contrasted. The general plan of facial growth is similar in both species, but major differences exist in the area of the muzzle. The maxillary arch in the monkey is entirely depository in nature, and it grows in a forward and downward direction as the maxillary tuberosity simultaneously grows backward. In the human, the forward part of the maxillary arch is resorptive in character. This contrasting growth factor results in a downward but not forward movement of this area. The result is decreased prognathism. Other differences in growth pattern exist in the forehead, malar, chin, and orbit. The developmental and phylogenetic basis for the upright human face is discussed and evaluated.

Distribution of hereditary blood groups among Indians in South America. I. in Ecuador

Abstract: Blood samples were procured from the following populations of putatively pure Indians in Bolivia: 503 Aymara from the Altiplano and Yungas, 30 Chama, 11 Tacana, 14 Chacobo, 109 Itonama, 67 More, and 27 Siriono from the Beni and lowland rainforest. Erythrocytes from these 761 specimens were tested for antigens in the A-B-O, M-N-S-s, P, Rh-Hr, Lutheran, Kell-Cellano, Lewis, Duffy, Kidd, and Diego systems, and for the Wright agglutinogen. The serum samples were tested for haptoglobins and transferrins; and hemolysates were prepared and examined for hemoglobin types. Results of these tests are presented as phenotypes and calculated gene frequencies on appropriate tables. A map is included to show the locations of the populations from which blood samples were obtained. Frequencies are generally high for the O gene, it being the only gene of the ABO system which appears in the Chama, Chacobo and Siriono. The presence of A1, A2 or B genes in the Bolivian Indians is interpreted as being most probably of caucasoid introduction. Excepting the Siriono the frequencies are high for M and low for N genes as is usual for Amerinds, the M gene being the only one detected in the Chama. The s gene frequency in high and the S low except in the small isolated Chacobo population in which S gene frequency is extremely high for Amerinds. Inbreeding and perhaps genetic drift in this small isolate may account for this aberrancy from normal. The Bolivian specimens presented the high frequencies for genes R1 (CDe) and R2 (cDE) and the low frequencies for genes r (cde) and R0 (cDe) usually observed in American Indians. The Lua factor was observed in only one of 120 Aymara at Santa Fe in the Yungas. The Lua factor, when observed in Amerinds, suggests foreign introduction of the responsible gene. Fya gene frequencies are consistently high and excepting the Aymara and Chama so also are Jka frequencies. Frequencies for the Diego (Dia) factor vary from 3.70% in 27 Siriono to 73.33% in 30 Chama. No K, Mia, Vw or Wra antigens were demonstrable in the Indian blood samples from Bolivia. Phenotypes and calculated gene frequencies for haptoglobins and transferrins are presented. All Bolivian Indian bloods tested electrophoretically contained only hemoglobin (A) as a major component.

Growth rates and phylogeny in primates.

Abstract: There is sufficient evidence to indicate that man grows for a longer period of time than chimpanzee who in turn has a greater duration of growth than rhesus monkey. The problem of this paper was to determine if there was a concomitant decrease in a rate of growth. Using the relative growth rate of Fisher ('21), it appears that for most of their period of growth, the rate of change is the same. Immediately after birth, when we have no data for children, rhesus monkey grows significantly faster than chimpanzee. By a year and a half their rates are the same, and neither species shows a sex difference. From seven years (age of youngest children) until children start through puberty, there is no sex difference in Homo sapiens, and the human rate does not differ from the chimpanzee rate. Because of the resemblance between the primate curve for rate and that for dairy cattle, it is postulated that this curve is more mammalian than primate and that during phylogeny the primates have merely increased the duration of time when growth is possible. Man does show one new feature, the puberal growth spurt, which is not found in the non-human data considered. The implications of these conclusions for primate phylogeny and for growth are discussed.

Bone density, breaking force and leg muscle mass as functions of weight in bipedal rats†

Abstract: Femur density, femur breaking force and muscle weight on the hind limbs of normal and bipedal rats have been measured. The bipeds had more muscle on the hindlimbs than controls. Increasing muscle mass was associated with increasing femur density and breaking force. It is concluded that weight bearing influences bone density and breaking force through muscle mass.

