Download Human Origins and Behavior

Chapter 8
Primate Models For Human
Variation
Chapter Outline
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Human Origins and Behavior
Brain and Body Size
Language
Primate Cultural Behavior
Aggressive Interactions Between Groups
Affiliation, Altruism, and Cooperation
The Primate Continuum
Human Origins and Behavior
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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.
Brain and Body Size
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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.
Brain Growth and
Development
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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.
Developmental Changes in the
Skulls of Chimpanzees and
Humans
Primate Language Abilities
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Social interactions and problem-solving
abilities demonstrate primate intelligence.
 Vervet monkeys have three different
vocalizations to indicate types of predators.
 The fact that apes can’t speak has more to do
with their anatomy and the language related
structures of the brain than intelligence.
Development of Language
Abilities
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Ape language experiments suggest that the
earliest hominids must have had ape-like
communicative abilities.
 We don’t understand why communication
became increasingly important in the hominid
lineage, and why natural selection acted to
enhance our ancestors’ ability to use spoken
language.
Evolution of Human Language
Criteria for Cultural Acts in
Other Species
Innovation
Dissemination
Innovation
Dissemination
New pattern is invented or
modified.
Pattern is acquired (through
imitation) by another from an
innovator.
New pattern is invented or
modified.
Pattern is acquired (through
imitation) by another from an
innovator.
Criteria for Cultural Acts in
Other Species
Diffusion
Tradition
Nonsubsistence
Naturalness
Pattern spreads from one
group to another.
Pattern persists from
innovator’s generation to the
next.
Pattern transcends
subsistence.
Pattern is shown in absence
of direct human influence.
Nonhuman Primate
Cultural Behavior
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Cultural behavior is learned and passed
from one generation to the next.
Chimpanzee culture includes tools such
as termite fishing sticks and leaf
sponges.
Aggression
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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.
Altruism
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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.
Cooperative Behaviors
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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.
The Primate Continuum
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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.
Primate Behavioral Models for
Human Evolution