Pharyngula

Cats, candy, and evolution

i-ccbc028bf567ec6e49f3b515a2c4c149-old_pharyngula.gif

Here’s a small taste of Roald Dahl’s Charlie and the Chocolate Factory, a sweet story about a poor boy and his visit to an amazing candy factory…you’ve probably heard of it, since the new movie is getting a lot of press.

Only once a year, on his birthday, did Charlie Bucket ever get to taste a bit of chocolate. The whole family saved up their money for that special occasion, and when the great day arrived, Charlie was always presented with one small chocolate bar to eat all by himself. And each time he received it, on those marvelous birthday mornings, he would place it carefully in a small wooden box that he owned, and treasure it as though it were a bar of solid gold; and for the next few days, he would allow himself only to look at it, but never to touch it. Then at last, when he could stand it no longer, he would peel back a tiny bit of the paper wrapping at one corner to expose a tiny bit of chocolate, and then he would take a tiny nibble—just enough to allow the lovely sweet taste to spread out slowly over his tongue. The next day, he would take another tiny nibble, and so on, and so on. And in this way, Charlie would make his ten-cent bar of birthday chocolate last him for more than a month.i-a420ae8c62e074dde7e2fce0652d306e-tinystop.gif

That’s how it is published, at any rate. What if it read something like this?

Only once a year, on his birthday, did Charlie Bucket ever get to taste a bit of chocolate. The whole family saved up their money for that special occasion, and when the great day arrived, Charlie was always presented with one small chocolate bar to eat all by himself. And each time he received it, on those marvelg ynfg, jura ur pbhyq fgnaq vg ab ybatri-a420ae8c62e074dde7e2fce0652d306e-tinystop.gif, ur jbhyq i-a420ae8c62e074dde7e2fce0652d306e-tinystop.gifrry onpx n gval ovg bs gur cncre jenccvat ng bar pbeare gb rkcbfr n gval ovg bs pubpbyngr, naq gura ur jbhyq gnxr n gval avooyr-whfg rabhtu gb nyybj gur ybiryl fjrrg gnfgr gb fcernq bhg fybjyl bire uvf gbathr. Gi-a420ae8c62e074dde7e2fce0652d306e-tinystop.gifr arkg qnl, ur i-a420ae8c62e074dde7e2fce0652d306e-tinystop.gifbhyq gnxr nabgure gval avooyr, naq fb ba, naq fb ba. Naq va guvf jnl, Puneyvr ji-a420ae8c62e074dde7e2fce0652d306e-tinystop.gifhyq znxr uvf gra-prag one bs oveguqnl pubpbyngr ynfg uvz sbe zber guna n zbagu.

All sense of the story is lost, isn’t it? That’s just a garbled mess. You’d probably return it to the bookstore with loud complaints.

Here’s something similar. This is the amino acid sequence for a human gene called TAS1R2; it may look like a garbled mess, too, but this sequence actually codes for an important and functional protein that you enjoy every day.

  1 mgpraktics lffllwvlae paensdfylp gdyllgglfs lhanmkgivh lnflqvpmck
 61 eyevkvigyn lmqamrfave einndssllp gvllgyeivd vcyisnnvqp vlyflahedn
121 llpiqedysn yisrvvavig pdnsesvmtv anflslfllp qitysaisde lrdkvrfpal
181 lrttpsadhh veamvqlmlh frwnwiivlv ssdtygrdng qllgervarr diciafqetl
241 ptlqpnqnmt seerqrlvti vdklqqstar vvvvfspdlt lyhffnevlr qnftgavwia
301 seswaidpvl hnltelghlg tflgitiqsv pipgfsefre wgpqagpppl srtsqsytcn
361 qecdnclnat lsfntilrls gervvysvys avyavahalh sllgcdkstc tkrvvypwql
421 leeiwkvnft lldhqiffdp qgdvalhlei vqwqwdrsqn pfqsvasyyp lqrqlkniqd
481 iswhtvnnti pmsmcskrcq sgqkkkpvgi hvccfecidc lpgtflnhte deyecqacpn
541 newsyqsets cfkrqlvfle wheaptiava llaalgflst lailvifwrh fqtpivrsag
601 gpmcflmltl llvaymvvpv yvgppkvstc lcrqalfplc fticisciav rsfqivcafk
661 masrfprays ywvryqgpyv smafitvlkm vivvigmlat glspttrtdp ddpkitivsc
721 npnyrnsllf ntsldlllsv vgfsfaymgk elptnyneak fitlsmtfyf tssvslctfm
781 saysgvlvti vdllvtvlnl laislgyfgp kcymilfype rntpayfnsm iqgytmrrd

TAS1R2 is short for “Taste receptor 1, member 2”. It’s part of what is called a G protein-coupled receptor, which is a protein that binds to some substance on the outside of a cell, and transforms that binding into activation of other proteins inside the cell, which then cause changes in the membrane properties of the cell that lead to an electrical signal being generated. What this protein does is detect sugar, and then instruct your taste buds to start sending nerve impulses up to your brain. When Charlie let that “lovely sweet taste to spread out slowly over his tongue”, what he was experiencing was the activation of TAS1R2.