Cranial capacity and neuron number: a critique and proposal.

Abstract: Some recent studies correlating cranial capacity with behavioral development and more molecular parameters such as neuron number are critically examined. These studies are found lacking in terms of basic assumptions and empirical support from other studies. In general, it is shown that these studies have overlooked an important aspect of brain evolution in the Primate Order, i.e., reorganization, or the shifting quantitative relationships of subsystems and components of the nervous system. A distinction is made between two approaches to the problem of the evolution of brain and behavior: (1) the “quantitative-specific” and (2) the “quantitative-general.” Attempts to derive specificity in terms of estimates of the number of cortical neurons in different pongid and hominid brains are premature unless basic data regarding organizational shifts are known. A supporting argument for the priority of the “quantitative-general” approach for all levels of the primate nervous system is made. Such a descriptive level is more amenable to synthesis with current neurophysiological knowledge and primate field and laboratory studies than the “quantitative-specific” approach.

Heights and weights of Jamaican schoolchildren of various ethnic groups.

Abstract: In Kingston, Jamaica, it is possible to disentangle racial and environmental factors, both of which influence the size of children, because secondary school children, of similar socio-economic status, can be grouped as being predominantly of African, European, Afro-European or Chinese racial origin. The heights and weights of about 5,000 children, aged 11 to 17 years, were measured. The stature of Africans, Afro-Europeans and Europeans was similar, indicating that in Jamaica the potential height of the African is at least as great as that of the European race. Chinese were consistently smaller than the others, a difference due to inherited racial factors.

Ossification sequence polymorphism and sexual dimorphism in skeletal development.

Abstract: Ossification sequence polymorphism and sexual dimorphism are prevalent in the postnatal skeletal development of the hand, foot, elbow, knee, shoulder and pelvis. For some ossification polymorphisms the sex-discriminatory efficiency is greater than 70%. Current evidence, including population comparisons, and children with kwashiorkor and marasmus, favors a genetical explanation for common sequence polymorphisms. However, ossification sequence polymorphism is more clearly defined in later-developing children, where the appearance of ossification centers is distributed among a larger number of radiographic class intervals. This observation may explain the apparent relationship between ossification sequence polymophism and developmental delay or retardation.

A comparison of somatotype methods

Abstract: In order to compare Parnell's and Heath's somatotype methods, the authors independently somatotyped a series of 59 adult male and 61 adult female subjects, (1) using the criteria of Heath's method, (2) using the criteria of Parnell's method, and (3) taking into consideration tentatively adapted Parnell criteria in addition to Heath's criteria. The authors conclude that when use similar rating criteria their mean differences are smaller, their overall correlations are similar, and their percentage agreements to a half-unit are higher (96%) than for comparisons reported by other investigators. The study considers the potentially important relationships of measurements of subcutaneous fat to ratings of the first component. The similarity of distributions of subcutaneous fat measurements and of first component ratings in selected samples suggest important interrelationships among ratings of the first component, height/ weight ratios and subcutaneous fat measurements. The authors feel: (1) that Parnell's method fails to modify the basic weaknesses in Sheldon's somatotype method; and (2) that analyses of the anthropometric data basic to Parnell's method, if guided by the criteria of Heath's method, will further objectify and simplify Heath's method, will improve agreement among independent raters, and will increase the usefulness of somatotyping as a research instrument.

The correlation of bone robusticity with the perforation of the coronoid-olecranon septum in the humerus of man

Abstract: Hrdlicka ('32) theorized that the tendency towards perforation of the coronoid-olecranon septum of the humerus was phylogenetic in origin, but its appearance also seemed to be negatively correlated with bone size. By determining the correlation between the occurrence of the perforation and certain standard anthropometric measurements, the present study provides a statistical tool to test Hrdlicka's hypothesis more rigorously. The minimum middle diameter of the humerus is shown to be significantly related to the occurrence of septal perforation, in samples of archeological skeletal material. Using the minimum middle diameter of the humerus as a quantitative assessment of robusticity, more robust samples were found to have smaller mean percentages of perforation.

