Planned obsolescence

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Planned_obsolescence 

Planned obsolescence (also called built-in obsolescence or premature obsolescence) in industrial design and economics is a policy of planning or designing a product with an artificially limited useful life, so that it becomes obsolete (i.e., unfashionable, or no longer functional) after a certain period of time. The rationale behind this strategy is to generate long-term sales volume by reducing the time between repeat purchases (referred to as "shortening the replacement cycle"). It is the deliberate shortening of a lifespan of a product to force consumers to purchase replacements.

Producers that pursue this strategy believe that the additional sales revenue it creates more than offsets the additional costs of research and development, and offsets the opportunity costs of repurposing an existing product line. In a competitive industry, this is a risky policy, because consumers may decide to buy from competitors instead if they notice the strategy.

Planned obsolescence tends to work best when a producer has at least an oligopoly. Before introducing a planned obsolescence, the producer has to know that the consumer is at least somewhat likely to buy a replacement from them. In these cases of planned obsolescence, there is an information asymmetry between the producer, who knows how long the product was designed to last, and the consumer, who does not. When a market becomes more competitive, product lifespans tend to increase. For example, when Japanese vehicles with longer lifespans entered the American market in the 1960s and 1970s, American carmakers were forced to respond by building more durable products.

History and origins of the phrase

The 1923 Chevrolet is cited as one of the earliest examples of annual facelifts in the car industry, because it had a restyled body covering what essentially was nine-year-old technology.

 

In the United States, automotive design reached a turning point in 1924 when the American national automobile market began reaching saturation. To maintain unit sales, General Motors head Alfred P. Sloan Jr. suggested annual model-year design changes to convince car owners that they needed to buy a new replacement each year, an idea borrowed from the bicycle industry, though the concept is often misattributed to Sloan. Critics called his strategy "planned obsolescence". Sloan preferred the term "dynamic obsolescence".

This strategy had far-reaching effects on the auto business, the field of product design, and eventually the American economy. The smaller players could not maintain the pace and expense of yearly re-styling. Henry Ford did not like the constant stream of model-year changes because he clung to an engineer's notions of simplicity, economies of scale, and design integrity. GM surpassed Ford's sales in 1931 and became the dominant company in the industry thereafter. The frequent design changes also made it necessary to use a body-on-frame rather than the lighter, but less easy to modify, unibody design used by most European automakers. 

Ending the Depression Through Planned Obsolescence, by Bernard London, 1932

The origins of phrase planned obsolescence go back at least as far as 1932 with Bernard London's pamphlet Ending the Depression Through Planned Obsolescence. The essence of London's plan would have the government impose a legal obsolescence on consumer articles, to stimulate and perpetuate consumption. However, the phrase was first popularized in 1954 by Brooks Stevens, an American industrial designer. Stevens was due to give a talk at an advertising conference in Minneapolis in 1954. Without giving it much thought, he used the term as the title of his talk. From that point on, "planned obsolescence" became Stevens' catchphrase. By his definition, planned obsolescence was "Instilling in the buyer the desire to own something a little newer, a little better, a little sooner than is necessary."

The phrase was quickly taken up by others, but Stevens' definition was challenged. By the late 1950s, planned obsolescence had become a commonly used term for products designed to break easily or to quickly go out of style. In fact, the concept was so widely recognized that in 1959 Volkswagen mocked it in an advertising campaign. While acknowledging the widespread use of planned obsolescence among automobile manufacturers, Volkswagen pitched itself as an alternative. "We do not believe in planned obsolescence", the ads suggested. "We don't change a car for the sake of change." In the famous Volkswagen advertising campaign by Doyle Dane Bernbach, one advert showed an almost blank page with the strapline "No point in showing the 1962 Volkswagen, it still looks the same".

In 1960, cultural critic Vance Packard published The Waste Makers, promoted as an exposé of "the systematic attempt of business to make us wasteful, debt-ridden, permanently discontented individuals". Packard divided planned obsolescence into two sub categories:

• obsolescence of desirability; and
• obsolescence of function.

"Obsolescence of desirability", a.k.a. "psychological obsolescence", referred to marketers' attempts to wear out a product in the owner's mind. Packard quoted industrial designer George Nelson, who wrote: "Design... is an attempt to make a contribution through change. When no contribution is made or can be made, the only process available for giving the illusion of change is 'styling!'"

Types

Contrived durability

Contrived durability is a strategy of shortening the product lifetime before it is released onto the market, by designing it to deteriorate quickly. The design of all consumer products includes an expected average lifetime permeating all stages of development. Thus, it must be decided early in the design of a complex product how long it is designed to last so that each component can be made to those specifications. Since all matter is subject to entropy, it is impossible for any designed object to retain its full function forever; all products will ultimately break down, no matter what steps are taken. Limited lifespan is only a sign of planned obsolescence if the lifespan of the product is made artificially short by design.

