The Truth About the Single-Celled Dog

Is it possible for there to be a dog that is made of one very determined cell? Learn about this fascinating creature with Hank in a new episode of SciShow! Let's go!
Hosted by: Hank Green
Thumbnail Image Credit: commons.wikimedia.org/wiki/Fi...
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#SciShow #dog #cancer #science
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Sources:
www.ncbi.nlm.nih.gov/pmc/arti...
www.ncbi.nlm.nih.gov/pmc/arti...
www.hhmi.org/news/cancer-cell...
www.cancer.gov/about-cancer/u...
pubmed.ncbi.nlm.nih.gov/25867...
Image Sources:
www.gettyimages.com/detail/ph...
commons.wikimedia.org/wiki/Fi...
commons.wikimedia.org/wiki/Fi...
commons.wikimedia.org/wiki/Fi...
www.gettyimages.com/detail/vi...
www.gettyimages.com/detail/ph...
www.gettyimages.com/detail/vi...
www.gettyimages.com/detail/vi...
commons.wikimedia.org/wiki/Fi...
www.gettyimages.com/detail/vi...
www.gettyimages.com/detail/vi...
commons.wikimedia.org/wiki/Fi...
www.gettyimages.com/detail/vi...
commons.wikimedia.org/wiki/Fi...
www.gettyimages.com/detail/ph...
www.gettyimages.com/detail/ph...
commons.wikimedia.org/wiki/Fi...
commons.wikimedia.org/wiki/Fi...
www.gettyimages.com/detail/ph...
www.gettyimages.com/detail/ph...
commons.wikimedia.org/wiki/Fi...
commons.wikimedia.org/wiki/Fi...
commons.wikimedia.org/wiki/Fi...
www.gettyimages.com/detail/ph...
www.gettyimages.com/detail/ph...
commons.wikimedia.org/wiki/Fi...
commons.wikimedia.org/wiki/Fi...
commons.wikimedia.org/wiki/Fi...
www.gettyimages.com/detail/ph...
www.frontiersin.org/articles/...

[@plucas1]

Ah yea, the Immortal Cancer Dog. It's like a real life horror movie monster. And interesting bit of trivia not mentioned in the video: The breed of the original dog the disease came from has long since died out many centuries ago, along with most other native North American dogs. Those cancer cells are the last living remnant of that breed, having outlived all other members.

[@dabloons4days]

isn’t that whole thing crazy how this cancer succeeded it’s a living thing now wow

[@alex_zetsu]

Wait how do we know what breed it came from if we can't compare it to the original dog?

[@lisaschuster686]

You mean the small barkless dog the conquistadors described?

[@plucas1]

@@alex_zetsu The cancer cells has the dog's fully intact DNA and we have the DNA of many native North American breeds from animal remains. i can't imagine it was too difficult comparing them and finding a match.

[@plucas1]

@@lisaschuster686 I guess there were a number of Pre-Columbian North American breeds that lived with native American tribes, but most of them died out from diseases from European dogs or were absorbed completely into European breeds through copious interbreeding. I think the few survivung NA breeds include Greenland dogs and Malamutes. I'm not an expert and people definitely should look it up themselves if they get the chance. It's a fascinating bit of canine history.

[@LordBrittish]

I will call my single celled dog Uno!

[@OrangePiggy]

+4 color, red

[@sebastian8922]

That’s the name of my cat, he has one brain cell.

[@orangexylem]

Shane Dawson?

[@rahilraval9097]

We don't talk about Uno

[@AccidentalNinja]

If it expanded to have two cells, would it be Duo?

[@shinerstheseagull]

“They have human DNA, but they have started living for themselves instead of for you…” Such a raw line. Sound like it came straight out of a horror science-fiction novel

[@clockworkkirlia7475]

It's an excellent metaphor for selfish exploitative actions within the global organism as well.

[@notdumbrella6399]

Now, also experience.

[@sprout4096]

im not religous but those cells need a god

[@marblecar1162]

​@@sprout4096that seems a bit outta left field but ok

[@wiilov]

​@@clockworkkirlia7475It's all a pattern repeating.

[@m0urn1ng5tar5]

That dog really said "Can't die of cancer if I *become* the cancer."

[@DanielButler-sf4li]

It did die of cancer, the cancer survived the dog

[@Forsakenruler]

@@DanielButler-sf4liI always wondered this but but if your brain dies but your body makes a new one are you a different person

[@sybilknight]

Biologist here, and to be honest, I had never seen cancer this way, "successful unicellular life, going rogue inside your multicellular body". A beautiful way of seeing something so bad as cancer. "It is not a malfunction, but a terrible evolutionary success". WOW. And then people ask, why I did study sciences!!! XD

[@Obscurai]

Changes in perspective is what science does well. Often these shifts in perspectives is considered heretical - even by the scientists themselves.

[@jeaciamo]

Sup biologist you know how to cure insomnia

[@thou_dog]

That sense of dizzying realization is probably why a lot of people stay in STEM even if they might otherwise make a better living in a different trade or industry. That feeling of "...oh... OH WOW" when you see something that forces a perspective shift, and from the new angle, things suddenly make more sense than before. People live for that kind of moment.

[@ranth18]

There's an ongoing hypothesis (speciated by cancer development animals or SCANDAL) that myxosporeans started out as a transmissable form of tumors before evolving to its own species.

[@Cr3zant]

@@sybilknight I believe they were being very rude by insinuating that biology is boring and therefore puts people to sleep. For the record I also as a casual observer find biology incredibly fascinating and constantly being exposed to new and different ways of looking at it is endlessly enjoyable to me.

[@devinsmith4790]

To be fair, HeLa is also singled celled but also technically a human. Biology is weird sometimes, especially when it comes to cancer. Like cancer cells are just the rebels who don't follow the system, and people suffer because of that.

[@gutterball10]

Hela cells have only been around for ~100 years. These dog cells have been around for at least 10X longer than that.

[@devinsmith4790]

@@gutterball10 Yeah, but both are immortal cells. It's just one has spread naturally via sex.

[@jessefigueroa2682]

@@gutterball10 and even so, there are already some scientists saying that HeLa cells are different enough to constitute a brand new species

[@ProjectPhysX]

These cells are complete aliens by now, with somewhere around 80 chromosomes.

[@yYSilverFoxYy]

At least HeLa was only preserved by humans in lab conditions, it didn’t evolve to be able to live on its own.