Numerical variation of the presacral vertebral column in three population groups in North America

Abstract: A total of 1,239 skeletons from among Mongoloid, Caucasoid and Negroid population groups in North America was examined for variations in the number of presacral vertebrae. The overall incidence of variation was 11%; 6% with 23 and 5% with 25 presacral vertebrae. Differences in total variation among the three groups were not significant, but differences in the incidence of 23 and 25 presacral vertebrae among the groups were highly significant. Numerical vertebral variation occurred in 11% of both sexes, but with males having a higher frequency of 25 presacral vertebrae and females having a higher frequency of 23 presacral vertebrae. The incidence of the specific variation of 23 or 25 presacral vertebrae was not significantly different among the males of the three groups studied, whereas 23 presacral vertebrae were found significantly more often in the Negroid females. Numerical variation of vertebrae was not associated with age. The data strongly support the conclusion that the total frequency of variation in the number of presacral vertebrae is a specific characteristic of any particular population group and that there is a tendency in all population groups toward an increase in number in males and a decrease in number in females.

On the presence of cribra orbitalia in apes and monkeys.

Abstract: One hundred and six skulls of various species of apes and monkeys were examined for the presence of cribra orbitalia. The condition was found in 15 (14.1%) of the animals. As in humans, cribra orbitalia was found localized mainly in the anterior parts of the orbital roof and appeared more frequently in infants and young animals. Only mild degrees of cribra orbitalia, i.e., the porotic type of lesions, were found in this series of animal skulls studied. More advanced degrees of development, as observed in human skulls, were not found. The etiology of the condition is not known; some type of nutritional deficiency is considered to be the most likely cause. The occurrence of cribra orbitalia in animals opens up possibilities of experimental work on the subject and may help to solve the problems of its etiology.

Morphology of Liberian Negro deciduous teeth I. Odontometry.

Abstract: An odontometric study of the deciduous teeth of 21 Liberian Negro children is reported. These data were obtained from dental casts alone. Statistical comparisons were made of the mesiodistal diameter alone with two American White populations and the three Japanese populations. Maxillary teeth, with the exception of the cuspids were larger in the Negro sample, while only the Negro mandibular molars were significantly wider. This situation resulted in an alteration of Negro maxillary tooth size order. Comparisons were made with other populations reported in the literature which led us to stress the fact that, as yet, no satisfactory sample of deciduous tooth measurements are available for any population. A discussion of tooth form differences stresses the point that teeth differ in both attributes of form, i.e., in shape as well as in size between the several major racial groups. The processes by which these shape differences are brought about were discussed and it was suggested that differing relative growth rates may well be one cause. An allometric analysis of fetal molar tooth growth showed, again, that a sharp interphase occurs in all teeth, with a subsequent decrease in specific growth rate. This interphase corresponds to the initiation of cuspal calcification.

The skin of primates. XXXI. The skin of the black-collared tamarin (Tamarinus nigricollis).

Abstract: The black-collared tamarin represents the first detailed study of a member of the family Callithricidae. Although certain features are unique, some of its characteristics resemble those of Prosimii and those of Anthropoidea. The epidermis is moderately pigmented, and the dermis contains numerous elestic fibers. Scattered melanocytes are found throughout both layers. Hair follicles grow in groups of 3 to 4 over the general body surface, including the muzzle. One apocrine gland is associated with each hair group. In the periinguinal region is a large concentration of gigantic sebaceous glands. Apocrine glands occur over the entire hairy skin. Aggregations of these glands on the ventral wrist (in conjunction with sinus hairs) and chest represent the ulnar gland and suprasternal gland, respectively. Apocrine secretory coils of the ulnar gland and external genitalia are surrounded by melanotic, dendritic melanocytes. Eccrine sweat glands are confined to the volar surfaces of the pes and manus. Cholinesterase-reactive granules are dispersed throughout the cytoplasm of the myoepithelial cells.

The population characteristics of howler monkeys (Alouatta caraya) in Northern Argentina.

