Osteological and Radiological Study of Femoral Bicondylar Angle among Nepalese Population

Introduction: The femoral bicondylar angle of femur is an angle between the axis of shaft of the femur and a line perpendicular to the infracondylar plane. The bicondylar angle was studied from earliest known bipedal human ancestors: australopithecines from about 4.2 million years ago. The bicondylar angle of the femur of australopithecines is often used as a marker of bipedality and is therefore an indicator of human lineage. Objectives: The main objective was to study the femoral bicondylar angle by osteological and radiological method as to show their relation between different measured parameters as well as the angle under respective method. Methods: A total sample of 200 (100 dried femurs-for osteological method and 100 radiological films-for radiological method) from Medical colleges of Nepal were included in this study. Femoral bicondylar angle was measured by using osteometric board, goniometer, vernier caliper and accessories. Collected data were analyzed statistically and presented in the form of tables and graph. The mean of femoral bicondylar angle was calculated and correlated with other parameters using the Pearson’s correlation. Result: The mean value of femoral bicondylar angle obtained were 9.31⁰±2.13 and 9.37⁰±2.25 for right and left femurs respectively by the osteological method. The mean value calculated from radiological method were 8.96⁰±2.24 for right and 9.40⁰±2.44 for left in males whereas in females 8.70⁰±2.48 for right and 9.31⁰±2.58 for left. Apart from the average value and standard deviation, the mean angle correlation with height and side, showed statistically insignificant (P>0.005). Conclusion: The finding of the study showed the femoral bicondylar angle was greater in left femur than right in osteological method whereas it was greater in both right and left femur of male when compared to female as per radiological method. Overall, the bicondylar angle was found to be greater in left femur than right. Thus, obtained observation of the bicondylar angle could be useful in forensic discipline to ascertain the age and sex of the dried femur in controversial situation.

Comparative anatomy of the gluteal muscles of Sapajus libidinosus / Anatomia comparativa dos músculos da região glútea de Sapajus libidinosus

New World primates Sapajus sp. unexpectedly display cognitive aspects, tool use, social behavior, memory and anatomical aspects similar to Old World primates, such as chimpanzees and baboons. Convergent evolutionary aspects must have occurred between Sapajus and Old World primates and should be verified not only in terms of behavior analysis, but also of anatomical structure. The pelvic region can provide data for evolutionary verification trends, since taking standing position is one of the characteristics associated to the use of tools by early humans and pongids. We used eight specimens of Sapajus libidinosus to describe the deep muscular structure of the pelvis. Unlike humans, the gluteus medius muscle in S. libidinosus is completely covered by the gluteus maximus and elongated as compared to humans and chimpanzees, putatively by the elongated pelvis of S. libidinosus. Considering origin and insertion, the gluteus maximus muscle resembles more its counterpart in baboons than in humans and chimpanzees, since this muscle in baboons is associated to semibiped posture and to the tail. Gluteus minimum, piriformis, superior gemellus, internal shutter, gemellus and lower square muscles are positioned in this order in relation to the cranial-caudal axis, with all of its tendons converging for a common insertion in the greater trochanter. The muscles of the gluteal region of S. libidinosus are similar to the baboon, especially regarding the gluteus maximus, which points to the evolutionary kinship of these animals.(AU)

Os Sapajus sp apresentam aspectos cognitivos, uso de ferramentas, comportamento social e memória, além de aspectos anatômicos, similares à primatas do Velho Mundo, como chimpanzés e babuínos, fatos inesperados para estes animais, que são primatas do Novo Mundo. Aspectos evolutivos convergentes devem ter ocorrido entre Sapajus e primatas do Velho Mundo que devem ser verificados não somente em termos de análise do comportamento, mas da estrutura anatômica. A região pélvica pode fornecer dados para a verificação de tendências evolucionárias, pois assumir a posição bípede é uma das características associadas ao uso de ferramentas pelos humanos primitivos e pongídeos. Para descrever a estrutura muscular profunda da pelve, foram utilizados oito espécimes de Sapajus libidinosus. O músculo glúteo médio em S. libidinosus, diferente de humanos, é totalmente recoberto pelo glúteo máximo, é alongado em relação aos humanos e chimpanzés, putativamente pela pelve alongada dos S. libidinosus. O músculo glúteo máximo se assemelha, considerando origem e inserção mais aos babuínos do que em humanos e chimpanzés, uma vez que em babuínos esse músculo está associado à postura semibípede e à cauda. Os músculos glúteo mínimo, piriforme, gêmeo superior, obturador interno, gêmeo inferior e quadrado estão posicionados nesta ordem em relação ao eixo crânio-caudal com todos seus tendões convergindo para uma inserção comum no trocânter maior. Os músculos da região glútea de S. libidinosus são semelhantes ao babuíno principalmente no que se refere ao músculo glúteo máximo, o que reflete o parentesco evolutivo desses animais.(AU)