[@50bottlesofpinklemonade]

Clueless person: Cancer is scary! Person learns a bit more: Cancer isn't *that* scary! Person learns even more: Cancer is absolutely terrifying!

[@victorconway444]

The bell curve of cancer

[@book_roblox]

​@@victorconway444that ain't just a bell but a damn DIVE

[@jessebeegee]

almost like they aren’t even clueless

[@mrmagnamalo7864]

It's not generally the cancer itself but it reproducing a lot you currently have cancer statistically speaking it is unlikely that you don't currently have at one cancer cell

[@rob_bg1668]

Hearing him mention cancer is weird after hearing about his recent journey listening. So happy he is doing well, and wishing him nothing but good health going forward!!

[@spicysmooth2]

I always had this thought of a cancer cell replicating like “The Thing” and I appreciate you Hank for confirming my fears.

[@RNCHFND]

This perspective reminds me of the black goo monster from Resident Evil 5

[@JohnGardnerAlhadis]

This was the first thing that came to mind when I saw the thumbnail.

[@ToyKeeper]

@@JohnGardnerAlhadis At first, I thought the thumbnail was a metaphor for zygotes because of today's bad health care news. Then when he said they have human DNA but have started living for themselves to the detriment of the host organism, it seemed like a metaphor for Libertarianism. But then it was actually about dogs. Quite a rollercoaster of an episode.

[@jeffthompson9622]

This topic and your reference to "The Thing" reminds me of Ray Bradbury's story, "Fever Dream."

[@JohnGardnerAlhadis]

_"That's not dog. That's imitation."_ - A wise man named Blair

[@adam1993365]

Absolutely loved the jokes. "... when that happens, the organism can no longer pass on its genes, because of how it is dead". LOL.

[@fghsgh]

Yeah... organisms that are dead do indeed tend to have quite some trouble passing on their genes. Except in this case somehow.

[@billyalarie929]

I cackled at that.

[@genghiskhan6809]

People die when they are killed.

[@sumitrana2420]

I didn't cause I did not even realise cause of how matter of factly that was said

[@daniellewilson8527]

@@fghsgh it passed to another host before its first host died, I also love how it was said

[@JJ-xz8dk]

So sorry, Hank, that you had to “find out what cancer is” in a personal way… Wishing you all the best.

[@friibird]

My stomach dropped once I connected the date, the host, and the topic....

[@BFRIZZLE909]

When I heard him say that about cancer, I frowned. I hate cancer with every ounce of my being.

[@drippingwax]

Cancer sucks. I lost a friend to it several weeks ago.

[@bobafettjr85]

He's in remission now.

[@drippingwax]

@@bobafettjr85 Good for him.

[@drewwalls1000]

Hey Hank! CTVT is a super scary and also fascinating concept, as its one of only 3 known contagious cancers in nature. Some recent studies however have shown that in fact, the cancerous cells that are thought to cause the tumors may actually be infected by a giant virus! This mimivirus was found when filtering much larger particles than previously tested, which seems to show that the CTVT cells are a sort of freaky blend from thousands year-old cancer cells and a pathogen. It also led to the realization that a lot of similar giant viruses have been isolated from humans cancer samples, which suggests humans may have more infectious cancers than originally thought. This discovery though has led to some breakthroughs in treatment for CTVT though, and currently a vaccine program is going through trial with rather promising results!

[@akeem2983]

I didn't knew that there are ofganisms that have symbiosis with viruses. Does it even count as symbiosis?

[@MommyOfZoeAndLiam]

Well seeing as some cervical cancer is caused by HPV it is a good link to consider.

[@Ydrakar]

If they could figure out how the ctvt makes use of telomerase to protect itself against genetic damage and apply that to humans, we would no longer die of old age. Consider that this is a 1,200-2,500 year old animal “organism” it shouldn’t be possible…

[@pileofjunkinc]

Have there been any updates on what you brought up a year ago?

[@bladeswillxbleed]

"At once the oldest and the smallest dog..." But would it be a stretch to say possibly the largest dog. If you were to gather ALL the currently alive CTVT cells would their mass exceed any currently living dog?

[@markjacobson4248]

I don't know that this is a useful way to look at it. There are multicellular organisms, such as poplar trees, that clone themselves and may remain connected or become disconnected, and to some extent it can be useful to look at each of these trees as being collectively one organism, but they're not a single organism in the way that a group of mushrooms are a single organism, where all the visible mushrooms are interconnected in a dependent way. With clonal tree colonies, the individual trees can often survive on their own if disconnected from the rest of the colony. In the case of these cancer cells, the cancer cells are no more one organism than a bacterial film is. I don't know that it's even necessarily useful to consider the entirety of a tumor to be one organism, because often times even single cells that separate are viable on their own. So no, I think that you can't really consider them to all collectively be one dog. If anything, it is a single celled pathogen that is descended from a dog and, due to cladistics, is technically also a dog.

[@skrimper]

​@@markjacobson4248 I like how you ignored his main question and just spammed random ecological information, nice try though 😂

[@garethdean6382]

Yes, oh yes, easily yes. Though this raises a question. A lot of species replicate by cloning, some kinds of aphids for example. They are a lot of individuals but genetically pretty identical. Does that make them similarly old and large? It's not like this 'dog' is a single united hive organism here.

[@kirstjohnson862]

That wud b so cool if we cud somehow figure that out...

[@hughcaldwell1034]

All I thought when he said that was "So, if you've ever wanted to see a big pile of the tiniest little dogs all together - here it is..."

[@lsedge7280]

There is a similarly interesting case, the Dwarf Tapeworm (hymenolepis nana) infected a man with HIV (diagnosed 2006), the tapeworm infection was identified in 2013 when he arrived in hospital with fatigue, a fever, coughing, and weight loss, which is when doctors found tapeworm eggs in his stool. However they also identified that the patient additionally had lung tumours, and presumably tumourous lymph nodes (described as "grossly abnormal, solid, nodular masses", with those in his neck being several centimeters large). Cell samples from the lungs and lymph nodes were sent for biopsy which is where the case took a weird turn from simply a tapeworm infection and relatively typical cancer to something far more peculiar. These tumour cells were non-human in origin, they were far to small to be human cells, and sometimes fused back together (something human cancer cells do not do). A molecular DNA analysis revealed that these cells were in fact those of the Dwarf Tapeworm, the continued infection of which in the man enabled it to acquire mutations which eventually led to at least on tapeworm in him becoming cancerous, and subsequently that tapeworm tumour then metastasized throughout the man's body. While this situation seemingly requires a very specific set of conditions (compromised immune system alongside a severe dwarf tapeworm infection, or possibly an infection by any autoinfectious parasite), in the developing world these conditions do crop up frequently, and could overlap with somewhat frequency, and so may in fact be occurring multiple times but being misdiagnosed as human cancer. It's an example not as successful as the CTVT, but it shows a cancerous tumour spreading at least for a short time beyond it's originator, and significantly of a tumour jumping species, a key trait of many dangerous pathogens.

