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Munk Pack offers bars which are low sugar,  plant-based, gluten free, and keto friendly. Click the link in the description  and use code “scishow” to receive 20% off your first  purchase of any Munk Pack product! [ ♫ INTRO ] We tend to talk about the  evolution of species as something that happened in some ancient time.

Almost as if all species  evolved to their modern forms and just… stopped. But evolution is a never-ending process. And while we humans are still  evolving ourselves, our existence is also driving the evolution  of many other species.

From mosquitos to coyotes, species  from all walks of life are evolving because of ways we’ve influenced the environment. Today we’ll look at five of them. One major way that humans are  influencing the environment is through urbanization: essentially,  turning rural areas into cities and towns.

Urbanization can have all sorts of  consequences for the species in an area, starting with habitat loss. As forests, swamps, and other natural environments are bulldozed to make way for concrete jungles, many plant and animal populations disappear. But some luckier species  are able to make themselves at home in their new environment.

Coyotes are a great example of this. Coyotes are native to North  America, west of the Mississippi. And in the 1800s, as U.

S. settlers moved westward and built up towns and cities, they started  breaking up coyotes’ natural habitat. In response, some coyotes  relocated to less populated areas. But some stayed put… and actually  learned to thrive in human cities.

And even though they’re not naturally nocturnal,   some started looking for food  at night to avoid humans. And they happily adopted human food as their own. In a 2020 study, researchers looked at the  diets of coyotes living in the Los Angeles area by analyzing food in their poop and  trace elements in their whiskers.

And they found that up to 38% urban  coyotes’ diets consisted of human food, most of which they likely fished out of the trash. They supplemented this with a mouthful  of birdseed or ornamental fruit… or Pet cats. So basically, coyotes are doing more than fine.

They’ve even spread east and made surprisingly  successful homes out of places like New York City. But this change in lifestyle  has changed coyotes themselves. As they adapted to their new, fractured habitats, different groups stopped mating with each other, so their gene pools became isolated.

Over time, these coyotes have evolved  into genetically distinct populations. Today, thanks to urbanization, there are distant rural populations of coyotes that are more genetically  similar to each other than rural and urban populations that live side by side. Coyotes aren’t the only animals  that have responded to urbanization by making themselves at home in cities.

Another is the white ibis. That’s a wading bird related to egrets and storks that lives along the coasts  of the southeastern U. S.

It’s also found along the coasts  of Mexico and Central America. Naturally, white ibises hang out  in estuaries and shallow wetlands… but in the last century, their natural  habitats have gotten developed by humans. And rather than crowd into dwindling wetlands, some have adopted cities as their new homes.

Because, like urban coyotes, ibises  learned that living around humans means living around food. These birds spend a lot of their  time eating handouts from people as well as scraps from dumpsters and garbage cans. The ibis has a long, gently curved bill that originally evolved for  plucking things like insects and crabs out of the mud.

But it happens to be pretty handy  for foraging through garbage too. Unfortunately, while ibises love our garbage, it’s low in the essential nutrients and protein that they need for survival, and higher in carbs. This poor nutrition can change the  types of bacteria living in their guts,   much like an unbalanced diet changes the  bacteria in the human digestive system.

Researchers have also found  that the birds’ diet of garbage is also associated with higher  levels of pathogens like Salmonella. That doesn’t always bother the birds, but they can transmit these pathogens  to humans if the two come in contact. Fortunately for them, preliminary  research suggests that, in spite of their poor diets, so far city  ibises don’t seem to be any worse for the wear.

Some researchers even found that urban ibises are   better off than their rural  counterparts in a few ways. For instance, eating literal trash  toughens up their immune systems, so they’re better at fighting  off bacteria like E. coli. They’re also less stressed, possibly because finding garbage to  eat is so much easier than hunting.

And researchers have noticed that they  also have fewer parasites, which may be   because they have more time to clean themselves  since they’re not working so hard to find food. Researchers have yet to determine whether  these changes are just behavioral, or if any of them reflect a genetic change. Whichever it is, we’re forcing  ibises to adapt quickly to a fast changing environment.

Many of the animals that hang out  in cities have specifically adapted to those unnatural environments  and get along pretty well. But while the arrangement might work out for them, it’s not always great for  the people in those cities. Today, humans around the world are plagued by an especially annoying species of mosquito, with a special taste for human blood.

Its name  is literally Latin for “annoying mosquito.” But this pest hasn’t always been around. It  appears to have evolved in just the last few   hundred years, from another species  of mosquito that only bites birds. For a long time, researchers  believed that it’s evolution into the annoying mosquito  happened in the London Underground.

