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Non-Human Examples

Evolutionary mismatch can occur any time an organism is exposed to an environment that does not resemble the typical environment the organism adapted in. Due to human influences, such as global warming and habitat destruction, the environment is changing very rapidly for many organisms, leading to numerous cases of evolutionary mismatch.

Examples with Human Influence

Sea Turtles and Light Pollution

Female sea turtles create nests to lay their eggs by digging a pit on the beach, typically between the high tide line and dune, using their rear flippers. Consequently, within the first seven days of hatching, hatchling sea turtles must make the journey from the nest back into the ocean. This trip occurs predominantly at night in order to avoid predators and overheating.

Hatchling sea turtles must make their way back into the ocean.

In order to orient themselves towards the ocean, the hatchlings depend on their eyes to turn towards the brightest direction. This is because the open horizon of the ocean, illuminated by celestial light, tends to be much brighter in a natural undeveloped beach than the dunes and vegetation. Studies propose two mechanisms of the eye for this phenomenon. Referred to as the “raster system”, the theory is that sea turtles’ eyes contain numerous light sensors which take in the overall brightness information of a general area and make a “measurement” of where the light is most intense. If the light sensors detect the most intense light on a hatchling’s left side, the sea turtle would turn left. A similar proposal called the complex phototropotaxis system  theorizes that the eyes contain light intensity comparators that take in detailed information of the intensity of light from all directions. Sea turtles are able to “know” that they are facing the brightest direction when the light intensity is balanced between both eyes.

This method of finding the ocean is successful in natural beaches, but in developed beaches, the intense artificial lights from buildings, light houses, and even abandoned fires overwhelm the sea turtles and cause them to head towards the artificial light instead of the ocean. Scientists call this misorientation. Sea turtles can also become disoriented and circle around in the same place. Numerous cases show that misoriented hatchling sea turtles either die from dehydration, get consumed by a predator, or even burn to death in an abandoned fire. The direct impact of light pollution on the number of sea turtles has been too difficult to measure. However, this problem is exacerbated because all species of sea turtles are endangered. Other animals, including migratory birds and insects, are also victims to light pollution because they also depend on light intensity at night to properly orient themselves. (See Threats to sea turtles for more information.)

Dodo Bird and Hunting

Dodo birds became completely extinct due to hunting.

The Dodo bird lived on a remote Island, Mauritius, in the absence of predators. Here, the Dodo evolved to lose its instinct for fear and the ability to fly. This allowed them to be easily hunted by Dutch sailors who arrived on the island in the late 16^th century. The Dutch sailors also brought foreign animals to the island such as monkeys and pigs that ate the Dodo bird's eggs, which was detrimental to the population growth of the slow breeding bird. Their fearlessness made them easy targets and their inability to fly gave them no opportunity to evade danger.Thus, they were easily driven to extinction within a century of their discovery.

The Dodo's inability to fly was once beneficial for the bird because it conserved energy. The Dodo conserved more energy relative to birds with the ability to fly, due to the Dodo's smaller pectoral muscles. Smaller muscle sizes are linked to lower rates of maintenance metabolism, which in turn conserves energy for the Dodo. Lacking an instinct for fear was another mechanism through which the Dodo conserved energy because it never had to expend any energy for a stress response. Both mechanisms of conservation of energy was once advantageous because it enabled the Dodo to execute activities with minimal energy expenditure. However, these proved disadvantageous when their island was invaded, rendering them defenseless to the new dangers that humans brought.

Peppered Moths during the English Industrial Revolution

Before the English Industrial Revolution of the late 18th and early 19th centuries the most common phenotypic color of the peppered moth was white with black speckles. However, that changed when the Industrial Revolution produced high levels of pollution. Due to the Industrial Revolution the trees blackened in urban regions, causing the original phenotype to stand out significantly more to predators. Natural selection then began favoring the rare dark peppered carbonaria moth in order for the species to camouflage and prevent attacks. The dark moth’s population expanded rapidly and by the 1950s vast amounts of England saw carbonaria frequencies rise above 90%. The once favorable white speckled phenotype quickly became mismatched in the new environment and since evolution did not have enough time to take its course, the white speckled coloring became disadvantageous.

