We, humans, hold a lot of livestock. 19 billion in chickens alone. Cattle, sheep and pigs each also number over 1 billion. Currently these animals cannot evolve freely; they are selected on certain characteristics that are beneficial to their human use.

However there are more and more animal well-being laws implemented throughout the world demanding changes in farming practices. What changes to the livestock industry could (inadvertently) cause these animals to freely evolve again? Preferably in such a way that they become smarter, and at some point a real threat to humanity.

I could imagine something like mixing the male and females together and grabbing them individually for slaughter so those that are cleverer would get more offspring.

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    $\begingroup$ Consider the timeline of human evolution. Evolution requires massive amounts of time. Anatomically "modern" humans required hundreds of thousands of years. Humanity required 2.5 million years. Let's assume the evidence for the shortest period: hundreds of thousands of years... Do you believe we'll still be stockpiling cattle and chickens after all that time? $\endgroup$
    – JBH
    Jan 31, 2019 at 16:20
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    $\begingroup$ I know it's not the point, but we are already evolving the animals to become a threat to humanity, just not the way you point. For example: We are injecting them too many antibiotics, and so, when they get sick is usually a mutated superbacteria. When a strain goes pandemic, we are usually helpless against it. You need more? How about the "mad cow disease" caused because we made the cattle eat the remains of dead cattle (cow cannibalism? :D ) $\endgroup$ Jan 31, 2019 at 16:21
  • $\begingroup$ Can't the massive numbers, together with the strong selective pressure of the situation, greatly speed up things? $\endgroup$
    – Herman
    Jan 31, 2019 at 16:23
  • $\begingroup$ @Stormbolter you're talking about bacteria evolving, not a cow. Not even close to the same level in terms of evolution speed. Bacteria live,breed, and die super fast, cows dont $\endgroup$
    – Crettig
    Jan 31, 2019 at 16:24
  • $\begingroup$ @Stormbolter, ooooh. That's a good idea! There is a lot of pseudo-science today wondering if the massive increase in allergies, glutton-intolerance, etc., isn't due in part (if not in full) to the artificial modifications Man is making to its own food supply. The idea that the meat industry could cause the evolution of animals that are no longer consumable to humanity or even toxic.... I love it! $\endgroup$
    – JBH
    Jan 31, 2019 at 16:24

6 Answers 6


Think small

Horror movies in the monster sub-genre have the humans threatened by large animals with dangerous teeth / claws / tentacles. This is because these can be made to look cinematically spectacular and lead to a decisive showdown at the end where the (singular) monster is destroyed. Real life is a different story - ever since the invention of the spear, humans have been killing large, threatening and/or tasty animals en masse. Working our way down in size through some examples of the animal kingdom:

  • whales and sharks in their own preferred environment are easily and frequently killed by humans, with only the sharks taking only a handful of humans each year in return
  • cows cause a smattering of human casualties each year, but humans turn them into hamburger by the herd
  • chickens, ducks and other birds may cause minor injuries but die by the flock to feed us

Methods of killing all of these animals as sport, let alone for survival, are well developed. As other answers have explored, the only serious threat model for these animals lies with diseases that may be transmitted to humans from the animals.

However, the larger lifeforms (including chickens) are possibly not the future of protein in an increasingly overpopulated and environmentally stressed world. While there is cultural resistance in much of the western world, it is strongly suggested that eating insects may be the future trend in providing animal-based protein. Advantages include a potential 4:1 ratio between energy input to protein output compared to 54:1 for warm blooded livestock and the ability to keep insects in much more densely populated enclosures.

Assuming that insects do become the preferred protein source (or the only animal protein affordable by the majority of the human population), how might humans guide their evolution? Well, I would imagine that we would want to selectively breed insects that:

  • could eat just about anything
  • not pass on any diseases that were in their feed
  • reproduce rapidly in a variety of climates
  • have immobile queens so that any insects which escape cannot breed
  • cannot sting / harm people

If everyone breeding insects ensure that all of these characteristics are maintained then there is no threat model. However, assume that someone gets creative and is trying cross-breeding with a species with a mobile queen and there's an escape - it's plague of locusts time. The insects cannot and will not directly attack humans but they will go after every food source around. They will nest in houses, machinery, vents. Think about every cockroach or ant infestation you have ever dealt with but worse. Insects crawling into the mouths and nostrils of sleeping people...