Cats don’t get to experience that. If you’re a cat owner, you may have noticed the general indifference cats have towards sweet things; it turns out that their TAS1R2 gene carries a substantial mutation that destroys its function, precisely analogous to my mangled version of the passage from Charlie and the Chocolate Factory above. There is a small deletion near the beginning of the sequence that chops out 247 base pairs. This deletion puts the remainder of the sequence out of register (this is called a frame-shift), turning it into non-functional nonsense, and also generating multiple stop sequences scattered throughout. The cat’s TAS1R2 has been reduced to a useless pseudogene.

Here’s a diagram detailing the differences between cat and human TAS1R2. The key things to note is that there are 6 solid black bars which represent the exons or protein coding regions of the gene, and that the cat has a chunk cut out of the third exon; and the red asterisks, which indicate the position of new stop codons sprinkled into exons 4 and 6. That is one dead gene.

i-40038dd4461ceefde9db05fd04809bb9-cat_tas1r2_struc.gif
Gene Structures of Cat Tas1r2, Human TAS1R2. The exons are shown in black (size in bp of each exon is in parentheses). The locations referred to in the vertical explanation text above the asterisks and the spade symbol indicate the position in bp within each exon. Intron sizes shown in the figure are not proportionally scaled because of the large size of Tas1r2 introns. Under each human exon is the percent similarity between each human exon and its cat counterpart at the nucleotide level. The exons for cat Tas1r2 refer to parts corresponding to human exons. The spade symbol (♠) indicates the position of microdeletion in exon 3 of cat Tas1r2. Asterisks (*) indicate the stop codon positions in exon 4 and 6 of cat Tas1r2. Note that nucleotide numbers of the exon 3 in human TAS1R2 and cat Tas1r2 are not identical.

Poor kitties. They don’t even know what they are missing.

It’s nice to have an explanation for why cats prefer fish to candy bars, but there’s more to the story than that. It’s also another piece of evidence for evolution.

The cat TAS1R2 gene has been thoroughly blasted into uselessness, but there is obviously more than one way to do that. A larger deletion that took out the whole gene would be just as effective, as would a 1 base pair deletion at the beginning of the sequence. Any random scrambling would do. So how do you explain this?

i-8d27fd8b1300c88fbf8e7b44679f4ca1-tas1r2_stop_codons.gif

The sequence was analyzed in house cats, but the gene was also examined in samples taken from a tiger and a cheetah. They have exactly the same mutation, with stop codons mapped to exactly the same places. This is an example of “plagiarized errors “, a phenomenon that is most simply explained by common descent. The last common ancestor of house cats, tigers, and cheetahs had this mutation, and passed it on to all of its progeny.

We can also make an evolutionary prediction: I expect that lions, leopards, and lynxes will also have the same 247 base pair deletion, and a similar array of stop codons. We expect some variation—you can see that there are some variants in exon 6, for instance—but the scar of this ancient gouge in their DNA will be present in all cats.


Li X, Li W, Wang H, Cao J, Maehashi K, Huang L, Bachmanov AA, Reed DR, Legrand-Defretin V, Beauchamp GK, Brand JG (2005) Pseudogenization of a Sweet-Receptor Gene Accounts for Cats’ Indifference toward Sugar. PLoS Genetics 1(1):e3.

Comments

  1. #1 Shygetz
    September 25, 2006

    Now if only the Intelligent Design advocates would submit the obvious hypothesis; that all creatures with similar dietary preferences will have a similar mutation in the homologous gene.

    But no, the Designer works in mysterious, untestable ways…

  2. #2 Miguelito
    September 25, 2006

    So, what you’re saying is that, if I don’t want to be eaten by a big cat, I should smear myself with chocolate?

  3. #3 RavenT
    September 25, 2006

    Yeah, but then you’ll draw bears, Miguelito–you just can’t win.

  4. #4 Stanton
    September 25, 2006

    Would it be possible to create cats with sweet teeth if one were to splice a functioning TAS1R2 gene (e.g., from a human) into the genome of a cat egg?

  5. #5 Bokanovsky Process
    September 25, 2006

    Cool. Wonder what Jason will say (whatever it is, it’ll bear a close resemblence, after disemvowelling, to the feline TAS1R2 gene…)? After all, on his new site he’s made it his mission to refute PZ wholly and openly.

    Or maybe not – at least one of my comments on his site seems to have been Raptured. It was a silly toss-off comment, swear-free, but I still got ignored. When confronted with real arguments, the silence will be similarly deafening, I’m sure.

  6. #6 Will Von Wizzlepig
    September 25, 2006

    It’s really a shame that the 1000+ year-old religious texts fail to predict how things really work. It would be much nicer if they did so very well, and then modern science could go onward without inane, obtuse, fiction-based interruption.

    I’m a relative newcomer to this blog, but I really love the teeth it has.

    If I may, has research on par with the cat gene example above ever resulted in information which went against the Theory of Evolution? Oh, the ID people would be all over it already, so I suppose not, eh?

  7. #7 andy.s
    September 25, 2006

    I suppose most things in nature that are sweet are carbohydrates, and cats have no dietary requirement for carbohydrates. So there’d be no selection pressure to retain this gene.

    I wonder how the gene looks in closely related critters: canines, hyenas and civets? Or do all mammals have it?

    Another evolutionary prediction is that this gene would be present in the closest relative of felines that was not an obligatory carnivore.

