[INTRO] A lot of people think evolution on Earth happens a little something like this: a slimy creature crawls out of the ocean, and hundreds of millions of years later its descendants peel themselves off the sofa, wondering how they managed to binge-watch all five seasons of Breaking Bad in less than three days. -- In other words, evolution is a long, slow process. But it's not always that way-- Some species can rapidly adapt to cope with fast changing environmental conditions like: human encroachment; invasive species; climate change; you know-- things that are 100% our fault. Biologists call this high-speed adaptation "evolutionary rescue." Though that kind of makes it sound awesome-- when really it's how some species are able to respond
in times of severe population stress. Take cliff swallows,
for example-- that's a species of swallow that builds nests on cliffs. Except, lots of them don't do that anymore. Today, many cliff swallows make their nests on bridge supports. That, of course, means there are large populations of cliff swallows living next to roads. Birds that live next to roads
face a strange new enemy. They're fast, they're hard- -they're cars. It seems like cliff swallows are quickly adapting to this threat. In fact-- since the 1980s the number of road-killed swallows has declined- -even though there are more birds than ever nesting next to roads. That's probably because populations near roads have rapidly evolved shorter wings. Biologists studying the birds have found
that road-killed cliff swallows tend to have longer wings
than the not road-killed variety, a little over 5% longer, on average; and they think that's because shorter wings give the
swallows an advantage against vehicles. Longer wings are better for air speed and gliding,
but shorter wings make the birds more maneuverable- -so they can quickly take off vertically and evade oncoming cars. What's really impressive is that
the change in wing length happened in
less than three decades. Also, shorter wings may help the swallows cope with climate change. In 1996, half of a cliff swallow population that scientists were studying starved to death during a cold snap - probably because the freezing temperatures killed a lot of the insects they normally eat. What was really noticeable though, was that the birds that survived had shorter wings. Researchers think the birds with
shorter wings were much more maneuverable, and that made them better at catching the few insects that didn't freeze. So it's possible the short wings they evolved for dodging cars will help them survive the more frequent and severe cold snaps brought on by a changing climate. Commercial fishing operations catch a lot -A LOT - of fish every year. In fact, they catch so much that species -like Salmon, Cod, and Herring- have all evolved quickly to avoid extinction. Basically, they're now living fast and dying young. You see, human fishing tends to favor larger specimens; so many species evolved to be smaller overall, or are becoming sexually mature at a younger age, or doing both of those things. In some populations the change is really dramatic, like: the average adult fish is 20% smaller than the species used to be, and lives only 75% as long. The advantage of this is pretty obvious - smaller fish are less likely to be harvested by humans. So--fish that stay small -or reach sexual maturity sooner, can pass their genes on before they end up someone's dinner. Fishes: well-done. and these changes can happen really quickly. For example: after they were over-harvested in the 1920s, Chinook Salmon took only about 30 to 40 years to get roughly 25% smaller; and that's great, for them-- unless we start letting people catch smaller fish to keep up with the demand. When the London Underground was built in 1863, workers inadvertently created a tidy isolated habitat for the world's favorite bug-- the mosquito. Standing water would collect in the tunnels, which made a perfect breeding ground for the bloodsuckers. Humans discovered this the hard way during World War Two, when the tunnels were used as overnight bomb shelters and the mosquitoes took to feasting on those people. It's bad enough when you're underground trying to avoid getting exploded, without being covered in blood-sucking bugs. What's actually weird about this is that they were biting people at all. Because the mosquitoes that live in the London Underground are a subspecies of Culex pipiens - a species that -above-ground- usually feeds on birds. So in the eight decades or so it had spent apart from its kin, the London Underground mosquito has switched to preferring the blood of mammals. Probably because rats are a bit more common than pigeons in the new habitat. And that's not the only difference between the underground mosquito and the species it evolved from-- Unlike the above-ground version, the London Underground mosquito doesn't hibernate in the Winter, and the females don't need blood in order to lay their eggs. In fact, the two types are now so genetically distinct that they can't mate and produce offspring. So the metro mosquitoes are arguably a new species - not just a subspecies. Anyhow, whatever you want to call them, researchers think it only took a few hundred mosquito generations for this new pest to evolve. So like, "yay evolutionary-rescue" i guess Okay, all sorts of garbage and pollution get dumped into the sea, but one species may have evolved a trick to survive this refuse onslaught. Turtle-headed sea snakes seem to be adapting to chemical pollutants through an evolutionary phenomenon called industrial melanism - in other words, they're getting darker. All members of this species of Australian sea snake have black and white stripes or they did until recently. Around 17 years ago, researchers noticed that the turtle-headed sea snakes living in the Noumea Lagoon in New Caledonia were mostly black instead. They get that color from the pigment melanin and it just so happens that it not only gives black animals their color, it's also very good at binding to heavy metals. Heavy metals are substances like zinc, lead and arsenic, which can accumulate in animals tissues and being toxic, eventually cause their death; the waters around New Caledonia are full of heavy metals, from nearby nickel mining activities and industrial runoff. Scientists actually collected shed skins from New Caledonia snakes and found higher amounts of zinc, nickel and lead. So they think the snakes are protecting themselves from these pollutants by storing the heavy metals they ingest inside their melanin-rich skins. Then they can shed that skin, effectively ridding themselves of the dangerous substances-- which is probably why researchers have found that blacker snakes shed their skins about twice as often as their striped relatives. Speaking of oceans full of garbage, let's talk about garbage patches. There are large areas of the ocean where our trash collects, thanks to water