The strategy of contrived durability is generally not prohibited by law, and manufacturers are free to set the durability level of their products. While often considered planned obsolescence, it is often argued as it's own field of anti-consumer practices. 

A possible method of limiting a product's durability is to use inferior materials in critical areas, or suboptimal component layouts which cause excessive wear. Using soft metal in screws and cheap plastic instead of metal in stress-bearing components will increase the speed at which a product will become inoperable through normal usage and make it prone to breakage from even minor forms of abnormal usage. For example, small, brittle plastic gears in toys are extremely prone to damage if the toy is played with roughly, which can easily destroy key functions of the toy and force the purchase of a replacement. The short life expectancy of smartphones and other handheld electronics is a result of constant usage, fragile batteries, and the ability to easily damage them.

Prevention of repairs

Pentalobe screws used in an iPhone 6S. Critics have argued that Apple's use of pentalobe screws in their newer devices is an attempt to prevent the consumer from repairing the device themselves.

The ultimate examples of such design are single-use versions of traditionally durable goods, such as disposable cameras, where the customer must purchase an entire new product after using them a single time. Such products are often designed to be impossible to service; for example, a cheap "throwaway" digital watch may have a casing which is simply sealed in the factory, with no designed ability for the user to access the interior without destroying the watch entirely. Manufacturers may make replacement parts either unavailable or so expensive that it makes the product uneconomic to repair. For example, inkjet printers made by Canon incorporate a print head which eventually fails. However, the high cost of a replacement forces the owner to scrap the entire device.

Planned obsolescence: a plastic latch (indicated by the head of a match) designed to break after a certain number of deformations, making it difficult to use Bosch blenders

 

Other products may also contain design features meant to frustrate repairs, such as Apple's "tamper-resistant" pentalobe screws that cannot easily be removed with common consumer tools. Front loading washing machines often have the drum bearing - a critical and wear-prone mechanical component - permanently molded into the wash tub, or even have a sealed outer tub, making it impossible to renew the bearings without replacing the entire tub. The cost of this repair may exceed the residual value of the appliance, forcing it to be scrapped.

Bosch, despite the up to 10-year availability of spare parts declared on websites, assembles in the popular MaxoMixx mixers easily breaking plastic latch, refusing users to sell the latch later and proposing to replace the entire drive consistent of many elements as a single spare part, which is almost equivalent to buying a new device.

According to Kyle Wiens, co-founder of an online repair community, a possible goal for such design is to make the cost of repairs comparable to the replacement cost, or to prevent any form of servicing of the product at all. In 2012, Toshiba was criticized for issuing cease-and-desist letters to the owner of a website that hosted its copyrighted repair manuals, to the detriment of the independent and home repair market.

Non-user-replaceable batteries

Some products, such as mobile phones, laptops, and electric toothbrushes, contain batteries that are not replaceable by the end-user after they have worn down, therefore leaving an aging battery trapped inside the device. While such a design can help make the device thinner, it can also make it difficult to replace the battery without sending the entire device away for repairs or purchasing an entirely new device. On a device with a non-openable back cover (non-user-replaceable battery), a manual (forced) battery replacement might induce permanent damage, including loss of water-resistance due to damages on the water-protecting seal, as well as risking serious, even irreparable damage to the phone's main board as a result of having to pry the battery free from strong adhesive in proximity to delicate components. The manufacturer or a repair service might be able to replace the battery. In the latter case, this could void the warranty on the device.

The practice in phone design started with Apple's iPhones and has now spread out to most other mobile phones, notably Samsung Mobile starting in 2015 with the Galaxy S6. Earlier mobile phones (including water-resistant ones such as the Samsung Galaxy S5 and the Sony Xperia V) had back covers that could be opened by the user in order to replace the battery.

Perceived obsolescence

Obsolescence of desirability or stylistic obsolescence occurs when designers change the styling of products so customers will purchase products more frequently due to the decrease in the perceived desirability of unfashionable items.

Many products are primarily desirable for aesthetic rather than functional reasons. An obvious example of such a product is clothing. Such products experience a cycle of desirability referred to as a "fashion cycle". By continually introducing new aesthetics, and retargeting or discontinuing older designs, a manufacturer can "ride the fashion cycle", allowing for constant sales despite the original products remaining fully functional. Sneakers are a popular fashion industry where this is prevalent - Nike's Air Max line of running shoes is a prime example where a single model of shoe is often produced for years, but the color and material combination ("colorway") is changed every few months, or different colorways are offered in different markets. This has the upshot of ensuring constant demand for the product, even though it remains fundamentally the same. 

To a more limited extent this is also true of some consumer electronic products, where manufacturers will release slightly updated products at regular intervals and emphasize their value as status symbols. The most notable example among technology products are Apple products. New colorways introduced with iterative “S” generation iPhones (e.g. the iPhone 6S’ “Rose Gold”) entice consumers into upgrading and distinguishes an otherwise identical-looking iPhone from the previous year's model.