  8. #8 Sven
    September 25, 2006

    Cat: Hey hey hey, I’ve got you now, buddy! J, O, Z, X, Y, Q, K!
    Lister: That’s not a word.
    Cat: It’s a Cat word.
    Lister: What does it mean?
    Cat: It’s the sound you make when you get your sexual organs trapped in something.
    Lister: Is it in the dictionary?
    Cat: Well it could be, if you’re reading in the nude and close the book too quick.

  9. #9 Day Phex
    September 25, 2006

    For a minute there, I thought you were letting Jason write blog entries. Whew!

  10. #10 Joe Shelby
    September 25, 2006

    Stanton: I wouldn’t use a human’s sequence, not least for which it may end up illegal if Frist gets his way. 🙂

    at any rate, its almost always best to go with the closet ancestor one could ethically go with, so i’d stick to something else in the carnivore line.

    but then again, how many other sequences that cats “expect” to find in certain places will be thrown off by the insertion?

  11. #11 Dan
    September 25, 2006

    Ah, Red Dwarf. Still one of the best shows ever put on television.

    Let the holographic happiness spread.

  12. #12 Adam
    September 25, 2006

    Strange, I have a cat that has taken a liking to Ben & Jerry’s Chocolate Fudge Brownie ice-cream.

    My cat is obviously special, if it was designed, then it was designed to be unique among cats. So, I guess I should worship my cat…?

  13. #13 Kevin Klein
    September 25, 2006

    [blockquote]…the scar of this ancient gouge in their DNA will be present in all cats.[/blockquote]

    This is exactly what the Bible predicts. All cats descended from the same two original cats on Noah’s ark.

  14. #14 Siamang
    September 25, 2006
  15. #15 Steviepinhead
    September 25, 2006

    Well, but–and if you were merely waxing ironic, I apologize, my irony meter is in the shop today for scheduled warranty work–there were two kitty-cats, and also two panther/leopards, and two lions, at least, and probably two cheetahs too, judging from the Assyrian monumental panels (those are all different Biblical animals, not just one undifferentiated cat “kind,” correcto, since they show up in the Old Testament, within a few generations of the “Creation”? you do remember Daniel in the lion’s den, doncha, KK?), so we have no “Biblical” reason whatseover to expect the same genetic deletion in each of these Biblically-separate animals.

    Thus PZ’s prediction is a completely valid evolutionary “test” which, for anyone in touch with consensual reality, threatens not only to support the ToE but to falsify the Noah story.

    Dang, are you sorry that you brought that up?

  16. #16 TheBrummell
    September 25, 2006

    Strange, I have a cat that has taken a liking to Ben & Jerry’s Chocolate Fudge Brownie ice-cream.

    I’m thinking your cat likes the taste of the milk-derived proteins and fats in the ice-cream, and is ignoring the sugar content because it (you didn’t specify sex) can’t detect it anyways. Have you tried it on other flavours of ice-cream, to isolate what ingredient(s) the cat is really going for?

  17. #17 Gentlewoman
    September 25, 2006

    Adam, if you’re serious, please don’t let your cat eat chocolate. It’s not good for them. I have an adopted stray cat who likes Cherry Garcia, but I pick the chocolate bits out before I let her have any. She likes vegetarian tomato sauce, too, but only my homemade variety. She won’t touch sauce from a jar or tin. Cats are weird.

    PZ, did you see any of the articles about the supposedly allergen-free cats? They’re produced by selective breeding. They’re selling them for around $4K, and there’s apparently a waiting list.

  18. #18 Sam
    September 25, 2006

    Adam, if you’re serious, please don’t let your cat eat chocolate. It’s not good for them. I have an adopted stray cat who likes Cherry Garcia, but I pick the chocolate bits out before I let her have any.

    As long as we’re on the topic: or dogs. Dogs and chocolate are also a serious no-no.

  19. #19 Mary
    September 25, 2006

    Two of our three cats seemed to have massive appetities for sweets: apples, cantaloupe, tomato sauce, pancakes, etc. They could be reacting to other taste elements, of course, but I’m wondering if some mutant cats could be sensitive to sweetness.

    I once tested our little black cat in several sessions across a couple of days. She loved fresh, cold water and would always drink some whenever we put down a fresh bowl, so I made up a bowl of plain water, a bowl of mildly sweet water (sucrose only) and a bowl of mildly salty water (table salt). No matter what order I placed the bowls in, she spent several more seconds drinking the sweet water, with plain water her second choice, across all the sessions.

    Of course, I could still get these results with a single cat just by chance, but could she have been a mutant?

  20. #20 andy.s
    September 25, 2006

    Wait a minute…
    I just remembered this:

    http://www.petshealth.com/dr_library/antifreeze.html

    Cats and dogs both have a taste for ethylene glycol, which is sweet tasting. (IIRC, it’s a gas that fruits secrete to force other fruits to all ripen at the same time).

    What’s up with that?

  21. #21 dogscratcher
    September 25, 2006

    “Adam, if you’re serious, please don’t let your cat eat chocolate. It’s not good for them. I have an adopted stray cat who likes Cherry Garcia, but I pick the chocolate bits out before I let her have any.”

    And onions, don’t forget onions.

  22. #22 Mary
    September 25, 2006

    Ben and Jerry make onion ice cream? Faaaaaaar out.

  23. #23 sean
    September 25, 2006

    “If I may, has research on par with the cat gene example above ever resulted in information which went against the Theory of Evolution?”

