chapter 14 the images on this cd have been lifted directly, without change or modification, from...

Chapter 14

The images on this CD have been lifted directly, without change or modification, from textbooks and image libraries owned by the publisher, especially from publications intended for college majors in the discipline. Consequently, they are often more richly labeled than required for our purposes. Further, dates for geological intervals may vary between images, and between images and the textbook. Such dates are regularly revised as better corroborated times are established. Your best source for current geological times is a current edition of the textbook, whose dates should be used when differences arise.

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Early hominid sites The Great Rift Valley of East Africa holds a local exposure of rocks that has yielded

remarkable fossils from the early part of hominid evolution. Sites in the Great Rift Valley, especially at Olduvai Gorge, hold an exposure of rocks at the needed time horizon (several million years ago). Fossil preservation was favorable, and the site is accessible (sort of) to anthropologists.


Ape and hominid skeletons Respectively, the backbone joins the back of the skull or bottom. The backbone is arched or

S-shaped. The arms are long in both, but shorter than hindlimbs in the ape compared to the hominid. The hips are long or bowl-shaped and the femur (upper leg bone) is angled out or in.


Bipedalism Walking comfortably on two hindlegs, bipedalism, evolved early in hominids. Many of the

changes in body design and eventually in social systems derive in part from this fundamental change in posture. Some of the major branches in hominid evolution are shown.


Bipedal adaptations I In hominids, the upright, bipedal posture is derived from primates that are dependent upon

a four-footed, quadrupedal posture. Such upright carriage of the body poses special problems in engineering. To accommodate this posture and stabilize it, the hominid gluteus muscles are large (balance leg swing), hips are wide (broad support), the spine curved (centers body weight, shock absorbing), and the position of the spine is beneath the skull (accommodate erect stance). (see also Bipedal adaptations II)


Bipedal adaptations II Further adaptations (see also Bipedal adaptations II) to bipedalism include a change of the

big toe (hallux) from grasping in apes to striding in hominids, repositioning of the hominid knee more under the pelvis, and shortening of the hips to a broader base of support of the upper body.


Hominid evolution Approximate times of appearance, skull design, and cultural artifacts are indicated.


Hominid relationships Hominids generally evolved in two directions. One, a “robust” line that became extinct

about 1 million years ago. The other, is the “gracile” line continuing down to modern Homo sapiens.


FIGURE 14.1 Diversity of Terrestrial Vertebrates The width of the “balloon” expresses the relative diversity of each group. Notice that

during the Mesozoic, the numbers of primitive mammals shrunk significantly compared to the predominant reptile groups of the time, which included the dinosaurs and allied groups (see also figure 13.12).


FIGURE 14.2 Goslings’ Following Behavior Konrad Lorenz himself raised these greylag goslings from first hatching, so it was to him

that they imprinted, expressing their normal behavior of following their “parent.”


FIGURE 14.3 Nature and Nurture—Speech Human language comes in a variety of dialects, here represented as A–G. In humans,

genes (nature) provide a person with the innate ability to speak a language, but the culture (nurture) into which the person is born provides the particular language learned. The final behavior is built with guidance from genes and culture.


FIGURE 14.4 Nature and Nurture—Bird Song (a) Three calls of the male meadowlark are shown, one set produced by a freeliving individual and one produced

by a hand-reared male kept isolated from ever hearing the songs of another male. The meadowlark’s genetic program is sufficient to produce normal songs. (b) The free living male chaffinch produces a complex song, but if raised in song isolation, its song is much different. If the chaffinch is exposed to the song of a tree pipit, then the chaffinch song picks up some of this vocal culture. Not only is the chaffinch genetic program insufficient to produce the normal song, but song culture (exposure to the tree pipit) can modify it. These recorded songs were played back through a sonograph to produce these visual displays of time versus frequency. ([a] is based on Lanyon 1960; [b] is based on Thorpe 1961.)


FIGURE 14.4 (continued)


Table 14.1 Classification of Primates


FIGURE 14.5 Primate Relationships Primates divide traditionally into two major groups. The prosimians tend to be small and

nocturnal, including bush babies of Africa, the lemurs of Madagascar, and lorises and tarsiers of Southeast Asia. The anthropoids are more derived, including monkeys plus gibbons, apes, and hominids.


FIGURE 14.8 Brachiation in Primates Locomotion by swinging through the trees suspended from the forelimbs places special

weight on the shoulders. To accommodate this, the shoulder joint is braced in the back by the broad scapula (shoulder blade) and in the front by the clavicle (collar bone). Hands are modified for grasping.


FIGURE 14.9 Lucy Skeleton, Australopithecus afarensis The lower jaw and parts of the skull survive, along with some of the arm bones, ribs,

backbone, left hip and upper leg bone, and some right lower leg bones.


FIGURE 14.10 Birth Canal Hips of the human male (a) and the human female (b). In humans, the birth of a baby with

a relatively large head requires a relatively large birth canal. Note that the inner rims of the hips of a female define a larger birth canal than do those of a male.


FIGURE 14.11 Hip Mechanics and Birth Canal The larger birth canal of human females crowds the hip joint and reduces the lever advantage upon which the

gluteus complex of muscles act. Consequently, these muscles are large in humans to compensate. (a) Hips of Lucy, Australopithecus afarensis. (b) Hips of human, Homo sapiens. When walking, the weight of the upper body (solid, vertical arrow) balances on the head of the femur (fulcrum, represented by a triangle) against the force produced by the gluteus complex (cross-hatched vertical arrow). Like a teeter-totter, the balancing of these is represented between the drawings. Note that the position of the fulcrum in the human (open triangle) is offset, making the action of the gluteus complex different than in Lucy (solid triangle). In humans, the enlarged birth canal and shortened “neck” of the upper leg bone, the femur, produces these mechanical differences in humans.

chapter 14 the images on this cd have been lifted directly, without change or modification, from...

Documents

hominid knee

hominid skeletons

early hominid sites

hominid relationships

bipedal posture

hominid gluteus muscles

body design

upper body