Intelligence isn’t a given in evolution. It’s a very expensive adaptation in terms of resource use, cost of upbringing, and risk of failure, so while it occurs in many species across the animal kingdom, not all animals would benefit from it, so they just stay dumb.
Dumb animals are usually specialists – physically honed to precisely accomplish what they need to do to pass on their genes. There’s no need for a box cutter to have a computer chip inside it, any more than there is for an owl to ponder what it would be like to be a mouse. They only have one job, and there’s no reason to complicate it.
Other animals are sort of smart, but either restrict their mind to a very specific task or blow all credibility enjoying things they really should know better than to do. More on that later.
We like to believe farm animals are pretty dumb because it makes us feel better about the horrific torture we put them through for a happy meal, but research shows otherwise.
Pigs are smarter than dogs. Cows have besties and like to play fetch. Chickens are, ”Cunning, devious, and capable of envy”. Horses, on the other hand… well, they’re a bit of an exception.
Let’s take a closer look at the 10 dumbest animals on the planet.
Horses are considered to be one of the most intelligent animals on Earth, due to their ability to learn quickly and remember things.
But even humans can do that, and this information comes from horse people, whose grasp on reality is on par with people who talk about themselves to their cats in the third person.
Horses have long, thoughtful faces, and this has led to people assuming they’re contemplative, but in reality, they’re high maintenance, prissy, and terrified of everything.
Panic is a good indicator of intelligence, and horses love to panic.
The door swings open on a portable toilet? Panic. A butterfly is getting too close? Panic. The sound of velcro? Panic. A sweet wrapper, blowing in the wind? Well, you get the idea.
In their defence, they have a wide range of variability between individuals, and some of them can count to three. They’re also quite good at reading cues from stupid people, and this has led to such impressions that they’re smarter than they are, see: Clever Hans.
So, horses don’t rank very high on the stupidity list, but they do have to get a mention. 1
9. Afghan Hounds
Thousands of years of inbreeding have carved out some peculiar domestic animals.
Dogs are among them and are one of humanity’s best accomplishments, as a whole, and that can be mostly accredited to the genetic flexibility and overall brilliance of the grey wolf, rather than the people breeding them to fit into handbags.
But even they have their embarrassing experimental failures: Afghan hounds are the only animal dumber than the rugs you can make out of them.
They complain entirely too much, they have poor working memory and they’re notoriously difficult to train. Without beating around the bush, this is because they’re very stupid.
But to be fairer to them, they’re not failures as animals, only as pets. They were bred for speed and to hunt, not to jump through hoops under gazebos full of pompous, third-person talkers.
And they’re very good at that.
The thing is, the job of running really, really fast doesn’t require any smarts at all, which is quite lucky for the Afghan hound since that’s exactly how much it’s got. 2
Another job that doesn’t take a lot of thought is munching on eucalyptus. That’s already a pretty dumb thing to do; Eucalyptus leaves have almost nothing of nutritional value in them and will even screw up the soil around the tree for most other plants.
Koalas are dumb enough to pick this as their go-to strategy, and this is hardly surprising because they have one of the smallest brain-to-body ratios of any mammal, with a brain that makes up only 0.2% of the animal’s mass.
This is roughly the same brain power as a bowling ball, and with a smoothness to match.
Koalas can’t afford expensive, clever brains because their diet is so bad, but they do have some of the biggest guts relative to body mass of any mammal. This helps them scrape the barrel when it comes to nutrients, but it doesn’t stop them from being so dumb they pull each other out of the tree when trying to mate. 3
7. Orange Cats
If you’ve ever heard a neighbour’s cat yowling from the top of the stairs at night for no apparent reason, chances are it was orange. While cats on the whole are far smarter than they want us to find out, the same can’t be said for the orange mutated variety.
Legend has it that orange cats are all male, and have to take turns sharing a brain cell, but this is only partly true: 20% of them are female.