Some smartphone manufacturers release a marginally updated model every 5 or 6 months compared to the typical yearly cycle, leading to the perception that a one-year-old handset can be up to two generations old. A notable example is OnePlus, known for releasing T-series devices with upgraded specifications roughly 6 months after a major release device. Sony Mobile utilised a similar tactic with its Z-series smartphones.

Systemic obsolescence

Planned systemic obsolescence is the deliberate attempt to make a product obsolete by altering the system in which it is used in such a way as to make its continued use difficult. Common examples of planned systemic obsolescence include not accommodating forward compatibility in software, or routinely changing screws or fasteners so that they cannot easily be operated on with existing tools. This may either be designed to intentionally cause obsolescence, or by interface standards being superseded by better standards that were not available when the product was designed, such as serial ports, parallel ports, and PS/2 ports largely being supplanted or replaced by USB on newer PC motherboards in the 2000s.

Programmed obsolescence

In some cases, notification may be combined with the deliberate disabling of a product to prevent it from working, thus requiring the buyer to purchase a replacement. For example, inkjet printer manufacturers employ smart chips in their ink cartridges to prevent them from being used after a certain threshold (number of pages, time, etc.), even though the cartridge may still contain usable ink or could be refilled (with ink toners, up to 50 percent of the toner cartridge is often still full). This constitutes "programmed obsolescence", in that there is no random component contributing to the decline in function. 

In the Jackie Blennis v. HP class action suit, it was claimed that Hewlett Packard designed certain inkjet printers and cartridges to shut down on an undisclosed expiration date, and at this point consumers were prevented from using the ink that remained in the expired cartridge. HP denied these claims, but agreed to discontinue the use of certain messages, and to make certain changes to the disclosures on its website and packaging, as well as compensating affected consumers with a total credit of up to $5,000,000 for future purchases from HP.

Samsung produces laser printers that are designed to stop working with a message about imaging drum replacing. There are some workarounds for users, for instance, that will more than double the life of the printer that has stopped with a message to replace the imaging drum.

Software lock-out

Another example of programmed obsolescence is making older versions of software (e.g. YouTube's Android application) unserviceable deliberately, even though they would technically be able to keep working as intended. 

This could be a problem, because some devices, despite being equipped with appropriate hardware, might not be able to support the newest update without modifications such as custom firmwares. 

Additionally, updates to newer versions might have introduced undesirable side effects, such as removed features or non-optional changes which might be unsolicited and undesired by specific users.

Software companies sometimes deliberately drop support for older technologies as a calculated attempt to force users to purchase new products to replace those made obsolete. Most proprietary software will ultimately reach an end-of-life point—usually because the cost of support exceeds the revenue generated by supporting the old version—at which the supplier will cease updates and support. As free software and open source software can always be updated and maintained by somebody else, the user is not at the sole mercy of a proprietary vendor. Software that is abandoned by the manufacturer with regard to manufacturer support is sometimes called abandonware.

Legal obsolescence

Governments wanting to increase electric vehicle ownership through purchase subsidies mechanisms could increase the replacement rate of cars. Several cities such as London, Berlin, Paris, Antwerp and Brussels have introduced low-emission zones (LEZ) banning older diesel cars. LEZs force people owning cars affected by these legislations to replace them.

Advantages and disadvantages

Estimates of planned obsolescence can influence a company's decisions about product engineering. Therefore, the company can use the least expensive components that satisfy product lifetime projections.

Also, for industries, planned obsolescence stimulates demand by encouraging purchasers/putting them under pressure to buy sooner if they still want a functioning product. These products can be bought from the same manufacturer (a replacement part or a newer model), or from a competitor who might also rely on planned obsolescence. Especially in developed countries (where many industries already face a saturated market), this technique is often necessary for producers to maintain their level of revenue.

While planned obsolescence is appealing to producers, it can also do significant harm to the society in the form of negative externalities. Continuously replacing products, rather than repairing them, creates more waste and pollution, uses more natural resources, and results in more consumer spending. Planned obsolescence can thus have a negative impact on the environment in aggregate. Even when planned obsolescence might help to save scarce resources per unit produced, it tends to increase output in aggregate, since due to laws of supply and demand, decreases in cost and price will eventually result in increases in demand and consumption. However, the negative environmental impacts of planned obsolescence are dependent also on the process of production, as well as technical details pertaining to product disposal. Products that are difficult to disassemble can be very difficult to recycle properly.

There is also the potential backlash of consumers who learn that the manufacturer invested money to make the product obsolete faster; such consumers might turn to a producer (if any exists) that offers a more durable alternative.

Regulation

In 2015, as part of a larger movement against planned obsolescence across the European Union, France has passed legislation requiring that appliance manufacturers and vendors declare the intended product lifespans, and to inform consumers how long spare parts for a given product will be produced. From 2016, appliance manufacturers are required to repair or replace, free of charge, any defective product within two years from its original purchase date. This effectively creates a mandatory two-year warranty.