[@marycarolynkane8720]

i think they did a video on that case a few weeks ago actually, the title was something like “the rarest cancer in history”

[@HappyBeezerStudios]

And then there are prion diseases, which are basically just misfolded proteins that turn other proteins into misfolded versions. So it is infectious and deadly, but the danger persists after the death of the host and it is invisible to the immune system, because the prions are made of the hosts strunctures.

[@lsswappedcessna]

Yep, they already did an episode on tapeworm cancer. Someone needs to send that one to Chubbyemu.

[@yukinagato1573]

Imagine how crazy it would be if the tapeworm cancer have somehow managed to survive. Wouldn't be nuts if we had a single celled-tapeworm too?

[@kaythreefox6005]

Hey L Sedge...you should totally make a video on this. Its so fascinating!

[@Dreezie]

Hank talking about cancer before the diagnosis is strange, so glad he’s in remission now

[@dumpsterfire6466]

It's so crazy that technically the dog never died, he lives on in other pups and similar things, roaming the earth. Changing and evolving as the generations go by

[@MasterTaiki]

He got that dawg in him

[@Drakonus_]

@@MasterTaiki Damn right.

[@Graphomite]

Technically it did die. Procreating is not the technical definition of remaining alive. You're being figurative, not technical.

[@sophiaschier-hanson4163]

Eh, whether or not something is alive is a fuzzy social construct and this is DEFINITELY an edge case. Given the much smaller amount of genetic drift over 11,000 years compared to every multicellular dog on Earth, I’d argue the original dog is CLOSER to being still alive than any other dog from 11,000 years ago!

[@Sniperboy5551]

@Graphomite Technically, the dog itself died, but the dog’s cells still survive. A single piece of that dog is still “alive,” it has nothing to do with procreation.

[@SilliS]

Makes me wonder whether we could clone a dog from this cell. Not that it would be very ethical or necessary but still intriguing

[@nikhilpolekar8325]

Creating RE style creature in process?. 😂

[@blepblep7245]

i dont think we can, it probably only has unfunctional genes left overs of genes that was once really crucial for multicellular life

[@italucenaz]

nah, it lacks a lot of important genes and also how do you get rid of the genes that makes it duplicate like crazy and be cancerous? the most you would do is bring back a lot of genes that were absent in dogs nowadays but ultimatelly it wouldn't make much of a difference, except the tons of failed fetuses and puppies that would die for that

[@Sarappreciates]

It's like trying to explain why early abortion should be protected. This cell, yes it's the dog, the entire dog even, but it's NOT *A* DOG. Also, you can't imagine what it would be if you were ALL cancer cells. That's some Akira-level shiz.

[@SciShow]

We definitely could not. It’s been evolving for its new lifestyle for so long that it’s lost a bunch of chromosomes.

[@1.4142]

Tasmanian devils also suffer from cancers transmitted through biting, leading to fatal tumors in the face. Devil facial tumour 1 (DFT1) was first recorded in the 1990s and devil facial tumour 2 (DFT2) in 2014.

[@MiIIiIIion]

Wait, there's two of them now?

[@arielmccarthy4892]

They are actually really adorable animals (tasmanian devils) and I hope their numbers bounce back😊 thanks stranger

[@MeppyMan]

Came here looking for this comment!

[@kingofmemes5017]

@@arielmccarthy4892 they're not adorable, they bite each other's faces when they mate and assert dominance and transmit the facial tumours. I've seen the pictures of them with tumours covering their eyes. Not adorable to me.

[@MalcolmCooks]

I thought they went extinct in the 1800s?

[@jordanedwards1501]

Hearing hank talk about cancer here hits different after him beating it all this time later

[@user-ol7bt4wp1j]

So you’re telling me Cancer is like a Cell going "Reject modernity, embrace tradition."

[@Coastal_Cruzer]

More or less

[@HelixyYT]

I’ve been working in a cancer research lab for over a year now and it is absolutely terrifying the things cancer cells are able to do because they really do act more like colonies of single celled organisms than they do a malfunctioning cell

[@FarremShamist]

I mean, if you consider it, a cancer cell that merely is out for itself only would have a very poor survivability, where those that cooperate with other cancer cells would be much more successful and able to take control of their host more easily.

[@LineOfThy]

they're thinking way too short term@@FarremShamist

[@FarremShamist]

@@LineOfThy It works within those confines, for a time. They don't really 'think' though, it's just an attempt at an alternate path of propagation. I use the word attempt loosely here, as no part of this is intentional. It just happens.

[@juska4235]

​@@FarremShamistinstead of thought or intention it should more so be called that this kills the being and now cancer has no way of gaining nutrients therefore dying therefore all that cancer genome line is done for, where here this didn't happen because it actually escapes the living being that was brought down by it and keeps on living to produce more and more cells So that short term " thought" is a good metaphor for what is happening to regular none infective parasitic cancers, until they can live on their own their independence from other cancers or the being itself is quite short sighted aka dooms their genes and doesn't make them any progress thankfully That's why ctvt seems like an apocalypse waiting to happen it evolved way too much and can still evolve as it preserves the progress until unstoppable

[@FarremShamist]

@@juska4235 It's a completely understandable and natural extension of evolution that, as cells divide, the immediate advantage of cancer is enormous for selection. It can grow very easily once it gets off the ground, but it only goes as far as its host survives... Which does not really happen often, as most don't take a step into becoming infectious, it's not something often selected for. And evolution usually extends to immediate reproduction, what helps or allows more reproduction now, instead of a plan for later.

[@gutterball10]

I agree with Hank, this is one of the most bizzare case studies in biology I have ever heard. WOW.

[@coraldelaluna]

Same

[@InstantK0ed]

Many cancer, much doggo, wow.

