Organismal Biology #29
PRIMATES

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Order Primates: Monkeys, apes, humans, lemurs, tarsiers, and related animals.

Primate characteristics, mostly related to arboreal adaptations (life in the trees):
  • Arboreal locomotion
  • Grasping hands and feet (which wrap around branches)
  • Opposable thumb and/or big toe (wrap around in opposite direction from other digits)
  • Increased freedom of rotation in forearm
  • Increased reliance on vision (including color) and less on smell
  • Binocular, stereoscoptic vision (in depth)
  • Expanded visual centers in brain; more folds in brain surface
  • Visual inspection and manipulation of objects
  • Increased intelligence
  • Greater reliance on learned behavior; juvenile inexperience
  • Longer and more intense parental care
  • Uteri fuse into uterus simplex
Illustrations

Plesiadapoidea or Paromomyiformes: Extinct, archaic primates.

Lemuroidea or Strepsirhini: Lemurs, lorises, and galagos.

Tarsioidea: Tarsius and its extinct relatives.

Platyrrhina: New World monkeys and marmosets, with 3 premolars in each jaw, flat noses, and strong tails that aid in locomotion.

Catarrhina: Old World monkeys, apes (gibbons, orangutan, gorilla, chimpanzee) and humans, with 2 premolars in each jaw, protruding noses (nostrils opening downward), and reduced tails, native to Africa, Asia, and Europe.

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 8,000 years ago.

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