The impossible predicament of the death newts
186 comments
·June 5, 2025arp242
mekoka
I think it might be more useful to look at the author's claim from the other side of the lense. We do carry around barely useful traits, like resistance to toxins that we seldom come in contact with. We can assume that carrying such traits is cheap. If resistance to tetrodotoxin was one such cheap trait, it might have been more prevalent, but it's not so, it could be inferred that it's expensive. Or at least, not cheap.
xenadu02
This is another case of a huge fallacy humans seem endlessly afflicted with: The Root Cause Fallacy.
You are assuming there is but one cause for development and/or loss of resistance.
There may not be much pressure to develop resistance to tetrodotoxin for most species. Simultaneously there might be a higher metabolic cost to retaining it for some species but not for others. It is also possible that resistance with low cost is very rarely lost which is why we carry resistance to toxins we don't often see but population bottlenecks in ancestral lines can cause loss of a trait to propagate - even by accident. And much like Vitamin C loss if it doesn't matter the loss sticks. We should not forget that there are multiple resistance mechanisms as well: an immune system generally primed to fight certain common causes of mortality can, entirely by accident, also be primed to recognize and destroy certain proteins conferring resistance to some toxins and not others.
I have barely scratched the surface above. The random walk of evolution and its constant hoarding tendencies should make everyone skeptical simplistic mechanisms of action as well as "just so" explanations of evolutionary history.
FWIW most things are multi-causal. I previously made the same argument about house prices. People who claim it is caused by foreign money, low interest rates, restrictive zoning, etc all want their pet theory to be The One True Reason. In reality the market is complex and many of the proposed causes are merely contributing factors.
mekoka
> You are assuming...
I made no assumptions. As I pointed out to another commenter, you might be in too much of a haste to play at being a contrarian. It might be more useful to pay closer attention to what you're objecting to.
Evolutionary game theory demonstrates that evolution is a matter of fitness payoffs. If cost of a trait increases, fitness is reduced. The prevalence of a trait in a fit population is indicative that, at best, the trait increases fitness, at worst, it doesn't hinder it. In both cases, the genes tend to be passed on and the game is allowed to continue. When carrying the trait becomes costly, there's pressure to get rid of it (through the usual evolutionary means).
The above model encompasses all the unnecessary specificity you tried to bring into the matter. If you object to it, address your concerns to the scientists that are leading us all astray.
For now, let's circle right back to the author's original argument. Absence of an actually useful trait to increase fitness (i.e. protecting ones from certain food sources and others from predators) might be indicative of a hefty tax to pay for carrying it.
pegasus
That resistance to toxins we don't encounter often enough to constitute selective pressure, we carry around only if it's the accidental byproduct of another selected-for trait. Otherwise entropy would take care of it, sooner or later. Parent is right, evolution doesn't pay an annual subscription fee for some service which was useful in the past and might come in handy in the future.
mekoka
You may just be trying to disagree with the author for sport.
> we carry around only...
Not true. We can carry resistance to some ancestral pressure which isn't part of the current environment.
> sooner or later...
Yes, sooner when it's costly, later when it's less so, through normal evolutionary pressure (entropy and all).
The point is, most species at time T do carry traits that aren't that useful to them anymore. The costlier ones yield enough negative fitness points in evolutionary game theory to rid the gene pool of them quicker. It brings us right back to the author's original argument.
nkrisc
> like resistance to toxins that we seldom come in contact with.
Is that because resistance to those toxins was strongly selected for in humans, or because the source of those toxins did not strongly select for effectiveness in humans?
Retric
It’s not some binary thing but degrees of adaptation.
People can handle significantly more of a wide range of plant toxins like theobromine and caffeine (both found in chocolate) which harm more pure predators like dogs in very low doses, but where rare for out imitate ancestors.
