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Evolution, which means "change over time," is a never-ending process affecting all living organisms. As certain species evolve, others must adapt to keep up, or they risk fading into oblivion.
Human activities have significantly shaped the environment, compelling other species to evolve in order to continue existing. This phenomenon, called "human-induced evolution," highlights examples of animals that have had to change their physical traits, behavior, mating patterns, and even their very forms to survive in a world dominated by Homo sapiens.
10. Elephants: The Tuskless Mutation
Elephants, the largest land mammals on Earth, face little protection from poachers who hunt them for their valuable ivory tusks. Despite over a century of legal efforts to protect these majestic creatures, their population in the wild has dramatically decreased.
In response to this threat, elephants have started evolving to live without tusks. In 1969, only 10.5 percent of Zambian elephants were born with a genetic mutation preventing tusk growth. By 1989, during a peak in ivory poaching in Zambia, that number increased to 38.2 percent.
Elephants without tusks are less likely to be targeted by poachers, offering them a better chance of survival amid the devastating destruction that has plagued their species for centuries.
9. Atlantic Cod: Early-Onset Fertility and Reduction in Size
The Atlantic cod was once one of the most heavily overfished species in the ocean until a ban was introduced to prevent its extinction. While the species hasn't fully rebounded, its size and reproductive behavior have undergone notable changes.
Due to humanity’s constant craving for this delectable fish, we tend to catch them at a certain size and return those that aren't yet mature. In the past, the fish would begin their reproductive journey at six years old, when they were considerably larger than those at five years.
Now, these fish begin reproducing at just five years of age. They’ve evolved to mature sexually 16 percent faster, giving them a better shot at having offspring before they grow too large and tempting for a human fisher to catch.
8. Bedbugs: Tougher Exoskeleton and Resistance to Poison
No one enjoys dealing with bedbugs. It’s clear that we aren’t fond of creatures that feed on us while we sleep. But due to evolution, these pests have become remarkably difficult to eliminate.
Bedbugs have developed greater resistance to the pesticides we’ve created to combat them. Their exoskeletons have thickened, and they've mutated other natural defenses in response to the poisons we use against them.
There are various types of bedbugs. The ones that feed off humans have evolved distinctly from those that primarily feed on bats and other mammals. Their evolution has closely followed that of humans, allowing them to continue making our lives miserable.
7. Mice: Mutation for Poison Resistance
The main poison used to eliminate mice is warfarin, which is widely used around the world. Humans have been battling mice ever since agriculture began and these little creatures became dependent on us. However, a new hybrid species has evolved a resistance to our go-to poison.
Usually, hybrid animals, like mules, are sterile. But this particular hybrid decided that reproduction was an essential survival strategy. A German mouse and an Algerian mouse have combined their genetic traits to create an adaptation known as "point mutation" to withstand warfarin.
This mutation renders the poison nearly ineffective against this type of mouse, and they will likely pass it down to other mouse populations. As a result, they will become even more difficult to exterminate.
6. Tibetan Snow Lotus: Human-Induced Dwarfing
The Tibetan snow lotus has undergone a process known as "human-induced dwarfing." This means the plant has evolved to develop a shorter stalk, growing closer to the ground.
This adaptation occurred because humans typically harvest the taller flowers that grow higher off the ground. The largest blossoms are taken, leaving the smaller ones to continue their growth, which has led to this evolutionary shift.
This has forced the plant to evolve so it might avoid being picked. Over the last century, its average height has decreased by more than 10 centimeters (4 inches). This evolutionary strategy isn't entirely effective, as we still tend to pick the flowers. Though the plant is endangered, there is hope for its survival as efforts are being made to protect the species.
5. Hudson River Fish: Pollution Resistance
Humans have never been great at keeping our waterways clean. From oceans to seas to lakes… you get the idea. In the Hudson River, one of the most polluted and heavily trafficked waterways in the world, a fish has had to adapt to survive or perish.
The Atlantic tomcod is a small, bottom-dwelling fish that has evolved incredibly quickly to develop immunity to the harmful effects of PCBs. These toxic chemicals, once used in electrical insulators, were banned in the 1970s. (LINK 16) As environmental toxicologist Isaac Wirgin states, “This is very, very rapid evolutionary change.”
Instead of taking millennia for these fish to evolve, changes have occurred in just 20–50 generations. Unfortunately, this swift evolution could lead to the Atlantic tomcod’s downfall. As efforts are made to remove PCBs from the Hudson River, the environment may become unsuitable for these small fish.
4. Human Immunodeficiency Virus: Rapid Variant Evolution
The reason scientists and doctors have yet to develop a vaccine to halt the spread of human immunodeficiency virus (HIV) lies in the process of evolution itself.
When it comes to viral evolution, few viruses evolve as rapidly and easily as HIV. In a single day, one HIV virus can produce billions of copies, and it does so with considerable error. This means the virus mutates frequently as it duplicates.
Mutations are the engine of evolution. HIV’s fast replication speed and rapid mutation rate make it evolve faster than it can be treated. With changes in the virus’s genetic structure, treating it becomes a major challenge. This has always been an issue when addressing pathogens like HIV. However, there is hope that one day we’ll find a way to eliminate this virus just as we’ve conquered many others.
3. Methicillin-Resistant Staphylococcus Aureus: Resistance to Antibiotics
One of the most alarming issues humanity faces today isn't nuclear conflict or an asteroid impact. It's the simple fact that our antibiotics are losing their effectiveness. Well, that's not entirely true. However, due to the over-prescription of antibiotics in the past, bacteria have evolved to resist them.
This is a major concern. Think back to the life expectancy of humans before penicillin was discovered. Not exactly a rosy picture. The hard-to-pronounce methicillin-resistant Staphylococcus aureus (MRSA) is a bacteria that is increasingly difficult to treat in humans.
Thanks to natural selection and horizontal gene transfer, these bacteria are developing immunity to antibiotics. Initially a hospital-acquired infection, which spread in hospitals due to open wounds, MRSA has now made its way into the general population and is becoming a serious health threat. Remember to clean your cuts and scrapes so you can avoid dealing with this.
2. Tawny Owls: Color Changes Due to Global Climate Change
As we discuss how human-driven climate change is impacting species worldwide, we can't overlook these adorable owls. A recent study of a tawny owl population revealed that plumage color is a trait easily passed down through generations. Due to the changing climate, the owls have started turning brown.
In this species, gray feathers have traditionally been dominant. However, as temperatures rise due to climate change, more owls are turning brown. The increased number of brown owls has actually enabled them to thrive.
In the past, darker birds were more likely to die during especially harsh winters. But with the winters becoming shorter and temperatures rising, the tawny owl population, which is gradually becoming browner, is thriving.
1. Pink Salmon: Migrating Earlier
Human activity has had a profound impact on the environment, compelling numerous species to either adapt or disappear. The pink salmon is one such species that has evolved its behavior and even its DNA, now migrating earlier in the year to cope with environmental changes.
Salmon need to swim upstream before the waters get too warm, or they risk dying before spawning. With climate becoming increasingly unpredictable, several generations of pink salmon have lost a genetic trait that used to delay their migration until later in the season.
As the salmon with this genetic marker die off, the remaining population begins migrating earlier, which could help them survive in an ever-changing environment. While environmental shifts have historically prompted genetic changes in species, we now see these changes accelerating due to human influence on the environment.
