All-Predator Ecosystem: Could Earth Survive If Every Species Was A Carnivore?

Cows don’t eat humans... (As far as we know) They eat plants, and are eaten by predators…  

that’s how ecosystems work. But what if we turned  cows into predators, along with every herbivore   species? Could a world of endless predation even  function, how would we possibly simulate it,   and what kind of terrors would it produce? Let’s  go down the list… First problem: Energy. Flip a  

switch that turns all life into predators, and  you’ll very quickly have no more life. In nature,   carnivores eat herbivores which eat producers  which eat THE SUN (photosynthesis). But if we   remove the producer plants that convert sunlight  into chemical energy, we’ll have no base to build  

our all-predator utopia upon, and it’s not like  there are predatory plants – oh wait there totally   are. Fly-traps, pitcher plants, sundews — deprive  our leafy friends of nitrogen and they’ll get a   craving for flesh, so let’s say all photosynthetic  plants in our alternate earth moonlight in  

carnivory, and now we can have vegetation while  technically staying ‘all-predators.’ Okay,   but plants only transfer energy to animals when  eaten: which leads us to issue two: herbivores.   Swap Earth’s A+ prey over to the predator track,  and not only would the biosphere collapse,  

but so too would said species’ grades (F-)  in not starving. To illustrate: elephants are   pretty tough. Throw an elephant in the ring with  virtually any animal and the one with the trunk is   taking home the belt, but just because elephants  can easily KO a testy buffalo, doesn’t mean they  

could run one down predator-style. An elephant’s  top speed is maybe half a water buffalo’s,   a quarter of a gazelles. If they want to pass  carnivore 101, something needs to change. This   gets us to the core of our herbivore vs carnivore  dilemma: what makes a good plant-eater usually  

makes a terrible meat-eater. Reversing  things, though a deer could outrun a wolf,   even if they had sharp teeth, actually subduing  one is out of the question. A deer adapted for   predation would need to look completely different.  Likewise, our carnivorous elephant will require  

more than new dentures. They’d likely have to be  lighter and faster, with body parts specifically   adapted to neutralizing prey after catching up to  them. There’s a lot more to say about how insane   animals in our all-predator ecosystem will look,  but the more immediate issue is, again, if nobody  

is eating plants, there’s no energy coming in, and  the planet will be out-of-order in a week. Nature   has a fix here… albeit a horrifying one. See,  horses already hunger for flesh. Oh, they might   prefer grass, but place a rodent or baby animal  in front of them and its chow time. Deer will do  

the same, so will cows, giraffes, rabbits, hippos  — the disturbing truth is in nature, categories   aren’t clean and nobody likes passing up on free  nutrients. But that goes both ways: wolves will   sometimes eat plants, same with bears. So all  told, primary consumers in our predator-world  

could still eat a sustainable quantity of  plants, while technically remaining facultative   carnivores/omnivores — so to make this work, let’s  just tweak how nutrition functions in this reality   so that any grazers also need to stay on the  predator grindset. So that’s herbivores fixed,  

but now predators have a problem. Because to be  a predator of predators, a hunter in a reality   where grass-eaters are also honed for the hunt,  would be a tricky job indeed. It’s possible we’d   see predators adopt defenses typically just for  prey: physical barricades like spines or shells,  

active deterrents like horns and antlers, maybe  even some chemical spray. It may sound outlandish,   but you can see examples of this in nature —  compare for instance, tigers and scorpions. Tigers   are privileged: sleek and fast and unarmored  because no one eats them and they eat everyone.  

Scorpions meanwhile are in the nightmare zone of  the food web; they’re carnivores that eat insects   and mice twice their size, but are also prey  themselves. Hence why scorpions must be armed from   tip to tail in a way few predators are. And brief  aside: ever notice how no predators have horns?  

You’d think some spiky bits would be helpful, but  with the dubious exception of certain lizards,   horns are only for the hunted — on hunters they  seemingly get in the way. But in a reality where   that herd of bovines are just as likely to flip  the script and eat you, investing in some defense  

might be a good call. We can get a better sense  of what specific traits our predators-of-predators   would favor through simulating natural  selection. This program by MinuteLabs.io,   inspired by those evolution videos from the  channel Primer, essentially works by throwing  

a bunch of blobs into an environment with limited  food, and with each generation the blobs favor   better and better traits. When a blob gets big  enough it can eat other blobs, so let’s mess with   the blob’s stats to make them mostly carnivores  and see what happens. Many, many generations  

later, what’s notable is that while a lot of  blobs stay big and bad, just like in nature,   smaller builds prioritizing keen senses and raw  speed manage to eke out their own niche. Goes to   show that even in a world of predators, there’d  be diversity: agile pursuit predators, ambush  

