Ever since Darwin, animal behaviour has intrigued
and perplexed human observers. The elaborate mating
rituals, lavish decorative displays, complex songs,
calls, dances and many other forms of animal signalling
raise fascinating questions. To what degree can animals
communicate within their own species and even between
species? What evolutionary purpose do such
communications serve? Perhaps most importantly, what can
animal signalling tell us about our own non-verbal forms
of communication? In The Handicap Principle, Amotz and
Ashivag Zahavi offer a unifying theory that brilliantly
explains many previously baffling aspects of animal
signalling and holds up a mirror in which ordinary human
behaviours take on surprising new significance. The
wide-ranging implications of the Zahavis' new theory
make it arguably the most important advance in animal
behaviour in decades. Based on 20 years of painstaking
observation, the Handicap Principle illuminates an
astonishing variety of signalling behaviours in animals
ranging from ants and ameba to peacocks amd gazelles.
Essentially, the theory asserts that for animal signals
to be effective they must be reliable, and to be
reliable they must impose a cost, or handicap, on the
signaller. When a gazelle sights a wolf, for instance,
and jumps high into the air several times before
fleeing, it is signalling, in a reliable way, that it is
in tip-top condition, easily able to outrun the wolf. (A
human parallel occurs in children's games of tag, where
faster children will often taunt their pursuer before
running). By momentarily handicapping itself-expending
precious time and energy in this display-the gazelle
underscores the truthfulness of its signal. Such
signalling, the authors suggest, serves the interests of
both predator and prey, sparing each the exhaustion of a
pointless chase. Similarly, the enormous cost a peacock
incurs by carrying its elaborate and weighty
tail-feathers, which interfere with food gathering,
reliably communicates its value as a mate able to
provide for its offspring. Perhaps the book's most
important application of the Handicap Principle is to
the evolutionary enigma of animal altruism. The authors
convincingly demonstrate that when an animal acts
altruistically, it handicaps itself-assumes a risk or
endures a sacrifice-not primarily to benefit its kin or
social group but to increase its own prestige within the
group and thus signal its status as a partner or rival.
Finally, the Zahavis' show how many forms of non-verbal
communication among humans can also be explained by the
Handicap Principle. Indeed, the authors suggest that
non-verbal signals-tones of voice, facial expressions,
body postures-are quite often more reliable indicators
of our intentions than is language. Elegantly written,
exhaustively researched, and consistently enlivened by
equal measures of insight and example, The Handicap
Principle illuminates virtually every kind of animal
communication. It not only allows us to hear what
animals are saying to each other-and to understand why
they are saying it-but also to see the enormously
important role non-verbal behaviour plays in human
communication.
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