Primate%20Models%20For%20Human%20Variation

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Chapter 8

• Primate Models For Human Variation

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Chapter Outline

• Human Origins and Behavior
• Brain and Body Size
• Language
• Primate Cultural Behavior
• Aggressive Interactions Between Groups
• Affiliation, Altruism, and Cooperation
• The Primate Continuum

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Human Origins and Behavior

• Humans and chimpanzees share more than 98 of
  their DNA, yet contrast in aspects of anatomy and
  behavior.
• Behavioral and anatomical adaptations were
  selected for as early hominids spent more time on
  the ground and exploited different food resources.

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Brain and Body Size

• The relationship between body and brain size is
  expressed as the index of encephalization.
• Most primates have brain sizes close to their
  expected values given their body sizes.
• Modern humans have a brain size much larger than
  expected for their body weight.
• Early members of the genus Homo, as well as
  Australopithecines were not as encephalized as
  modern humans.

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Brain Growth and Development

• In nonhuman primates, the most rapid period of
  brain development occurs either before or
  immediately after birth.
• In humans, brain growth occurs before and after
  birth, resulting in greater brain expansion
  during the first year after birth.

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Developmental Changes in the Skulls of
Chimpanzees and Humans
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Primate Language Abilities

• Social interactions and problem-solving abilities
  demonstrate primate intelligence.
• Vervet monkeys have three different vocalizations
  to indicate types of predators.
• The fact that apes cant speak has more to do
  with their anatomy and the language related
  structures of the brain than intelligence.

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Development of Language Abilities

• Ape language experiments suggest that the
  earliest hominids must have had ape-like
  communicative abilities.
• We dont understand why communication became
  increasingly important in the hominid lineage,
  and why natural selection acted to enhance our
  ancestors ability to use spoken language.

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Evolution of Human Language
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Criteria for Cultural Acts in Other Species
Innovation New pattern is invented or modified.
Dissemination Pattern is acquired (through imitation) by another from an innovator.
Innovation New pattern is invented or modified.
Dissemination Pattern is acquired (through imitation) by another from an innovator.
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Criteria for Cultural Acts in Other Species
Diffusion Pattern spreads from one group to another.
Tradition Pattern persists from innovators generation to the next.
Nonsubsistence Pattern transcends subsistence.
Naturalness Pattern is shown in absence of direct human influence.
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Nonhuman Primate Cultural Behavior

• Cultural behavior is learned and passed from one
  generation to the next.
• Chimpanzee culture includes tools such as termite
  fishing sticks and leaf sponges.

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Aggression

• Primates might defend a core area within their
  permanent home.
• Jane Goodall witnessed unprovoked, brutal attacks
  of chimpanzees by other chimpanzees.
• Territoriality and acquisition of females are the
  motives suggested for chimpanzee male aggression.

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Altruism

• Altruistic behaviors benefit another while
  involving some risk to the performer
• The majority of altruistic acts consist of the
  mother protecting her offspring.
• Primates deviate somewhat from this pattern in
  that the recipient and the performer of the
  altruistic acts may not be closely related to
  each other.

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Cooperative Behaviors

• Include alliances, coalitions, and grooming
  partnerships.
• Chimpanzees form alliances to increase their
  status or to gain protection from others.
• Chimpanzees frequently cooperate with each other
  in hunts.
• The patterns of cooperation in chimpanzee hunting
  behavior may provide clues to the development of
  human hunting behavior.

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The Primate Continuum

• Human brains are larger than primate brains, but
  the neurological processes are functionally the
  same.
• That humans are part of an evolutionary continuum
  is the basis for animal research, yet we cage
  nonhuman primates with little regard for their
  needs.
• Nonhuman primates should be maintained in social
  groups and introduced to habitat enrichment
  programs.

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Primate Behavioral Models for Human Evolution