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Cats Cannot Taste Sweets (2007) (scientificamerican.com)
181 points by JumpCrisscross on Nov 14, 2019 | hide | past | favorite | 156 comments



> "This may be why cats are getting diabetes," Brand offers. "Cat food today has around 20 percent carbohydrates. The cats are not used to that, they can't handle it."

It's worse than that, usually 35-50% carbohydrates. The good (expensive) dry stuff is usually 10-20%. Wet food is often lower, depending on the type, as low as 7% as-fed with pates.

The weight-control labelled food is terrible both for weight and diabetes risk. It trades protein for carbohydrates under the assumption that cats don't absorb the carbohydrates as easily because the cat's liver has to process them. But this means the liver processes them to body fat, and the lack of protein leaves the cat less satiated, so it eats more food.


Our vet did point out that cats eat carbohydrates; they tend to love the innards of their prey, and those often contain the undigested things mice etc eat. No idea what percentage of their diet that makes up though. (It wasn't a conversation about carb percentages in cat food)


That’s also an interesting point. People have an aversion to those innards, or “by-products,” being included in food, but our disgust isn’t rational, and cats don’t share it. Just because a cat food includes meat by-products doesn’t make it any worse than just muscle meat, and it can be cheaper because of that. Cats like the flavor and it’s good for them.


> innards, or “by-products,”

the tasty innards you're talking about and the “by-products” that are in the industrial cat food are 2 very different things. The “by-products” is hide, horns, hooves, etc. with very heavy dose of strong preservatives, desinfectants and other chemicals.


I found this out when asking myself the question "are animals fooled by artificial sweeteners". The rabbit hole that that led into is not only do we not know the answer to that question, many animals don't even taste "sweetness" (or if they taste it they don't like it or don't prefer it). Not even all primates, if I recall correctly.

And we've seen drift -- apparently we used to be able to bait cockroaches with sweet bait (through the middle of the century), but they have adapted to it and it no longer works as bait.

Taste and smell are very strange and defy attempts at reductionism; our brains are basically very evolved olfactory organs. Dealing with smells was so hard that brains evolved to deal with the problem, and then it was just evolution asking the question "what else can we do with this giant block of computational power -- what about ... memory? vision? hearing?"


> Dealing with smells was so hard that brains evolved to deal with the problem, and then it was just evolution asking the question "what else can we do with this giant block of computational power -- what about ... memory? vision? hearing?"

Hmm, interesting. If I remember correctly, Stephen Jay Gould argued something similar about the human brain, except it wasn't about smell, it was about walking upright. He argued -- or quoted people who argued this -- that it's likely human intelligence arose as a side-effect from the brain structures needed for an upright stance.

Quoting from Wikipedia [1]:

"Gould was a champion of biological constraints, internal limitations upon developmental pathways, as well as other non-selectionist forces in evolution. Rather than direct adaptations, he considered many higher functions of the human brain to be the unintended side consequence of natural selection."

[1] https://en.wikipedia.org/wiki/Stephen_Jay_Gould


> He argued -- or quoted people who argued this -- that it's likely human intelligence arose as a side-effect from the brain structures needed for an upright stance.

As stated this doesn't pass the smell test because a long list of animals are able to "stand" and walk upright (cats, primates, bears, what have you...) if they so chose. Not to mention kangaroos, birds (who are also capable of things like flight with generally much smaller brains), etc.

On top of that we have taught neural nets to control a humanoid body doing plenty of things, even parkour, but we didn't manage to teach them human levels of intelligence yet. Even non-neural-network solutions do pretty well here with just old-school algorithms.

Walking upright really seems like something you don't need "much of a brain" for. You don't even need to teach a monkey to do it.


You raise some good points, for which I don't have the answer. However:

> Walking upright really seems like something you don't need "much of a brain" for. You don't even need to teach a monkey to do it.

You do need much of a brain for it -- not intelligence, but brain; Gould argued that "intelligence" and higher brain functions arose as a side-effect. Keep in mind that AI researchers found out "the easy things are hard and the hard things are easy" (i.e. locomotion and fine-grained motor skills are harder than they seem, while logic games, chess and go are easier than they seem).

