limit the size of individuals that can develop within the typical physical ecosystem. Conversely, the endoskeletal form of the vertebrates tends to facilitate a number of the physical characteristics that enhance the evolutionary prospects of all species within the phylum in general, and Homo sapiens specifically.

An internal skeleton is one of the hallmarks of the vertebrates. An internal skeleton, specifically of all mammalians, is composed of bones, which are, in turn, comprised of an organic and an inorganic component. The inorganic component is primarily calcium phosphate. Bone provides an excellent structural component for the body. Its internal structure provides a superior strength per mass ratio, meaning that bone provides support for the body without increasing its weight too much. Bone provides the mechanical component of the body which, when coupled with musculature, provides mobility or motor facilities. Structurally, endoskeletons offer superior support characteristics compared to exoskeletons, allowing the body of the individual to grow bigger without incurring as many liabilities due to increased weight. Exoskeletons, on the other hand, provide significant safety and security benefits by providing protection to sensitive organic material contained within the external skeleton and thus shielded from predatory or other physical threats. The internal skeleton of the human body provides support for the full sensori-motor systems that are suspended from it as well as enhanced mobility that improves the survival characteristics of the species.

While noting that the defining feature of the vertebrates is the internal skeletal structure, it is also interesting to observe that two of the skeleton’s primary features, the skull and the spinal column, actually function in an exoskeletal manner: the skull protects the brain and the spinal column protects and supports the primary central nerve that traverses the body of all species within the phylum chordata. These structures certainly manifest themselves within the primates. First, let us consider the spine.

The spinal column is composed of thirty-three short segments of bone called vertebrae, which are tied together in a stable, but highly flexible structure. Between each pair of adjoining vertebrae is an intervertebral disc made of cartilaginous material that serves both to hold the vertebrae together and to provide a flexible joint that allows the two vertebrae to move relative to each other, albeit in a highly constrained manner. The spinal column contains within it the main nerve, the spinal cord that emanates from the brainstem within the skull of the individual and descends through the abdomen. It terminates in the bony structure called the coccyx, which is a vestige in humans of the prehensile tail that exists in the lower primates and in other vertebrate species.

Vertebrate species generally derive a facility for independent movement from their four appendages tipped with phalangeal mechanisms and from the tip of the vertebrae skeletal feature; that is, from the development in many species of the feature called the tail. The motor (or muscular) sub-system of the body provides the propulsive force that allows the individual the freedom to move relative to its surrounding environment. Such movement enhances the ability of the individual to obtain sustenance. The range and speed of movement varies tremendously across the vertebrate species; from the slow crawling turtles and sloths to the highflying eagles and condors.

Mobility of the human body certainly has a significant impact on the ability of the species to both control its environment and to compete with other species. Mobility allows humans to escape from the heat or the cold by migrating to more moderate climes, and it allows people to avoid predators and to conquer prey. Mobility also translates into an extremely expanded set of metaphorical

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