It just seems like it would be a really cool thing to have gills and be able to populate the oceans in the same way we populate the land. We could have houses and shops and vehicles, andgo on walks/swims and just kind of live underwater.
Start a whole new second species of human here on earth maybe, Who knows?
There’s not enough oxygen in water to support our metabolisms, even if we had gills.
Fish are adapted to conserve and use less oxygen, from slower metabolic rates to more options for anaerobic respiration that doesn’t poison oneself from within.
Well thats not really the most relevant thing here even if correct because you could give someone gills and let them keep their lungs too just having the gills to extend how long we can dive would be useful
I don’t believe this. Sailfish, barracuda, tuna, huge mass, highly active… I’m sure they use a HELL of a lot more oxygen than I do on a good day. Gills extract MORE oxygen than lungs do, they’re more efficient.
My unscientific opinion tho.
This article estimates at a 40kg sailfish uses about 2.7 megajoules per day of energy when hunting. That’s about 650 kcal.
An 80kg human weighs about twice as much and needs about 3 times the energy, without even exertion.
Warm blooded animals spend a lot of energy just maintaining body temperature. Plus water doesn’t have very much oxygen in it, compared to the atmosphere.
Oh sure, if you’re going to use facts and science we may as well not even talk.
Seriously though, thanks for the insight.
This is the whole “if humans were going to have wings we’d have to redesign the whole organism from the ground up” fiasco all over again.
Exactly.
We still theoretically could, I guess, but people already have enough body image problems just from getting wrinkly or kinda bald, let alone being a freak mostly made of human-skin batwings.
Yeah, evolving lungs ended up clearing the way to make use of the much more plentiful oxygen in the air compared to what is dissolved in water. Amphibians and reptiles have pretty low metabolisms, but birds and mammals basically evolved endothermy (aka warm bloodedness), probably in support of much higher muscular power output. Ectotherms (aka cold blooded animals) have metabolisms that are correlated to temperature, which means they can’t exert themselves as well when it’s cold. Endothermy allowed animals to be warm all the time, and therefore use higher muscular power output in any environment, especially sustained.
That means mammals and birds were able to cover more distance, and survive in places where reptiles and amphibians can’t, and all the advantages that carries.
That last line is one reason we’re able to fish successfully. Even large fish tire out because they can’t pull enough oxygen from the water to struggle forever.
Did Jeff Goldblum teach us nothing?
🤮✊ 🤮🦶
But what about
How does Brundlefly eat?
In short, we could, but the cost would be incredible.
All vertebrates are animals that develop from a series of segments, with a vertebra at the core. In our time from eel-like fish, we’ve specialised these segments so, for example, we have ribs on the vertebra corresponding to the rib cage.
To support arms and legs, specific vertebra have become highly specialised in the form of hips and shoulders.
Gills are composed of a series of gill arches, one on each vertebra in the neck area. These structures have (in eels) a lot of blood vessels to carry the blood that needs reoxygenation.
An interesting thing happened as the eel-like creatures differentiated, evolved jaws and ultimately ended up as mammals and humans: nature co-opted the specific vertebra that had these gill features and turned them into jaws and ears and a variety of other features in the head and neck. For example the tiny bones in your ear were once fish jawbones which were previously one (or more) gill arches.
The stupendously complex anatomy in this area comes from all the short-term ‘decisions’ evolution took to make all the magnificent creatures that inhabit the earth.
For example the nerve that connects the brain to the larynx (the recurrent laryngeal nerve) emerges from a vertebra high up in the neck, decends down under the aorta in the chest and then back up into the neck to the larynx. In the giraffe, the nerve is many meters long, even as it’s direct path could be a few centimeters. The reason is that the heart used to be close to the gills in fish and sharks. As the heart moved in land animals, the nerve was caught in a loop around the critical aorta and it was ‘pulled’ along for the evolutionary ride.
So, in order to turn your gills back on, you need to unprogram 450m years of evolution of the structures you call your head, face and neck.
I’d recommend ‘Your inner fish’ by Shubin - it’s a wonderful read and explains this in far more detail that I can manage.
Fascinating.
If you like this, this goes under the moniker ‘evo/dev’ - evolution of the ‘development’ of the organism. A lot of genes don’t code for proteins that ‘do’ something in the body, like haemoglobin or fingernails - they code proteins that tell the body how to develop from a single cell. Many are active for a short window in development. Some are active in a single location, like at the thumb end of the limb bud, and tell the cells where to become a finger, thumb or palm bone. Some work across vastly different animal classes - the ‘build an eye here’ gene works in humans and flies and everything in-between.
So there isn’t a way to “add” a feature on top of the existing organism’s physical system? We have to lose ribs to get gills? That kinda sucks.
In a way, your jaw is a gill arch, just built in a different way with some interesting diversions. After a couple of 100 million years, the changes do add up.
If you really had to add in a gill, i have a plan, but I need to talk about one important evolutionary trick: duplication and divergence.
A fairly common DNA copying error causes a section of a chromosome to be duplicated in the offpring. In most cases this is fatal or prevents children, but some duplications work out just fine.
For instance mammals lost colour vision in the time of the dinosaurs - mammals were probably nocturnal. The loss was caused by losing genes for the yellow colour receptors in the eye. This is why dogs and cats see in something akin to black and white (they do see red and blue and all the yellows and greens are just shades of red and blue).