The other issue is that rapid reproduction means relatively rapid evolution post-escape. Some handwavium may be required here, as ant queens, for example, often live for years, but if the entire lifecycle of the selected insect is days or weeks then changes are possible in smaller timespans than are possible for warm blooded animals. Realistically though, it will be selective breeding pre-escape for the "eat anything" and "reproduce rapidly" characteristics that will make these insects more of a threat than existing bugs.

  • $\begingroup$ Oh yeah of course! With insects we hardly have a recourse. The mosquito being a good example; it's the only animal that killed more humans than humans itself; and still our courses of retaliation are meager. I like this one! $\endgroup$
    – Herman
    May 15, 2019 at 13:54

I think the closest you're going to get to this is breeding a species of highly genetically related chickens which have enough benefits to become the dominant chicken livestock population on the planet, and have them develop a new treatment-resistant variant of avian flu that is non-fatal to chickens but deadly to humans.

If both chickens and humans can be vectors for this disease then that increases the rate of transmission, and the low genetic variety of the chickens would mean that they're unlikely to develop resistance to it to nullify that additional vector before significant damage is done to the human population. The genetic similarity would also allow the disease to easily spread to all populations of the chicken.

Nothing else is particularly feasible on a timescale that wouldn't be described as 'nearly geological'.

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    $\begingroup$ "have them develop a new treatment-resistant variant of avian flu that is non-fatal to chickens but deadly to humans." : I know have this image of a bunch of chickens in white lab-coats working away with microscopes & suchlike, the lookout yells that the farmer is coming & the lab-coats & equipment all gets hidden away like it's a Colditz escape committee & they wander around clucking like normal chickens :) $\endgroup$
    – Pelinore
    Jan 31, 2019 at 17:03
  • $\begingroup$ @Pelinore Chicken Run would be a lot darker of a movie if that was their plan! $\endgroup$ Jan 31, 2019 at 17:06

There could be a greater demand for brain sandwich. This would require larger brains for greater yields. Somehow selected breeds become smart enough to plan an escape. The now feral animals collaborate in an effort to rescue their peers. And yes, pigs are the smartest livestock.

Brain sandwiches: https://en.m.wikipedia.org/wiki/Fried_brain_sandwich

  • $\begingroup$ I love this!! Us making a species smarter and smarter while also making them despise us by inhumanely locking them up and slaughtering them by the millions is truly signing the a contract of our demise. It shows not only the heartlessness but also the stupidity the bureaucracy is capable off. $\endgroup$
    – Herman
    Feb 7, 2019 at 15:50

I need to convert my numerous comments into an answer...

The reality of evolution is that you really can't speed it up. The process of changing from something you aren't into something else (e.g., a chicken into a tool-using, vulgarity-spewing creature) requires about 100 million years.

There is plenty of evidence that behavioral adaptation can occur very quickly. Consider the Peppered Moth, where the black versions were better able to survive due to better camouflage during the Industrial Revolution. But that's not "evolution." The changes were merely superficial adaptations. The Black Peppered Moth is still a moth. Indeed, it's still a peppered moth.

Keep in mind that one of the complaints against evolution is the idea of a creature "becoming something else." It's easy to draw a line between apes and humans, but a lot harder to draw a line between "fish" (ocean-dwelling creatures) and apes. (I'm not arguing against evolution, just making a point).

**But here is where we need to discuss what it means to be a "threat to humanity."

Basic problem-solving skills can develop in any animal. Think of mice in a maze. Given enough experience over enough generations (and not too much time from an evolutionary standpoint), the mouse can develop (evolve) better problem-solving skills such that the maze can be analyzed and resolved more quickly. Is that intelligence? Sure. Does it threaten humanity?

Well... no.

