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Part V
ARE HUMANS DIFFERENT?
E
volutionary principles for cooperation that have been developed
from studies of diverse social organisms should apply to humans.
The more immediate roots to human cooperation and conflict also
may be seen in primates. However, there are challenges in studying
humans and their close relatives. Objectivity is essential. There are many
possibilities for study techniques (such as the questionnaire or survey)
in humans, but these also offer many opportunities for confusion. One
powerful approach to studying human cooperation is to look at what
humans do and what the outcomes are, just as one might do for other
social animals. This technique can be particularly informative when the
human group lives in ways consistent with humans over most of their
evolutionary past. The Dogon people of Mali, reported on by Beverly
Strassmann in Chapter 14, are millet-and-onion-farming agriculturalists
who do not use contraception, adhere largely to indigenous religions,
practice polygyny, and have high mortality rates. In a 25-year-longitudinal
study, Strassmann has investigated the hypothesis that the Dogon are
cooperative breeders, where some individuals help rear nondescendent
kin rather than their own progeny. She does not find that the data sup-
port this hypothesis. First, neither women nor men delay reproduction
in order to raise siblings. Although parents force daughters to care for
extra siblings, this is better viewed as parental manipulation because the
presence of siblings reduces survivorship. Similarly, grandmothers do not
appear to be effective alloparents. Rather than increasing survivorship, the
presence of paternal grandmothers does the opposite, doubling the hazard
299
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300 / Part V
of death for a child. What matters most for survival is the presence of the
mother, and other relatives are not adequate replacements. Task coopera-
tion occurs within the groups that work and eat together, but conflict is
always present in ways that Strassmann carefully explains.
In an overview of vertebrate interactions, Dorothy Cheney demon-
strates in Chapter 15 that animals ranging from chickadees to chimpanzees
are aware of their own status, and that of their companions, and behave
accordingly. Eavesdropping on how individuals interact with others can
change behaviors. Relatednesses are often known and impact interactions.
In vervet monkeys, for example, an individual who has been attacked
may turn and subsequently attack a relative of her opponent. Dominance
hierarchies also impact such interactions. But some animal interactions are
more subtle. Ravens are more likely to cache food in hidden sites when
competitors are present, for example. However, the calculations of gain,
cost, and punishment necessary for reciprocal altruism (here called contin-
gent altruism) seem largely lacking outside of humans. Instead, there is a
great deal of tolerance in interactions and a lack of direct payback among
close relatives and long-time partners. Yet it is in these relationships where
cooperation overwhelmingly occurs. A common feature of cooperative
acts is that they are not necessarily transitive. Some individuals consis-
tently take on the risky jobs, be it male chimps patrolling their territorial
edges or female lions leading the hunt. This is also true in organisms
(such as wasps) with much simpler brains, where cooperation flows from
workers to the queen.
Observations of humans and primates in natural situations can teach
us much about behavior, but environmental complexity can make causa-
tion difficult to discern. An alternative is to examine choices made under
highly regulated circumstances. To address social acts such as generosity,
trust, fairness, and punishment, many purportedly relevant games have
been applied to humans, one simple example being the Dictator Game
that allows a subject to decide whether to share a quantifiable resource
with an unseen other. [This game typically yields donations of 20–30%
of the resource.] Although such games have weaknesses, they seem to
indicate that humans are willing to donate but only at levels indicating
they consistently value themselves most highly. These and other experi-
ments further indicate that humans favor relatives, long-term partners,
and group members over outsiders, and they will suffer costs to punish
cheaters. As described by Joan Silk and Bailey House in Chapter 16, ver-
sions of social games involving food or tools that likewise have been used
with primates produce complex results. Cooperation clearly occurs and
tracks levels of sociality in the groups, but some results are controversial
and remain open to alternative interpretations.
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Are Humans Different? / 301
In the modern world, most of a person’s material possessions are items
that no individual could possibly make by herself. Instead they were pro-
duced with the learned and specialized expertise of others. In Chapter 17,
Robert Boyd and colleagues argue that learning from others (and not
intelligence alone) is the key to human success, the characteristic that
has made us so adaptable. Initially in human history, most adaptations
involved direct climatic protection, food acquisition, and food storage.
Thus, the sharing and acquiring of information from others is a particular
kind of intelligence. Boyd and his coauthors argue that cultural learners
have an advantage because they can grasp the best from the past even if
they innovate personally only occasionally. Tools and customs certainly
make life for humans easier or possible.
The study of cooperation and conflict has come a very long way from
the time, almost 50 years ago, when Hamilton (1964a,b) first pondered
how to explain the evolution of worker behavior in social insects with
a strange genetic system. Such analyses have spread out taxonomically,
extending even to microbes. They have deepened mechanistically as we
probe the molecular and genetic basis of cooperative phenomena. The
findings are also beginning to show practical applications, as in medi -
cine, and they have proven essential for understanding the structure of
life, from cells to multicellular organisms to societies. Not least, study of
the complex mix of cooperation and conflict helps us to understand what
makes the human animal both ordinary and remarkable.
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