Abstract: Howler monkeys, Alouatta caraya, were collected in family groups from islands in the Rio Parana in northern Argentina. The body weights, lens weights, dental age and reproductive status of 261 individuals illustrated sexually dimorphic body weights after a period of accommodation as young adults, a large proportion of older females (even though there are more young adult males than females) and a higher percentage of pregnancies among these older females. Seventeen families, representing the entire social system of one island, showed that about three quarters were adult (equally divided between the sexes but with fewer older males than females) and the remaining quarter were immature (with an equal sex ratio). Half of the adult females were either pregnant or suckling young. The mean family size is seven which includes peripheral males. Group size and composition as well as adult to immature proportions compared closely with data on A. caraya in the Chaco of Argentina and the 1951 census of A. palliata on Barro Colorado Island. It can be said that when these two species of Alouatta occur in small size families, they have in common: a high proportion of adults to immature, a low proportion of infants, and can have either an equal sex ratio (A. caraya) or preponderance of females (A. palliata).

Body composition: Models and estimation equations

Abstract: Several approaches have been developed to a quantitative description of the “inner man.” The present attempt at a synthesis of the basic methodological aspects begins with the anatomist's handiwork and goes on to somatometric models and to procedures based on determinations of body density and body water. The estimation equations used in the densitometric and the hydrometric analysis of body composition are derived afresh from information on an empirically defined “reference body.” The Minnesota model is based on considerations of the composition of the reference body and of the “obesity tissue,” initially defined as body mass gained during a prolonged intake of excess calories. Subsequently, information has been obtained on the composition of weight losses and of the mass differentiating “lean” and “fat” young men of the same height. Due consideration is given to the approaches based on the measurement of whole-body radioactivity generated by the naturally occurring isotope of potassium (K40), and to the multicomponental system developed by F. D. Moore and his co-workers in the context of surgical treatment and research. While the very nature of the field is interdisciplinary, the presentation endeavors to be intelligible to students, teachers, and investigators approaching the problem from the point of view of any scientific specialty.

The skin of primates XXVIII. The stump‐tail MACAQUE (Macaca speciosa)

Abstract: Though having some similarities to that of the rhesus monkey, the skin of the stump-tail macaque has several unique features. The epidermis has a sparse population of active melanocytes, and there is practically no pigmentation in the dermis. The dermis is rich in elastic fibers, the function of which seems to be to anchor the hair follicles and the arrectores pilorum muscles, and the superficial blood vessels. Large numbers of eccrine and apocrine sweat glands in the forehead and scalp are reminiscent of the axillary organ in the Hominioidea. The very large sebaceous glands on the face and bald forehead and scalp resemble those of man. The forehead and anterior portion of the scalp are bald in the adult but not in juvenile animals. In spite of an apparently rich pelage, these animals seem to show a trend toward nakedness.

A recent occurrence of an African type tooth mutilation in Florida.

Abstract: A Negro skull with mutilated teeth was found in Saint Augustine, Florida. There are clear indications that the specimen is recent. Unfortunately, it is impossible to determine the country of origin of the skull. However, anthropologists should be sensitive to the possibility of tooth mutilation currently being practiced among Negro groups in the Western Hemisphere.

Genes and phenotypes in the Samaritan isolate.

Abstract: A genetic and anthropological survey of the Samaritan community in Israel carried out in the autumn of 1963 included tests for about 30 blood group antigens, several serum proteins, hemoglobin variants Glucose-6-Phosphate Dehydrogenase activity, secretor status, color-blindness and some 18 anthropometric measurements and 18 morphological observations. About 90% of the total group were studied. The results obtained show that in blood groups, the Samaritans have the highest O frequency in the Middle East, A2 is more common than A1, and there are more N genes than M. Not a single case of G6PD deficiency was found. The incidence of color-blindness is very high (27%). There is heterogeneity in physical type and large variations between individuals are also manifested in hair and eye-color distribution.

The sixth skull cap of Pithecanthropus erectus.