Critics and supporters

Shortening the replacement cycle has critics and supporters. Philip Kotler argues that: "Much so-called planned obsolescence is the working of the competitive and technological forces in a free society—forces that lead to ever-improving goods and services."

Critics such as Vance Packard claim the process is wasteful and exploits customers. With psychological obsolescence, resources are used up making changes, often cosmetic changes, that are not of great value to the customer. Miles Park advocates new and collaborative approaches between the designer and the consumer to challenge obsolescence in fast-moving sectors such as consumer electronics. Some people, such as Ronny Balcaen, have proposed to create a new label to counter the diminishing quality of products due to the planned obsolescence technique.

In academia

Russell Jacoby, writing in the 1970s, observes that intellectual production has succumbed to the same pattern of planned obsolescence used by manufacturing enterprises to generate ever-renewed demand for their products.

The application of planned obsolescence to thought itself has the same merit as its application to consumer goods; the new is not only shoddier than the old, it fuels an obsolete social system that staves off its replacement by manufacturing the illusion that it is perpetually new.

Camille Paglia characterizes contemporary academic discourse influenced by French theorists such as Lacan, Derrida, and Foucault as the academic equivalent of name brand consumerism. "Lacan, Derrida, and Foucault," she says, "are the academic equivalents of BMW, Rolex, and Cuisinart." Under the inspiration of the latest academic fashions, academic planned obsolescence is to manufacture content with little merit for the same reason fashion designers come out with new fashions.

Laws

In 2015 the French National Assembly established a fine of up to 300,000 euros and jail terms of up to two years for manufacturers planning the failure of their products in advance. The rule is not only relevant because of the sanctions that it establishes but also because it is the first time that a legislature recognized the existence of planned obsolescence. These techniques may include "a deliberate introduction of a flaw, a weakness, a scheduled stop, a technical limitation, incompatibility or other obstacles for repair".

The European Union is also addressing the practice. The European Economic and Social Committee (EESC), an advisory body of the EU, announced in 2013 that it was studying "a total ban on planned obsolescence". It said replacing products that are designed to stop working within two or three years of their purchase was a waste of energy and resources and generated pollution. The EESC organised a round table in Madrid in 2014 on 'Best practices in the domain of built-in obsolescence and collaborative consumption' which called for sustainable consumption to be a consumer right in EU legislation. Carlos Trias Pinto, president of the EESC's Consultative Commission on Industrial Change supports "the introduction of a labeling system which indicates the durability of a device, so the consumer can choose whether he/she prefers to buy a cheap product or a more expensive, more durable product".

Ambush predator

From Wikipedia, the free encyclopedia

 

A female goldenrod crab spider (Misumena vatia) ambushing the female of a pair of mating flies

Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey by stealth or by strategy (typically not conscious), rather than by speed or by strength. Ambush predators sit and wait for prey, often from a concealed position, and then launch a rapid surprise attack. 

The ambush may be set by hiding in a burrow, by camouflage, by aggressive mimicry, or by the use of a trap. The predator then uses a combination of senses to assess the prey and to time the strike. Nocturnal ambush predators such as cats and snakes have vertical slit pupils, helping them to judge the distance to prey in dim light. Different ambush predators use a variety of means to capture their prey, from the long sticky tongues of chameleons to the expanding mouths of frogfishes. 

Ambush predation is widely distributed in the animal kingdom, spanning some members of numerous groups such as the starfish, cephalopods, crustaceans, spiders, insects such as mantises, and vertebrates such as many snakes and fishes.

Strategy

Play media

Video of a water bug nymph attacking a fish

Ambush predators usually remain motionless (sometimes hidden) and wait for prey to come within ambush distance before pouncing. Ambush predators are often camouflaged, and may be solitary. Pursuit predation becomes a better strategy than ambush predation when the predator is faster than the prey. Ambush predators use many intermediate strategies. For example, when a pursuit predator is faster than its prey over a short distance, but not in a long chase, then either stalking or ambush becomes necessary as part of the strategy.

Bringing the prey within range

Concealment

Ambush often relies on concealment, whether by staying out of sight or by means of camouflage.

Burrows

Trapdoor spider Misgolas rapax in its burrow

 

The trapdoor spider Sason robustum and its nest

 

Ambush predators such as trapdoor spiders on land and mantis shrimps in the sea rely on concealment, constructing and hiding in burrows. These provide effective concealment at the price of a restricted field of vision.