Intelligence actually varies quite a lot in cats, and a lot of the low end of that variance appears to be condensed into the orange cats. There seems to be a correlation between orange fur and disabilities, and for some reason, they appear to be more talkative, so they have formed a community of vocal runts.
But on the other hand, they score highly in friendliness and trainability, which makes them quite endearing, while no other branch of cats is dumb enough to listen to human instructions. 4
Like the koala, crocodiles live a life that doesn’t require any philosophical reflection. Their unexamined life is very much worth living, as it perpetuates a reptilian lineage that precedes the dinosaurs.
Crocodilians are immensely successful animals, and they’ve gotten to where they are without much thought at all. Yet, this is another case of being dumb in some ways and smart in others.
A croc can sit still in the mud for days on end without doing much other than breathing, and having a mind that needs constant stimulation (and calories) to stay sharp would make this impossible.
The crocodile metabolism is so low they can get by on just one or two breaths per minute, and the energy requirements of a smart brain would ruin that entirely.
But this isn’t to say they’re entirely dumb – they have been known to hunt collaboratively and set traps, which suggests some level of cunning. Still, whether they do this as a result of smarts, or simply instinct, is something we’re not clever enough to have figured out yet. 5
5. Orb Weavers
You might not think of spiders as being intelligent, but there’s a lot of ground-breaking research of late that would prove you wrong. Along with many other arthropod species being studied, spiders are emerging as a surprising site of substantial brain power in the critter phylum.
That is, except for orb weavers.
Orb weaver spiders are members of the Araneidae family, which you might recognise from your common garden spider. They’re responsible for some of the most intricate architectural masterpieces in the animal kingdom, and they do it all on autopilot.
The geometric perfection of the orb weavers’ webs belies a ruthless stupidity, reflecting an entirely passive approach to life.
After mating, the female will eat the male, after which she will lay a bath of up to 2,500 eggs.
Hatchlings will immediately turn on one another, reducing their number significantly. In species where the mother is present, they’ll turn on her, too, and if she’s not around, her sisters might volunteer for the honour of becoming baby food.
Once fed, the little ones won’t explore or venture very far at all, they’ll just make a web wherever they find themselves and hope not to be eaten. At least, until it’s time to mate again.
This life is so basic that it requires little-to-no mindfulness at all, and as such these might be the dumbest spiders in the world. 6
When it comes to dumb ways to mate, the anglerfish might have it down. Male anglerfish are essentially giant sperm vessels, swimming around full of smaller spermatozoa, looking to latch onto a female in a final kamikaze shag. The male is essentially a malformed pair of testicles with a tail.
On finding a suitable mate – and this female might be 500,000 times heavier than he is – the male makes a beeline and attaches like a poison dart to her body. There, he’ll gradually dissolve until it’s just his testicles that remain, and in the process, his reproductive cells enter her and they both hope for the best.
A female angler fish can often be seen swimming around with up to eight of these tiny idiots buried into her skin, slowly decomposing.
In order for her body to not reject the suicidal male assimilating with her, she has to shed her immune system. Nobody knows how they survive without one, but they appear to do okay. 7
3. Bony-eared Assfish
This is the kind of creature an animal blog writer might invent when struggling to meet the word count for a post, but it is in fact a very real and very stupid fish.
We don’t know exactly how well this fish responds to riddles, but we do know that it has one of, if not the, smallest brain-to-body-weight ratios of any vertebrate.
One soft and flabby little 40g fish had a brain that weighed only 30 mg. That’s a worse ratio than the koala, by far.
Research suggests that it dedicates what little brainpower it has to sensory perception, living, as it does, in the dark depths of the ocean.
A lack of food and the immense pressure of the ocean make large brains prohibitively expensive for animals like the ass fish. 8
If we were doing this list by species, it would be mostly owls.
Inside the skull of an owl sit two elongated, fleshy organs, but these contain only around five types of neurons and are, in fact, eyes. These are some of the most exceptional night-vision organs in the bird world; so much so, that the animal has sacrificed a lot of brain space for them.