    No, because evolution is a scientific theory. If something comes up which goes against it or some part of it, the theory is then adapted to conform to the newly discovered facts.

  24. #24 Jody
    September 25, 2006

    I once had a basset hound that ate our compost heap.

    I stopped worrying about what it ate after that.

  25. #25 John Owens
    September 25, 2006

    Who cares about cats’ sweet teeth or lack thereof? I want to know why they react to catnip the way they do, and we don’t. What’s the magic chemical in that stuff anyway? (I’m guessing that that’s a single chemical that works its magic, rather than some more complicated mixture of chemicals.)

  26. #26 George
    September 25, 2006

    Cool! Serves to protect the teeth from decay, right?

  27. #27 Interrobang
    September 25, 2006

    I’ve had the same experience as Mary. I have a cat who seems to have an insane sweet tooth. He also loves tomato sauce, but he’ll go after fruit, too. My mom used to have a cat who would go nuts begging for cantaloupe. So, could there be cats with working TAS1R2 mutations, or just individually insane cats with preferences that work in similar directions? (Occam would dictate the latter, I think.)

  28. #28 Calladus
    September 25, 2006

    Siamang,

    Rerunning articles from last year?

    Yes, many bloggers will re-run a selection of decent posts.

    PZ helpfully identifies each re-run with a “Repost” graphic at the top of the article, allowing you to easily identify and skip a rerun if you wish.

  29. #29 folderol
    September 25, 2006

    There is no Twinkie* that is safe in my house. My cat will rip up the cardboard box to get to one.

    Oh, and Pop-Tarts*.

    But will he eat more than three different varieties of canned cat food, all in the poultry family? Oh, noooooooo.

    *I don’t know the html code for the “registered trademark” sign, so just pretend.

  30. #30 ebohlman
    September 25, 2006

    The active ingredient in catnip is nepetalactone; it apparently exerts its effects by interacting with olfactory receptors. Not all cats have the necessary receptor protein for it; catnip-susceptibility is highly heritable. It appears to have evolved as an insect repellent.

  31. #31 redwagon
    September 25, 2006

    My ex-wife adopted a cat that used to cruise dumpsters.
    He will generally eat any protein based food stuck in front of him but he loves to chew on cantaloupe rind that he fished out of the garbage disposal. It just goes to show you can take the cat out of the alley but you can’t take the alley out of the cat.
    Cantaloupe rind and Tomato Sauce are both pretty acidic, it probably meets a dietary need.
    Cats also eat grass but thats to promote furball emesis.

    Ken

  32. #32 Mike Crichton
    September 25, 2006

    If housecats evolved from tigers, then why are there still tigers? Answer me that, smart guy! 😉

  33. #33 Suzanne Rebert
    September 25, 2006

    My cat loves many things that happen to be sweet, but he could indeed be liking them for reasons unrelated to their sweetness. The fact that I’m eating them, for instance. Actually, Pete wants a taste of anything being eaten by anyone, including the alfalfa I used to feed to the guinea pigs before they died.
    (Of old age.)

  34. #34 grendelkhan
    September 25, 2006

    Wild guess about ethylene glycol: maybe they can smell it, just not taste it? I eagerly await someone who actually knows anything about animals to tell me if I’m right…

  35. #35 Alex
    September 25, 2006

    It seems to me that the “sweet” smell or taste from ethlene glycol probably isnt because of sugar.

  36. #36 Amy
    September 25, 2006

    “Adam, if you’re serious, please don’t let your cat eat chocolate. It’s not good for them… As long as we’re on the topic: or dogs. Dogs and chocolate are also a serious no-no.”

    And pennies. And I don’t mean as a choking hazard: the zinc in pennies can kill Fido.

    Better just seal their mouths. Safer that way.

  37. #37 Calladus
    September 25, 2006

    My current cat is the first one I’ve ever owned that did NOT like to snack on other foodstuffs.

    He loves his dry catfood, and he loves the small spoon of wet canned food that I add in the morning. But he turns his nose up at kitty treats, leftovers, or anything else I’ve offered him. He hates every hairball med I’ve tried too – so I have to ‘hide’ it by mixing it with his wet food.

    The only ‘treat’ that has caught his interest is dried squid shavings. He seems to like squid.

    He also likes to chew on cardboard – but he doesn’t eat it. He doesn’t seem to notice Catnip.

  38. #38 Adrienne
    September 25, 2006

    I read once that part of the reason animals may drink antifreeze is just that it might be one of the only available liquids to them in winter..when their regular water is frozen (this would be for animals that are outside). Not because they prefer the taste.

    I had a friend whose cat adored cantaloupes too, incidentally. I once had a cat who loved bread and cookies. And I once put granulated sugar on my finger and let my current cat lick it, and she came back for more sugar licks after the first taste. I think that cats (or some of them) might be able to taste a *little* bit of sweetness, maybe? Just not at all to the same extent or depth that we humans do?

  39. #39 Robster
    September 25, 2006

    Of our three cats, our main cat will self medicate with nip when stressed, eating it. Our auxiliary cat only needs to smell it to fall over and start going bonkers. Our emergency cat isn’t real big on catnip, but we can get her going by slipping a pinch into her mouth.

    A friend’s cat, on the other hand, reacts to menthol like other cats do catnip. She has to hide her cough drops in airtight tins.

