Scientists have traced human tail loss to a short sequence of genetic code

https://www.cnn.com/2024/03/23/world/humans-tails-genetic-mutation-junk-dna-scn/index.html

by priyankanath • 2 years ago

192 222 2 years ago

cnn.com

Joel_Mckay• 2 years ago

Some do, but get corrective surgery as babies.

K0balt• 2 years ago

They buried the lede:

Even if the driving mutation identified in the study could be undone, “it still wouldn’t bring back the tail.”

Oh well.

Waterluvian• 2 years ago

So I’m guessing this is less like, “we found the flag that toggles tail production” and more “we found a chunk of code that belongs to tail production”?

The first bit of the article sure makes it sound like this DNA is what does it all.

icegreentea23• 2 years ago

The scientists believed that the extra AluY element was functionally working to block out a part the TBXT gene (exon6). In their mouse model, they first directly snipped out exon6, and found that mice that were heterogeneous wildtype TBXT and exon6 removed TBXT developed a full spectrum of tail phenotypes from no tail to full length tail. At this point, the statement is "These results provide further evidence that the presence of TBXTΔexon6 is sufficient to induce tail loss".

They then tried to "more realistically" replicate the scenario. Instead of just snipping out exon6, they tried inserting in various elements into the mouse TBXT gene to emulate their model of how AluY is cutting out exon6. They attempted a few different methods which resulted in different models that would end up with different relative amounts of TBXT missing exon6 being produced. I'm having a hard time tracking all their conditions and lines at this point, but they seem to claim here that higher amounts of exon6 drop out correspond to shorter tails.

They also found that they could not get any viable mice with exon6 snipped from both copies of TBXT.

TBXT itself is a transcription factor, meaning that it controls the expression of other genes. There's probably a set of genes elsewhere that together make up the "tail-making machinery" that TBXT heavily interacts with. In this sense, TBXT 'might' be the most important single point lever, but at the same time not be fully in control of the underlying machine.

What does seem persuasive is that idea that this mutation kicked off some rate of tail lose in our ancestors, which then lead to some sort of selection advantage. The advantage was then made more durable by accumulating additional mutations to lock in the phenotype. In addition, once the "tail making machinery" is inactive, we have no idea how those genes might have been repurposed. I think it's in this sense that the scientists say that we probably can't bring tails back just by "fixing TBXT".

layer8• 2 years ago

Probably the difference between necessary and sufficient.

ummonk• 2 years ago

We found the flag that toggled tail production, but the tail production code is no longer in the codebase so turning on the flag again wouldn't do anything anymore.

Standards12• 2 years ago

So close!

7thaccount• 2 years ago

The greatest thing on this thread is how disappointed we all are for some bizarre reason lol. It would be cool to get them back for better balance.

datavirtue• 2 years ago

They aren't trying hard enough,then.

Natsu2• 2 years ago

There are some people who are born with tails, though:

https://www.webmd.com/baby/what-is-a-human-tail

FrustratedMonky2• 2 years ago

A tail is grabbable.

I'd think in primate fighting, a tail would be big negative. It could be grabbed.

Can you imagine Chimp fights if they had tails that could be held on to and the owner dragged around.

moffkalast• 2 years ago

The problem might be size, lots of smaller primates have tails which can be very useful as a fifth arm for holding onto branches. As you get larger, tree foraging becomes less viable and the tail less useful and it would need to be oversized to be able to function properly.

whycome• 2 years ago

This seems like one of the times I can mention that dolphins and elephants have evolved prehensile penises. Sometimes nature finds a way.

vbezhenar2• 2 years ago

Most of animals don't use tails as a fifth arm. My cat seems to use it for extra balance. I think that humans could do that as well.

amelius• 2 years ago

Replace tail by arm in your comment and see what is wrong about it.

feisuzhu• 2 years ago

Arms are powerful but tails are not.

mkoubaa• 2 years ago

Seriously? Cost benefit. Arms have more benefit but not this cost.

vbezhenar2• 2 years ago

I don't follow. You can grab leg and drag owner around. How's tail different?

marginalia_nu• 2 years ago

A leg has rigidity due to its endoskeleton, as well as strong muscles with good leverage, which when conditions are right gives it insane strength as it can act as a mechanical lever.