Trapdoor spiders excavate a burrow and seal the entrance with a web trapdoor hinged on one side with silk. The best-known is the thick, bevelled "cork" type, which neatly fits the burrow's opening. The other is the "wafer" type; it is a basic sheet of silk and earth. The door's upper side is often effectively camouflaged with local materials such as pebbles and sticks. The spider spins silk fishing lines, or trip wires, that radiate out of the burrow entrance. When the spider is using the trap to capture prey, its chelicerae (protruding mouthparts) hold the door shut on the end furthest from the hinge. Prey make the silk vibrate, and alert the spider to open the door and ambush the prey.

Camouflage

Tasselled wobbegong relies on its disruptive camouflage to ambush fish and invertebrates.

 

Striated frogfish uses camouflage and aggressive mimicry in the form of a fishing rod-like esca (lure) on its head to attract prey.

 

Many ambush predators make use of camouflage so that their prey can come within striking range without detecting their presence. Among insects, coloration in ambush bugs closely matches the flower heads where they wait for prey. Among fishes, the warteye stargazer buries itself nearly completely in the sand and waits for prey. The devil scorpionfish typically lies partially buried on the sea floor or on a coral head during the day, covering itself with sand and other debris to further camouflage itself. The tasselled wobbegong is a shark whose adaptations as an ambush predator include a strongly flattened and camouflaged body with a fringe that breaks up its outline.

Aggressive mimicry

Claimed mimic: zone-tailed hawk

 

Prey and possible model: Turkey vulture

 

The orchid mantis, Hymenopus coronatus, mimics a rainforest orchid of southeast Asia to lure its prey, pollinator insects.

Many ambush predators actively attract their prey towards them before ambushing them. This strategy is called aggressive mimicry, using the false promise of nourishment to lure prey. The alligator snapping turtle is a well-camouflaged ambush predator. Its tongue bears a conspicuous pink extension that resembles a worm and can be wriggled around; fish that try to eat the "worm" are themselves eaten by the turtle. Similarly, some reptiles such as Elaphe rat snakes employ caudal luring (tail luring) to entice small vertebrates into striking range.

The zone-tailed hawk, which resembles the turkey vulture, flies among flocks of turkey vultures, then suddenly breaks from the formation and ambushes one of them as its prey. There is however some controversy about whether this is a true case of wolf in sheep's clothing mimicry.

Flower mantises are aggressive mimics, resembling flowers convincingly enough to attract prey that come to collect pollen and nectar. The orchid mantis actually attracts its prey, pollinator insects, more effectively than flowers do. Crab spiders, similarly, are coloured like the flowers they habitually rest on, but again, they can lure their prey even away from flowers.

Traps

Antlion larva with grasping mandibles

 

Antlion's sandpit trap

 

Some ambush predators build traps to help capture their prey. Lacewings are a flying insect in the order Neuroptera. In some species, their larval form, known as the antlion, is an ambush predator. Eggs are laid in the earth, often in caves or under a rocky ledge. The juvenile creates a small, crater shaped trap. The antlion hides under a light cover of sand or earth. When an ant, beetle or other prey slides into the trap, the antlion grabs the prey with its powerful jaws.

Some but not all web-spinning spiders are sit-and-wait ambush predators. The sheetweb spiders (Linyphiidae) tend to stay with their webs for long periods and so resemble sit-and-wait predators, whereas the orb-weaving spiders (such as the Araneidae) tend to move frequently from one patch to another (and thus resemble active foragers).

Detection and assessment

Many nocturnal ambush predators like this leopard cat have vertical pupils, enabling them to judge distance to prey accurately in dim light.

 

Ambush predators must time their strike carefully. They need to detect the prey, assess it as worth attacking, and strike when it is in exactly the right place. They have evolved a variety of adaptations that facilitate this assessment. For example, pit vipers prey on small birds, choosing targets of the right size for their mouth gape: larger snakes choose larger prey. They prefer to strike prey that is both warm and moving; their pit organs between the eye and the nostril contain infrared (heat) receptors, enabling them to find and perhaps judge the size of their small, warm-blooded prey.

The deep-sea tripodfish Bathypterois grallator uses tactile and mechanosensory cues to identify food in its low-light environment. The fish faces into the current, waiting for prey to drift by.

Several species of Felidae (cats) and snakes have vertically elongated (slit) pupils, advantageous for nocturnal ambush predators as it helps them to estimate the distance to prey in dim light; diurnal and pursuit predators in contrast have round pupils.

Capturing the prey

Mantis shrimp captures its prey rapidly with its mantis-like front legs.

 

Frogfish traps its prey by suddenly opening its jaws and sucking the prey in.

 

Ambush predators often have adaptations for seizing their prey rapidly and securely. The capturing movement has to be rapid to trap the prey, given that the attack is not modifiable once launched. Zebra mantis shrimp capture agile prey such as fish primarily at night while hidden in burrows, striking very hard and fast, with a mean peak speed 2.30 m/s (5.1 mph) and mean duration of 24.98 ms.