predators, insectivores with sharp eyesight…. you  can see such variety in the world today. And it's   worth reemphasizing we didn’t tell the simulation  to mimic natural patterns: it just did so through   the blind force of selective pressures and the  laws of energy efficiency. Not every predator can  

be at the top. Which is indeed problem four: Apex  Predators. Predators-of-predators-of-predators   are essential keystones for ecosystem health,  but what could be head-predator in a world like   this one? There’s two possible answers, the first  of which is its own massively insane rabbit hole,  

so let’s start with the second. Simply put: even  in hypercompetitive ecosystems, apex predators   still tend to emerge. After millions of years of  theropods jockeying for dominance, the ol’ t-rex   enjoyed a lengthy, uncontested reign with almost  no rivals. Time and sufficient pressure will forge  

monsters among monsters. Of course, trying to  determine what specific species would go on to   become apex-hunters in our new timeline is pure  conjecture… but that’s kinda what we’re here for.   Give all species on Earth a fighting chance  at predation and you’d likely see some very  

unexpected candidates rise to the top of their  ecosystems. While it might seem improbable for   kangaroos to become colossal predators or koloas  to become ambush hunters — stranger candidates   have become top-carnivores before. Bringing it  back to the dinos, the ancestor of the T-rex and  

other theropods was a tiny, chicken-sized omnivore  — hardly the betting pools favorite for becoming   the largest hunter on land. Give predation to  the masses, and monster predators could truly   come from anywhere. We also need to remember  that ‘monster’ predators might not look like we  

expect. The deadliest predator on Earth today is  arguably the dragonfly, with a 95-97% successful   hunt rate. Lions, you wish. Likewise, one of the  most lethal hunters in the ocean is the seahorse:   goofy from our perspective, but if you’re a brine  shrimp, the seahorse is basically the grim reaper.  

Strange as it might sound, there’s no reason to  think certain existing apex hunters like the great   horned owl would need to change their strategies  if booted into predator-world. They’d be like:   “oh, rodents have fangs now? Pfft, whatever.”  Hyper-effective hunters come in all shapes and  

sizes. Which at last leads us back to the  massive rabbit hole — humans. Would squishy   homo sapiens once again ascend to the apex  of the food web in this alternate timeline,   or might a different species be taking the  top spot? This is the biggest missing piece  

in determining the fate of predator-world, and  an exceedingly tricky question to answer. Like,   imagine you’re a stone-age tribesperson living at  the end of the last glacial maximum. How do you   like your chances in this world where anything,  pure-predator or no, sees you as a potential  

food source? To simulate this experience, I’ll  be playing Minecraft with its code modified so   that all species try to eat me. I only use the  most (laughs) the most advanced tech on this   channel. Okay crudeness aside, the experience of  surviving in an ecosystem where there’s absolutely  

zero safety in any species was surprisingly  illuminating. Funny though it was to be pursued   by a pack of carnivorous chickens — always being  on the run meant all my plans for tools, shelter,   and sustainable food were pushed out of my brain  by the constant need to stay alive. Though hardly  

a controlled experiment I found myself doing  very little home building or weapon crafting,   because literally all I could think about  was where to get my next meal, and how to   avoid becoming one. This, one can easily assume,  would be the experience of primitive humans in  

predator-world — an experience that doesn’t seem  particularly conducive to building civilization.   And indeed, a lot of the tools required for a  civilization-starter-pack might be walled off   entirely in this timeline — most obviously: animal  domestication. Our first puzzle piece within the  

larger puzzle piece of human success, penning  and selectively-breeding animals is a major key   to a stable-society, but let me tell you, it’s  a lot harder to establish a farm when that flock   of sheep is moving on you like a wolf pack. A  lot of familiar herbivores that made for great  

domesticated animals would suddenly become  terrible candidates if they had a predation   side-job. And that’s not just because they might  eat us — even if you can domesticate a carnivore,   keeping one fed is a costly novelty. In the  case of herbivores, humans can’t eat grass,  

so feeding a regular cow is no big hassle for  us — but hunting down a steady diet of meat for   your penned carnivore? Pricy, pricy work in an  early-agrarian world. Consider that pandas are   basically semi-carnivorous cows — same coloration,  same refinement when it comes to eating — yet you  

don’t see a lot of humans hitching tractors to  them. And that’s not just because pandas are   lazy — it’s also because they’re still very much  bears: solitary, unpredictable, territorial, with   a powerful bite and the instinct to use it. Hardly  an ideal partner to get into the agriculture  

business with. And in an all-predator-timeline,  there might be no partners, period. So, are humans   cooked? Well, I’d hardly say we’re out of the oven  — but there are other factors to consider. Sure,   trying to tame a carnivorous, pack-hunting horse  is a horrifying prospect, attempting to do so in  