However, in the late 1900s, the English made efforts to reduce air pollution, causing the trees to turn back to their normal shade. The change in color lead the dark skin phenotype to revert from beneficial to disadvantageous. Once again, the moth was not able to adapt fast enough to the changing environment and thus the carbonaria phenotype became mismatched. Since The trees’ return to their natural color caused the original phenotype to become advantageous again since it allowed the peppered moth to hide from predators.

Giant Jewel Beetle and Beer Bottles

The Jewel Beetle has a shiny, brown exterior similar to that of a beer bottle

Evolutionary mismatch can also be seen among insects. One such example is in the case of the the Giant Jewel Beetle (Julodimorpha bakewelli). The male jewel beetle has evolved to be attracted to certain features of the female jewel beetle that allow the male jewel beetle to identify a female as it flies across the desert. These features include size, color, and texture. However, these physical traits are seen manifested in beer bottles as well. As a result, male jewel beetles often consider beer bottles more attractive than female jewel beetles due to the beer bottle’s large size and attractive coloring. Beer bottles are often discarded by humans in the Australian desert that the jewel beetle thrives in, creating an environment where male jewel beetles prefer to mate with beer bottles instead of female jewel beetles. This is a situation that is extremely disadvantageous as it reduces the reproductive output of the jewel beetle as fewer beetles are mating. This condition can be considered an evolutionary mismatch, as a habit that evolved to aid in reproduction has become disadvantageous due to the littering of beer bottles, an anthropogenic cause.

Examples without Human Influence

Information Cascades Between Birds

A group of Nutmeg Mannikins at a bird feeder

Normally, gaining information from watching other organisms allows the observer to make good decisions without spending effort. More specifically, birds often observe the behavior of other organisms to gain valuable information, such as the presence of predators, good breeding sites, and optimal feeding spots. Although this allows the observer to spend less effort gathering information, it can also lead to bad decisions if the information gained from observing is unreliable. In the case of the nutmeg mannikins, the observer can minimize the time spent looking for an optimal feeder and maximize its feeding time by watching where other nutmeg mannikins feed. However, this relies on the assumption that the observed mannikins also had reliable information that indicated the feeding spot was an ideal one. This behavior can become maladaptive when prioritizing information gained from watching others leads to information cascades, where birds follow the rest of the crowd even though prior experience may have suggested that the decision of the crowd is a poor one. For instance, if a nutmeg mannikin sees enough mannikins feeding at a feeder, nutmeg mannikins have been shown to choose that feeder even if their personal experience indicates that the feeder is a poor one.

House Finches and the Introduction of the MG disease

Evolutionary mismatch occurs in house finches when they are exposed to infectious individuals. Male house finches tend to feed in close proximity to other finches that are sick or diseased. This is due to the fact that sick individuals are less competitive than usual, in turn increasing the chances of the healthy male to win an aggressive interaction if it happens. To ensure that there is a lower possibility of losing a social confrontation, healthy finches are inclined to forage near individuals that are lethargic or listless due to disease. However, this disposition has created an evolutionary trap for the finches after the introduction of the MG disease in 1994. Since this disease is infectious, healthy finches will be in danger of contraction if they are in the vicinity of individuals that have previously developed the disease. The relatively short duration of the disease’s introduction has caused an inability for the finches to adapt quickly enough to avoid nearing sick individuals, which ultimately results in the mismatch between their behavior and the changing environment.

Exploitation of Earthworm’s Reaction to Vibrations

Worm charming is a practice used by people to attract earthworms out of the ground by driving in a wooden stake to vibrate the soil. This activity is commonly performed to collect fishing bait and as a competitive sport. Worms that sense the vibrations rise to the surface. Research shows that humans are actually taking advantage of a trait that worms adapted to avoid hungry burrowing moles which prey on the worms. This type of evolutionary trap, where an originally beneficial trait is exploited in order to catch prey, was coined the “rare enemy effect” by Richard Dawkins, an English evolutionary biologist. This trait of worms has been exploited not only by humans, but by other animals. Herring gulls and wood turtles have been observed to also stamp on the ground to drive the worms up to the surface and consume them.