From Wikipedia (https://en.wikipedia.org/wiki/Moravec%27s_paradox):

"Moravec's paradox is the observation by artificial intelligence and robotics researchers that, contrary to traditional assumptions, high-level reasoning requires very little computation, but low-level sensorimotor skills require enormous computational resources."

> As stated this doesn't pass the smell test because a long list of animals are able to "stand" and walk upright (cats, primates, bears, what have you...)

None of those walk upright as their primary means of locomotion, nor are they capable of walking exactly like humans do.

> Not to mention kangaroos, birds (who are also capable of things like flight with generally much smaller brains), etc.

Good point. I don't have an answer for this. Guess you'll have to read some Stephen Jay Gould. I recommend his writing, which is fascinating :)


I was just trying to make the point that as stated I wouldn't buy it. I'm sure who you paraphrased gave it some more in-depth thought though.

For instance if you were to tell me that walking upright opened up possibilities, such as creating and using advanced tools, which required larger brains, then I'd definitely be on board with that possibility.

I just choose to interpret that sentence literally and narrowly to make a point about it specifically, not about Gould's theory as a whole (which I haven't read).


> For instance if you were to tell me that walking upright opened up possibilities, such as creating and using advanced tools, which required larger brains

I can't quote him exactly because I don't have the book nearby, but Gould argued that higher brain functions (intelligence) were a byproduct of the brain development required for walking upright, no tools or opened possibilities. It's not that walking upright enabled the development of tools and this in turn helped develop intelligence; it's that the brain structure necessary for bipedal walking had the potential to be used for other things, they had "emergent properties". I think he argued the same about the body shape itself, the shape of hips, legs and arms all "enabled" the emergence of human-like intelligence.

Stephen Jay Gould was a pretty well-known scientist (who sadly passed away in 2002) and, regardless of what you think of my possibly misleading summary, I urge to read his books if you have any interest at all in evolutionary science and biology.


>many animals don't even taste "sweetness" (or if they taste it they don't like it or don't prefer it). Not even all primates, if I recall correctly.

The article said cats are the only mammals that can't taste sweet.


A quick search suggests that's not true.

>Our feline friends carry broken versions of the genes that build sugar detectors on the tongue. As such, they’re completely oblivious to the taste of sweet things. So are Asian otters. And spotted hyenas. Sea lions and dolphins too.

https://www.nationalgeographic.com/science/phenomena/2012/03...


Guess we are getting some https://www.epsilontheory.com/gell-mann-amnesia/ in one of the articles. I suspect you are right.


> Dealing with smells was so hard that brains evolved to deal with the problem,

That's fascinating, where can I read about it?



Kind of like the current ML boom. We evolved faster and faster GPUs for gaming and now are trying to use them for other things.


Without the consumer market (read: games), CPUs probably would have evolved slower, too.


I wonder if the cockroach thing is evolution/selection in action... The cockroaches that preferred sweet all fell for the bait got killed. I believe high protein diets cause roaches to make, so those that weren't drawn to sweets lived and were more likely to reproduce. Maybe it's not that they adapted or their tastes changed, just that certain ones survived with given traits.


Yes, it was an evolutionary drift. Cockroaches do not live enough for any other interpretation of the GP's comment to make sense.


Whoa. Smell was more important than sight for brain evolution? Is there somewhere I can read more about this?


There are lots of blind animals that can smell. I don't know of any sighted animals that can't smell.


some humans have a mutation that means they don't smell


There are animals whose signalling mechanisms are very nearly fully scent/chemical based, ants particularly.

Lower order than mammals, admittedly.


Sight is pretty confined dimensionally. R,G,Bx100x100 + focal plane gets you basically all the resolution you need.

We can’t even model smells.


Some of the stuff I've seen our cat eating, it's both obvious and a blessing that he doesn't have much of a sense of taste.

Goes nuts for the plastic wrappers you get around Pepsi cans and won't stop licking them. Little weirdo.


I have a cat who loves to lick crinkly plastic wrappers and bags. I use shopping bags for my bedroom trash can and I'll wake up to him just sitting there licking the folded over edge for upwards of 10 minutes.