A chameleon's tongue striking ballistically at food

 

Chameleons (family Chamaeleonidae) are highly adapted as ambush predators. They can change colour to match their surroundings and often climb through trees with a swaying motion, probably to mimic the movement of the leaves and branches they are surrounded by. All chameleons are primarily insectivores and feed by ballistically projecting their tongues, often twice the length of their bodies, to capture prey. The tongue is projected in as little as 0.07 seconds, and is launched at an acceleration of over 41 g. The power with which the tongue is launched, over 3000 W kg⁻¹, is more than muscle can produce, indicating that energy is stored in an elastic tissue for sudden release.

All fishes face a basic problem when trying to swallow prey: opening their mouth may pull food in, but closing it will push the food out again. Frogfishes capture their prey by suddenly opening their jaws, with a mechanism which enlarges the volume of the mouth cavity up to 12-fold and pulls the prey (crustaceans, molluscs and other whole fishes) into the mouth along with water; the jaws close without reducing the volume of the mouth cavity. The attack can be as fast as 6 milliseconds.

Taxonomic range

Ambush predation is widely distributed across the animal kingdom. It is found in many vertebrates including fishes such as the frogfishes (anglerfishes) of the sea bottom, and the pikes of freshwater; reptiles including crocodiles, snapping turtles, the mulga dragon, and many snakes such as the black mamba; mammals such as the cats; and birds such as the anhinga (darter). The strategy is found in several invertebrate phyla including arthropods such as mantises, purseweb spiders, and some crustaceans; cephalopod molluscs such as the colossal squid; and starfish such as Leptasterias tenera.

Gene-centered view of evolution

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Gene-centered_view_of_evolution 

 
The gene-centered view of evolution, gene's eye view, gene selection theory, or selfish gene theory holds that adaptive evolution occurs through the differential survival of competing genes, increasing the allele frequency of those alleles whose phenotypic trait effects successfully promote their own propagation, with gene defined as "not just one single physical bit of DNA [but] all replicas of a particular bit of DNA distributed throughout the world". The proponents of this viewpoint argue that, since heritable information is passed from generation to generation almost exclusively by DNA, natural selection and evolution are best considered from the perspective of genes.

Proponents of the gene-centered viewpoint argue that it permits understanding of diverse phenomena such as altruism and intragenomic conflict that are otherwise difficult to explain from an organism-centered viewpoint.

The gene-centered view of evolution is a synthesis of the theory of evolution by natural selection, the particulate inheritance theory, and the non-transmission of acquired characters. It states that those alleles whose phenotypic effects successfully promote their own propagation will be favorably selected relative to their competitor alleles within the population. This process produces adaptations for the benefit of alleles that promote the reproductive success of the organism, or of other organisms containing the same allele (kin altruism and green-beard effects), or even its own propagation relative to the other genes within the same organism (selfish genes and intragenomic conflict).

The gene-centered perspective can be traced to the philosopher Henri Bergson who wrote:

Life is like a current passing from germ to germ through the medium of a developed organism. It is as if the organism itself were only an excrescence, a bud caused to sprout by the former endeavouring to continue itself in a new germ.

— Creative Evolution (1907)

Overview

John Maynard Smith

 

Richard Dawkins

The gene-centered view of evolution is a model for the evolution of social characteristics such as selfishness and altruism.

Acquired characteristics

The formulation of the central dogma of molecular biology was summarized by Maynard Smith:

If the central dogma is true, and if it is also true that nucleic acids are the only means whereby information is transmitted between generations, this has crucial implications for evolution. It would imply that all evolutionary novelty requires changes in nucleic acids, and that these changes – mutations – are essentially accidental and non-adaptive in nature. Changes elsewhere – in the egg cytoplasm, in materials transmitted through the placenta, in the mother's milk – might alter the development of the child, but, unless the changes were in nucleic acids, they would have no long-term evolutionary effects.

— Maynard Smith

The rejection of the inheritance of acquired characters, combined with Ronald Fisher the statistician, giving the subject a mathematical footing, and showing how Mendelian genetics was compatible with natural selection in his 1930 book The Genetical Theory of Natural Selection. J. B. S. Haldane, and Sewall Wright, paved the way to the formulation of the selfish-gene theory. For cases where environment can influence heredity, see epigenetics.

The gene as the unit of selection

The view of the gene as the unit of selection was developed mainly in the works of Richard Dawkins, W. D. Hamilton, Colin Pittendrigh and George C. Williams. It was mainly popularized and expanded by Dawkins in his book The Selfish Gene (1976).

According to Williams' 1966 book Adaptation and Natural Selection,

[t]he essence of the genetical theory of natural selection is a statistical bias in the relative rates of survival of alternatives (genes, individuals, etc.). The effectiveness of such bias in producing adaptation is contingent on the maintenance of certain quantitative relationships among the operative factors. One necessary condition is that the selected entity must have a high degree of permanence and a low rate of endogenous change, relative to the degree of bias (differences in selection coefficients).