According to the lore, it got trapped  down there in the 19th century and adapted to suck other  creatures’ blood for survival,   gradually evolving into a separate species. And a study conducted in the late 1990s did find that the mosquitoes living in the London  Underground are a separate species from the mosquitoes that live above ground. But a 2022 study found that the same species found underground in London already  existed in the late 1700s in Egypt, almost 100 years before the  London Underground was built.

The authors of that study speculated that  these mosquitoes actually arose there. Thanks to the long history  of agriculture in the region, there were plenty of damp, enclosed spaces  like root cellars where they could breed, plus lots of humans to feast on. Basically, they found a niche to fill, so they  diverged from their bird-biting ancestors.

It’s hard to verify the exact history  behind the rise of this mosquito, but one thing is pretty clear:  It had to do with humans. Regardless of whether it arose in the  London Underground or old Egyptian cities, this particular mosquito thrives  in spaces humans have created, like damp underground  cellars, sewers, and subways. So, thanks to changes we’ve  made to the environment, we will probably always be  living right alongside them.

Now, urbanization isn’t the only  driver of recent species evolution. Long before big cities existed, humans were  already making their mark on some species. And one big way they did that was through fishing.

For thousands of years, humans have cast  their nets or their rods in search of large , hearty fish that would make a good meal. And our methods have typically  relied on fish being bold enough to go after a hook or swim into a net. So, more often than not, we’ve taken the biggest, boldest fish out of the population first.

As a result, people’s fishing practices have shaped the evolution  of species we like to fish. In populations that get fished a lot, survival  of the fittest favors timid, smaller fish, which are less desirable to humans and  less likely to get themselves caught. In a four-year study, carried out between  2007 and 2010, researchers in Europe actually measured the differences between  various populations of northern pike living in a lake in Germany.

By assessing the differences, researchers hoped to understand the effects on populations  that had been heavily fished. So, for four years, they caught fish,  marked them, and collected data on them. Then they released them back into the water.

By the end of the study, they found that they had caught, and marked, bigger, bolder fish, and the population not  sampled was smaller and shyer. Had they actually been removing those  fish, rather than releasing them, the small, shy fish would have  been the only ones left to breed. This shows how, over time, fishing practices have  changed the course of this species’ evolution, and the same may be true of other  commonly fished species too.

This may not seem like a big deal, and researchers haven’t yet explored the impacts in detail. But one thing we do know is that  food webs are incredibly complex, and a shift in the size and behavior of a  population could have far-reaching consequences for both this species and  the ones that depend on it. These are some of the less obvious  consequences of fishing and hunting by humans.

But the northern pike isn’t the only  species to go through a change like this. The bighorn sheep, a species found in  mountainous regions in North America, went through a similar population shift. From the early 1970s until 2011, people  heavily hunted rams, or male bighorn sheep, living on Ram Mountain in Alberta, Canada.

These rams were killed for their horns,  which are famously long and curly. But only certain rams were  legally allowed to be hunted. Their horns had to reach a certain length and  curl before they could be killed as a trophy.

It takes time to grow horns that long, and  some rams grow them faster than others. The big guys with the fanciest horns were between 4 and 7 years old by the time  their horns reached the legal length. The problem was, by this  point, the rams hadn’t reached the peak of their success in mating,  which comes between the ages of 8 and 10.

So trophy hunting wiped out the large-horned males   before they came of age and could pass  on their genes to the next generation. A group of researchers in Canada  analyzed almost 40 years’ worth of data, including 23 years of intense hunting , to better understand the consequences of this  selective pressure on bighorn sheep populations. And they found that the average size  of horns in their study area declined by over 20% in the 40-year study period.

That happened because hunting practices were knocking out the larger-horned  males before they could reproduce, while the smaller males kept  contributing to the gene pool. Not only that, but since the most  intensive hunting stopped in 1996, bighorn sheep’s horns have yet to  return to their previous length, hinting at a permanent change in the  genetic makeup of this population. These sheep are just one example  of many animals being hunted for their size and paying  the price evolutionarily.

And it underscores just how wide-ranging and  profound humans’ effect on other species can be. By selectively killing organisms  that have traits we value, or by building cities in their natural habitats, we accelerate changes that would otherwise  happen through natural selection. Almost everything we do as  humans has the potential   for an accidental evolutionary consequence.

So, it’s important to remember and  factor into our conservation plans, every time we harvest resources and develop land. While some harvests may impact evolution,  they’re still a huge part of our daily lives. After all, we’ve got to eat.

And if you’re lying down and  comfy watching this video, the last thing you want to do is get up  to quiet the grumble in your stomach. In a perfect world, you’d have a snack right next to you that you  could just reach over and start munching on. And those are the moments you’ll  be thankful for Munk Pack.

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