Bio Review Notes #94
HUMAN EVOLUTION

Humans walk upright. The many consequences of this include tool use, speech, and anatomical changes such as an S-shaped vertebral column (with a lumbar curve) and a more rounded cranium from which the spinal cord exits at the bottom.

Family Hominidae (humans): Catarrhine primates distinguished from apes
    (fam. Pongidae) principally by upright locomotion. Characteristics include:
  • Upright, bipedal locomotion (walking, running)
  • Larger and more rounded braincase
  • Spinal column exits (through foramen magnum) at bottom, not rear, of the skull
  • Reduced spines on neck vertebrae
  • Spinal column gently S-shaped, with lumbar curve (concave to rear along lower back)
  • Pelvis wider; iliac crests expanded
  • Gluteus maximus enlarged and rotated to the rear, pulling leg to the rear instead of sideways
  • Canine teeth reduced (tools are now major weapons)
  • Lower jaw symphysis strengthened by chin
  • Tooth rows rounded instead of parallel
  • Habitual use of tools (hands free to hold them)
  • Habitual use of language

    Origin of Hominidae: Approximately 5-6 million years ago when upright posture was attained. Human footprints at Laetoli, Kenya, are 4.1 million years old.

    Evolutionary "dead ends": A number of hominid fossils are now considered to be evolutionary "dead ends," not ancestral to modern humans. These include Sahelanthropus, Ororrin, Kenyapithecus, Ardipithecus, and the large or "robust" Australopithecus robustus and A. boisei.

    Australopithecus: The best-known early hominids, from South Africa and East Africa. Certain early species (Australopithecus anamensis, A. afarensis) may have been ancestral to Homo, but later species were not. One nearly complete skeleton of A. afarensis, nicknamed "Lucy," was only about 4 feet tall and walked upright.

    Homo habilis: An East African contemporary of Australopithecus, from about 4 to 1.5 million years ago. Body size about 4 feet tall. Perhaps responsible for early stone tools.

    Homo erectus: Lived in the middle Pleistocene, after the extinction of Australopithecus. Fossils known from Europe, Africa, Asia. In a cave near Beijing, China, heat-fractured rocks show that fire was used.

    Homo sapiens: First appeared in the late part of the Ice Age. Taller skull than earlier species. Used more advanced tools. Invented agriculture around 6,000 years ago.


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