Since a tail does not have a rigid endoskeleton, it can not act well as a lever. It's functionally a rope attached to your butt. Like even if you go full kangaroo mode and make the tail more muscular than the legs, making the tail rigid by flexing really hard, it basically turns into an inefficient leg with enormous mechanical disadvantages.

Macha• 2 years ago

Legs have a lot more muscle to allow the owner to resist, along with the downward weight of the body somewhat adding to stability?

t-3• 2 years ago

Hair is much worse in that regard, as the tail would be positioned too low to practically grab (it would asking for a knee to the face or punches to the back of the head or spine if you tried). I think the driver is more likely to be bipedality. A tail doesn't provide a lot of benefit for balance or rearside whisker utility when moving on two legs, and would interfere with sitting and lying postures. I think humans are probably too large for practical prehensile tails too.

ohyes• 2 years ago

I think humans are probably too large for practical prehensile tails too.

There’s only one way to find out! Who wants to join my ‘prehensile tails for humans’ (and other great apes with cash) startup?

Capitalism, wow!

thaumasiotes• 2 years ago

I think the driver is more likely to be bipedality.

Given that the tail was lost before the development of bipedality, how could this possibly be the case?

underlipton4• 2 years ago

and would interfere with sitting and lying postures.

I think that assumes that a hypothetical modern human tail would still be attached to the spine. A tail structure attached to the main body only through soft tissues could be flexible enough at the root to not be an issue.

didgetmaster• 2 years ago

The NFL would definitely have to come up with a rule about grabbing the tail of an opposing player.

bilsbie• 2 years ago

If we did have rails do you think we would cover it up or keep it out like our hands?

nutrie• 2 years ago

Not sure about rails, but I'd definitely mount an umbrella on my tail, just in case it rains.

Razengan• 2 years ago

Imagine the fashion accessories!

(and sexual kinks)

DonHopkins2• 2 years ago

My favorite "Scan Scene" from The Congress (Ari Folman's film based on Stanislaw Lem's novel "The Futurological Congress"), in which Harvey Keitel's character "Al" tells Robin Wright's character "Robin" the twisted tail of "Joey Fairytail"...

https://www.youtube.com/watch?v=pPAl5GwvdY8

tomtomistaken• 2 years ago

I love the book!

DonHopkins2• 2 years ago

"The Congress" is to "The Futurological Congress" is to Stanislaw Lem like "Blade Runner" is to "Do Androids Dream of Electric Sheep" is to Philip K Dick.

Both great movies loosely based on both great but very different books by great authors, each with something unique and deep and important to say, that all stand on their own and are worth knowing.

29athrowaway• 2 years ago

Monkeys have tails to swing and walk in trees.

ndsipa_pomu8• 2 years ago

Yet there's plenty of animals that have tails and don't spend time in trees, such as dogs, horses and cows.

dboreham• 2 years ago

The tail seems like vestigial anatomy (originally useful in fish) that has three possible states in mammals: 1. Repurposed for a new function (tree swinging, signals) 2. Not much used but still in the repo (mice) 3. Garbage collected (apes).

Hackbraten2• 2 years ago

Yet, according to TFA, apes had already lost their tail while they were still tree dwellers.

blacksmith_tb• 2 years ago

Presumably as primates got bigger, tails were less useful (not strong enough to be prehensile appendages, and not as handy for balance if you climb methodically instead of carefree leaping).

pfdietz• 2 years ago

It takes metabolic resources to grow a tail. If the benefit was less than the cost, mutations that prevented the tail from growing were selected for.

ekaryotic2• 2 years ago

And they're unhygenic. Sheep farmers for instance routinely cut the tails of their flock because it is difficult to shear and becomes a breeding ground for blowfly larvae. That said, i saw a movie called Shallow Hal(2001) which had a scene in which a man was shown to have a tail. Now it may have been cgi, but it made me think that there must be a minority of humans with that mutation.

userbinator• 2 years ago

but it made me think that there must be a minority of humans with that mutation

There certainly are, but it is extremely rare: https://en.wikipedia.org/wiki/Tail#Human_tails

ssijak2• 2 years ago

Its not because of the tail but because of the farms. Sad state of how we do farming at scale.

ginko• 2 years ago

Why does the article mainly focus on the great apes? All apes, including gibbons lost their tails.

anamexis• 2 years ago

Presumably because humans are great apes.

guerrilla• 2 years ago

I feel like people don't focus on gibbons enough in general. It's all great apes and monkeys all the time.