Cattle, deer etc however can handle many of those at much higher doses.
kylebenzle
You wildly misunderstood the topic being discussed and user above you is correct.
pokpokpok
Not wrong, but one could frame that as a "cost" that you pay in the space of genealogical problem solving. Having one less constraint makes it easier to adapt to other evolutionary pressures
arp242
I omitted some bits from the quote for brevity and HN's faux-quoting sucks, but that's not really the type of "cost" the article is talking about: "maybe they’re suffering from much more subtle neurological effects, like being prone to insomnia or hallucinations or sexual dysfunction. Or maybe they’re just a bit dim."
y-curious
Agreed, it's just shorthand/abstraction. Just like my for-loop in python doesn't actually mean my computer speaks Python
odyssey7
That claim jumped out to me as well. Evolution is supply and demand, cost and benefit, capacity and constraints, none of it balanced by anything apart from luck.
mattigames
This is categorically false, we know evolving bigger brains required us to reduce our muscle mass compared to other primates, for the energy budget required to create such brains.
pegasus
And those adorable koalas made the opposite bet, shrinking brain size in order to conserve energy so as to be able to carve a niche no other mammal cared for: https://youtu.be/dXUp_JMQjvg
mr_toad
Do we know that? I thought that the evidence suggested that early hominids lost muscle mass, especially in our arms, as they came down from the trees. We also switched from stronger muscle fibres to high endurance muscles.
You’re right that there was an energy trade-off, but it was being able to run faster and longer that was more important than strength for our ancestors, who still had quite small brains (the brain of an Australopithecus is only 35% the size of a human).
Brain size developed later, probably in a feedback loop with our diet - as we began to eat more meat our brains got bigger, which made us better hunters. And hominids actually got bigger and stronger as their brains grew.
odyssey7
That cost and benefit trade-off emerged as an opportunity only through luck and it survived only through luck, even if the odds were in its favor.
ashoeafoot
Reptilian Predation squeezed mamalian reproduction into the fast and the furious . Meanwhile birds and turtles reproduce hapoy at methusalem ages. No creator, no design, just merciless pressure that stupidly rewards successful maiming to adapt.
aqme28
But a nonzero number of animals and people die of tetrodoxin poisoning, so there is some pressure. Therefore if it were cheap and easy enough, it’s likely we all would have evolved it. That cheapness threshold might just be incredibly high.
amanaplanacanal
If it is rare enough it probably doesn't exert much selection pressure.
Has anybody modeled what percent of a population has to die from something for the protective gene to become widespread?
gptacek
If you're willing to abstract a bit from populations of animals to populations of bacteria, there is the minimum selective concentration (MSC), which is the smallest amount of antibiotic you can add to the growth medium and detect antibiotic resistant bacteria competing out non-antibiotic-resistant bacteria:
https://revive.gardp.org/resource/minimal-selective-concentr...
thaumasiotes
> Has anybody modeled what percent of a population has to die from something for the protective gene to become widespread?
The question is incoherent. The gene spreads if the organisms carrying it average more children. It unspreads if they average less. All of them could be dying of the same thing, and it wouldn't matter.
The rate of spread is given by the https://en.wikipedia.org/wiki/Selection_coefficient , but cause of death isn't relevant.
pfdietz
> There is no disadvantage to being able to synthesise vitamin C,
Synthesizing vitamin C takes energy, energy that could be used for other biological processes. It's also possible excess vitamin C has some minor deleterious effect. For example, it's an antioxidant, and these render immune cells somewhat less effective against certain threats (which they use oxidizing chemicals to destroy). It's been found larger doses of the ACE vitamins causes increased growth of lung cancer, probably due to reduced immune attack.
Some have argued against this idea, though, although I'm not convinced by the argument (see if you can spot the problem.)
skipants
Yes! Thank you! I’m barely knowledgable when it comes to biology and I still get annoyed when evolution is framed as cause-and-effect.
bsder
Well, there is some "cause-and-effect" in evolution.
Whenever a species winds up isolated in a cave, it loses eyesight really quickly in evolutionary terms because making and maintaining an eye is so metabolically expensive. So, while the mutations are random, any of them that can save the energy of developing vision get selected for very quickly.
So, even though the mutations are random, it really looks like "cause-and-effect" from the outside: get isolated in cave->lose vision; get exposed to outside light again->regain vision.