Origins of Bipedalism

ABSTRACT This article aimed to review various theories of bipedalism and provide a holistic answer to human evolution. There have been two questions regarding bipedalism: i) why were the earliest hominins partially bipedal?, and ii) why did hominins become increasingly bipedal over the time and replaced their less bipedal ancestors? To answer these questions, the prominent theories in the field, such as the savanna-based theory, the postural feeding hypotheses, and the provisioning model, are collectively examined. Because biological evolution is not a simple causation; there may be multiple answers to the evolution of bipedalism. The postural feeding hypothesis (reaching for food/balancing) provides an explanation for the partial bipedalism of the earliest hominins. The savannah-based theory describes how the largely bipedal hominins that started to settle on the ground became increasingly bipedal. The provisioning model (food-gathering/monogamy) explains questions arising after the postural feeding hypothesis and before the savannah theory in an evolutionary timeline. Indeed, there are no straight lines between the theories, and multiple forces could have pushed the evolution of bipedalism at different points. Finally, the arboreal hominins that possessed ambiguous traits of bipedalism were eliminated through the choice and selection. Using the biological analogy of the okapi and giraffe, efforts were put to explain how one of the branches (Homo) became increasingly bipedal, while the other (Pan) adapted to locomotion for forest life by narrowing the anatomical/biological focus in evolution.

El dilema obstétrico / Obstetric dilemma

Resumen: La teoría darwiniana indica que los seres humanos somos producto de la evolución y la selección natural, que ha tomado millones de años para traernos a nuestra situación actual. En el transcurso de ese tiempo el cuerpo de los animales que nos precedieron y del humano mismo cambiaron en varias formas, y una de los cambios más trascendentales fue el paso de la locomoción cuadrúpeda a bípeda. Ese cambio requirió numerosas adaptaciones entre las que están las del esqueleto de la pelvis y las extremidades inferiores, que redujeron el tamaño del anillo pélvico, por lo que si el feto esperara a nacer hasta que su cerebro madurara completamente, su gran cabeza no pasaría por ese anillo. La solución a este problema, que se ha llamado el dilema obstétrico, fue que el nacimiento ocurriera cuando la cabeza del feto aún no es demasiado grande, lo que implica que el cerebro todavía no está completamente maduro; aun así, el feto pasa con dificultades por el canal y el anillo pélvico. Al momento del nacimiento el cerebro del neonato no está completamente desarrollado y tiene que terminar de madurar fuera del útero, lo que toma tomar alrededor de 20 años. Esto puede explicar no solamente el comportamiento desorganizado de los adolescentes en general, sino también el inicio temprano de algunas enfermedades neurológicas cuyas consecuencias no se ven hasta la edad adulta, cuando la maduración del cerebro ha terminado.

Abstract: Darwinian theory indicates that human beings are products of evolution and natural selection, processes that have taken millions of years. During that time animals and humanoids changed in many ways and one of the most remarkable is the transition of a quadrupedal to a bipedal gait. Such a change required numerous adaptations, many of which are in the skeleton and lower limbs, that reduced the diameter of the pelvis in such a way that if the fetus had to wait to be completely developed to be born his large head would not pass through the pelvic channel. This problem is known as the 'obstetrics dilemma' and its solution was to allow the birth of an immature fetus, which implies a long process of extra uterus development. Even so, to be born the fetus has many difficulties to negociate the pelvic channel. At birth the fetus brain is incompletely developed and has to finish developing out of the uterus, a process that takes about 20 years. This delay might explain no only some unpredictable adolescent behaviors, but also the onset of some diseases whose consequences are seen until the adult years, when brain development has finished.