Gibbon1• 2 years ago

I agree with this 100 percent

samatman• 2 years ago

The actual article in Nature points out that there have been independent tail-loss events in non-hominoid monkeys. Which makes it all the more frustrating that gibbons aren't mentioned anywhere. Given when they identify the mutation as having occurred, we can tentatively conclude that gibbons lack a tail for the same reason other apes do: 25 million years for the mutation, and 16.8 million years for the divergence of gibbons from the great apes.

sschueller• 2 years ago

How long until humans have an actual "shelve" (indentation) on their pinkie at birth to rest their phone on?

lbotos• 2 years ago

a long time? You probably need at least 7-9 generations to select "strong pinky shelf" as desirable and I'm not sure any culture is yet?

coldtea3• 2 years ago

You probably need at least 7-9 generations to select "strong pinky shelf" as desirable

It not only has to be convenient, but also to be sexually selected (partners with that seen as more attractive) or helping with survivability (partners with that live longer and get to reproduce more), which ain't really applicable anyway.

Which is the reason we don't have traits for any other minor "convenience" attribute either, but instead for long standing evolutionary benefits.

coldtea3• 2 years ago

Given evolution? Thousands of years...

raincole• 2 years ago

Never.

Actually, considering how low the birth rates in developed countries are, humans would probably (very slowly) become less and less suitable for modern life.

hawski• 2 years ago

I would hope that phones would not remain the last point in the evolution of a personal computing device in so far as to make it able to steer the evolution of humans.

zare_st• 2 years ago

Never. Individuals with that kind of mutation have to be born per random chance, and then selected via sexual preference.

ngvrnd• 2 years ago

There is no "why" -- it happened and was not selected against; it may have been adaptive and that is a kind of why, I guess. I think it would be better to be clear about this in science communication.

Smaug123• 2 years ago

The article itself is very clear about the sense of the word "why" intended here.

JBiserkov• 2 years ago

Yes:

But while the new study explains the “how” of tail loss in humans and great apes, the “why” of it is still an open question.

Title is still clickbait.

Hackbraten2• 2 years ago

The article itself states that this may be the case, or that it might have had some evolutionary advantage that we're just not aware of.

o-o-• 2 years ago

There has to be more to it.

If it’s not selected against, it wouldn’t spread at the cost of the tail gene.

Somehow, somewhere along the genome line, non-tailers overtook tailers.

BoiledCabbage• 2 years ago

There is no "why"

Of course there is a why. It happend and not only was it not selected against, presence of a tail was selected against. Meaning it was, or came along with a beneficial adaptation. That benefit is why it took over our gene pool and why we don't have tails now.

tzs• 2 years ago

Probably good that we lost them. Judging by photos [1] of some of the rare cases of humans who were born with tails human tails wouldn't be aesthetically pleasing. Although perhaps human tails that are the result of something going awry might not be a good indicator of what human tails would be like if we had kept them.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3263034/

GordonS2• 2 years ago

If we'd never lost tails, probably we wouldn't find then so "un-human". Also, presumably most people would have "normal" (as in, the same as most others) tails, rather than like the images in that article.

jezzamon• 2 years ago

If we kept tails both the tails and our sense of what is attractive would be under evolutionary pressures so they probably would be normal to us!

gigglesupstairs• 2 years ago

Exactly. I still find noses and ears to be such noticeable protrusions once I let go of my knowledge of human faces.

atomlib2• 2 years ago

Clearly you haven't heard of catgirls.

happymellon• 2 years ago

Although those photos were more dickbutt than catgirl.

withinboredom• 2 years ago

NSFW, in case you are thinking about checking the link out.

GirkovArpa• 2 years ago

This comment needs to be higher.

tialaramex• 2 years ago

If we're doing germline edits, the obvious thing to fix first is vitamin synthesis. There are a bunch of useful things other living things synthesise from first principles, and we don't so we need to eat something that has already synthesised the thing we wanted, and we can't cook or preserve it in any way that destroys the material we needed or it won't work. That's what scurvy is, a tree or a lizard just makes its own vitamin C, but humans don't, so, if you're stuck on a ship eating preserved food for months your body runs out of vitamin C and you get very sick and eventually die. But synthesising vitamin C isn't hard per se, it's just that the synthesis instructions can be deleted and the humans are descended from an ancestor who had such a deletion, we can put it back.