[@pressaltf4forfreevbucks179]

This hits hard with the recent revelations😮‍💨🤕🤕

[@cockatoode705]

One of my favorite things about cancer is how *innocent* it is. Cancer isn't some malicious disease. It's just doing its job, even if it's confused. If we could give cancer sentience, it would never have realized it did anything wrong. It's efforts to grow and do its job often leads to its own death, and in this case, the death of other organisms. That viewpoint has helped me cope with the frequent cancer diagnosis' in my family, I don't see cancer as a villain any more

[@mrpickles-hb6zx]

U do have a point, plus sometimes people cause their own cancer knowingly and willingly, "tanning beds" "toxic makeup" etc

[@benjaminmiller3620]

It's happening again in fact: Devil facial tumor disease (DFTD). Also there are a handful of documented cases of transmitted human cancers, but AFAIK they were all due to bad surgical procedure, not "naturally" occuring. But the real question: So what are the Dog Breeders Association show standards if I wanted to compete my CTVT?

[@coleames514]

Can’t forget about the cancers that have spread from one bivalve species to another species off the coast of Spain

[@Obscurai]

Human papillomaviruses 16 and 18, carry a risk of becoming cancerous.

[@AccidentalNinja]

@@coleames514 I think the bivalve transmissible cancer is a lot scarier because it's waterborne, not requiring direct contact with the carrier. What happens when that starts to be able to jump species?

[@lialaokami]

The breed standards are: must be unicellular organism of x size. Obviously.

[@benjaminmiller3620]

@@coleames514 I'd forgotten about that one, thanks for reminding me.

[@samwill7259]

Oh good. CONTAGIOUS, SEXUALLY TRANSMITTED CANCER. No that's much less terrible and upsetting a thought, thanks Hank! I'm gonna go never sleep again!

[@GuitarGuise]

Never sleep with anyone again*

[@glenngriffon8032]

Ah, there it is. The daily reminder that the world I live in is a bleak hellscape.

[@DangerDurians]

@@GuitarGuise Never sleep with DOGs again

[@Obscurai]

Welcome to the real world of biology. Unobscured by belief and dogma.

[@iota-09]

Oh no worries, all you need to avoid that is never have sex anyway.

[@nuclearcrayons3511]

Foreshadowing 😅 glad you made it buddy !❤

[@YuBeace]

Hank: "Hank, I know what cancer is." Me, coming from a year into the future: *Sweats nervously.*

[@ThatFreeWilliam]

Once upon a time, there was an adorable puppy named Cloney. Cloney was the tiniest a puppy could be. He was so tiny that none of the other dogs even knew he was there. Poor Cloney was all alone and scared. “Oh! I know how to make a puppy!”, he thought. “Then I’d have a friend!” So Cloney went to work and started to make a puppy friend. (It was a little weird) When he was finished, there, right in front of him…was an adorable puppy like himself! “I’m Cloney!” said the new puppy. The original Cloney nodded sagely, setting a bad precedent. So Cloney and Cloney frolicked. And they played. And then Cloney had an idea. “I could make another puppy to play with too. If we BOTH made puppies to play with, we’d have two more friends!” Cloney thought this was very clever. And so they set to work (It was twice as weird) “Hi! I’m Cloney!” Said the new friends. And they played. After a lot of playing, and more than a lot of weirdness, it started to get crowded. “Maybe we could work together and be something more than a collection of disorganized puppies?” asked Cloney. “Nah”, replied Cloneys democratically Cloney was seriously embarrassed and was never heard from again. There was a long pause with lots of fidgeting. “Maybe we can find somewhere new to play!” said Cloney desperately when too many of Cloneys all looked at him at once. “Oh yes, that sounds much easier” replied Cloneys. Cloney, who long suffered from social anxiety, was the most relieved puppy ever that day. So they looked and they looked. “I see a way!’ said a different Cloney Indeed, there was a way. The way was torturous and not all survived But some brave Cloneys found footholds in new lands …and from then on, as long as there were dogs or foxes or coyotes or even hyenas; Cloney knew he’d always have friends. So began the Apuppyacolypse.

[@FORGOTTENMINDFREAK23]

Apupcolypse?

[@CrownofMischief]

Armageddog? Dognarok? Pupture?

[@proloycodes]

dang!

[@karishadkit27]

This dog puns make me barking mad But Apuppyacolypse is good.

[@ThatFreeWilliam]

@@karishadkit27 It's also extremely fun to say :)

[@Omnifarious0]

"Is this a dog?" ... You're making an Elden Ring reference. I'm surprised and amused that your sense of humor led you there.

[@Genus39]

I think the Elden Ring reference is actually an "is this a butterfly?" meme reference, which is what the title is referencing

[@Omnifarious0]

@@Genus39 - The video thumbnail has "Is this a dog?" on it.

[@Genus39]

@@Omnifarious0 yes. And that is referencing a meme, not elden ring. Lol

[@Omnifarious0]

@@Genus39 - I've played Elden Ring all the way through, and "Could this be a dog?" shows up all over the place.

[@Decrepit_biker]

This video hits different now. Get well soon Hank !

[@Auric-BraiNerd]

Coming back to this video after he is successfully in remission. I'm sure this one and others on the topic have some new significance to him

[@IceMetalPunk]

Evolution is extremely simple: it requires only three properties, which can be summarized in a single sentence. "If something can make imperfect copies of itself, and those imperfections change how many copies the copies can make, then that thing will either go extinct or evolve." Keyword is "will", not "may": with those properties, anything will always evolve or die, and that's not even limited to biological things, either. In this case, we've got cancer, which makes lots of copies of itself, until it kills the host, and then all those copies stop happening, thus making it a short-term success and long-term extinction. Except in this one case, where the copies *didn't* stop happening when the host died, leading to the most successful dog ever.

[@HauntedHarmonics]

fun fact: a similar thing has happened to Tasmanian Devils, also due to their low genetic diversity. Their contagious tumor disease is known as DFTD, or “devil facial tumor disease”.

[@remus-alexandrusimion3439]

OMG, I've seen a documentary about this years ago (before YT) and have absolutely forgotten about it until now. I recall the documentary saying the cancer was spread through bites during fights between the animals...

[@manfredconnor3194]

​@@remus-alexandrusimion3439Yep. I saw that too.

[@michaelmcchesney6645]

Watching and listening to Hank talk about cancer a year after this video was published is weird and a little disturbing.

[@bwayagnes2452]

Yeah… O___O

[@OlleLindestad]

This is one of the best SciShow episodes ever. Bizarre subject, great dramatic arc, clear and perspective-widening explanation.