By the same token, changes that aren't very expensive metabolically will have very weak "cause-and-effect" because there is no particular pressure to carry the mutations forward or clean them up.
pegasus
No need to be annoyed. I think if you look deeper, you might find that, in fact, all occurrences of what we call cause and effect are of a similar nature.
bsder
> An ancestor lost the trait for vitamin C synthesis by chance, and because these primates were living in trees eating lots of fruit with vitamin C, evolution simply didn't notice. There is no disadvantage to being able to synthesise vitamin C, and no advantage in dropping the trait.
The fact that guinea pigs, fruit bats, and passerines (almost half of all bird species!) also have a mutated GULO gene suggests that there is in fact some pressure to get rid of it as soon as it is bioavailable from diet.
wbl
Eh, enzyme mutations leading to inactivity aren't uncommon. It could just be drift when enough vitamin C is available.
k__
I recently learned, there is a dangerous plant in many gardens around the US. If you stand under it for more than 10minutes, you're pretty much dead.
Turns out, it's the water-lily.
kulahan
Water lillies not only are not dangerous, they’re partially edible and have also been used in medicines. Do you mean peace lilly or calla lilly? Neither is deadly, but they can make you ill. Water hemlock is deadly and has white flowers?
rishi_devan
The joke here is that: If you stand under a water lily for 10 minutes, you are underwater for 10 minutes
kulahan
Well you see, I’m not smart
nyanpasu64
I recently learned that (Wikipedia) "Vascular cambia are found in all seed plants except for five angiosperm lineages which have independently lost it; Nymphaeales, Ceratophyllum, Nelumbo, Podostemaceae, and monocots.[1]" Four of these lineages are aquatic plants (including water lilies) and some scientists theorize monocots may have also evolved in the water. I seem to recall reading that aquatic plants don't "need" woody growth for structural stability, but can't find a source right now.
SwtCyber
Though now I kinda want a horror short where someone slowly realizes the water-lilies are the real apex predators
jakey_bakey
> Turns out there is an answer: the garter snakes sequester the tetrodotoxin, storing it in their livers. This makes them toxic to their own predators.
Second-order effects are so cool
atentaten
Interestingly written article. Raises some questions:
>Newts with weaker poison? They get eaten. Snakes with less resistance? Have trouble finding newts they can choke down, and don’t get to steal their poison. So the arms race continues.
How does a snake know that the Newt has weaker/strong poison? Is it leaving some Newts along and eating others, or is it eating any Newt it runs across? Does a strong-poison newt survive snake consumption attempts?
riffraff
it was mentioned elsewhere on the article that the snake may spit out the newt of it's too strong, kinda like a human with chili peppers, I suppose.
stevenwoo
Maybe a better way to frame it is over time, there's some genetic sequence that gave the snake a preference for eating this newt in particular out of all potential prey and some other genetic sequence that gives them a bit of resistance so they can store the poison inside them. Those snakes that eat more of them with that genetic makeup, up to a point, are better able to reproduce. Run a few thousand years of iterations over this process, where the snake and newt are in a red queen situation, both running faster and faster just to keep up. It is possible to look at this as situation where neither the snake or newt is conscious of the choices or there is no ability to make decision, there is only following the built in behavior.
calebkaiser
I think the preceding sentence in that paragraph answers it. Important context here is that garter snakes tend to swallow prey whole. tldr: a strongly poisoned newt survives consumption attempts.
> And it explains why the newts keep evolving to be more toxic: the snake may want to eat newts generally, but if an individual newt packs enough of a wallop, the snake may just retch it up and go after a different one. Newts with weaker poison? They get eaten. Snakes with less resistance? Have trouble finding newts they can choke down, and don’t get to steal their poison. So the arms race continues.
thaumasiotes
> Snakes with less resistance? Have trouble finding newts they can choke down, and don’t get to steal their poison.
That's got to be an extremely weak effect. No snake gets an individual benefit from eating the newts. They get a collective benefit, that predators recognize the species as poisonous, in which all snakes, poisonous and delicious alike, share equally.
The problem is large enough that actually-poisonous animals routinely have delicious mimics of entirely different species who free-ride off of the work the originals do to be poisonous.