Two theories I've heard are that beef tallow is sometimes used in the manufacture of such bags so they might be smelling that. Or it could be as simple as they enjoy the sensation and/or sound of licking the bag. Though, they certainly are weirdos.


Huh, one of our cats does the same. We don't want her to choke on plastic, so we no longer leave any plastic bags out in the open. She also tries to lick olive oil and butter, so the beef tallow theory would follow the same pattern of looking for fat.


Try her on taffeta.


I remember reading that it's the chemical used as a softener for plastic products, at least for cables, wouldn't be surprised if the same stuff is used with other plastic products.


Cats can be motivated by texture, so that may be part of it.


That's my theory. Every cat I've had had some level of addiction to licking/chomping plastic. All kinds of plastic, so I don't buy the made-with-tallow theory. Grocery bags, cling wrap, rubber bands, 6-pack rings. One of the current ones likes to chew holes in the plastic shower curtains. Little freak. :-)


This is great. I have a partner whose cat loves chewing plastic, rubber bands and hair elastics, foam... we always thought it weird but I haven't heard of others with this experience til today. So now I wonder if his other peculiarities are common.

The cat is very attached to my partner, and won't let anybody else touch him (always ready with tooth and claw). Not quite as possessive as a parrot, but he's a bit of a terror. He gets especially violent when he's hungry -- you're allowed to walk past his bowl once, but if you don't return with food, watch out.


Ah beef tallow, hadn’t thought of that. Good suggestion.

The best theory I had was that he was getting a buzz from solvent in the ink or the plastic itself.

Or that he was just odd.


From memory, I think the tallow is used to lubricate the rollers in bag making machines. Though if that were the case I'd expect dogs to do the same. Those dummies will eat anything.


Cats' taste (in the strict sense) sense isn't great but isn't awful by mammal standards. What's notable, as pointed out in the article, is that the specific receptor for sugars is broken. Their ancestor lost it due to a mutation, and because the species was a strict carnivore it wasn't selected against.

But the "taste" you're talking about is the one we tend to use in general language, and it's a complicated mix of touch/texture/temperature sense in the mouth and tongue, taste bud chemical reception, and more than anything else smell, which "fills in the chemical blanks" that the coarse taste senses miss.

Cats miss one but have the others in spades. When they lick and eat random junk, it's for a very good sensory reason. Still weirdos, obviously, but ones with a good excuse.


One thing I've noticed with cats in general is they seem to have a thing for human earwax. I'm not the only one to have noticed this: https://www.gwern.net/Questions#cats-earwax


Interesting. On the rare occasion that I use a q-tip I've noticed my kitten would aggressively fish them out of the trash and chew on them.

I always figured that they were just fun to bat around. This explains a lot.


I hear ya! Mine is obsessed with eating cobwebs.


My dog used to love eating bees. Then her little muzzle would get all swollen. Silly gal :)


A friend’s dog used to catch the bee in his mouth, carefully turn it round and bite the stinger off.


That’s pretty wild. Do you remember what breed?


Spicy flies


I had a cat that went nuts for spaghetti. He'd jump up on the counter and slurp the noodles. Same cat also loved cucumbers.

My mom's cat prefers to drink water from a glass like a human. Either that, or from the toilet (to which he can open the door).


One of our cats loves to lick the adhesive side of packing tape.


Knowing this, when my cats desire something sweet that I was eating, I have always assumed they wanted something else they tasted in the food -- if ice cream, then the cream, etc.


I realize that raisins are not safe for cats and did not feed them to my cat deliberately.

That said, I had a cat that was absolutely obsessed with eating raisins to the point where we simply couldn’t have them around. To this day I cannot understand what was going on if sweetness was not a factor.

Same cat ate the tops off an entire box of glazed donuts once as well while we were out.


Perhaps it was pica, or something like it?

The second paragraph here is about pica in cats:

https://en.wikipedia.org/wiki/Animal_psychopathology#Pica

and a brief web search for alternative sources finds

https://www.cathealth.com/behavior/how-and-why/2231-pica-in-...


Interesting.