Minecraft definitely made me appreciate how fast  these monsters are... But horses are only horses   because humans got their grubby domesticating  hands on them — early prehistoric equines were   both smaller and not as singularly bred for speed.  And while I don’t relish the idea of getting  

attacked by, like, a pony, it sounds a fair bit  more manageable. And humans have managed to strike   bargains with similarly sized facultative  carnivores in the past. Wolves are indeed   the first animals we ever domesticated, dangerous  beasts who nonetheless hunted and lived alongside  

us, and got more and more used to following orders  and eating whatever scraps we have leftover.   Modern dogs are proof that under the right  circumstances, predator domestication is not only   possible — it can be an award-winning success.  But successfully kickstarting civilization  

usually requires both domesticated animals, and  a ‘caloric surplus’ – or enough food to not only   meet immediate needs, but provides a nutritional  excess so that people can start focusing on more   specialized tasks. That means permanent farms,  which one must defend and maintain — a perilous  

operation for the people of predator-world. How  could humans protect large swaths of land from   constant animal attacks? …Well, they might not  have to. It’s time we finally faced the fact that,   while Hollywood teaches us that predators are  heat seeking missiles — torpedoes hurtling  

towards the nearest prey species — the reality is  most predators aren’t nearly as single-minded as   the dinosaurs of Jurassic Park suggest. Catching  prey is a calorically-costly endeavor that often   involves bodily risk — species only attempt it  if they’re very confident they’re about to get  

a worthwhile meal. You can see this in our blob  simulation — big blobs only chase down little   blobs when absolutely necessary, predators won’t  waste energy on a hunt if there’s any reason to   be apprehensive. It’s why sharks and wolves  rarely attack humans: we’re freaky and stinky  

and unpredictable. This is a truth we’ve kind of  danced around all video — but it’s a critical one.   Even if you gave chickens a predation instinct,  it’s unlikely they would actually see humans   as food. They might nip at us because they’re  jerks, but they do that already; on the whole,  

carnivorous chickens wouldn’t be that different  from regular chickens, and are another animal that   predator-world humans could likely domesticate.  Like, if chickens had to snack on the occasional   mouse, I’m sure we could handle that, seeing  how they already eat various insects. But  

back to the point: even if defending significant  territory, humans in this timeline are unlikely   to be overwhelmingly menaced by wild beasts —  because make it clear you aren’t an easy meal,   and generally, most predators won’t bother. So  it seems like humans might be able to maintain  

the farmland and domesticate the animals required  to reach the top of the all-predator reality after   all. But there’s one other, more disturbing  possibility for this world’s apex hunter… a   species adapted specifically to hunt humans.  Because here’s the thing: for early hominids,  

animal attacks were a part of life — big  cats, hyenas, wild dogs, crocodiles — all   occasionally snacked on our ancestors according  to the fossil record. Yet for the most part,   these animals were not human hunting specialists:  hominids rolled onto the evolutionary scene rather  

quickly, and they had a habit of traveling to  new ecosystems where predators were unfamiliar   with them — making them a rare food source.  There’s tangential evidence one big-cat species   learned to feed on hominids specifically, but  it’s been increasingly debunked. Humans simply  

powerwalked their way to civilization too quickly.  But say, in predator-reality, hominids make slower   progress — giving more and more opportunity  for carnivores to adapt to our behaviors,   until eventually, a species emerges that knows  our every weakness and hunts us with ease. What  

exactly a predator adapted for hunting humans  would look like could frankly be its own video,   but it’s a downright chilling concept. Admittedly  not the most likely one, as large specialist   predators are somewhat uncommon — but they do  happen. Polar bears are a seal’s worst nightmare,  

as the bulk of these bears’ diets and therefore  the bulk of their adaptations is specialized to   take out our flippered friends — and another side  note, they’re also one of the few species that   explicitly sees humans as food, though they aren’t  specially adapted to hunt us. But if humans had  

an equivalent specialist predator, our progress  might be greatly stalled, which means – “Hey man,   you’ve been talking about humans for a while, is  this rabbit hole almost finished?” “It’s finished   when I permit it to finish.” Because there  is one last elephant in the room here — not  

the weighty mammal — but the equally weighty  possibility, that in this all-predator timeline,   homo sapiens would have fundamentally different  defensive capabilities. Assuming our primate   ancestors ever emerged in this reality in the  first place, they would have done so in the  

midst of increased predation pressures, and might  therefore have invested in biological protections   that would make them more difficult to prey upon.  We are admittedly pretty far out on a hypothetical   limb here, but pushing past uncertainties is what  this video is all about. Because, (brief rant),  

there are plenty of other potential issues with  predator-reality we’ve had to gloss over — for   instance, even if the majority of predators  were also eating plants, there’s probably   not still enough energy to go around without  modifying vegetation itself. It’s also true that  