  40. #40 DominEditrix
    September 25, 2006

    This cantaloupe thing is pretty pervasive, I guess – I had a cat who had to be hauled out of the trash bin on a regular basis because of his cantaloupe jones. Other of my cats could not have cared less.

    Then there was the one who liked Chinese food so much that he used to hurl himself at the delivery man. Ignored the pizza guy.

  41. #41 DominEditrix
    September 25, 2006

    Re: the onion warning link: The title seems to suggest that one should not allow one’s cat to eat babies who have been fed onions. Does this mean I can let them eat onion-free babies?

  42. #42 Robster
    September 25, 2006

    My wife just told me told me to mention her parent’s cat and citronella. Back when we were dating, we went to a local Shakespeare fest. We decided to try citronella candles (the kind in a tin) to keep at least some of the mosquitos away. Of course, we had to see how Muffin reacted to the interesting new smell. Seeing a tin held down for him to inspect, he ran over and sniffed it. He physically recoiled from the smell. As though he was thinking, “nothing could actually smell that bad,” he leaned forward to check it out again. Yes. It really does smell that bad. He ran off and didn’t come back. Even though he isn’t the smartest cat, he did recognize the tin, and would flee if it made an appearance.

  43. #43 David Harmon
    September 25, 2006

    Cats can get a little weird about their diets, including getting fixated on odd foods. They often do like chocolate (unfortunately), and they’re usually at least curious about whatever you’re eating.

    Based on the effects, catnip is clearly a feline hallucinogenic. About 1 in 10 cats is immune — I’ve heard of one such cat, who happened to have a catnip patch in “his” backyard. He made himself “king cat” of his neighborhood by luring his rivals to the patch, and then beating them up when they were too stoned to resist.

  44. #44 bioephemera
    September 25, 2006

    Robster’s cat sounds like my cat, when she is confronted with a Sharpie marker. Except she punctuates her distate by faux-retching several times before running away.

    At first I guessed maybe cats could taste a bit of sweetness through TAS1R3, which they do still have, but it appears not to function as a homodimer. And I haven’t been able to find anything verifying that cats are attracted to ethylene glycol laced water over plain water. So maybe they really don’t have any particular desire for antifreeze. I did once read that some cats may get antifreeze poisoning by licking it from their feet and fur while grooming themselves, rather than by drinking the standing liquid.

  45. #45 Phoenician in a time of Romans
    September 25, 2006

    So, what you’re saying is that, if I don’t want to be eaten by a big cat, I should smear myself with chocolate?

    It won’t stop you being eaten, but it might give it tooth decay later.

    We had a cat who developed a taste for our milkshakes, to the point of sticking its head right down our glasses to slurp at the stuff when we put them down. This also had the happy side effect, from the cats point of view, of making the humans unwilling to consume the stuff from then on.

  46. #46 thwaite
    September 26, 2006

    It’s about dogs and rats (not cats), but this brief study documents that these animals’ consumption of antifreeze is inversely proportional to its concentration of ethylene glycol. And they prefer plain water to any kind of antifreeze. The authors speculate on why this might occur, not very decisively.

    This is from scholar.google.com. Ordinary google just returns cautions.

  47. #47 sleepyinsaudi
    September 26, 2006

    My cat loved peaches. If we were eating one, the cat would go nuts until we gave him a piece, which he would then lick with his rasp-like tongue until only the peel was left. Just the smell of peaches was enough to make him come running, and howl for some. He lived to be 19, so I guess it didn’t hurt him.

  48. #48 lazarou
    September 26, 2006

    On the subject of cats liking wierd things I have a two year old Maine Coon who won’t stop licking plastic bags. Seriously, whether it’s carrier bags from the supermarket, bin bags, packaging, he’ll sit and lick a plastic bag for hours while purring away happily (never eats it, just licks).

    Generally has no interest in other snacks apart from his cat food either, tried giving him bits of fish, chicken, pork, beef, not interested in any of them. Only plastic.

    Why is he doing this? What’s going on? Help me science!!!

  49. #49 Bess
    September 26, 2006

    Never heard of the plastic bag thing, but I know some cats do exactly the same thing with wool. Siamese cats have been known to destroy entire sweaters by licking them threadbare.

  50. #50 Sara
    September 26, 2006

    I have a cat who does like cookies.

    HOwever, he only likes shortbready cookies. He also likes buttery crackers and doritos.

    He used to like mushrooms and tofu, but in his old age doesn’t seem to go for them anymore.

    In his case, the “sweet tooth” that makes him nibble the sides off cookies seems to be a desire for crumbly fatty things rather than a desire for sugary things. He likes ice cream too — for the cream — but he’s so lactose intolerant he hurls almost immediately after having some, so that’s off his list.

  51. #51 Edmund
    September 26, 2006

    I keep reading the same thing in these comments: “my cat likes something that tastes sweet to me, therefore it must be because the cat is reacting to the sweet taste.”

    NO. You and your cat don’t perceive things the same way. There are many possible reasons an animal that can’t taste sugar might want to eat it anyway. I speculate that sugars still exert changes in blood glucose levels in cats, this possibly being a reinforcing effect.

    Semi-sweet chocolate, cocoa, dark chocolate, baker’s chocolate: those are the ones to really be concerned about if your cat or dog ingests them. They contain significant amounts of theobromine. Milk chocolate is typically quite dilute in comparison, perhaps containing one-tenth of the theobromine in more pure chocolates.