These eyes make the owl a precision killing machine; an incredible silent assassin with a kill rate of up to 85%. They also make them as thick as a bag of oatmeal, and despite being considered wise by humans, they are likely the slowest birds in their class.
Owls get double dumb marks for looking smart when they’re not, which brings us to our final species, and likely the dumbest animal on the planet: 9
1. Homo sapiens
It’s often said that humans are the most intelligent animals, but even if you look very closely, you’d never find that statement coming from any other species. Humans have neither the most complex language nor the largest brain, nor even the lowest ratio of brain to body mass (that medal goes to the Brachymyrmex ant at 12% of its body mass).
Humans are so dumb they think horses are smart. They also feel compelled to rank other species by intelligence to make themselves feel superior.
What they do have is fingers, and that goes a long way. Humans can manipulate the world around them for an entire lifetime and then pass on those lessons in a single book or fairy tale.
But there’s no reason to assume the raw intelligence of humans is any better than that of other smart animals like sperm whales, octopuses, or gorillas. All the tests that we set for these animals use our own unique perspective as a reference point, so are inherently biased.
On the contrary, there is a lot of evidence against human intelligence: Monotheism, climate change, and Black Friday stampedes, to name just a few examples. Humans like to announce their smarts while destroying the very environment they depend on due to a lack of control over the most basic animalistic functions.
Like a toddler being handed a gun, our brains are not fast enough to use our fingers responsibly.
The global devastation caused by unrelenting human consumption is the environmental equivalent of shitting in the bath, and not since the end of the Permian has one species been this stupid.
Humans have a very narrow scope of intelligence. It’s what allows them to come back from the rocket surgery lab and order a meal that needs to be grown on deforested land, essentially cutting off their own air supply.
These are animals that have the keys to the nuclear launch codes and are still afraid of moths.
Having arguably the closest thing to omnipotence over all the global ecosystems of any living creature in the history of life on Earth, and then squandering it for cheap Christmas decorations, steamed haddock and war, might be the dumbest thing that ever happened.
For this reason, humans have to take the number one spot on this list. Sorry folks! 10
This list isn’t to be taken too seriously. For one thing, it was written by the dumbest animal on this list.
But further, intelligence in animals (including humans) is impossible to quantify. And that’s because it’s not a single thing. Emotional intelligence doesn’t correlate with special awareness, which doesn’t correlate with the ability to use language, tools, or TikTok.
Many, many facets make up what we consider ‘intelligence’ and different animals have different ratios of these. Of course, they also have different amounts.
And it’s worth repeating that intelligence isn’t some aspiration of evolution; becoming smart is only smart if the benefits outweigh the costs. Having an enormous, expensive brain and not getting any benefit from it is, well, pretty dumb.
The point is, that being dumb is sometimes the smart choice, and we shouldn’t consider it a flaw at the species level. At the individual level, however, go nuts.
Fact Sources & References
- Sarah Paull (2013) “24 weird things our horses are scared of“, SmartPak.
- David Hepburn (2022) “Here are the 10 most stupid breeds of adorable but dumb dog“, The Scotsman.
- “Koala (Phascolarctos cinereus)“, Comparative Brain Anatomy.
- Dannie Aildasani (2021), “Reddit thread about Jorts, the dumb orange cat, goes viral“, SCMP.
- George Sranko (2023), “How Smart Are Crocs?“, Animals FYI.
- “Watch Baby Spiders Eat Their Mothers Alive“, National Geographic.
- David B. Clear (2020), “The Horrific Mating Habits of the Anglerfish“, Medium.
- M. L. Fine, M. H. Horn and Brian Cox (1987), “Acanthonus armatus, a deep-sea teleost fish with a minute brain and large ears“, Proc. R. Soc. Lond.
- “Are Owls Smart?“, Birdfact.
- Martin McGuigan (2022), “Which animal has the largest brain relative to its body size?“, Live Science.