Once vitamin synthesis is back working, next up is amino acid synthesis. Amino acids are the constituent parts of proteins, your DNA is a bunch of instructions to fasten together a series of 22 different coded amino acids to make proteins. When you eat something, any proteins are broken back down into amino acids. Given some amino acids you can in principle make the others, but humans only make about half of them this way. As a result if your protein mix is wrong you are eating amino acids, and your body needs amino acids but some of them are different amino acids - and instead of synthesising the ones needed from spares you don't need using energy, which is abundant in most human societies, you just get sick and eventually (if you don't fix your diet) die. We should fix that.

ruined• 2 years ago

and then, crispr cat ears

klyrs• 2 years ago

Not the bombardier beetle's hydrogen peroxide cannon? I'll never understand furries.

m4rtink• 2 years ago

Like that might be a bit problematic due to the existing ears but whatever - like, if designed well you might as well have an extra pair of fluffy cat/dog/fox ears and use it for improved echolocation. ;-)

canadiantim• 2 years ago

Makes you wonder why we naturally selected for ancestors who didn't have the vitamin synthesis machinery. Clearly there must have been some evolutionary disadvantage associated with vitamin synthesis, or else as you say it's clear benefits should have conferred an evolutionary advantage and still be with us today.

tsimionescu• 2 years ago

Not necessarily. If any early human diet that produced enough calories for them to live and procreate also happened to have plenty of vitamins, then synthesizing your own really didn't confer any evolutionary advantage.

I'd also note I don't see any reason we'd want to synthesize our own vitamins now. It's virtually impossible to get a vitamin deficiency unless you try to eat a very restrictive diet for some other reason.

smegger001• 2 years ago

There was little selection selecting against the loss it when it was abundant in out ancestors diet at that particular time and place. so by the time it became an issue it was already missing from the gene pool and as it is easier for a mutaion to break a gene than it is to gain function so its unlikely to mutate back into the genome by chance.

tgbugs• 2 years ago

Vitamin synthesis is one of the most pointless things to add because it is something that is lost in many lineages over evolutionary time. The reason is that as long as there are environmental sources of a molecule the pressure to retain the ability to synthesize that molecule natively is zero or even negative, because the synthesis pathways for some of those molecules are quite nasty. You could do it, but those people would probably have increased cancer rates due to running nasty biochemistry in their own cells and eventually their descendants would lose the ability the synthesize it again because vitamin C is naturally present in their environment unless they are e.g. British sailors stuck on a boat for months with a evolutionary strange diet.

Ovah• 2 years ago

I'm surprised how the conversation shifted from genetics to unethical germline editing of things that barely have clinical relevance. The rates of scurvy in the 21th century are low and definitely don't warrant super invasive editing germline cells (!), changes which become hereditary. Adding vitamin synethesis is super complex: it's not just a single SNP change but would require a whole new enzyme system. It's a very fine line from opening up a big old can of eugenics worms. Adding extra tRNAs is sometimes done in microbiology but any health benefits are extremely questionable. I've never before seen germline editing be a proposed 'solution' to malnutrition.

ordu2• 2 years ago

If we are on this topic then we need to discuss a genetically modified gut microbiota. We do not need to edit genetically ourselves for some pityful vitamins. Microbiota could give us all we want. It could enable us to digest plastic, so we could eat food without removing its packaging. We could reduce severity of our waste problems by digesting plastic into relatively harmless poop.

emiliobumachar• 2 years ago

Sounds unappetizing. Would you want to eat packaging if not for the - for now inevitable - digestion issues?

teddyh• 2 years ago

Maybe fix uricase production as well (eliminating gout).

1letterunixname• 2 years ago

The main issue is that evolutionary pressures have optimized for and against certain things that have fragile interplay of consequences with other genes.

While it will become possible to restore auto-synthesis functionality, there are unknown risks associated with germ line edits reengineering Vit C or essential AA synthesis.