[@patrickmccurry1563]

Tasmanian Devils suffer a communicable cancer as well. In some populations, it had a 100% fatality rate. Thank goodness nothing like that exists in humans... yet.

[@Obscurai]

Human papillomaviruses (HPV) 16 and 18 is sexually transmitted and carries a risk of becoming cancerous.

[@limiv5272]

I was looking for a comment about that. Thankfully, humans aren't as prone to biting each others' faces

[@pigcatapult]

It has, actually, but the buck has always stopped at the one degree of transmission. Hank only touched on genetic bottlenecking briefly in the video, but it's absolutely necessary for a transmissible cancer to keep going. If your body would reject an organ from someone, your body would reject cancer from them, too. Thus, every instance of transmissible cancer in humans has involved either surgery (e.g. transplant of an organ that turned out to have some cancer cells in it) or a disease like AIDS (e.g. that poor guy who caught tapeworm cancer from a tapeworm and died before doctors figured out why the cancer cells were so tiny). And then there are transmissible viruses that can *cause* cancer, like HPV!

[@patrickmccurry1563]

@@pigcatapult Some transmissable cancers have jumped species in shellfish though. So bottle-necking isn't absolutely necessary.

[@dragonairdragon6173]

@@patrickmccurry1563 It needs a bottleneck to get settled in first. It won't learn to jump species overnight, it has to slowly learn to infect different host in one species first.

[@kylesty6728]

You might consider doing a video one day about how this particular cancer is so ancient that it almost “wants” to die. Its genome is stable now, mostly benign to its hosts, and, intriguingly, it doesn’t seem to have the tools anymore to fight the most basic cancer treatments. It’s extremely easily treated and will likely go extinct this century.

[@mal2ksc]

That might just be the natural asymptote approached in any system that has to balance its own reproduction against not killing its meal ticket. It becomes more efficient by dropping the abilities it's not currently using.

[@Zmiana_Pogody]

...and [imo] all of that not because it "wants", but because of pure chance, accident, charade of probabilities...

[@kylesty6728]

I was just giving them a clickbate title suggestion, y’all ;)

[@Appletank8]

@@mal2ksc So kinda like a normal cell, eh? If it kills its host, it can't reproduce.

[@screwyourhandle]

@@Zmiana_Pogody I think most people here understand that cancers don't literally want things and it's just a rhetorical device

[@willmendoza8498]

Been a while since a SciShow video blew my mind, but this one sure did. Great work.

[@onyxianna]

I have to agree with Hank. In all my years of study as a biologist, this may very well be the strangest thing I have ever learned regarding biology.

[@rachels8334]

I found out about a different contagious cancer roughly 10 years ago. I turned on my car to the middle of a story about it on NPR. I was so incredibly perplexed and afraid of contagious cancer! The way it spread was terrifying. These were external tumors typically on the face. They'd spread when the tumor was bit or scratched and then cells spread to the one that did the biting or scratching! Or even with blood from the wound encountering damaged skin or entering the mouth. I was about to panic about a zombie apocalypse when finally they reached the end of the story and recapped. This is a cancer among Tasmanian devils! I had listened to most of a 4 or 5 minute story horrified thinking this was human behavior and a human disease.

[@MarianaSilva-kh4io]

lol... Don' t do drugs kids XD

[@Chorismos]

Lmfao

[@blockhead4791]

I do wonder if cancer zombies could actually happen like this though.

[@finnmckinlay]

Yeah they covered this story in my ecology undergrad! Transmissible cancers are gnarly

[@yabi333]

​@blockhead4791 we have those, they're called Redditors (joke)

[@saltenzy449]

Yes! The last surviving breed of new world domestic dog, otherwise known as a sexually transmitted cancer! When I first heard about CTVT I was floored. It was like suddenly getting the right prescription glasses and being able to see the horizon for the first time. The scale of what life is and what it can end up doing to survive just hit me and my already growing flame of interest into biology and evolution kicked up into a brush fire. This parasite is the main reason why I have 4 organisms planned out in a speculative evolution project that all take their own crack at becoming cancers. So glad y'all finally covered it!

[@RealRedKoopa]

There are other living New World dog breeds like Chihuahuas but still interesting that this one is technically alive lol.

[@kindlin]

How do you have 4 distinct "organisms" that you'll presumably let evolve over time until they "become cancer"? What does that mean, exactly? That sounds sarcastic, but honestly, I'm perplexed.

[@daniellehaythorne7949]

You’re planning on creating favorable conditions to encourage more types of cancer to exist in the world…

[@daniellehaythorne7949]

Just kind of think you could learn so much from watching the currently existing, rapidly reproducing and therefore more rapidly evolving lifeforms. You could study evolution at the cellular level. There are so many different types of cancer cells to learn from and even compare.

[@daniellehaythorne7949]

This dog cancer outlived its host and it naturally came into existence. New cancer encouraged into existence by humans, that may eventually outlive its host even though it kills its host…that is one more contribution I’d not rather we make in this world, especially since we’re only beginning to understand how much we’ve already ‘helped’ so many other lifeforms suffer and eventually die out. But do as you choose. I just ask that you consider whether you may find the answers you need in a way that will truly be beneficial to life on our planet in the big picture.

[@benedixtify]

It's weird watching Hank talk about cancer when he still had straight hair, before chemo

[@astaphe9186]

Weird having this cross my dash in light of recent events with Hank.

[@combatking0]

The good thing about a single celled dog is that it's easy to store in most overhead compartments.

[@DefnitelyNotFred]

😂😂😂

[@fakjbf3129]

It’s perfect for apartment living!

[@primarytrainer1]

I was diagnosed with cancer this April. Thank you for helping understand what's wrong with me in a new way and in a way that makes me feel like I can understand it.

[@Nikento]

Dam hope you overcome it and recover. It might not mean much coming from some random guy on youtube but stay strong and i wish u luck.

[@donnalombardo4368]

I hope you and your doctors can overcome your cancer, so that you remain with us.

[@omniscientgoat]

Good luck, mate, I hope things get better. Stay strong, like Nikento already said.

[@pacomatic9833]

Stay strong man.

[@lavinialadlass9432]

Good luck.

[@daianmoi8528]

I think this kind of nuanced understanding helps to combat the mindset of “why haven’t we cured cancer yet?” You don’t cure growth, you control it.

[@KPopsicleSNSD]

Very cool video, thank you Hank!