Mine gained the nickname "Cupcake" (alongside his variety of other nicknames) when he licked the frosting off a cinnamon-spice cupcake that was out on the counter for a party we were hosting once.

He also licked the powdered sugar off half a box of linzer cookies another time.

The frosting, I can definitely see being for the fat...the powdered sugar, I'm baffled by.


I had a cat who loved bread. Would climb on top of the refrigerator, tear open the bag, go to town. I would occasionally demonstrate by dropping a bit of meat and a bit of bread on the ground, cat would go for the bread.

His most glorious moment (in his own head, as I imagine it) involved leaping from a loft bed onto a coffee table, grabbing an empty cupcake wrapper (still covered in cupcake crumbs) and swallowing it whole before anyone recovered enough from their shock to stop him. He just sat there afterwards licking his lips with the most satisfied kitty look on his kitty face.


That's pretty glorious by cat standards. Total score. Smooth.

We had one that loved good, sticky bud.

One day, back in the 90's when good pot was hard to get, my brother in law set a big, dank bud on the coffee table. And he was all about having a smoke and good meal too.

Kitty perked right up! She could totally smell it, and from there?

Game on!

So, she jumped up on the table, snatched it and ran!

For the next 20 minutes we all watched this hilarious "get that cat" game happen. Brother in law went after the cat. Room to room. It escalated into closed doors and the cat still escaped him!

At one point, we heard crashing, yelling, and when the door opened, he started to apologize only to have the cat squeak through the cracked door and run out the little outside cat door with that bud.

He found it later, drool and hair covered after the cat had thoroughly mauled it, much like catnip.

Yeah, he smoked on it anyway. We all said, "pass."

The cat had an awesome time. Like, "this is what I DO!"

He was total mess. Loved that cat, but never brought bud anywhere near her again.

Yeah, that look. She had it, mixed with tail up, fur slightly puffed, eyes alight excitement. Total, "YES!" moment for the cat.


My cat will lick the inside of mugs that contained black coffee - I know caffeine isn't good for cats so I don't encourage this behaviour but he definitely seems to enjoy the taste (I don't take sugar so its not sweetness he is after).


To me, dried coffee residue from black coffee smells absolutely delicious, sweet, almost pastry-like.


Well, I can confirm that it tastes quite nice as well - thought fortunately I am working at home today so nobody saw me conduct that particular experiment!


Interesting! Now I have to try this.


Be warned that my patent for dried coffee licking powder is now in the works! Prior art be damned.

;-)


Noted, lol


Many of the things that we eat that have “sweet” as part of the flavor profile also have fats as part of ingredients - those are things that cats do taste and recognize.

When one looks at cat treats, the fat component is higher than non-treat cat food.


There's no fat in the jam or preserves that my cat likes.


I strongly suspect that many cats develop an enjoyment of certain textures. Mine is completely uninterested in most greens, but delights in chewing on broccoli.


I had a cat who loved gnawing on grape stems. Not grapes. Just the stems.


One of my (5) cats loves papaya. He finds every other fruit offensive as much as his brothers, but goes crazy over papaya (and I think he kinda likes cantaloupe).


Mine loves cantaloupe. I’m curious which part of that she likes other than the sweetness.


This is probably the first time I've seen someone else say this online.

The cat I grew up with (lived 21 years) loved cantaloupe as well. It would smell it from far away and come trotting into the kitchen. Seemed to be able to eat as much of the fruit as we were willing to chop for it.


Me three.


Our best guess? Melons smell like meat to the felid mind:

https://feline-nutrition.org/the-blogs/cats-and-cantaloupe-a...


I also had a cat that went absolutely bananas for (especially ripe) cantaloupe. She could smell it across the house, would aggressively beg for it, and would purr the whole time she was eating it.


Exactly; its interesting to think about. One of my cats LOVES melty chocolate chips from freshly baked cookies.

When I read the article, I wondered what they could like in marshmallows, but looking it up I bet its this: https://en.wikipedia.org/wiki/Marshmallow#Protein


FYI, Like dogs or birds, cats should not be given Chocolate, as it is toxic to them:

https://www.purina.co.uk/cats/health-and-nutrition/what-not-...