Abstract: The sixth skull cap of Pithecanthropus erectus (or skull V, since the Modjokerto skull has not been given a number) was found in the upper layers of the Trinil beds of Sangiran (Central Java) in 1963, associated with fossils of the Sino-Malayan fauna. No stone tools were discovered in direct association with the find. The specimen consists of the occipital, both parietals, both temporals, sphenoid fragments, the frontal and the left zygomatic bone. We consider the skull to be a male in his early twenties. The occipital, parietal, frontal and temporal bones demonstrate definite pithecanthropine characteristics, and the cranial capacity is estimated to be 975 cm3. Of the superstructures, the supraorbital torus is extraodinarily thick, approaching the condition in Australopithecus boisei and Rhodesian man. And the sagittal torus is certainly higher than in skulls I and II, but lower than in skull IV. In addition, the angle between the occipital and nuchal planes is larger than in the previous finds. As revealed by various features, the gap between the robustness of skull IV on one hand, and skulls I, II and III on the other, is bridged by the present find. There is no reasonable taxonomic need to ascribe this specimen to a new species, because it seems to be merely an intrapopulational variant of the same species. Other skulls of P. erectus suggest that the bregmatic eminence, and hence the vertex, is invariably situated at bregma, but this new skull cap deviates from the pattern. Its pteric regions disclose the anthropoid X and I types. The middle meningeal groove pattern is similar to other Pithecanthropus skulls; however, it betrays a known anomaly in that the main stem is covered for a short distance by a bony plate. The mastoid process is fairly well developed, and is also well pneumatized as in P. pekinensis, with its air cells invading the pronounced supramastoid crest. The zygomatic bone, the first one recovered of P. erectus, does not show characters of particular importance. In fact, its thickness is in the range of modern man. We would like to stress that the absence of the cranial base does not necessarily indicate that the specimen must be a poor victim of cannibalism, since the morphology of the base renders it more susceptible to post-mortem natural traumata.

Notes on Ramapithecus, the earliest known hominid, and Dryopithecus

Abstract: Recent paleontological analysis of the Higher Primate subfamily Dryopithecinae shows that fossils in this group can be referred to two genera, Ramapithecus and Dryopithecus. Ramapithecus is known from India and East Africa in Late Miocene or Early Pliocene time (about 14 m. years ago). The remains of Ramapithecus resemble closely the equivalent parts of the later Hominidae and contrast with those of the Pongidae. It is concluded that Ramapithecus is the earliest known hominid, some 5 or 6 times older than the oldest Pleistocene hominids. Dryopithecus is a pongid and contains as subgenera (Dryopithecus), (Proconsul), and (Sivapithecus). Probably part of (Proconsul) is ancestral to the chimpanzee and part to the gorilla, while part of (Sivapithecus) is ancestral to the orang-utan.

The annual reproductive cycle of the Barbary Ape (Macaca sylvana) in Gibraltar.

Abstract: Data collected in Gibraltar demonstrate that Macaca sylvana has both a sharply demarcated mating and a sharply demarcated birth season. The mating season begins in November and may last until March. Births occur between May and September, gestation being of five or six months' duration. The annual reproductive cycle of the Japanese macaque is strikingly similar to that of the Barbary Ape. Matings occur in both areas in the fall, a period of decreased daily temperature and day length. The mating season begins with an increase in rainfall in Gibraltar and with a decrease in rainfall in Japan. From the data presented it seems probable that decreasing day length is the most important ecological factor in the timing of the onset of mating in Barbary Apes and in Japanese macaques.

Caryology and taxonomy of the Catarrhine monkeys.

Abstract: The number and the morphology of chromosomes are a characteristic of the species. Knowledge of the mechanisms of chromosome breakage and rearrangement offers the possibility of understanding caryotype evolution. On the basis of this knowledge, we can trace the phylogeny and organize the taxonomy of a group of living forms. In the present paper, the available data on the number and morphology of the chromosomes of the Catarrhine monkeys have been analyzed from the standpoint of taxonomy and evolution. According to this karyological revision, the suborder Catarhine might be divided into two groups (superfamilies): Cercopithecoidea and Hominoidea. Within the Cercopithecoidea the following main groups should be further distinguished: 1. a group which includes all the species of the genus Cercopithecus; 2. a group which includes the different species belonging to the genera Papic, Macaca, Theropithecus and Cercocebus; 3. a group which includes the genus Colobus, Presbytis and Hylobates. Within the Hominoidea, the three anthropoid apes (Pan, Pongo, Gorilla) can be distinguished from man by the difference in the number of chromosomes. Moreover, among the anthropoid apes, the Orang-outang can be differentiated from the others by the morphology of the chromosomes.