— Williams, 1966, pp. 22–23

Williams argued that "[t]he natural selection of phenotypes cannot in itself produce cumulative change, because phenotypes are extremely temporary manifestations." Each phenotype is the unique product of the interaction between genome and environment. It does not matter how fit and fertile a phenotype is, it will eventually be destroyed and will never be duplicated.

Since 1954, it has been known that DNA is the main physical substrate to genetic information, and it is capable of high-fidelity replication through many generations. So, a particular gene coded in a nucleobase sequence of a lineage of replicated DNA molecules can have a high permanence and a low rate of endogenous change.

In normal sexual reproduction, an entire genome is the unique combination of father's and mother's chromosomes produced at the moment of fertilization. It is generally destroyed with its organism, because "meiosis and recombination destroy genotypes as surely as death." Only half of it is transmitted to each descendant due to independent segregation.

And the high prevalence of horizontal gene transfer in bacteria and archaea means that genomic combinations of these asexually reproducing groups are also transient in evolutionary time: "The traditional view, that prokaryotic evolution can be understood primarily in terms of clonal divergence and periodic selection, must be augmented to embrace gene exchange as a creative force."

The gene as an informational entity persists for an evolutionarily significant span of time through a lineage of many physical copies.

In his book River out of Eden, Dawkins coins the phrase God's utility function to explain his view on genes as units of selection. He uses this phrase as a synonym of the "meaning of life" or the "purpose of life". By rephrasing the word purpose in terms of what economists call a utility function, meaning "that which is maximized", Dawkins attempts to reverse-engineer the purpose in the mind of the Divine Engineer of Nature, or the utility function of god. Finally, Dawkins argues that it is a mistake to assume that an ecosystem or a species as a whole exists for a purpose. He writes that it is incorrect to suppose that individual organisms lead a meaningful life either; in nature, only genes have a utility function – to perpetuate their own existence with indifference to great sufferings inflicted upon the organisms they build, exploit and discard.

Organisms as vehicles

Genes are usually packed together inside a genome, which is itself contained inside an organism. Genes group together into genomes because "genetic replication makes use of energy and substrates that are supplied by the metabolic economy in much greater quantities than would be possible without a genetic division of labour." They build vehicles to promote their mutual interests of jumping into the next generation of vehicles. As Dawkins puts it, organisms are the "survival machines" of genes.

The phenotypic effect of a particular gene is contingent on its environment, including the fellow genes constituting with it the total genome. A gene never has a fixed effect, so how is it possible to speak of a gene for long legs? It is because of the phenotypic differences between alleles. One may say that one allele, all other things being equal or varying within certain limits, causes greater legs than its alternative. This difference enables the scrutiny of natural selection.

"A gene can have multiple phenotypic effects, each of which may be of positive, negative or neutral value. It is the net selective value of a gene's phenotypic effect that determines the fate of the gene." For instance, a gene can cause its bearer to have greater reproductive success at a young age, but also cause a greater likelihood of death at a later age. If the benefit outweighs the harm, averaged out over the individuals and environments in which the gene happens to occur, then phenotypes containing the gene will generally be positively selected and thus the abundance of that gene in the population will increase.

Even so, it becomes necessary to model the genes in combination with their vehicle as well as in combination with the vehicle's environment.

Selfish-gene theory

The selfish-gene theory of natural selection can be restated as follows:

Genes do not present themselves naked to the scrutiny of natural selection, instead they present their phenotypic effects. [...] Differences in genes give rise to differences in these phenotypic effects. Natural selection acts on the phenotypic differences and thereby on genes. Thus genes come to be represented in successive generations in proportion to the selective value of their phenotypic effects.

— Cronin, 1991, p. 60

The result is that "the prevalent genes in a sexual population must be those that, as a mean condition, through a large number of genotypes in a large number of situations, have had the most favourable phenotypic effects for their own replication." In other words, we expect selfish genes ("selfish" meaning that it promotes its own survival without necessarily promoting the survival of the organism, group or even species). This theory implies that adaptations are the phenotypic effects of genes to maximize their representation in future generations. An adaptation is maintained by selection if it promotes genetic survival directly, or else some subordinate goal that ultimately contributes to successful reproduction.

Individual altruism and genetic egoism

The gene is a unit of hereditary information that exists in many physical copies in the world, and which particular physical copy will be replicated and originate new copies does not matter from the gene's point of view. A selfish gene could be favored by selection by producing altruism among organisms containing it. The idea is summarized as follows:

If a gene copy confers a benefit B on another vehicle at cost C to its own vehicle, its costly action is strategically beneficial if pB > C, where p is the probability that a copy of the gene is present in the vehicle that benefits. Actions with substantial costs therefore require significant values of p. Two kinds of factors ensure high values of p: relatedness (kinship) and recognition (green beards).

— Haig, 1997, p. 288

A gene in a somatic cell of an individual may forego replication to promote the transmission of its copies in the germ line cells. It ensures the high value of p = 1 due to their constant contact and their common origin from the zygote.

