A. Human behavior B. Culture
attributes C. Physiology of Homo sapiens D.
Classification of Homo sapiens E. Human society
F. Structure of Homo sapiens Human, common name given to any
individual of the species Homo sapiens and, by extension, to the entire species.
The term is also applied to certain species that were the evolutionary
forerunners of Homo sapiens. Scientists consider all living people members of a
single species. 41.__________ Homo sapiens is identified, for
purposes of classification, as an animal with a backbone and segmented spinal
cord that suckles its young; that gestates its young with the aid of a placenta;
that is equipped with five-digited extremities, a collarbone, and a single pair
of mammary glands on the chest; and that has eyes at the front of the head,
stereoscopic vision, and a proportionately large brain. The species belongs to
the family Hominidae, the general characteristics of which are discussed
below. 42.__________ The details of skeletal
structure distinguishing Homo sapiens from the nearest primate relatives-the
gorilla, chimpanzee, and orangutan-stem largely from a very early adaptation to
a completely erect posture and a two-footed striding walk. The uniquely S-shaped
spinal column places the center of gravity of the human body directly over the
area of support provided by the feet, thus giving stability and balance in the
uptight position. Complete bipedalism in the human freed the
hand to become a supremely sensitive instrument for precise manipulation and
grasping. The most important structural detail in this refinement is the
elongated human thumb, which can rotate freely and is fully opposable to the
other fingers. The physiological requirements for speech were secondarily
established by erect posture, which positions the vocal cords for controlled
breathing, and by the skilled use of the hands. The latter development occurs in
association with the enlargement and specialization of a brain area that is a
prerequisite for refined control of the lips and tongue.
43.__________ The large brain of Homo sapiens is approximately
double that of early human toolmakers. This great increase in size in only 2
million years was achieved by a process called neoteny, which is the
prolongation of retention of immature characteristics. The juvenile stage of
brain and skull development is prolonged so that they grow for a longer period
of time in relation to the time required to reach sexual maturity. Unlike the
early human adult skull, with its sloping forehead and prominent jaw, the modem
human skull-with biologically insignificant variations-retains into maturity a
proportionately large size, in relation to the rest of the body, a high-rounded
dome, straight-planed face, and reduced jaw size, all closely resembling the
characteristics of the skull in the juvenile chimpanzee. Its enlarged dimensions
required adaptations for passage through the birth canal; consequently, the
human female pelvis widens at maturity, and the human infant is born
prematurely. 44.__________ The physiological
adaptations that made humans more flexible than other primates allowed for the
development of a wide range of abilities and an unparalleled versatility in
behavior. The brain’s great size, complexity, and slow maturation, with neural
connections being added though at least the first 12 years of life, meant that
learned behavior could largely modify stereotyped, instinctive responses. New
environmental demands could be met by rapid adjustments rather than by slow
genetic selection; thus, survival in a wide range of habitats and under extreme
conditions eventually became possible without further species differentiation.
Each new infant, however, with relatively few innate traits yet with a vast
number of potential behaviors, must be taught to achieve its biological
potential as a human. 45.__________ The human
species has a unique capability for culture in the sense of conscious thinking
and planning, transmission of skills and systems of social relationships, and
creative modification of the environment. The integrated patterns of behavior
required for planning and fashioning tools were accomplished at least 2.5
million years ago, and some form of advanced code for vocal communication may
also have existed at this time. By 350, 000 years ago planned hunting, fire
making, and the wearing of clothing were well established, as was possibly
ritualized disposal of the dead. Evidence of religion, recorded events, and art
date from 30, 000 to 40, 000 years ago and imply advanced language and ethics
for the complex ordering of social groups required for such activities. From
about that time the genus Homo began to stabilize into the one generalized
species of Homo sapiens.