TOEFL Experts Reading Practice 37
There is a history of controversy within evolutionary biology over why honesty exists in animal communication. All animals, humans included, engage in communication that involves both a sender and a receiver, and this communication occurs both within and across species. The sender communicates a signal to a receiver, who then acts upon that signal. Male peacocks seek to signal their worthiness to females of the species by growing vibrant tail feathers, and gazelles engage in spectacular leaping displays, called stotting, upon seeing approaching predators in order to indicate their athletic prowess and therefore dissuade the predator from attacking.
In some cases, a signal may be honest, meaning that the sender is conveying accurate information, but signals can also be dishonest when the sender is providing false information to a receiver. All signals, however, share the additional feature of being costly to produce and send. A peacock’s tail feathers have significant weight and take excessive energy to produce. A bird chirping to alert others in the flock of a nearby predator has now exposed its own location to that same predator, potentially making it more vulnerable to attack.
Biologists have found that, in general, animals communicate with honest signals, but why? Deception would seem to provide short-term gains. For example, the male fiddler crab is known for its one large fighting claw, which it uses to compete for a mate with other male crabs. If a fiddler crab loses its claw in the fight, another claw that is lighter in weight and therefore less effective grows in its place. Although the crab can still scare off other mates with its new claw that is similar in size to the original, it is sending the dishonest signal to other males that it is strong and able to fight, although if challenged it would likely lose. Scientists theorize that signals must be honest on average, at least to a certain degree. If not, the intended receiver would eventually evolve to ignore the signal, rendering it useless. In the early 1970s, biologist Amotz Zahavi proposed the handicap principle: honesty is maintained through handicaps, or high-cost signals, which are naturally more believable.
The handicap principle relies on the assumption that prominent signals of fighting ability or selection may be impossible, or impossibly costly, to fake. For example, a full-grown bull elk’s rack of antlers may weigh in excess of 40 pounds, a weight greater than a young, weak, or sickly individual could hope to carry. Therefore, an elk able to grow a large rack of antlers is honestly signaling its ability to defend itself in a fight. Male peacock tail feathers present the same honest signal to females about the male’s strength and desirability as a mate. The long tail not only takes significant effort to produce, but also creates issues for survival. The bright colors are more attractive to predators, and the length of the tail somewhat restricts flight and therefore the bird’s ability to escape pursuit. As with the elk, a weaker or sicklier bird could not afford to produce such ornamentation. In both examples, the signal of strength is, in actuality, a handicap to the animal sending it.
Thus, these revealing handicaps are honest signals of strength in the sense that some members of the species are better equipped to handle the costs of these handicaps. While most biologists agree on the power of handicaps to maintain honest signaling, the question still debated is that of choice. Are handicaps the result of a genetic condition that allows only certain members of the species to express the handicap fully? Or do they happen when a more capable individual actively chooses to take on a visible hardship and therefore signal to others its underlying strength or abilities?
The condition-dependent model suggests that the level of display of a behavior or trait is directly proportional to genetic quality and environmental conditions and therefore cannot be faked. Some point to bright, iridescent plumage of some bird species as a condition-dependent, and therefore honest, handicap. Without limited physical wear, low parasite load, and a nutritious diet, these shiny feathers are impossible to maintain. The choice model, alternatively, was advocated in 1990 by biologist Alan Grafen, who claimed that all animals have the option to display a large handicap, but each must choose whether and to what extent to display that handicap, according to its knowledge of its own ability level. The optional signal remains honest because low-quality individuals will never signal at a level that is higher than would be advantageous for them, because of the increased cost of those signals.
There is a history of controversy within evolutionary biology over why honesty exists in animal communication. All animals, humans included, engage in communication that involves both a sender and a receiver, and this communication occurs both within and across species. The sender communicates a signal to a receiver, who then acts upon that signal. Male peacocks seek to signal their worthiness to females of the species by growing vibrant tail feathers, and gazelles engage in spectacular leaping displays, called stotting, upon seeing approaching predators in order to indicate their athletic prowess and therefore dissuade the predator from attacking.
In some cases, a signal may be honest, meaning that the sender is conveying accurate information, but signals can also be dishonest when the sender is providing false information to a receiver. All signals, however, share the additional feature of being costly to produce and send. A peacock’s tail feathers have significant weight and take excessive energy to produce. A bird chirping to alert others in the flock of a nearby predator has now exposed its own location to that same predator, potentially making it more vulnerable to attack.
Biologists have found that, in general, animals communicate with honest signals, but why? Deception would seem to provide short-term gains. For example, the male fiddler crab is known for its one large fighting claw, which it uses to compete for a mate with other male crabs. If a fiddler crab loses its claw in the fight, another claw that is lighter in weight and therefore less effective grows in its place. Although the crab can still scare off other mates with its new claw that is similar in size to the original, it is sending the dishonest signal to other males that it is strong and able to fight, although if challenged it would likely lose. Scientists theorize that signals must be honest on average, at least to a certain degree. If not, the intended receiver would eventually evolve to ignore the signal, rendering it useless. In the early 1970s, biologist Amotz Zahavi proposed the handicap principle: honesty is maintained through handicaps, or high-cost signals, which are naturally more believable.
The handicap principle relies on the assumption that prominent signals of fighting ability or selection may be impossible, or impossibly costly, to fake. For example, a full-grown bull elk’s rack of antlers may weigh in excess of 40 pounds, a weight greater than a young, weak, or sickly individual could hope to carry. Therefore, an elk able to grow a large rack of antlers is honestly signaling its ability to defend itself in a fight. Male peacock tail feathers present the same honest signal to females about the male’s strength and desirability as a mate. The long tail not only takes significant effort to produce, but also creates issues for survival. The bright colors are more attractive to predators, and the length of the tail somewhat restricts flight and therefore the bird’s ability to escape pursuit. As with the elk, a weaker or sicklier bird could not afford to produce such ornamentation. In both examples, the signal of strength is, in actuality, a handicap to the animal sending it.
Thus, these revealing handicaps are honest signals of strength in the sense that some members of the species are better equipped to handle the costs of these handicaps. While most biologists agree on the power of handicaps to maintain honest signaling, the question still debated is that of choice. Are handicaps the result of a genetic condition that allows only certain members of the species to express the handicap fully? Or do they happen when a more capable individual actively chooses to take on a visible hardship and therefore signal to others its underlying strength or abilities?
The condition-dependent model suggests that the level of display of a behavior or trait is directly proportional to genetic quality and environmental conditions and therefore cannot be faked. Some point to bright, iridescent plumage of some bird species as a condition-dependent, and therefore honest, handicap. Without limited physical wear, low parasite load, and a nutritious diet, these shiny feathers are impossible to maintain. The choice model, alternatively, was advocated in 1990 by biologist Alan Grafen, who claimed that all animals have the option to display a large handicap, but each must choose whether and to what extent to display that handicap, according to its knowledge of its own ability level. The optional signal remains honest because low-quality individuals will never signal at a level that is higher than would be advantageous for them, because of the increased cost of those signals.
P4 The handicap principle relies on the assumption that prominent signals of fighting ability or selection may be impossible, or impossibly costly, to fake…
P6 The condition-dependent model suggests that the level of display of a behavior or trait is directly proportional to genetic quality and environmental conditions and therefore cannot be faked…
- Why animal signaling is typically honest is a question that many evolutionary biologists have tried to understand.