TY, I've never heard this about cats. My one cat will get the remnants of a bowl of chocolate ice cream when I occasionally have one; I guess I should stop doing this!

I've heard this a lot about dogs, and I know it is stated by reputable sources, but the Vet we had growing up told us that this is a myth, and it depended upon the dog; he used to give his dog a pound of fudge every year for christmas, and it had no ill effects except for being somewhat hyper afterwards. I still wonder about his judgment; it doesn't seem like the thing a veterinarian should be telling people. But anyway I wont give chocolate to dogs.

We don't really give her (the cat who likes the melty chocolate chips) much, but she might sneak a lick here or there. I'll be more careful now. Thanks again!


Mine too. But what he really likes is papaya.


...and mine likes cucumber. Go figure.


One of ours loves golden syrup - isn't that basically just sugar?


Fun fact: the sodium lauryl sulfate in toothpaste dulls the sweetness receptors on your tongue. The taste of orange juice after brushing your teeth is what it would ALWAYS taste like to cats.


This is interesting. I've never experienced the absolute aversion that other people seem to have to drinking when Orange Juice after brushing my teeth (though I'll admit that I won't willingly combine mint and citrus.)

But I also specifically use toothpaste that doesn't has sodium lauryl sulfate because it aggravates canker sores in my mouth. I wonder if this is why.


You might have a sulfite allergy that’s triggering an immune response. Do you have any other skin conditions triggered by consuming food or drink preserved with sulphites or sulfides, e.g. red wine, dried fruits?


Nope, not at all. My skin has always been clear my whole life, and I often consume dried fruits (raisins are currently my favorite evening snack,) as well as many other commonly 'triggering' things (red wine among them, tea, alcohol and soda spring to mind, though I've cut back immensely on the last two)

That being said, you still might be right, since the science behind canker sores is a crapshoot to begin with, as I've learned

Personally, what works for me is: If I bite my lip, or feel a sore coming on in general, I immediately have to wash it out. After that, the only way to prevent a full week+ long sore is to put alum (pickling spice) on it for 90 seconds or so, once or twice a day. And of course, I need to make sure I meticulously brush and floss after every meal (of course with toothpaste without laurel sodium sulfate) Usually I can suffice for the normal once or twice a day

And that being said, this isn't exactly scientific. This is 100% just correlation and gathering personal anecdotal data. If I happen to stumble across something better, I'll take it. But all things considered, it's not a particularly bad thing to suddenly feel the need to take extra care of my mouth once a month or so


I've always been suspicious of that. Why is it specifically OJ that tastes awful, and not other juices, or chocolate, or bread?


You don't even need toothpaste. Taste is also a state of mind thing.

Bet a friend/family member that they can’t taste the difference between whole/2%/1%/skim milk, or some combination thereof. Blindfold them and have them begin tasting the milks. Now, replace the last milk with orange juice. The brain prepares the body for milk, and the unexpected acidity usually causes a gag reflex, and sometimes vomiting. Keep a bucket handy:

https://www.youtube.com/watch?v=FlhfIN_qbEk


I stopped drinking OJ as a teen after a decent run (4mi) and coming back super thirsty and drinking OJ just caused my mouth to keep salivating continuously (painfully) for minutes.

I vowed that day to stop drinking OJ and stick to water.


Bread isn't particularly sweet compared to other foods. Orange juice has a strange and very strong flavor compared to other juices and has a significant bitter component to its taste due to crushing the peels.

Never tried chocolate after brushing my teeth but I don't find 99% / unsweetened dark chocolate particularly offensive.


Hmmm good point maybe it's the bitterness profile of the peel


It's not. Many things taste awful, including other kinds of juices.


Wild guess: the acid amplifies whatever effect in some way.


So I thought so, but I've tried grapefruit juice, and I don't get the effect. And I can clearly taste sugar after toothpaste


> The taste of orange juice after brushing your teeth

I'm always wondering how so many people know of this first-hand.

Why are you drinking OJ, something extremely high in sugar, so soon after brushing your teeth?


Lots of people drink fresh OJ as part of breakfast.