circulation patterns. The North Pacific Garbage Patch alone contains about 79,000 tons of plastic in an area about the same size as the state of Alaska. And that's a massive amount of plastic, but it's not as massive as it should be. Scientists say they're only finding about a hundredth of the plastic they expect to find in the ocean. The garbage patches don't appear to be getting any bigger, though they definitely should be. Now, no one is entirely sure why this is; but some scientists think it's because of the rapid evolution of microbes that eat plastic. The mere existence of all our trash could be acting as a strong selective pressure driving the evolution of molecular pathways for chopping up plastics Plastic-eating microbes have been documented in other places. Scientists were recently able to isolate a type of bacteria called Ideonella Sakaiensis, which was nomming on plastic outside a bottle recycling facility. Considering the kind of plastic garbage they eat has only been a thing for around 70 years, they evolved really quickly; so it's possible that that's happening in the oceans too, but this is a guess. Research is needed to confirm plastivores are a thing and can account for the missing plastic. It could be explained other ways too, like, maybe this plastic is just sinking as its colonized by marine organisms. Recent research has suggested some plastics aren't as everlasting as we thought. -I'm rootin' for the microbes, though- Human beings cause all kinds of problems for nature all by ourselves; but sometimes, we go above and beyond, by introducing plants or animals that wreak havoc on our behalf. That's what happened to an isolated population of Edith's Checkerspot Butterflies, on a cattle ranch in Nevada. In their natural habitat, these butterflies lay their eggs on maiden Blue-Eyed Mary plants, a native species of wildflower; in this particular location, ranchers introduced an invasive weed called English Plantain. It turned out, the butterflies that laid their eggs on plantain actually fared a bit better since the plants live longer. So the butterflies quickly evolved to prefer this new host plant. Things were going swimmingly-- until the cattle moved away. When that happened, the fields were almost immediately taken over by grasses because -you know- they were no longer being eaten by cows. This grassy vegetation shaded the plantains, so the caterpillars living on them didn't get the warm sunlight they were used to; the poor butterflies simply weren't able to switch back to the wildflowers fast enough. So within a couple of years, the isolated population of Edith's Checkerspot Butterflies went extinct. This whole process from the introduction of English plantain to the extinction of the adapted population of butterflies, only took around a hundred years. Elephant tusks are highly sought after in the ivory trade. The presence of poachers gives tuskless elephants a profound biological advantage, which is probably why African elephants without tusks have become a lot more common in some areas. During Mozambique's Civil War, elephants were poached in large numbers for their ivory and meat in order to help sustain the fighting forces and pay for weapons. Since tuskless females were more likely to survive- lacking tusks went from being a relatively uncommon trait, to a common one possessed by up to a third of young female elephants. A similar thing has happened elsewhere on the continent. Nowadays in South Africa's Addo Elephant Park, up to 98% of female elephants never developed tusks. Incredibly, this has all happened over a period of a couple generations, that's probably because about 2-4% of females already possessed the tuskless trait. Sadly, those tuskless females were pretty much the only ones that survived long enough to breed, and that allowed the mutation to sweep through the population very quickly despite the fact that elephants reproduce extremely slowly compared to all of the rest of the animals on this list. While being tuskless is great when it comes to avoiding poachers, it's important to note that female elephants in this species had benefited from having tusks up until now. They're helpful for finding food, among other things. So while losing their tusks might seem like a win for rapid evolution, it's not an unqualified one. It might be tempting to think that we can stop worrying now about endangered species because this high-speed evolution is gonna swoop down and eat up all the plastic and save the elephants, evolutionary rescue can't save every species. Some simply aren't capable of adapting quickly, because evolutionary change happens over generations not years. Even hyperspeed adaptations like the ones, we just talked about, generally take ten to a hundred generations. Basically, the more babies you have and the quicker you have them, the faster [that] evolutionary changes can spread through a population. So we're talking about hundreds of years for species -like polar bears- to make big changes that might help them survive. Sometimes rapid evolution can happen faster, like the species already has an adaptation that helps them respond to a very bad situation, as we saw with the tuskless elephants; but for the most part it occurs in animals that breed fast and have lots of offspring. Even then, evolving quickly can totally backfire -- just ask the Edith's Checkerspot... So while examples of warp-speed adaptation are fascinating, we shouldn't see evolution as some superhero that's going save this planet. That is still on the folks who caused the problems in the first place, which is us. Though, I am thankful for many of the wonders that were brought to us as we did it. Thanks for watching this episode of SciShow. Don't forget to subscribe to get all of our episodes delivered in to your YouTube inbox. You can also subscribe to SciShow Psych and SciShow Space, where we talk about those topics in exclusion of all these other ones. If you were surprised to learn that evolution can happen so quickly, you might learn a lot from our episode on Evolution Misconceptions, so we've linked to it, for you to click on, and watch it. I hope you enjoy.
Excellent info and excellent for creationism. Creationists should welcome rapid change in populations. This guy keeps saying its amazing but why? For some of them it doesn't show selection on a few best ones. it could be other mechanisms to change them. for example the birds. its unlikely such a tiny number were selected based on shorter wings. it might be a general reaction.
anyways this shows how new research always is a gain for creationism and a loos to evolutionists in some ways.
Fine video.
“Some species can rapidly adapt to cope with fast changing environments” - like a global Flood and its aftermath, perhaps?
I think this is hilarious, because evolutionists ridicule us for believing in rapid speciation, and then they discover it themselves and give it their own evolutionary spin.