Stimulating a
sensory system is only the first step in influencing a mate choice
decision. Grabbing a potential mate's attention is a long way from
winning his or her heart. Granted, for animals that live widely
separated from one another, it may take a lot of effort to find
anyone of the opposite sex during the mating season. Under these
conditions, making a strong sensory impression would give an
animal a reproductive advantage. A whale song audible from
hundreds of miles away can help two lonely whales to find each
other. For many species, locating a mate—any mate—is a big
problem. The sensitivity of their senses may be crucial to finding
a mate, so may have a significant impact on sexual selection.
For highly social animals like most primates, finding potential
mates is not the problem. Many primates already live in large
groups, and interact regularly with other groups. They are spoiled
for choice. When mate choice depends more on comparing mates
than locating mates, the sensory engineering argument seems
weaker. Why should an individual be perceived as a more attractive
sexual partner just because its ornamentation happens to
excite some brain cells in the lowest level of one's sensory systems?
If it were that easy to make animals come running, predators
would more often evolve lures to dupe prey into approaching
them.
Our intuition may tell us that strong sensory effects are sexually
attractive, but I doubt this attractiveness is explained entirely by
sensory bias arguments. There are good adaptive reasons why ornaments that produce strong sensory effects make good fitness
indicators. Consider the list of sensory bias effects that Michael
Ryan and A. Keddy-Hector compiled in an important review
paper of 1992. They noted that animals usually respond more
strongly to visual ornaments that are large, brightly colored, and
symmetrical, and to auditory ornaments (e.g. songs) that are loud,
low in pitch, frequently repeated, and sampled from a large
repertoire. These responses could be attributed to sensory
engineering effects. But that begs the question of whether the
sensory engineering evolved to help animals choose good sexual
partners. Large, healthy, well-fed, intelligent animals can produce
larger, brighter, and more symmetric visual ornaments, and
louder, deeper, more frequent, and more varied songs. As far as I
know, there is no example of a sensory bias that leads animals to
favor sexual partners that are smaller, less healthy, less energetic,
and less intelligent than average. Most sensory biases are consistent
with what we would expect from adaptive decision-making
machinery that evolved for mate choice. It may not have evolved
specifically for mate choice, but it might as well have.
Many sexual ornaments may look as if they are merely playing
on the senses. They may appear to be nothing but fireworks, sweet
talk, eye candy, special effects, and manipulative advertising. But
maybe we should give the viewers more credit. What look like
sensory biases to outsiders may have a hidden adaptive logic for
the animal with the senses
sensory system is only the first step in influencing a mate choice
decision. Grabbing a potential mate's attention is a long way from
winning his or her heart. Granted, for animals that live widely
separated from one another, it may take a lot of effort to find
anyone of the opposite sex during the mating season. Under these
conditions, making a strong sensory impression would give an
animal a reproductive advantage. A whale song audible from
hundreds of miles away can help two lonely whales to find each
other. For many species, locating a mate—any mate—is a big
problem. The sensitivity of their senses may be crucial to finding
a mate, so may have a significant impact on sexual selection.
For highly social animals like most primates, finding potential
mates is not the problem. Many primates already live in large
groups, and interact regularly with other groups. They are spoiled
for choice. When mate choice depends more on comparing mates
than locating mates, the sensory engineering argument seems
weaker. Why should an individual be perceived as a more attractive
sexual partner just because its ornamentation happens to
excite some brain cells in the lowest level of one's sensory systems?
If it were that easy to make animals come running, predators
would more often evolve lures to dupe prey into approaching
them.
Our intuition may tell us that strong sensory effects are sexually
attractive, but I doubt this attractiveness is explained entirely by
sensory bias arguments. There are good adaptive reasons why ornaments that produce strong sensory effects make good fitness
indicators. Consider the list of sensory bias effects that Michael
Ryan and A. Keddy-Hector compiled in an important review
paper of 1992. They noted that animals usually respond more
strongly to visual ornaments that are large, brightly colored, and
symmetrical, and to auditory ornaments (e.g. songs) that are loud,
low in pitch, frequently repeated, and sampled from a large
repertoire. These responses could be attributed to sensory
engineering effects. But that begs the question of whether the
sensory engineering evolved to help animals choose good sexual
partners. Large, healthy, well-fed, intelligent animals can produce
larger, brighter, and more symmetric visual ornaments, and
louder, deeper, more frequent, and more varied songs. As far as I
know, there is no example of a sensory bias that leads animals to
favor sexual partners that are smaller, less healthy, less energetic,
and less intelligent than average. Most sensory biases are consistent
with what we would expect from adaptive decision-making
machinery that evolved for mate choice. It may not have evolved
specifically for mate choice, but it might as well have.
Many sexual ornaments may look as if they are merely playing
on the senses. They may appear to be nothing but fireworks, sweet
talk, eye candy, special effects, and manipulative advertising. But
maybe we should give the viewers more credit. What look like
sensory biases to outsiders may have a hidden adaptive logic for
the animal with the senses
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