Encyclopedia of Evolution.pdf - Online Reading Center

under natural conditions. A learned response may not be any
more conscious or reasoned than are the instinctive responses
within the animal’s behavioral repertoire. Many insects are
capable of learned behavior. For example, other experiments
with digger wasps have demonstrated that they memorize the
landmarks surrounding the entrance of their burrows.
In some cases, animals acquire information through
learning very rapidly soon after they are born and do not
change their minds when they are older. This behavior is
called imprinting. The most famous example of imprinting
occurred when behavioral scientist Konrad Lorenz studied
birds that had just hatched. The hatchling imprints upon the
first animal that it sees as its mother. The hatchlings, when
old enough to leave the nest, followed Lorenz wherever he
went.
Animals with brains that are large relative to their body
size have a greater ability to learn (see allometry). Mammals
have brains larger than other vertebrates of their size,
primates have brains larger than other mammals of their size,
and humans have brains larger than other primates of their
size. Evolutionary scientists are uncertain regarding at what
point in the history of the human species the brain became
large enough to allow reasoning ability and consciousness to
emerge (see intelligence, evolution of). Learning requires
neither consciousness nor intelligence, but intelligence greatly
enhances learning ability, because the animal can think about
behavior, evolution of
environmental stimuli, is not limited to fixed action patterns,
and need not learn every behavioral response separately.
Ultimate Causes of Behavior
The behavioral characteristics of animals, just like all other
characteristics, are the product of natural selection. It should
therefore be possible to investigate the intermediate steps in
the evolution of these behaviors, and the fitness advantage
that individuals within populations gain from various kinds
of behavior: from fixed action patterns, from the ability to
learn, and from the ability to reason.
1. Intermediate steps in the evolution of behavior. Intermediate
stages by which complex behavior has evolved have,
in numerous instances, been demonstrated. Consider the
example of bee foraging behavior, described above.
The most primitive form of bee foraging behavior, in
which a scout can direct other foragers to the food source,
would be for the other foragers to follow the scout as it
returns to the new food source for another load of nectar. In
fact, this behavior frequently occurs in honeybee colonies.
The next intermediate step in the evolution of the bee
dance would be for the scout to perform a dance in which the
straight run pointed directly at the food source. The honeybee
Apis mellifera is a temperate zone insect that nests in hollow
trees and in caves and builds vertical combs. One of its
closest relatives is the tropical dwarf bee Apis florea that can
This blue-footed booby in the Galápagos Islands has created a nesting area by depositing a ring of guano. The nesting behavior is a fixed action pattern,
not reasoning: The mother bird considers any nestling inside the ring to be her own, and any nestling outside the ring to not be her own. (Photograph by
Stanley A. Rice)