trying to be a top herbivore and a top carnivore  at the same time tends to be inefficient,   which is why most species find success in  emphasizing one or the other. So even if   someone was crazy enough to create predator-world  through means of… genetic engineering, give it a  

few tens of millions of years, there’s a chance  natural selection would just sort species back   out into mostly herbivores and carnivores, unless  you keep your thumb on the scale. But, the point   of a thought experiment is to experiment, not  to hit a dead end and just give up. Okay back  

to primates — what outlandish defenses might  they have in this alternate reality? Well,   assuming they’re still starting in the trees, any  deterrents like spines or armor plating might be   too heavy, but some semi-arboreal species, like  the pangolin, can still climb despite their  

armored fashion sense, so physical defenses are  indeed a possibility. Yet the greatest potential   defense for primates is one they already have  — cooperation. That’s right, the power of group   projects, everyone’s favorite! Seriously though:  in nature, there are few things more valuable than  

a species capable of effective coordination, and  that would hold true in predator-reality. Indeed,   chances are this trait would likely be even more  critical. Which brings us to our final essential   point for simulating this all-predator-biosphere  —determining how species would work together.  

Evolutionarily, cooperation is an inherent idea,  with various simulations demonstrating that it   can emerge spontaneously on both a cellular and  intraspecies level. Smaller units working together   to act as one big one is how all multicellular  life functions, and over and over again,  

said lifeforms have similarly learned to cooperate  with others of their own kind. Long story short,   teamwork makes the dream-work. But in a world of  all-predators, teamwork might look fundamentally   different — and that’s because a pack of predators  and a herd of prey do not function the same  

way. (Packs vs. Herds) Let me explain. Herds of  grazers tend to be disorganized — like, they group   together because there’s safety in numbers, but  they seldom put those numbers to use in terms of   planning or coordination — they’re more a crowd at  the same concert than a tight-knit unit. Indeed,  

far from the altruistic eusociality of insects,  most herbivorous mammals are kind of selfish,   as often times the individuals that got to  reproduce, and therefore pass on their genes,   were the ones that ditched their buddies  the fastest when predators descended,  

leading to entire species made entirely of  the type of unreliable jerks who will leave   you in the dust when you need them the most.  In contrast, packs of hunters, surprisingly,   tend to be much more cooperative — they need to  be in lock-step, divide up their labor, and plan  

ambushes in advance if they’re going to catch  their prey with minimal injuries. So in a world   where all animals have a mandatory predation quota  — even those who get much of their nutrients from   plants — the line between packs and herds might  have to blur, and effective coordination could  

become far more common. We can see examples of  the advantages a tight knit herd might look like   in nature. Herds of buffalo have a pre-planned,  military-style formation they’ll fall into to   protect their young. Elephants are also known  to group up effectively, and will even engage  

in more active predator deterrence. The final,  and most relevant example of herd-solidarity,   however, is in troops of primates. Gorillas, with  their careful coordination and social hierarchies,   are a preeminent example of highly-cooperative  herbivores. Likewise, chimps are an equally  

preeminent and rather terrifying example of  cooperative pack hunters. Battles between   primates are often referred to as wars, and  for good reason. When two highly organized   groups come to blows, the conflict tends to be  very intense indeed. So in predator-reality,  

if most species are coordinating, ecosystems  might be even more competitive than initially   thought — on a level typically only associated  with the world of insects. Solitary hunters like   tigers… might need to get over their introversion.  All told, an ecosystem of predators stretches the  

very bounds of nature, and might inspire  clashes that are difficult to fathom. Yet,   and I hope I’ve made this clear throughout this  video, such a reality would be far more complex   than simply a staging ground for eternal violence.  Even in a world of increased conflict, predators  

would still exercise caution and fill a variety  of niches beyond apex warmongers, and cooperation   would still be encouraged. Maybe even more so than  in our reality. And while humans ascending to the   top of this reality remains an unknown, there is  a chance — and either way, predator-world would  

assuredly give rise to fascinating—if  terrifying-- ecosystems. Ultimately,   a kingdom of predators would never be just a  kingdom of monsters. To quote one Dr. Henry Wu:   “Monster is a relative term. To a canary, a cat  is a monster. We're just used to being the cat.”  

…So, while trying to determine if humans  could survive in a world of all predators,   I started to wonder… what animal species could the  average person beat in a fight? Because though I   usually try to end these videos with a meaningful  question… sometimes I all I want to think about  

is what would happen if a person bare-knuckle  boxed a tiger. Trying to figure out how high   humans could climb in an animal battle-royale  was an unexpectedly wild trip — a trip you can   go on right now in a full second video, available  exclusively on Nebula. Nebula is… a lot of things:  

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