[@seatbelttruck]

No mention of "Devil Facial Tumor Disease?" You definitely alluded to it. It's a pretty fascinating topic! I was also wondering if you'd mention Henrietta Lacks. Her cancer's still alive and kicking, though only thanks to a laboratory.

[@DaimyoD0]

Yeah, I was thinking "I know there's at least one other contagious cancer, does that one follow the same mechanism?"

[@yukinagato1573]

The case of Henrietta Lacks is a bit different, as her cancer, though alive and kicking and incredibly fascinating on it's own, is being artificially maintained by humans. What CTVT and DFTD did, however, is remarkable on a whole other level. Those cancers evolved ON THEIR OWN to become transmissible. Like, naturally. Without any assistance. And this is completely nuts.

[@Hi_Im_Akward]

YES! I'm so glad you did an episode on this. I heard about this cancer recently and ever since the question of how has been bothering me. I'm so happy you covered this!

[@shelton9988]

So glad you covered this!! Only other time I heard of it was in Trey the explainers vid abt prehistoric dogs.

[@CODDE117]

Listening to Hank talk about cancer in 2023 changes the context quite a bit

[@Red7Viking]

This is the dog that never ends, it just goes on and on my friends...

[@Red7Viking]

Two doggies started doing it not knowing what it was, and they'll continue passing it forever just because...

[@makaylamusgrove4807]

Vet student/fostered a dog with TVT: luckily it's very responsive to chemo and dogs have way less side effects from chemo treatments than humans do. My foster only every had diarrhea after one round, her main side effect was low platelets and white blood cells so occasionally we had to wait an extra week for treatment. But it's an interesting disease, pretty sure the paper cited in this video was the one my professor referenced in his lecture.

[@NH_HN]

This video just taught me several things about cancer I didn’t know before. Thank you!

[@vaszgul736]

This is the perfect dog body. You may not like it, but this is what peak performance looks like.

[@honourabledoctoredwinmoria3126]

This type of thing actually happens to pathogenic viruses and bacteria, too, if you think of all the viruses in one host as a single organism whose goal is to get one of those viruses into a new host to spread their genes. For example, polio's strategy is to spread in poop. It's very, very good at this. It takes only 20 viral particles to make someone sick. Someone could spread polio entirely asymptomatically in poop for weeks before they even notice they are sick, if they even get sick. It can persist for a very long time, even when the body creates an immune response against it. And all this is not actually a problem for us, because unlike many other viruses of the digestive system, although polio obviously kills the cells it infects, it doesn't seem to infect enough cells to cause any disruption in organ function. In 90% or more of patients, it causes no disease. However, in some patients, in makes it into the blood, and from there, it can replicate in muscle and fat tissue, causing aches and pains and all sorts of unpleasantness. Worse, in about 10% of those patients it spreads from the muscles to motor neurons and the CNS, where it causes paralysis, meningitis and possibly death. But here's the thing. Someone with symptomatic polio is no more contagious, and might even be less contagious, than someone with asymptomatic polio. No matter how high the levels of virus in the blood, muscles, and brain end up, none of them leave the host and seed new infections. Because of this, there are plenty of successful mutant strains of poliovirus that have actually lost the ability to infect nerve cells. We even encouraged the evolution of some of these these strains to use as the oral polio vaccine. They can spread very successfully, being just as capable of seeding new infections as the strains that can infect nerve cells. And yet, something weird happens. These viruses "revert" to pathogenic ones. Mutations crop up to allow them to infect and kill nerves cells. But I just said that infecting nerve cells confers no survival advantage to polio. So why does polio repeatedly evolve to infect these cell lines? Well, the individual virus particles that have the ability to infect blood, muscles, and nerves can now exploit new niches and make billions of copies of themselves. Sure in the long run, they don't actually succeed in spreading their genetic information anymore than a lung cancer cell that makes billions of copies of itself succeeds in spreading. In the long term, when the host dies, they go extinct. In the long term, when the massive cell damage they cause alerts the immune system to their presence, they go extinct. But evolution doesn't work on the long term. It works on the now. Mutations that lead to more copies of the individual replicator spread, even if they have no survival benefit for the whole. This is why when people say "Viruses evolve to harmlessly coexist, because that's in their best interest", it's ignoring half the story. It may be in the best interest of the collective covid viruses in a body to become something like a cold that doesn't ramp up the immune system too much and lets the patient run around and carry on with their day and spread viruses everywhere. But if an individual virus particle develops a mutation that allows it to multiply unchecked in the brain, then the virus will multiply in the brain. Because what's best for the whole or what's best for the long term doesn't enter into it. All that enters into it is whether a mutation makes more copies of itself.

[@HappyBeezerStudios]

The thing with viruses is, they're basically treading the line of what can be considered "living". They aren't able to replicate on their own, which is often considered an important metric for life. Some viruses are so reduced, that they need the presence of other viruses to replicate. But I agree, it would be in the best interest of a virus to be less deadly. If you kill off 90% of the population, there aren't enough left to continue spreading it and the dead are pretty worthless as hosts. And for opening new niches: We are the only primate species with two kinds of herpes. And the evolutionary tree of the herpes simplex viruses closely resembles those of primates, suggesting that both developed together. Except for HSV-2 which is closer to ChHV than HSV-1, suggesting that at some point one of our ancestors caught a second strain from an ancestor of modern chimpanzees.

[@excluseive9769]

Thanks for this. That was good read

[@TheRABIDdude]

Really well written, and fascinating! Although that doens't mean viruses *won't* evolve to become less harmful, because that IS in that in their interest on the person to person scale. With humans, our cells can escape their constraints to become cancerous, which is bad for the whole. As a result, the whole has evolved a plethora of control mechanisms to make that escape scenario monumentally difficult to pull off. And the same will be true of viruses. If you're polio and you don't infect nerver cells normally because it's not good for the whole, but you have a gene which after just a handful of mutations will result in nerve cell infection, then over time you're going to evolve additional barriers to those mutations or ditch the proto-nerve infection gene entirely. Because the harder it is for one rogue virus to crash the party for everyone, the more likely it is for everyone to go unnoticed and transmit to another human. Which means on the global scale, polio viruses which ditch the genes which can be exploited by selfish rogues will increase in prevalence. The real dangerous scenario is when the harmful time period of an infection comes after and doesn't overlap with the transmissable time period. That creates a selection shadow, where the virus can do any amount of harm to the host without damaging its own chances of transmission because the transmission window has already passsed. That's like dementia in humans: it only really affects people who are well beyond their reproductive age, so our genome was never incentivized to create prevention mechanisms.