    Cats and dogs (and other animals) metabolize theobromine far less effectively than humans, making them vulnerable to toxic and lethal overdose.

    http://en.wikipedia.org/wiki/Theobromine_poisoning

  52. #52 Edmund
    September 26, 2006

    As for fruits and fatty (and sugary) snacks, there are even more potential reasons a cat will eat these things that are unrelated to the taste of sugar.

  53. #53 MJ Memphis
    September 26, 2006

    For those cats and dogs who like chocolate, you can get some really nice carob-based treats from your local dog bakery. Some of them smell good enough to be tempting to humans. 🙂

    The weirdest animal in my household, as far as diet goes, would have to be my toy poodle. He likes to finish the leftover food from my and my wife’s plates, which is not too unusual in and of itself- except that I am from Louisiana and she is from Thailand, so the food in our household is very, very, very hot. But the little bugger seems to have a very high resistance to capsaicin and can wolf down habanero-laced jambalaya and extra-spicy yum neau with no problems. The big dogs, on the other hand, wisely keep their distance from our food.

  54. #54 NJ
    September 26, 2006

    But if cats don’t like chocolate then how do you explain PYGMIES + DWARVES!!!

    Sorry, I couldn’t resist. Back to the dark chocolate Hershey’s…

  55. #55 Jon D. Moutlon
    September 26, 2006

    You could restore the reading frame by knocking out that 73 base intron fragment with a Morpholilno.

    Wait, then the cat would compete for your chocolate.

    – Jon

    When your only tool is a hammer, all problems resemble nails.

  56. #56 TomS
    September 26, 2006

    I had a cat that loved tomatoes. He used to jump on the counter and eat them. At one point he leaned the word “tomato” so I had to start using it out of context to untrain him.

    The other thing this cat liked was cashmere. To eat. He couldn’t digest it and puked up big cashmere hairballs after each sitting of eating my wife’s cashmere socks.

  57. #57 amphioxus
    September 26, 2006

    Nice story. Obviously, there are many similar ones.

    One example as a consolation for Kitty: God created man with a less than optimal talent for smelling compared to many other mammals. Small wonder when you look at the olfactory receptor genes. (See: Sharon et al. Genomics 61, 24-36 (1999)

    The olfactory receptor (OR) subgenome harbors the largest known gene family in mammals, disposed in
    clusters on numerous chromosomes. We have carried out a comparative evolutionary analysis of the best
    characterized genomic OR gene cluster, on human chromosome 17p13. Fifteen orthologs from chimpanzee
    (localized to chromosome 19p15), as well as key OR counterparts from other primates, have been identified
    and sequenced. Comparison among orthologs and paralogs revealed a multiplicity of gene conversion
    events, which occurred exclusively within OR subfamilies. These appear to lead to segment shuffling in the
    odorant binding site, an evolutionary process reminiscent of somatic combinatorial diversification in the
    immune system. We also demonstrate that the functional mammalian OR repertoire has undergone a
    rapid decline in the past 10 million years: while for the common ancestor of all great apes an intact OR cluster
    is inferred, in present-day humans and great apes the cluster includes nearly 40% pseudogenes.

    Apparently He decided in His wisdom that we would have defective versions of many of these genes.

  58. #58 G. Tingey
    September 26, 2006

    But “our” cat really likes white wine (and champagne!)

  59. #59 Ugo Cei
    September 26, 2006

    Kevin,

    assuming you are serious, which I would find hard to believe, what you are saying implies that creationists find it plausible for a single couple of kittens to produce tigers, lions, lynxes, etc. in a few thousand years, yet it is impossible for Darwinian evolution to have done the same over the course of million years?

    Of course, we know that, since god was involved, he could just have performed a miracle, right?

  60. #60 Bob O'H
    September 26, 2006

    Isn’t that second version an invocation of Shub-Niggurath, The Black Goat of the Woods with a Thousand Young?

    Bob

  61. #61 Rick @ shrimp and grits
    September 26, 2006

    Ahh, catnip:

    http://shrimpandgrits.rickandpatty.com/2006/07/19/friends-dont-let-friends-use-catnip/

    While the cat in the picture above doesn’t like sweets, he does for some reason go crazy for Sweet Sixteen doughnuts (white powdered sugar variety). It probably has little or nothing to do with the sugar content, but he doesn’t much care for other cake doughnuts.

  62. #62 David Harmon
    September 26, 2006

    Edmund et al: quite true, and don’t forget psychological factors. Most cats will at least consider eating anything their master (or even other humans) offers them. Obsessive licking of obvious inedibles is probably sublimated grooming, perhaps representing neurosis, anxiety, or stress.

    I have heard it suggested that giving your cat a weekly salad is a good thing and cuts down on untoward adventures against the houseplants. Yeah, skip the onions.

    MJ Memphis: I have heard of a squirrel who gained a taste, or at least a tolerance, for chili-laced birdseed. (Birds don’t taste chili, but squirrels do.)

  63. #63 Monado
    September 26, 2006

    Someone should check the gene in foxes. They’re a little more omnivorous and might have retained the taste for sweet things. Bears, too.

  64. #64 Monado
    September 26, 2006

    Cats definitely have tastes. My mother had one that would howl for potato peelings (perhaps for the crunch?) and my son swears his cat loves citrus fruits, which most cats seem to dislike. Most cats going for cookies probably want the fat.