It's currently illegal to do so in 70 countries. Specific, very positive beneficial edits that protect against infections, malnutrition, or pathological diseases should be allowed.

larodi• 2 years ago

time to bring it back then, alongside horn implants, and third tit.

polishdude20• 2 years ago

I'd I'd be drinking milk, it would be out of my nostrils right about now.

vba616• 2 years ago

How about a third eye?

"The parietal eye is found in the tuatara, most lizards, frogs, salamanders, certain bony fish, sharks, and lampreys...It is absent in mammals, but was present in their closest extinct relatives, the therapsids"

https://en.wikipedia.org/wiki/Parietal_eye

You may wish to consult your pineal gland.

agumonkey2• 2 years ago

wings

taneq• 2 years ago

Would be handy for navigating the warp. ;)

fnordpiglet3• 2 years ago

Third nipples are quite common believe it or not. Most people with them believe they’re moles.

phyzome• 2 years ago

Yup, I've seen a few. There's even a line on each side of the body that they tend to emerge along, arcing from the armpit down to the crotch.

manarth• 2 years ago

@dang Editorialized title; original title for the CNN article is "Why don’t humans have tails? Scientists find answers in an unlikely place"

leke• 2 years ago

Makes me think of the episode of the Simpsons where Marge was modified to be some kind of human feline in the episode The Island of Dr. Hibbert

speedylight2• 2 years ago

Would be cool if we had tails, so I could wag it with my future dog!

tempaccount420• 2 years ago

But imagine if your tail was hairless :/

cosmojg• 2 years ago

I imagine that it could still look cool if it were shaped/tapered in just the right way, maybe somewhere between that of a Sphynx cat and a lizard.

codetrotter2• 2 years ago

That sounds like an opportunity for a whole industry to emerge tbh.

Hi we are Tailstyle! For far too long we’ve been accepting that our tails need to be naked like the rest of our bodies. Today I am offering you a share in our company for a very good price. Sharks, listen, everyone knows that wigs and toupees are amazing. What if I told you that my company we can put semi-permanent hair on your tail to look like a tiger! Or a panther? Or you could even have your tail look like that big flying dog in that one movie from the 80s you know which one I mean.

And not only that. We’re also making tail socks that you can wear for special occasions! Christmas tail socks. Wedding tail socks. Funeral tail socks. Homecoming ball tail socks. You name it!

tormeh• 2 years ago

Imagine if it was covered in pubes. That would definitely be worse.

b1122• 2 years ago

Meanwhile, 140k years ago, our 3rd civilization approached our current level of tech. Fashion designers, specifically a group lead by Argot the Great, decided the tail made pants difficult, and broke the lay of suit jackets.

So they hired radicals to genetically engineer a retrovirus, to remove the tail. This worked, but due to unconsidered balance issues, all tail devoid children lost the capability for bipedal balance and therefore walking.

Most of these children, during their formative years spent their time on all fours, and thud their hand dexterity was pitiful, and society crumbled when they came of age.

It was another 46k years before a brain mutation emerged, re-enabling bipedal balance, but by that time all traces of the old civilization was lost, and thus, progress began anew.

QuantumG• 2 years ago

Dehydrate!

junon• 2 years ago

What is this referencing?

advaith08• 2 years ago

The dehydrate comment is a reference to the three body problem - a great book!

b1122• 2 years ago

Nothing. I just wrote it because it seemed amusing.

nelsondev• 2 years ago

If I had a tail, could I wave it with Kegels?

brcmthrowaway• 2 years ago

definitely

ijijijjij• 2 years ago

now all we need is for the tailbone/coccyx to disappear.

joshuamcginnis3• 2 years ago

I believe this suggests that we could CRISPR an embryo to knock-out the offending Alu element in the TBXT gene and the child will develop a tail.

KennyBlanken• 2 years ago

Rarely is human genetics this simple. For ages geneticists thought large swaths of the human genome were "junk" and over time more and more of it has been proven to have a purpose or function, it just wasn't readily apparent for various reasons.

Think of the human genome as sort of the ultimate dependency hell...

npstr• 2 years ago

Nature does not refactor. There's the laryngeal nerve somewhere in the neck of mammals that has to go around a blood vessel. On Giraffes, this runs all the way down the neck, around said blood vessel, than back up, all that just to connect two places in the upper neck that are inches apart. Evolution writes the ultimate spaghetti code.