[@MariaMartinez-researcher]

Very well said. A important thing to always remember, attributing to such a simple organism that we aren't quite sure whether is a living thing, the capacity of *having interests,* be short or long-term ones, is a really long stretch. We humans many times work against our own interests in multiple aspects of our lives seeking short-term advantages and *we have brains.* Expecting a virus to stop to consider long-term goals is like believing a car has feelings.

[@TheRABIDdude]

@@MariaMartinez-researcher When talking about what is and isn't in a virus's interest, people aren't talking about wants/desires experienced by the virus, nor the ability to plan. A virus is certainly incapable of both; there is no dispute over that. Rather, people are personifying the virus as a linguistic shortcut to discuss how the laws of natural selection play out. It's like how, to aid in the explanation of a car engine's function, I might say "the air pushes the piston up the cylinder because it *wants* to take the path of least resistance." We both know air is incapable of wanting or planning anything, but it's convenient to structure language that way.

[@Qui-9]

This is another level of blowing my mind. I perfectly understood it, but the fact that part of a dog decided to go rogue and "blow this joint", living an independent life, astounds me. "I'm inevitable"... No longer able to form a dog in their current state, the potential is invisible. That begs the question, are there any other existing pathogens which, if altered the right way, could have once been another creature? 😳

[@Nightfenyx]

yeah like for example the protozoa or protist, single cells with nucleus, where they in the past a multicelular organism?

[@rooster9116]

In Colombia, a guy got cancer from a tapeworm in a way similar to this. He had a tapeworm infection, the tapeworm got cancer, and the tapeworm cancer parasitically invaded the man’s body. It however died with the man, but it’s another example of cancer jumping between different organisms.

[@thephoenixsystem6765]

This video aged... a year

[@H2SO4pyro]

For those who wonder if it could happen with humans, you'll be pleased to know a single case of cancer transmission was recorded between a patient's cancer and a nurse, seemingly through a needle misshandling. So it indeed could happen again. For those who didnt ask i'm sorry for giving you a new phobia...

[@_shadow_1]

And that is yet another reason why you shouldn't share needles.

[@H2SO4pyro]

@@_shadow_1 i'm not really sure a nurse would "share" a needle with a patient, but who knows ? 😂

[@david2869]

Do you not know of the story of Henrietta Lacks? Although that cancer-turned-single cell instance doesn't spread among humans.

[@H2SO4pyro]

@@david2869 Of course i know. The thing im talking about is a different case. And a fascinating one at that ^^

[@eeveeofalltrades4780]

@@H2SO4pyro maybe it wasn't that kind of needle...

[@falcychead8198]

My niece had a small dog composed of, I would estimate, about 1,000 cells, 4 of which were brain cells and 900 of which made up the eyes and tongue.

[@lstein8670]

?

[@CL-go2ji]

@@lstein8670 I´m guessing the niece had a teecup Chihuahua.

[@lsswappedcessna]

@@CL-go2ji in that case, they're forgetting the extra approx. 500,000 cells, the purpose of which is generating pure, unadulterated hatred for existence itself. And little needle-like teeth, perfect for biting off noses and other extremities.

[@kieranh2005]

4? So many?

[@bruhmoment1835]

A teratoma?

[@mostlyimpulsive3462]

As someone who's set on studying biology for life, this is still one of the coolest case studies I've ever heard of.

[@quincyhotchkiss4775]

Bro truly has the dog in him

[@kotic79]

Lol. Luckily he's Cancer free as of now

[@yomin2162]

Reminds me of HeLa cells. Not to the same degree as TVT, but they also figured out how spread by aerosol and infect other cell lines that were worked on in the same cabinet. So many unique cell lines were later found to have been taken over by HeLa, and tons of research were discredited.

[@cuckoophendula8211]

I like looking at this like a sociological analogy. Whether we live in a society or not, we can see each of ourselves as an individual that wants to survive with our own survival instincts. While this can work within the "law of the jungle," it may not be in our best interest if we all live in such a way within a society (analogously, we are all cancer cells within the body of society). If society (or the body) dies, we each would have a lower odds of survival as well. Meanwhile, one kind of fail safe would be the law (immune system), which keeps us from wanting to become a cancer to our society.

[@josephhoward4697]

It’s all about competition.

[@orsaz924]

🤯

[@Soleilune1995]

@@josephhoward4697 Multicellularity likely evolved because cooperation + specialization tends to be more efficient for survival compared to constant competition. When you cooperate, you not only get the resources that you need, but you also end up saving precious energy, because you are not doing 100% of the work. That means you can sometimes actually produce surplus, which is not possible if everyone always looks out only for themselves. Evolution doesn't care about our ideas of morality, obviously, but our ideas of morality do have a basis in evolution. We evolved to believe that certain things are universally "good" (like sharing and being kind) and others are "evil" (like cheating and being unfair), because beliving these things is beneficial to our own survival in some way or another, even if it is difficult to fully explain. What nature clearly prefers does not always seem to make perfect sense, but you can't really deny that there is a reason for why things are the way they are.

[@josephhoward4697]

@@Soleilune1995 I thought about that shortly after I posted my response, but even then there’s competition between the cooperative and the competitive. Law competes against crooks, the body competes against cancer, and so on. Even your description of cooperation makes it sound like cooperation is a response to competitive pressure. Everywhere you go, it seems like competition always exists on some level.

[@donngreitontordilla1456]

What does this say about the tension between equality of opportunity on the one hand and liberty in the other, if we compare cells and organisms with humans and societies?

[@mellissadalby1402]

Hi Hank, speaking of Cancer, Henietta LAcks Postumously has greatly aided cancer research with her HeLa cell line.

[@violetskiy854]

This is so fascinating!

[@nickolaswilcox425]

the funny part of this one is that from what i recall they discovered something rather ironic about it when they did the genetic testing, its a new world pre contact dog, one of the extinct dog breeds the settlers wiped out and this sole survivor is continuing to make life hell for the descendants of those who replaced it

[@dragonairdragon6173]

May be this is what restless spirits really are.

[@italucenaz]

This feels like something out of a scifi body horror novel, "we enginered this single celled parasite out of human dna and now this is techically a person,but it no longer thinks or are even able to create tissues, and it's made by the body of your loved one"

[@Obscurai]

Read up on HeLa cells. They are exactly as you described, but are useful.