.. Which I would expect people to eat before brushing, not after.


I grew up thinking that this was correct. "Just got my teeth dirty, time to clean them."

At some point, I heard that the opposite was true, ostensibly from a dentist on reddit. According to this anonymous stranger, after eating, your enamel is at its weakest, and you'll do the most damage to your teeth by brushing them. The reason was something about saliva and/or plaque that's been recently fed, I think.

(As a side note, some other dentist(?) in the same thread said that if you're going to brush your teeth once a day, it's most important to brush before going to bed.)


My wife hates her unfresh breath so much that she won't eat before brushing.

I don't really get it since my mouth tastes like mint for 30 minutes after brushing, which makes food taste gross.


Does she not brush at night before bed?

That's the best time to brush. Otherwise, all the bacteria and the like in your mouth have all night to fester.


Most (?) of people brush before bed and after they wake up (before breakfast).

I also brush after breakfast, but this is kinda of common knowledge so I'm surprised you don't seem to know it.


My morning routine has always been to get up and use the bathroom, brush my teeth and then go about the rest of my day. If I eat breakfast at all, it's likely to be either after I've already left the house or the last thing I do before I leave. I've read somewhere (not sure how true it actually is) that you're not supposed to brush for half an hour after eating, so there's basically no point in time where I could brush after eating breakfast.


It depends on the morning routine.

When I'm in a hurry I just get all done in the bathroom, including brushing teeth, and grab a quick breakfast on my way out, which usually involves half a glass orange juice.

Those are the situations where the toothpaste aftertaste can sometimes collide with orange juice, making it super bitter.


I does not even have to be OJ. Think morning coffee with sugar, right after brushing. It tastes like crap.


does it not just taste like morning coffee without sugar?


This is the first time I’ve heard about this phenomenon.


Are you sure it only dulls the sweet receptors? Coffee (with no sugar or milk) tastes sweet when I brush my teeth. I always thought it was the sour and the sweet getting confused rather than the sweet going bye-bye.


This leaves me with more questions as I have a cat that absolutely will not leave you alone if you're holding ANY fruit. She will cry and whine and do all she can to get to that fruit. Apple, plum, orange, grapefruit, pineapple, melons, it doesn't matter. She goes especially nuts for dragonfruit.


Cats are weird. My cats will gag if you hold fruit near their nose. Same goes with most people-food. They are interested in meat though.

When I was younger, we had a cat would get into literally any food available. Fruit, cheese, Doritos, salad.

Though, people are weird, too.


My cat went bananas for the smell of strawberries. No interest in eating them but adored the smell.


Citrus in particular is famous for cats disliking. Interesting that your cat enjoys those.


I had a cat that freaked out when he smelled oranges. I always thought he associated it with an orange scented shampoo we used once on him.


My old cat was obsessed with margaritas. It made zero sense.

One time I caught him licking a counter that I had just sprayed with a bitter lime deterrent.

Cats are weird.


I would not describe grapefruit or melons as “sweet” at all.


Grapefruit I can see, but what kinds of melons are there that aren't sweet? The most common melons I can think of (watermelon, cantaloupe, honeydew) are all quite sweet. Through googling I found some other melons that appear to mostly be from asia, although I've never seen them in person, and there descriptions mention sweetness as well. Do you have examples of savory melons?


My taste buds are different, all canteloupe tastes slightly rotten to me, even when other people swear up and down it's fresh, but it tastes like it's rotten to me. Other melons are fine for me. I am not a super taster so it's just an idiosyncracy.


Evolutionarily, this makes sense. All felids are obligate carnivores that rely on meat for nutrients—for example, they need taurine for vision, which they can't synthesize and is only found in meat. So there's an evolutionary advantage for cats to not want to eat anything else.


Doesn't stop my cat from eating my plants.


And then puking them up!


Eating plants and subsequent regurgitation is said to aid digestion "much as humans pop an antacid tablet".

https://www.hillspet.com.au/cat-care/behavior-appearance/why...


Spoken like someone who has never had a cat. Cat's do not only eat meat, anyone who's had one knows this, and it's apparently important for their health (see https://www.petmd.com/cat/wellness/evr_ct_eating_grass for example). Evolution is slightly more complicated than you understand.