You can't explain why snakes apparently need to avoid sending a dishonest signal with a theory that predicts that mimics don't exist.
calebkaiser
Yeah that particular aspect of his claim feels like the weakest.
Here is a slightly more in-depth piece where a wildlife biologist mentions other possible forcing functions that cause the snakes to eat the newts: https://baynature.org/2022/04/06/the-bay-area-is-the-center-...
From the article:
> “When garter snakes are born in the late summer, they often live under mats of drying pond vegetation … That happens to be where the newly metamorphosed newts come out in the fall, and we suspect there could be a lot of interaction between predator and prey just because of this overlap in microenvironment. That could have led to strong selection in the past that resulted in such high levels of resistance.”
the_af
Interesting.
Let me see if I follow: once the snake population has the warning coloration, and predators know not to eat them, then individual snakes being successful at eating poisonous newts is unrelated to the snakes living long enough to pass their genes (i. e. being successful in terms of natural selection). So a snake which has the right colors will be successful, regardless of its diet.
I wonder, is there a point where mimicry can fail? Can predators at some point start to eat the mimics?
darkerside
> The problem is large enough that actually-poisonous animals routinely have delicious mimics of entirely different species who free-ride off of the work the originals do to be poisonous.
When cargo culting goes right.
kulahan
I found this on Wikipedia, but tldr they taste test it.
> Successful predation of the rough-skinned newt by the common garter snake is made possible by the ability of individuals in a common garter snake population to gauge whether the newt's level of toxin is too high to feed on. T. sirtalis assays toxin levels of the rough-skinned newt and decides whether or not the levels are manageable by partially swallowing the newt, and either swallowing or releasing the newt.
null
alkyon
The linked article about toxic blue-ringed octopus is even more interesting.
https://crookedtimber.org/2025/03/14/occasional-paper-the-in...
benlivengood
The author points out something I've thought about a few times; we are just giant robots that bacteria use to live in and move around rapidly.
csours
Nature is not kind.
ednite
Love the title, and great article.
This might be a total tangent, but every time I see “newts”, I think about how Karel Capek actually coined the word robot in his 1920 play R.U.R., and then later gave us War with the Newts...really smart amphibians. Thanks for sharing.
rossant
As a French person, it's the first time I see this word. My brain can't help but parse the title as "death news".
ednite
I can understand why. You rarely see newts mentioned, even though they’re biologically fascinating. Maybe it’s just because people mistake them for another kind of lizard.
the_af
The War with the Newts is fascinating. An indictment of mankind told with dark humor...
onlypassingthru
Apparently the snakes' immunity pales in comparison to the local caddisflies.
[0]https://www.discovermagazine.com/planet-earth/a-beautiful-we...
titanomachy
Newt poisoning of humans must be rare, I’ve lived in this region my whole life and I don’t think I’ve ever heard of this!
icameron
I think the article is exaggerating quite a lot
> It’s so toxic that the poison from a single newt can easily kill several adult humans. You could literally die from licking this newt, just once.
TBF there is one death reported in Oregon from someone eating an entire newt in 1979, but they aren’t as bad as the article would have you believe. Many of us have handled these newts. There would be a lot more dead people if licking is all it took.
> A 29-year-old man drank approximately 150 mL of whiskey at about 11 AM July 9, 1979. At 6 PM he swallowed a 20-cm newt on a dare. Within ten minutes he complained of tingling of the lips. During the next two hours he began complaining of numbness and weakness and stated that he thought he was going to die. He refused to be transported to a hospital and was left alone for 15 minutes and then experienced cardiopulmonary arrest
jaggederest
Yes, I must have played with these newts at least a couple dozen times as a child, they were under every leaf and log in the forest and near streams where I grew up.
waynecochran
I live in the PNW and I see hundreds of garter snakes, some newts, but never a Rough-Skinned Newt. I had no idea such a creature was around here.
pmarreck
I learned a new word: "aposematic"
I can already think of uses of this word jokingly in a people context
water-data-dude
Oooooh! I saw “I’ll have to teal deer it” and thought it must be some strange idiom. Had to go to Urban Dictionary to find out “teal dear = tl;dr”, and now I feel as dim as a garter snake that’s evolved resistance to large amounts of tetrodotoxin.
hn_acc1
I didn't get it either, but now I'm just sad that it's come to this, where we have to replace 5 characters with 9 just to seem "cool". Sure, it's 2 syllables instead of 4, but then we REALLY should have avoided using www as the prefix for the web. It's not like we talk about surfing "the WWW" - and even saying the 3 letters is WAY longer than saying "World Wide Web".