More info: https://berto-meister.blogspot.com/2011/08/unintelligent-des...

Zetobal• 2 years ago

There still is a lot of non-coding dna in there.

kennethwolters• 2 years ago

Yes, the genome-layer is nondeterministic. But there are also more layers that are probably just as nondeterministic, adding more complexity to your view.

Other layers include: epigenome-layer, transcriptome-layer, proteome-layer

Each layer can compensate for deficiencies in another layer.

So lets say you knock out a gene in utero and it has a phenotype. But when you do the same procedure in an adult organism, there is no phenotype, although the gene should be important in an adult. It's like phenotype and genotype are two states whose correlation is dependent on many variables. In this example at least time.

BizarroLand2• 2 years ago

The first domino between the present and a world full of cat girls has fallen.

swader9993• 2 years ago

At what age would it be too late to try this? Asking for a friend...

joshuamcginnis3• 2 years ago

It needs to be done at the embryonic stage before cell division so that as the cells replicate, they inherit the desired changes. The technology isn't quite there yet to transfect every single cell in an adult body with a virus containing the desired genetic modifications. Also, I can only imagine the downstream of effects of the body transcribing this modified dna in a fully-developed human. Have you ever seen the movie The Fly?

speedylight2• 2 years ago

The holy grail of gene editing will be when we can make “permanent” changes to the DNA of people alive today.

neonsunset• 2 years ago

Catgirls may be closer than we think.

gumby• 2 years ago

I’d really enjoy a prehensile tail, despite the adaptations required for trousers and chairs.

Also, I was enough a nerd growing up that other kids would have pulled it.

swasheck• 2 years ago

i suspect there would be adaptations to a variety of other things like sleep, bipedal locomotion, defecation, etc.

fnordpiglet3• 2 years ago

I suspect our tailed ancestors slept, locomoted, and defecated.

SpaghettiCthulu• 2 years ago

i suspect there would be adaptations to a variety of other things like sleep, bipedal locomotion, defecation, etc.

Sleep is easy: sleep on your side.

The rest sound like non-issues to me.

iSnow• 2 years ago

I am pretty sure there would be new dimensions to sexual behavior, details depending on the motor control we'd have.

itscomingnext• 2 years ago

Can't wait for the first Furry Liberation movement to take hold and campaign for their future kids to grow tails.

geraldwhen• 2 years ago

The decision to modify an embryo to have cat ears and a tail is a decision between doctor and parent!

As long as you get a doctor involved, no modification is too horrific.

j7ake2• 2 years ago

Link to the open access article : https://www.nature.com/articles/s41586-024-07095-8

If you scroll to the bottom check out how long this article went into peer review: almost 3 years!

Three years can get you a PhD in UK.

Received 14 September 2021

Accepted 19 January 2024

Published 28 February 2024

PunchTornado• 2 years ago

Is that normal? I imagine the poor bastards wanted to put it on their CV for their next job.

j7ake2• 2 years ago

https://www.nature.com/nature-portfolio/about/journal-metric...

Median time is 268 days to acceptance at Nature. So this article was closer to 1000 days, above average.

montag• 2 years ago

Neat. Now could they please do the same for hair loss? :)

atomlib2• 2 years ago

It would be terrific not to have any hair on my head as a male. I'm so sick of shaving my cranium every morning.

BlueFalconHD• 2 years ago

Those hackers might get what they wanted. Real life catgirls. It would be so awesome.

kinleyd• 2 years ago

I have always lamented the loss of the tail. Every time my dog, though almost entirely asleep, wags its tail to acknowledge my presence, I always say to myself "Now, THAT is efficiency."

I'm not a furry, but I'm open to the possibility of getting that back!

ssijak2• 2 years ago

It would be so cool to have a tail.

hwbunny• 2 years ago

Just give it a few years and besides pointed ears this will be doable. Anyways, I was thinking about whether our ancestors also wagged their tails, just like dogs and cats use them. And what were the triggers inside our nervous system.

heroku• 2 years ago

Humans never had tails, just ask charlie brown.

soygem• 2 years ago

Getting closer and closer to getting catgirls

Scientists have traced human tail loss to a short sequence of genetic code

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