Bipedal verticality, social behaviour, environmental adaptation and human evolutionary development
Romano, M.
Annali di Igiene Medicina Preventiva e di Comunita 1(6): 1351-1375
1989
ISSN/ISBN: 1120-9135 PMID: 2484472 Document Number: 345515
The author has planned this research utilizing two models theoretically supported through biomechanical and mathematical laws, as they were formulated by means of data selected from paleoanthropological literature and his own clinic-instrumental case studies, on patients who were stimulated through manual pressure. The hypothesis was: is the paradoxical advantage reasonable for attaining and validating the mode of habitual, vertically aligned posture among evolutionary human-like beings through a vertical load upon their spine, as it is possible clinically in the course of rehabilitation? For assessing this argument two models, one biomechanical and the other mathematical were made up. They test the above mentioned load, as it reaches the clinically ascertained threshold value for triggering a firm gravitational alignment which is in agreement with bipedal gait. The suitability of the biomechanical model derives from reliability of the successively advancing levels of evolution (Anagenesis) from monkeys, through apes, to humans. This model was selected among the postural behaviours that were roughly antecedent to Hominidae bipedalism. So it was possible to abstract an Ape-like anteriorly sloping being, who under the above described stimulation through a suitable load on his-her neck-trapezius muscle angle is submitted to the flow of vertical forces as they show a tendency to aligning vertically the gravitational centers of head, thorax, abdominal masses. So, the biomechanics of the Ape-like being becomes the biomechanics of a mere Man-like mode of functional firm vertical alignment. The suitability of the mathematical model is in agreement with the reliability of the body of a Man-like being which is likened to a cylinder progressing chiefly through rotational and translational torques. The detailed sequence of the mechanical laws of stationary and dynamic equilibrium of rigid bodies and of elasto-mechanical law leads us to an understanding of abstracted sites as they in the course of human evolution were centering the characteristic osseous changes of humans which became the adaptative changes such as they are shown in fossil remains. The vertical alignment should have been validating through the advantageous carrying of loads of suitable weight. This, in turn, should have contributed to evolution of functional erect posture and gait through minimization of the centralised force-tension by means of a stepwise widening about some muscular attachments. So the nuchal part of the occipital bone widened while the increased capacity of enlarging pelvis of the evolutionary woman became adapted to accepting a larger fetal skull.