    I wonder if the licking plastic is just for the sensual pleasure or if it’s a trace of a hunting/eating instinct. I had one cat that would pull the snap-buttons off a comforter with great neck-stretching. I later found out it’s the movement that cats use for plucking the feathers from large birds. (Small birds, they just lick until the skin wears off, supposedly.)

  65. #65 Timb
    September 26, 2006

    When I was in grade school my family had a black angora that literally would go crazy whenever we had cantalope. As soon as the cantalope was brought into the house the cat would start acting weird but the minute it was cut open the cat would start pawing at your leg and running around the house. It was funny to watch. When we finally gave the cat a piece of the cantalope it would be gone in the blink of an eye. I’ve always wondered what it was about the cantalope that caused the cat to act this way. I thought that it might be the sweetness but now it doesn’t look like sweetness would have been a factor.

  66. #66 Mooser
    September 26, 2006

    Cats are wonderful creatures, taken all around.

  67. #67 Junk Jungle
    September 26, 2006

    I read one line and immediately thought of Dembski, and how he might spin this. The key things to note is that there are 6 solid black bars which represent the exons or protein coding regions of the gene, and that the cat has a chunk cut out of the third exon; and the red asterisks, which indicate the position of new stop codons sprinkled into exons 4 and 6. That is one dead gene.

    Since they’re so hung up on quote mining, I’m sure they’d love this part here and say, “hey guys, if you take a piece out, it can’t function!!!111”

  68. #68 donna
    September 27, 2006

    I once got a cat drunk on chocolate Pernod pudding…

    But the weirdest thing I’ve heard of cats eating is asparagus. Apparently the longest-lived cat on record loves the stuff.

  69. #69 Ben Gregory
    September 27, 2006

    This study was very interesting and very informative, and I thought it represented a quality piece of reserach. Why do cats like the taste of antifreeze? I have heard people say for years that antifreeze taste sweet to cats, but that would not appear to be the case based on this research. Personally, I do not know if antifreeze is sweet or not. I’ve never tasted antifreeze, and don’t plan to do so because it is extremely destructive to kidney cells. Does anyone have knowledge as to why cats eat antifreeze? Could there have been a prey item for cats, in their distant evolution, that tasted sweet but reduced the cats fitness. Did cats evolve away from ‘sweetness’ due to evolutionary pressure? Thanks.

  70. #70 khan
    September 27, 2006

    But the weirdest thing I’ve heard of cats eating is asparagus. Apparently the longest-lived cat on record loves the stuff.

    Years ago, I was trimming asparagus, and one of the cats pulled a stem piece out of the compost bucket. She became frustrated as she was not equipped to eat it.

    After that, when I cooked asparagus, I would give her small cooked pieces; she could (and did) chew and eat them.

  71. #71 augustusB
    September 27, 2006

    Perhaps its also further proof that cats are smarter than dogs, at least when it comes to evolving successfully. The large doses of toxic theobromine in dark and baking chocolates can send the canine system into overdrive, causing increased urination, over-excitement, muscle tremors, increased heart rate and – in the worst case scenario – fatal cardiac attacks. Yet what happens when you lob a tasty-looking chunk of chocolate in a dog’s direction? Yep, the concept of death by chocolate is completely alien to it. Instead it, er, wolfs the stuff down much like its much more resilient ancient ancestor would. So why haven’t dogs – like cats – learned any better? Given the way we’ve tinkered with almost every aspect of their physiognomy in the name of selective breeding, should we take some of the blame?

    http://www.whypandasdohandstands.blogspot.com

  72. #72 meridian
    September 27, 2006

    Would it be possible to create cats with sweet teeth if one were to splice a functioning TAS1R2 gene (e.g., from a human) into the genome of a cat egg?

    What would be the purpose? Seriously. Other than to play God, why on earth would you want a cat with a sweet tooth?

    Generally has no interest in other snacks apart from his cat food either, tried giving him bits of fish, chicken, pork, beef, not interested in any of them. Only plastic.

    Why is he doing this? What’s going on? Help me science!!!

    It’s probably something in the chemical composition of the plastic that attracts him. We had a part-Siamese cat who did chew (and swallow pieces of) plastic bags and then would throw up all over the place. We had to tuck trashcan liners under lids, make sure all shrink wrap pieces were caught, etc.

    Plastic isn’t good for kitty; it’s full of toxic chemicals. I’d recommend not indulging kitty’s habit.

    Siamese cats have been known to destroy entire sweaters by licking them threadbare.

    Cats are attracted to the lanolin in wool. Theory is it smells like mother’s fur around the nursing site and brings back kitten memories.

    Cats also eat grass but thats to promote furball emesis.

    Grass and other greens contain folic acid, which cats need. They don’t always throw up grass (or hair) when they eat it.

    I have a Siamese male who will sit patiently for hours near a newly grown flat of kitty grass (which I have to keep out of his reach until it’s tall enough) and who literally cries for it. He doesn’t really care for catnip.

    Catnip is a member of the mint family. Another cat of mine goes bananas every time we brush our teeth. She loves catnip and will come from a different floor in the house to get some. She also likes the smell of citronella and cedar.

    I can’t explain why, except to point out that even though they have the same genome, not all these genomes are identical and they have been influenced by the conditions they grew up in and live in now.