You haven't explained what threat you're looking for. Cattle rising up in rebellion against their oppressive masters isn't going to happen. We kill aggressive animals. Indeed, we weed out anything that doesn't belong on a plate with an appropriate condiment. It's very hard to imagine a set of laws, industry regulations, or other conditions that would permit the development of that kind of intelligence.

It would be easier to consider what laws would need to change to permit the enslavement of humanity for the purpose of food. (C.F., Through Darkest America by Neil Barrett)

The problem is that intelligence, even primitive intelligence (insofar as we understand evolution) requires the ability to manipulate your surroundings first (hands, etc.). How must a cow change to do that? Shorter rear legs, lighter forward body, fingers rather than hooves... It's the hands/tentacles/fingers that are the problem. We need them to develop rational intelligence.

Condition #1: remove rather than kill

The scale of this problem makes it difficult to believe, but let's run with it. let's assume in a large enough national or international scale (America, the European Union, India... we need big) laws are passed to create no-kill farming from the perspective of defects can't simply be disposed of. Animals that change such that they're no longer ideal for the dinner plate must be put out to pasture rather than destroyed.

That preserves the tendency to evolve, but it also removes the evolutionary pressures that brought about whatever minor evolution set them free (a couple of digits on the end of a chicken's wing).

And I just shot down my own idea

I'm having trouble seeing where we can set evolution free while maintaining the evolutionary pressures and yet maintaining the corporate bottom line — and do it within a very short period of time (at worst, centuries rather than the millions of years normally needed). What I just proposed wouldn't do it. It's actually easier to justify turning humans into zombies via the meat industry than it is to justify a cow rebellion.

But what if the threat wasn't direct? The old idea that the world is just a handful of meals away from anarchy could be used. What if just enough intelligence is born to justify uncontrollability? The cost of keeping the "unhappy" animals under control gets so high that one of the dominant food sources (meat) is withheld from industrialized Man?

I can believe that.

And I can believe the chaos that would ensue in the world because of the massive shifts of price as other food sources become more expensive due to the rarity of the other.

Unfortunately, that's a long way away from what I think you were hoping to get.


To loosely paraphrase the late Terry Pratchett: "It was a sound that told early hunters 'Here comes either Dinner or Death, and either way it's pissed"

This is in reference to A couple of oxen who had some fresh hot ginger put in a sensitive place and then they wreck a whole lot of stuff. Why do I bring it up? Cattle, though generally docile, are still very large and very strong. Lots of folks are killed every year even by the gentle breeds you are familiar with.

You can build some coincidences into your world to reduce consumption of other food animals like chicken. Perhaps some avian virus that either wipes them out or makes them inedible. It could be man made or the result of ordinary evolution. This means we lean on good old beef to feed ourselves. All we need now is a way to make cattle really dangerous.

Start with the Heck Cattle. an attempt to breed back to the extinct Auroch in Europe. These cattle are very hardy, can survive and thrive in not so great conditions. They are also very aggressive and dangerous. Some mad scientist gets a good cross breed going with the American Bison and begins building a very large herd. Laws designed to require cattle get free range allows this herd of super cows to out breed other varieties and crowd them out. Also, the populace no longer has ready access to firearms. At the same time Mad Cow mutates enough to turn into Smart Cow disease. NOw the super cows are both very aggressive AND very smart. A stampede of this rapidly growing super herd should be able to level a small town like an f5 tornado.

Sadly the super cows do not have opposable thumbs. Humans do. Humans get in there and issue weapons in order to take out these crazed and dangerous bovines from a long distance.

The vast herd is slaughtered and the following massive BBQ causes the destruction of large portions of the populace due to heart attacks. Sadly, the Cardiologist was the first to go. Even the Vegans aren't safe. The lack of farmers means the soybean crop fails and they are left without Tofu. The central plains ecosystem was massively messed up by the herd, who overgrazed it and then poisoned it with manure...too much of a good thing.


It might have already happened.

There's always the vegan argument that cows are terribly inefficient ecological disasters that turn valuable land into worthless pastures. If one accepts those arguments, then you could say cows are already a threat to humanity's survival as our food needs grow and farmland gets turned into useless wastelands.


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