Animals are constantly  evolving to one up each other.

If you have siblings, you know  exactly what that feels like. But can you imagine that going  on for millions of years?!

It happens in nature all the time  in a process called coevolution. Although personally, I prefer the  term “evolutionary arms race”. Predators evolve to better capture prey, prey evolves to evade predators.

It’s a never ending back and  forth. It’s even happening to us! Here are four fascinating examples  of evolutionary arms races, including how snakes hijacked our brains. [♪ INTRO] The pronghorn is the second fastest land mammal on the planet.

At top speed, it can run  around 96 kilometers per hour— as fast as a car on the highway. And for a long time, we had no idea why! None of their natural predators in North America, like wolves or mountain lions, can even come close to that speed.

The only land mammal that can  run that fast is the cheetah. But they live in Africa, and  even in prehistoric times, these two species have never  overlapped geographically. It wasn't until the 1970s  that clues began to emerge that explained the pronghorn’s ridiculous speed.

During that time, scientists determined that fossilized remains found in North America were actually those of a cheetah-like cat. This North American cheetah was related to the modern day cheetah, and shared lots of similarities with its African counterpart. And one scientific study  suggests that the North American cheetah may have, in fact,  preyed on the pronghorn.

Carbon and nitrogen isotopes from the fossilized predator revealed that the pronghorn may have made up a pretty substantial part of its diet. Suddenly, the pronghorn’s  speed made a lot more sense! It’s fascinating to think about  how that evolutionary rivalry must have developed over millions of years.

The North American cheetah got  faster to catch pronghorns, pronghorns got faster to avoid becoming dinner. And when the cheetah went  extinct, we were left wondering why the pronghorn was so  fast for seemingly no reason! But keep in mind that this big  cat did, indeed, go extinct.

The pronghorn may have lost  many battles to the cheetah back in the day, but it seems to  have won the evolutionary war. Another evolutionary showdown that has raged for millions of years is a clash  between bats and moths. Many bat species feed predominantly on insects, and they use echolocation to  find these living gusher snacks.

Moths are often on the menu for the bats. What’s an insect to do when  other creatures of the night are using ultrasonic clicks to  locate them, sometimes midair? You click back!

Tiger moths have evolved the ability to make ultrasonic clicks,  the same kind the bats use. It’s believed that these clicks confuse the bats, essentially throwing off  their echolocation abilities, allowing the moths to evade the predators. Scientists studying the bats  have noticed a decrease in successful catches of moths  when the moths are clicking!

But if you thought the bats were going down without a fight, think again. Their counter punch is  essentially an adjustment to the last phase of their echolocation, which is called the “terminal buzz phase.” It allows the bats to hone in on  prey as they’re getting closer. Bats are learning to lengthen  their terminal buzz phase, increasing their success rate, even when the moths are clicking away!

This evolutionary back and  forth between bats and moths is an ongoing battle for the  title of ruler of the night sky! This SciShow video is supported by Brilliant, the online learning platform  with thousands of lessons in computer science, math, and science. One of the many things that  SciShow and Brilliant have in common is engagement in scientific thinking.

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OK, our next example is a race  between a parasite and its host. When I say the term  “parasite”, what comes to mind? Creepy crawlies?

Maybe blood  suckers like leeches and ticks? Don’t worry, this parasite is  a lot less… goosebump inducing. Which is ironic, because I’m talking about a bird.

Cuckoos, to be exact! The cuckoo bird is what’s  called a “brood parasite”, meaning it lays its eggs in the  nests of other birds in an effort to make the host birds care  for the cuckoo’s young. It often results in the loss  of the host’s young because so many resources are spent  on the parasite’s young.

The host bird should just kick  the cuckoos out though, right? Why would they spend their precious time and resources on an egg that isn’t theirs? Because the cuckoos are masters of disguise.

Common cuckoos, our parasite bird, have evolved the ability to match their own eggs to that of the ones in their host nest. Hosts then need to evolve to  better identify cuckoo eggs. This particular arms race has been well documented by a study of cuckoos in two different locations, parasitising two different host warbler species.

One in Hungary and one in Japan. And interestingly enough, these two cuckoo and warbler populations seem to be at different places in their evolutionary battle. Cuckoos have been able to more closely match their eggs to those  of their hosts in Hungary than those of their hosts in Japan, suggesting the parasite/host  relationship in Hungary may be older than the relationship in Japan.

However! The rate at which the  hosts reject the cuckoo eggs is pretty similar in both  places, despite cuckoo eggs in Japan not matching the host eggs all that well. So, it may be that the evolution  of egg matching in cuckoos and the parasite egg identification by the warblers don’t happen at the same rate.

Scientists are going to need to spend more time in the trees to be sure. This example does make me wonder, though… Who lived in that cuckoo clock  before the cuckoo took over? Our last example of an evolutionary arms race involves an animal with no arms at all.

SNAKES! Tell me, are you afraid of snakes? If so, don’t feel too bad.

That’s something that may have been etched into us by evolution. There’s something called “The  Snake Detection Hypothesis.” It suggests that primates, like us, have had a long history of  interacting with venomous snakes, creating a need to be able to quickly identify the serpents to save ourselves from deadly bites. One study tested this  hypothesis on a bunch of humans.

People were shown a series of  blurry photos of various animals. They had to identify the animal in the photos as the photos were slowly unblurred. And they were able to identify  snakes significantly sooner in this process than any other animal!

Like I said, snakes have  basically hijacked our brains. Now, because primates were evolving to better protect themselves  from snakes, the snakes need to try their hand… or tail,  I guess, at getting back at us. Cobras have evolved several of  their own defense mechanisms.

They have warning colorations  and displays such as hooding, suggesting a pressure to identify themselves to potential primate threats as a  truly deadly “danger noodle”. And they later evolved the ability to spit venom, allowing them to get it into  the eyes of their aggressors. Especially those pesky bipedal  primates who had the ability to use tools or projectiles to  harm the snakes from a distance.

But primates ain’t giving up that easy! It turns out that primates  that regularly encounter large snakes with neurotoxins have developed more resistance to those toxins  than primates that don’t. What will snakes and all  the creatures on this list do next in their stubborn skirmishes for survival?

Stay tuned over the next few  million years to find out! [♪ OUTRO]