    One of my cats is actively allergic to fish and dairy protein — his lip, chin, or paw will literally swell up like a balloon if he gets any. A lot of adult cats aren’t able to process milk sugars and get diarrhea.

    Cats have traits, but not every animal is a cookie cut out by a genome. Pointing to a string of alphanumeric characters representing genes and saying “that’s a cat” is a big mistake.

  73. #73 WWW
    September 27, 2006

    Some commenter asked about the ® symbol:
    ®

  74. #74 Keith Douglas
    September 28, 2006

    John Owens: Data points to help with investigating the catnip – it seems that cats can get too much of it and refuse to come near it for a while. It also affects both male and female cats, including neutered females. Does anyone know if it does anything to humans if we eat it (raw)? I was wondering if it perhaps does something but we are less sensitive to it. It seems also that whatever it is would have to be quite volatile, since it seems to escape being in cloth.

    ebohlman: Hm, interesting. But why the psychoactive effects? Incidentally, I know anecdotally from a former colleague that some cats also like marijuana. Any words from anyone on that?

    Sara: (re: lactose) My sister used to have a cat that loved cheese even though it repeatedly make her barf. Strange habit; the cat didn’t seem to ever learn, so we stopped feeding the cat cheese eventually once we wised up to what was going on.

    The same cat used to also eat these weird pulpy leaves on a strange low-growing plant my father kept. I think they made her barf too, but I can’t for the life of me understand why she would want to eat them. Some of us tried them (to see if we could guess what it was) and found them ridiculously bitter.

  75. #75 K.G.
    November 17, 2006

    Just because something tastes sweet to us doesn’t mean that sweetness is all that there is to the taste.

    I used to have a cat who liked peeled seedless grapes. She also liked raw carrots and steamed snap peas. (I never tried her on cantaloupe, probably because I don’t like it much myself.)

    From that, it seems likely that:

    1) it was about textures
    2) it was about moisture
    3) it was something else about the taste
    4) Clove was (and still probably is) just a weird cat who would eat anything.

    As for critters which are kin to the felidae, but still have this gene? I’d guess the viverridae.

  76. #76 Elliott
    July 6, 2007

    ® = alt 0174
    © = alt 0169

    (in windoze, at least)

  77. #77 Scrabcake
    September 26, 2007

    I had a cat go after a four year old candycorn once. I don’t think there was a dietary role that this was filling, or that the thing had any tastes that weren’t “sugar”. Maybe she liked the taste of whatever was growing on it?
    This cat would eat anything, though. She ate so much wildlife around our house that it’s a wonder she didn’t ever get worms 😛
    This is pretty cool, though. It’s always interesting to learn something new about something familiar in your life.

  78. #78 Stimpson
    January 24, 2008

    When I was young, my brother’s cat used to lick earwax. If you ever picked her up, she would climb onto your shoulder and stick her nose in your ear. Normally, she would just make little cat noises in your ear as you spoke, as if she were taking part in a conversation, but occasionally she would start licking your ear.

    It took years to find a possible cause. My brother cleans his ears with the ends of his glasses. He then sucks the wax off. When we were kids, he used to share with his cat.

    The big lesson I learned from this was that cat shouldn’t be separated from their mothers at six weeks (the owners were going to kill the kittens if no one would take then). Who knows what bizarre influences they will meet?

  79. #79 rijkswaanvijand
    July 30, 2008

    Obviously..

    Any obligatory carnivore with a taste for chocolate would risk starvation as most of it’s monthly income would probably be consumed by chocolate consumption…

    Hence an enormously higher relative fitness for the scrambled gene.

    Aaah chocolate!!!

  80. #80 frank
    August 20, 2008

    When I was young, my brother’s cat used to lick earwax. If you ever picked her up, she would climb onto your shoulder and stick her nose in your ear.
    that is disgusting

  81. #81 max fehler
    February 19, 2009

    Die LGT Bank fehler

    von Raivo Pommer

    Der Chef der skandalumwobenen Liechtensteiner LGT-Bank spricht über Fehler seiner Zunft, falsche Regulierung und eine Amnestie für Steuersünder.

    Rheinischer Merkur: Spätestens seit die Affäre Zumwinkel öffentlich ist, glauben die Deutschen, dass die LGT-Bank hilft, Steuern zu hinterziehen ?

    Max von und zu Liechtenstein: Das tun wir natürlich nicht. Unser Fokus liegt seit mehr als zehn Jahren auf dem Aufbau lokaler Banken in verschiedenen Märkten. So haben wir viel Geld investiert, um unter anderem in Deutschland eine Bank mit sieben Niederlassungen zu errichten. Hier werden wir von der deutschen Finanzaufsicht reguliert, und für die Kunden gilt das deutsche Steuerrecht

  82. #82 Phill
    May 11, 2009

    It’s unfortunate that evolution has not afforded us the gene to not malign the religious at every opportunity such as this when talking about sweet detection with amino acid pairs.

  83. #83 Susannah
    December 15, 2009

    Concerning human consumption of catnip: Catnip (aka “catmint”) is a type of mint, as are, for example, spearmint and peppermint. People have been drinking catnip tea for centuries, without displaying any of the feline silliness associated with cats’ consuming catnip. Here’s a website devoted to the subject of catnip tea, although I can’t personally vouch for any of the claims on it: http://catnipteaguide.com/.

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