It's great in german - 3 syllables for 3 letters, but english/french, it's NINE syllables for 3 letters. I always thought it should have been web.domain.org.
account42
> It's great in german - 3 syllables for 3 letters, but english/french, it's NINE syllables for 3 letters.
Kind of absurd to use multiple syllables for a single letter if you think about it.
> I always thought it should have been web.domain.org.
It should have just been "domain.org" - the web part is already specified in the protocol. And if you are concerned about domains only having a single IP that could have been (and for many protocols has been) solved with SRV records.
dole
Thanks to YOU for the teal dear.
SwtCyber
That just means you're adapting to survive the modern web
tanseydavid
I was thinking it must be a play on "steel-man" but nope.
Thanks for the taking the time to find out for the rest of us.
UncleOxidant
> Turns out there is an answer: the garter snakes sequester the tetrodotoxin, storing it in their livers. This makes them toxic to their own predators.
But this doesn't seem as immediate as the newt's defense where it's on the skin and thus causes potential predators to spit them out or even to seize up - meaning that at least some attacked newts survive the encounter. Eating the liver means the snake is dead. And since it's going to be impossible to tell if a particular snake is immune (and is thus potentially toxic) how would this deter predators? (Especially given the limited range of snakes with this immunity and the probability that there are predators of the snakes that don't necessarily have this same limited range - ravens, raptors, etc.)
tshaddox
If the predator species have heritable differences in prey selection, no matter how slight, natural selection can work with that.
null
xlbuttplug2
> how would this deter predators?
Maybe the predator's carcass next to a half eaten garter snake is meant to serve as a lesson to other potential predators.
Or perhaps the aim is not to deter but to simply take one natural predator down with them for the good of their species.
cyberax
Eating a snake might not kill a predator outright.
And higher predators (like mammals) also have food preferences. They don't always eat stuff indiscriminately, so predators that don't _like_ snakes will preferentially survive. Eventually, this can get established as a genetic trait.
Or as a behavioral one, if parents don't teach cubs to hunt snakes.
SwtCyber
How even when we think we've figured it out the system throws in a curveball. Nature's like, "Oh, you thought this was simple? Cute."
> Meanwhile, evolving resistance also comes at a cost. We don’t know that directly, but we can infer it pretty well. If resistance to tetrodotoxin were cheap and easy, everything would evolve it. [..] We don’t know, but we’re pretty sure there must be something. We know that garter snakes outside of the Pacific Northwest are much less resistant to tetrodotoxin. They’ll drop dead from doses that their Oregon cousins simply ignore. So evolving the resistance must have some cost or drawback.
I'm not so sure that's really the case; it's more that for many animals there simply isn't any pressure to evolve (or retain) this trait.
It's not like the natural selection process has a feature list it can tick off. It operates with zero foresight and an incredibly dumb principle: whatever helps procreation.
Cows are not dying due to tetrodotoxin poisoning in significant numbers, as far as I know, so there is no reason for them to evolve resistance to it. The same applies to most animals, including the snakes outside that area.
Your dog can synthesise their own vitamin C and will never develop scurvy. Most animals can do this – humans and some other primates are the exception. An ancestor lost the trait for vitamin C synthesis by chance, and because these primates were living in trees eating lots of fruit with vitamin C, evolution simply didn't notice. There is no disadvantage to being able to synthesise vitamin C, and no advantage in dropping the trait. It didn't affect procreation (at the time). Now we're all stuck with it.
Now, maybe all of this does have a cost for the snakes. But it's far from a given that there is one.