[@italucenaz]

@@Obscurai oh yeah, I know about it, but the horror there comes much from form the ethics than anything, idk if these cells can parasitize people just like CTVT does

[@DancingAngelOfSpira]

Have you read Parasite Eve or played any of its game adaptions? It's pretty much how you described 🥶

[@italucenaz]

@@DancingAngelOfSpira I'm afraid I never heard of it, no

[@mordechaisanders7033]

oh dear, the sad irony of this video. get well, hank.

[@maxdon2001]

Great video!

[@alemercado961]

I felt like I was on a bad acid trip on this one. Mind blowing video. Thank you for what you do ❤️

[@amelade]

for real!

[@Sandr0music]

What a great video, not only the fascinating content, but the pacing, the writing, the delivery... Thanks Hank!

[@naufalap]

the entire thing sounds like the worst monkey paw ever occurred when a dog owner wished his dog to be immortal

[@blazednlovinit]

This is fascinating and something I've never heard of before.

[@MagicHasArrived]

This changed the way I think about cancer. Neat. Thanks, Hank!

[@Yellowdigigod]

Those who play Elden Ring: 🐢 ← Could this be a dog?

[@NotThatUser]

Disparage this message? Yes Rated Poor

[@jaceyates6315]

what a wild video to watch now

[@julianbarajas684]

One of the craziest bits of evolutionary info I have ever learned. Thanks for blowing my mind

[@SaltpeterTaffy]

"I put the fires out!" "You made them worse!!" "Worse...or better?"

[@metametodo]

My most precious sci show episode in a long time, big thing considering I watch every other video here. That's an incredibly amazing new perspective on cancer. Seeing it like that exposes the true nature of multicellular organisms, a cooperation of cells, most times very well organized, but it's still a cooperation where some units, if successful evolutionary traits are developed, may "choose" to go by themselves again. A transmittable form of cancer isn't fnctionally very different from pathogens like bacteria and virus. You may call it a dog, but you shall also see those cells, with a dna that has many genes we identify as "doggy", as simply single celled organisms, with common pathogen behaviour, evolutionarily successful, abusing of their hosts' vulnerabilities. In a dramatic way, it's a cell that quit multicellular life and chose to go rogue, victorious in evolution, as evolution acts on every domain of selection, gene, cell and organism.

[@Johnny.j]

Hank throwing awesome facts at us as always, ILY

[@jayc7559]

You know, it actually makes a lot more sense as to why it is so hard to fight cancer with this explanation. It’s survival of the fittest and we are actively fighting against ‘the fittest’

[@theeccentric7263]

The “hot take” is appreciated- it is engaging to feel I’m viewing the bleeding age of science in a way :) One of my favorite parts about this channel.

[@alexusandmichi]

AGREE!

[@TheFunnyDictator]

Wdym?

[@ImmortalAbsol]

"Because of how it is dead" 😂

[@CLaw-tb5gg]

Being in the vet world I was aware of TVT, but I had always assumed like so many quite a few canine tumours it was viral in origin (causing tumours is one way that viruses have developed of evading the immune system, given they're most vulnerable to immune attack when they're outside cells - if they can infect one cell and then cause that cell to replicate wildly then they can effectively infect many cells without ever having to leave the first cell). So this was very interesting to learn.

[@Earthstar_Review]

I'm glad you addressed hotdogs as a sandwich being a deadly disease.

[@techman2553]

Imagine discovering a cancer cell in chickens that turns out to be a single celled dinosaur with the complete DNA from the animal that lived millions of years ago, and then we extract and clone it.

[@TheYeetedMeat]

No cancer Like that would ever have the complete DNA of the original organism, especially after that long. It would be unrecognisable.

[@LTD538]

Dont think thats how it works bro

[@ale-xsantos1078]

*Creates the Amebasaur*

[@iluvpandas2755]

I think if you tried to clone the dinosaur from that you would end up with a dinosaur shaped blob of cancer.

[@InfinityOrNone]

A thought: we have the science of cloning, and have done so successfully for dogs already. We also have the science of genetic engineering. So could we sequence the genome of these cells, identify and replace the mutated genes that have turned them into cancer, and then clone the original dog?

[@theodore970]

I was wondering the same thing

[@honourabledoctoredwinmoria3126]

@@theodore970 No. Because it is missing many of its chromosomes. And the chromosomes it has are full of mutations that are designed to help it in its present form as a transmissible cancer. That's why we can't even say whether the original dog was male or female. The cancer has no sex chromosomes. It lost them. Why would it need them? It's a single celled organism that doesn't have sex.

[@pakde8002]

I suppose so Dr Frankenstein, but why do you ask?

[@DoctorObscure]

@@pakde8002 Probably has something to do with the genetic diversity to be gained from reintroducing an extinct breed of dog (minus the cancer) back into the gene pool. A lot of the inbred purebred dogs produced today are closer to Frankenstien monsters than that.

[@Sodier402]

It’s missing a lot of the original genetic material, that’s why they can only tell it’s a new world dog with some coyote mixed. As it’s a new world dog there isn’t really a base model to use as it definitely didn’t resemble any of the few remaining breeds.

[@joshuawhinery208]

Wow! Fascinating!

[@40watt53]

This is like the coolest thing I've heard in a year, what the hell.

[@carpemkarzi]

Very cool and yeah the reasoning is sound. I also thought of HeLa as our more modern albeit man made version but a ‘wild’ transmissible cancer is a frightening idea that I hope remains as single species oddity.

[@garethdean6382]

Do yourself a favor and don't look into Tasmanian Devil facial tumors.

[@nathanlevesque7812]

worst STI ever

[@RobleViejo]

There is an X-Files episode where a dude became 100% cancer, all his cells were cancerogenous. He wasnt a Kronenberg monstrosity tho, he was literally immortal, any part of his body could grow into a new dude, because all of his cells were him. Pretty cool episode.

[@clownscum3517]

this is one of the most interesting videos i've seen in a while, we're pretty much conditioned to view cancer as a flaw of like that to see it as evolution succeeding is a very interesting take and can help see evolution and life though a completely different lens

[@danielsykes7558]

(Me seeing Hank talk about this with a year of history ahead of him ...)

[@almostacrone8046]

This I why I love this channel. I always learn something new for you all. 😊

[@ppsaha1994]

This episode is by far the most interesting scishow video in a long time, and I watch all of them, even the podcasts.

[@dragonairdragon6173]

Returns to single cell life style. Becomes immortal.

[@eewag1]

How ironic that they picked Hank to talk about cancer in this video