Genetic and selective factors in reduction of the hallux in Pongo pygmaeus.

Abstract: Extreme reduction of the hallux is unique to the orang-utan (Pongo pygmaeus) among Primates. Hallucal diminution has advanced so far that 60% of orang-utans lack both distal phalanges and nails. Absence of these structures occurs significantly more often in females than in males. Hypotheses on possible genetic control of the condition have been tested and indicate that either single gene inheritance or polygenic inheritance with variable expressivity is involved. Reduction of pollex and of hallux in Pongo have advanced with selection for a specialized four-digit grasp in hands and feet. Diminution has progressed farther in the great toe than in the thumb due to selection for fine manipulation in the latter digit.

Some physiological and developmental considerations of the temperature-gradient hypothesis of bone marrow distribution.

Abstract: In adult humans, active bone marrow is confined to the proximal portion of the skeleton. Huggins and Blocksom (J. Exp. Med., 64: 253, '36) concluded that a high temperature is needed for hematopoiesis in rats. However, precise thermal regulation of human marrow was not found (Petrakis, J. Appl. Physiol., 4: 549, '52). Because these experiments made on the rat tail are the basis for a commonly accepted hypothesis attempting to explain marrow distribution in man, it was considered of importance to re-examine the caudal vertebra model upon which the temperature-gradient hypothesis is based. The sacral and coccygeal vertebrae were examined in rats, mice and humans with respect to marrow cellularity and temperature. In rats and mice and man it was observed that the transition between hematopoietically-active and inactive (fatty) vertebral marrow cavities is abrupt, occurring at the level of the first and second caudal and coccygeal vertebrae. All vertebrae distal to this point have fatty marrow. Of significance was the finding that the vertebral and coccygeal temperatures, as measured with a thermister needle, remain unaltered over this area of changing cellular activity. These anatomical and thermal observations of the caudal vertebrae of rats, mice, and humans indicate that the use of the tail as an experimental model does not support the hypothesis that temperature is a primary factor in the physiological maintenance of hematopoiesis in bone marrow. The possible relationship of hematopoietic activity to developmental and other factors peculiar to the caudal vertebra model is under study.

Bone breaking stress as a function of weight bearing in bipedal rats.

Abstract: The effect of bipedal stance on the breaking stress in compression of rat femora is investigated as a function of animal weight. It is shown that the breaking stress is a linear function of body weight, bone density and specific calcium content of the femur. In all cases investigated, bipedal femora are shown to have a higher breaking stress than controls. It is concluded that there is a continuous change in the quality as well as the quantity of bone in the rat femur with age and that the increased strength of bone material found in bipedal animals compared to controls as well as large animals as compared to small ones, cannot be explained on the basis of bone mineral content alone.

Phenylthiocarbamide taste sensitivity and its relationship to growth variation.

Abstract: The hypothesis that there is a relationship between the tasting polymorphism and growth variation was tested on a sample of 425 Negro elementary school children. Twenty-seven non-tasters were found by testing with impregnated papers; 13 were male, 14 female, indicating no sex differences in this group. Matchedpair comparisons indicated no differences in weight, a tendency for tasters to be taller, and a stronger tendency for tasters of both sexes to be skeletally more mature. It was felt that the tendency for tasters to be taller might reflect their more advanced maturation status. The relationship to skeletal maturation might be indicative of the decreased thryoid activity found in other studies of phenylthiocarbamide tasting.

"Probable mutation effect" and the evolution of hominid teeth and jaws.

Abstract: In view of recent suggestions that tooth and jaw reduction in the hominid line was due to random mutation, it is pointed out that positive selective factors, involving greater chewing efficiency and increased speed in movements of the head, may have been at work.