I've been a cat dad for over a decade. Mine loves to chew on plastic, in particular :)


> there's an evolutionary advantage for cats to not want to eat anything else

Do we have evidence cats’ ancestors had such a receptor?

If not, it might be simpler to assume there wasn’t evolutionary pressure to not taste sweetness as much as there was a lack of any pressure to taste it.


Hyenas and mongooses are feliforms and can taste sweetness, as can all caniforms (I think). Presumably that means that the carnivoran ancestor could as well.

I'm not a biologist, but the lack of that gene is very conserved across all Felidae, I think (i.e. there isn't a single felid that can taste sweetness) which usually indicates that there's some evolutionary pressure.


What it indicates, rather, is that at the time of divergence from other Carnivora there was a lack of evolutionary pressure for conserving the taste of sweetness.

An example in primates is the loss of Vitamin C synthesis, which would have been a handy adaptation during the Age of Sail, but the gene was lost at a time when our common ancestor at a fruit-heavy diet.


The lack of genes for language, flight and laser eyes are also conserved across all cats, but I'm sure that those would be advantageous.


While I would love to meet a talking flying laser cat, all creatures have a fixed energy budget, and implementing any "feature" has an energy cost. So it could well be advantageous for creatures to not have a feature if they don't need it to survive in their EEA. Evolutionary pressure can make a feature go away or become vestigial if the energy requirement to support it is too great. This is how we get blind lizards in dark caves, for example. Or tailless humans (and other great apes).


I'm torn between upvote for funny and downvote for (probably) wrong. :)

The gene is present in all (most?) other mammals except cats. One can reasonably assume that there was some evolutionary pressure to it. A whole family/species most likely does not lose a gene without some major outside pressure. Either the population shrinks suddenly and is recovered from individuals missing the gene, or that gene is eliminated presumably for good reason. This is not evidence but it's the more likely explanation.

Of course laser eyes are great only for the first individual that evolves them. Then basically every other population tends to start dying off because you can't just not use them.


> Do we have evidence cats’ ancestors had such a receptor?

They say that all mammals studied so far, including ones close to cats, have the gene except cats... This seems to almost demonstrate that cats must have lost that gene at some point.


> All felids are obligate carnivores

I think you meant "felines".

[UPDATE] Nope, the OP meant felids (though my old eyes parsed it as "fields" (never heard of a "felid" before) which is why I thought it was spell checking or voice recognition gone wrong).



No, felid refers to a member of the felidae family.


“felid” comes from “Felidae”, the family for cats. It’s synonymous, but a bit more formal.


Etymologically, "felids" are "things descended from cats", while "felines" are "things that are like cats".


Like a tuxedo tshirt. It says I'm serious but like to party.


So then why doesn't this appear in any other mammal obligate carnivores?


Makes me wonder if this is just a result of genetic drift and/or bottlenecking. They clearly have no need for it, and are very specialized killers, but it being so widely present in mammals tells us that it's not really a costly gene to have.

I found the part about being able to register ATP interesting, as controlling for ATP is one of the most common techniques used to control the quality of hygiene in food production buildings and equipment. I don't know how this applies to nature where you would expect this to be found everywhere, but maybe it's valuable in deserts, snowy areas and similar? Or maybe higher than usual levels can be used to identify areas where rodents and other sources of food could be found?


For some reason, I had always assumed there were a number of mammals that didn't care much for sweets, even though in retrospect I know that ferrets, also carnivores, will obsess over sweet drinks.


In case it isn't known artificial sweetener specifically xylitol is toxic to cats (and dogs). So things like toothpaste which has artificial sweetener for humans is bad for cat. I'm sure there are some people with cats who brush their cats' teeth.


Perhaps because mustelids have an extraordinarily high metabolism for their size? https://nyti.ms/1Ur6S6C


As carnivores, I wouldn't expect them to have a use for tasting sweet things. The article doesn't address that point, but I think anyone who owns a ferret could tell you that they have a crazy metabolism!