The kin selection theory predicts that a gene may promote the recognition of kinship by historical continuity: a mammalian mother learns to identify her own offspring in the act of giving birth; a male preferentially directs resources to the offspring of mothers with whom he has copulated; the other chicks in a nest are siblings; and so on. The expected altruism between kin is calibrated by the value of p, also known as the coefficient of relatedness. For instance, an individual has a p = 1/2 in relation to his brother, and p = 1/8 to his cousin, so we would expect, ceteris paribus, greater altruism among brothers than among cousins. In this vein, geneticist J. B. S. Haldane famously joked, "Would I lay down my life to save my brother? No, but I would to save two brothers or eight cousins." However, examining the human propensity for altruism, kin selection theory seems incapable of explaining cross-familiar, cross-racial and even cross-species acts of kindness.

Green-beard effect

Green-beard effects gained their name from a thought-experiment first presented by Bill Hamilton and then popularized and given its current name by Richard Dawkins who considered the possibility of a gene that caused its possessors to develop a green beard and to be nice to other green-bearded individuals. Since then, "green-beard effect" has come to refer to forms of genetic self-recognition in which a gene in one individual might direct benefits to other individuals that possess the gene. Such genes would be especially selfish, benefiting themselves regardless of the fates of their vehicles. Since then, green-beard genes have been discovered in nature, such as Gp-9 in fire ants (Solenopsis invicta), csA in social amoeba (Dictyostelium discoideum), and FLO1 in budding yeast (Saccharomyces cerevisiae).

Intragenomic conflict

As genes are capable of producing individual altruism, they are capable of producing conflict among genes inside the genome of one individual. This phenomenon is called intragenomic conflict and arises when one gene promotes its own replication in detriment to other genes in the genome. The classic example is segregation distorter genes that cheat during meiosis or gametogenesis and end up in more than half of the functional gametes. These genes can persist in a population even when their transmission results in reduced fertility. Egbert Leigh compared the genome to "a parliament of genes: each acts in its own self-interest, but if its acts hurt the others, they will combine together to suppress it" to explain the relative low occurrence of intragenomic conflict.

Price equation

The Price equation is a covariance equation that is a mathematical description of evolution and natural selection. The Price equation was derived by George R. Price, working in London to rederive W. D. Hamilton's work on kin selection.

Advocates

Besides Richard Dawkins and George C. Williams, other biologists and philosophers have expanded and refined the selfish-gene theory, such as John Maynard Smith, George R. Price, Robert Trivers, David Haig, Helena Cronin, David Hull, Philip Kitcher, and Daniel C. Dennett.

Criticisms

The gene-centric view has been opposed by Ernst Mayr, Stephen Jay Gould, David Sloan Wilson, and philosopher Elliott Sober. An alternative, multilevel selection (MLS), has been advocated by E. O. Wilson, David Sloan Wilson, Sober, Richard E. Michod, and Samir Okasha.

Writing in the New York Review of Books, Gould has characterized the gene-centered perspective as confusing book-keeping with causality. Gould views selection as working on many levels, and has called attention to a hierarchical perspective of selection. Gould also called the claims of Selfish Gene "strict adaptationism", "ultra-Darwinism", and "Darwinian fundamentalism", describing them as excessively "reductionist". He saw the theory as leading to a simplistic "algorithmic" theory of evolution, or even to the re-introduction of a teleological principle. Mayr went so far as to say "Dawkins' basic theory of the gene being the object of evolution is totally non-Darwinian."

Gould also addressed the issue of selfish genes in his essay "Caring groups and selfish genes". Gould acknowledged that Dawkins was not imputing conscious action to genes, but simply using a shorthand metaphor commonly found in evolutionary writings. To Gould, the fatal flaw was that "no matter how much power Dawkins wishes to assign to genes, there is one thing that he cannot give them – direct visibility to natural selection." Rather, the unit of selection is the phenotype, not the genotype, because it is phenotypes that interact with the environment at the natural-selection interface. So, in Kim Sterelny's summation of Gould's view, "gene differences do not cause evolutionary changes in populations, they register those changes." Richard Dawkins replied to this criticism in a later book, The Extended Phenotype, that Gould confused particulate genetics with particulate embryology, stating that genes do "blend", as far as their effects on developing phenotypes are concerned, but that they do not blend as they replicate and recombine down the generations.

Since Gould's death in 2002, Niles Eldredge has continued with counter-arguments to gene-centered natural selection. Eldredge notes that in Dawkins' book A Devil's Chaplain, which was published just before Eldredge's book, "Richard Dawkins comments on what he sees as the main difference between his position and that of the late Stephen Jay Gould. He concludes that it is his own vision that genes play a causal role in evolution," while Gould (and Eldredge) "sees genes as passive recorders of what worked better than what".