There are a few related species to ferrets, like sables and pine martens, that are omnivores and will eat berries and whatnot.


If you're really interested in cat nutrition, comment history of alleged veterinary student https://www.reddit.com/user/Pguin15/ is gold. He posted a link for example that shows cats and dogs readily digest carbs, and that this is well known: https://en.wikivet.net/Digestibility_of_Carbohydrates

> Ground, cooked and extruded starches are almost 100% digestible in both dogs and cats, while digestibility of raw (uncooked) starches varies from 0-65% depending on the type of starch.



Cool to see this on HN. I briefly worked there on a closely related project during high school after this paper was published. It was my first real experience doing wet lab work-- learned a bunch, met cool people, was fun. (Also did a lot of pipetting and PCR.)


For some reason, our cat used to be absolutely crazy for anko. The first time he ever encountered it, he stole a dorayaki out of someone's hands and hid with it in the closet growling (it was wrapped in plastic so he couldn't actually eat it). After that, I used to give him a tiny taste any time I had some but I noticed he would always throw up soon after. Now that he's a bit older he seems to have no interest in it at all.

Could it be that they can taste sweets at a young age but gradually lose that ability?


I used to think my kitten was after the sweetness when i noticed that she only likes/prefers milk based sweets. But then she does have same affinity for chocolates and strawberries too.


Reminder: Chocolate can be lethal for cats...


About cats only eating meat: I have 3 cats, and all of them love any blades of grass, eating a full 'salad' every day.


Do you grow cat grass for them? Ours loves it. https://www.hillspet.com/cat-care/nutrition-feeding/cat-gras...


As obligate carnivores they don't only eat meat; they have to eat meat.


As I understand it cats eat grass in order to deal with hairballs in their stomach caused when they clean themselves.


There is a reason cats prefer meaty wet food to dry kibble, and disdain sugar entirely

This person has never met a cat. One of ours is obsessed with sweet foods like yoghurt, honey, pastries. Which we don’t generally let her have because of her teeth.


You're discounting several possibilities.

Yogurt has protein, and many varieties have a lot of fat. Pastries tend to be fatty (butter/lard). Honey's less obvious, but my cat would lick clean wooden spoons just for the texture; perhaps yours likes something about the stickiness?


My cat loves sweet things, regardless of the presence of fat. I need to make videos of this to post.


Strange. My buddies cat loves sweets. Especially pecan pie. I'm not sure if she's just trying to bond with him by eating the same food at the same time or she has a sweet tooth.


A friend of mine was born without the ability to taste sweet things. That doesn't stop their body from reacting to it, though. Most of their favorite foods are incredibly sugary.


{ plastic bags, various wires, a few DC adapter/chargers, the $10 soldering iron's AC cord, a used paper napkin that smelled like the sub sandwich it came with, crumpled up sheets of paper that are thrown and chased and batted around for some time, peanut butter, American cheese, tortilla chips (with or without Valentina and refried pinto beans and melted cheese), the spaghetti sauce or chili residue on the bowl, fluffy white rice, beef jerky (any flavor incl. peppered), roasted salted peanuts, dried fruits from trail mix, fresh voles }


What would happen if the cats eat miracle berries?


Yes, but this is only 8 out of 10 cats.


Large cats in zoos get treats like frozen blood ("bloodsicles").


Tell that to my cat, who fucking LOVES ice cream.


It’s the milk fat they love! My kitty also goes crazy for coconut oil, which helps with hair balls.


Yep. I recently tried this out with my cat: skim milk vs 2% vs whole milk vs heavy cream. No prizes for guessing what his preference ordering was. (He wouldn't even drink the skim! Just licked it, looked at me, and walked away.)


Yeah, and will give you that look too as he walks away...

My little chonk monster is actually pretty good with food, and isn't interested in human food much at all, possibly because he had to fend for himself for a few months before he imposed himself on me. He's certainly partial to the odd pigeon which are too slow/stupid to get away.

He currently has mostly dry kibble and water, but with the odd wet pouch for some variety.

I've tried him on a little milk before and he wasn't bothered, but I have semi-skimmed lacto-free, so I don't know if it offends his taste-buds or not.




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