But apes were lucky. An accident duplicated the existant red receptor and, over time, because there are now two genes, one gene was gradually selected for a higher and higher light frequency. This has become our green receptor and all apes see in red-green-blue colour.
Duplication is not necessarily fatal because it just codes for something we already have. But once there are 2 genes, evolution can select away for different capabilities and we end up with something new.
Ok, with that out the way let’s plan!
- Add in a few new sections into the human body by adding some new hox genes. This would give us a significantly longer neck - probably fatal without medical support.
- Duplicate and diverge the genes used to trigger gill arch/neck and jaw development and modify the developmental genes that respond to them. This would preserve the development the upper neck as humans (to keep the jaw and ear) while allowing something else to happen lower down
- In the lower section work out a way to develop like our basal forms (something eel-like) and trigger this development with the modified genes from step 2.
Step 1 might be possible today. Step 2 might be within current reach (but it would take incredible work to disentangle all the connected system in development and the working body. Step 3 is beyond current tech (as I understand).
Fun thought experiment! Thank you!
So do I understand correctly that a certain hox gene is activated in basically all cells which are in the “domain” of a certain vertebrae and they all activate some subset of homeobox genes which in combination with the original hox gene cause them to start turning into all the different parts associated with that vertebrae (so organs and other structures)?
Would we then need an entirely new hox gene to produce even a single gill? (I know you basically just laid out most of a response to this question.) Because I would assume although the exact point at which the development of our arms and legs begins is part of the whole hox gene “superstructure”, but couldn’t we ‘basically just’ highjack this same system and duplicate this gene to produce at least a single gill in the region where the current hox gene for our neck is expressed?
Long story short: what is the biggest reason why we can’t just hack into a later part of the sequence and continue on from there with what you said?
Or would your proposed plan also just end up like this in the final product and you laid it out like this because it’s already the most viable route into this mess? 😅
So do I understand correctly that a certain hox gene is activated in basically all cells which are in the “domain” of a certain vertebrae
Yes
and they all activate some subset of homeobox genes which in combination with the original hox gene cause them to start turning into all the different parts associated with that vertebrae (so organs and other structures)?
Not quite. The hox gene creates a protein that tells the nearby cells that they are in a specific segment. After this specific cells in that segment start signalling so they cooperatively lay out the cardinal directions to make that specific segment. In the shoulder segment, for example, a specific cell becomes the tip of the arm and tells all the cells about it with its signalling protein. All the cells in between it and the root now ‘know’ which part of the arm to grow.
This is a cascade of ever finer positioned ‘location markers’ that guide generic cells to specialise correctly.
Ultimately, as two bones grow into each other, they know to form a joint, and as that joint takes form the joint surfaces fit each other exactly.
Would we then need an entirely new hox gene to produce even a single gill? (I know you basically just laid out most of a response to this question.) Because I would assume although the exact point at which the development of our arms and legs begins is part of the whole hox gene “superstructure”, but couldn’t we ‘basically just’ highjack this same system and duplicate this gene to produce at least a single gill in the region where the current hox gene for our neck is expressed?
Assuming we want to keep our neck, jaw and ear features, we need to keep our existing hox gene and all the genes that turn on in this cascade to produce these structure. If we alter them, our development will change.
The issue is that in a fish or shark, exactly the same location marker is used to lay down their gills. So adding a shark hox gene will result in a human segment at that location. Hox is a marker - not the full set of instructions to build the segment.
We therefore need
- A new location marker for the gill
- And we need our developing cells to recognise this new signal
- And we need a development pathway to create a gill which includes new location markers, and the ability for cells to differentiate in the right place to new tissues
- New genes for specific proteins to create these new tissues (which may be copyable from other organisms)
Long story short: what is the biggest reason why we can’t just hack into a later part of the sequence and continue on from there with what you said?
Well, we can’t reuse the existing one because it creates human structure. So we need brand new genes for 2 and 3.
I’m not a professional in this area, but I haven’t seen anything that suggests we can fo this yet.
I think part 4 (the bit about creating new tissues) might in fact be the easier part. But to cause them to be developed at the right time in the right place and at the correct size with brand new signals is waaaay out there.
Or would your proposed plan also just end up like this in the final product and you laid it out like this because it’s already the most viable route into this mess? 😅
Speaking as someone whose last practical biology wiped out all the very expensive cell colonies, and that was 30 years ago, I hope my wild suggestions here are even vaguely in the right direction.
Fuck it, let’s do it. Super Mario Bros deevolve me
Of all the Justice League members you could choose to have the powers of, you chose Aquaman?
We’d be able to buy up all the soon-to-be-flooded coastal property up for a song.
Well, if the Wonder Twin powers are available…
cd ~/me npm install gills —saveThere actually is a gills npm package, lol.
Oh no, uninstall it! It automatically removes lungs as a peer dependency!
Yes, but being able to change genetic code does not mean being able to design entire organs and pop 'em in there during fetal development. That would be very challenging.
Gene editing has the most positive potential when it comes to things like curing/eradicating genetic diseases, doing microbiological research, or engineering metabolic products in microorgsnisms.
Single loci genetic diseases. Those with numerous genes contributing will me even more difficult.
Crisper isn’t changing an organism’s genes to that extent. When you’re designing an immune response with rna injection or other changes brought about with cytophages you can only get crispier. It’s sort of like how you can’t double fry fried chicken. It’s already crispy once, it just gets burned and dries out.
While it’s definitely not possible with current tech, I don’t see why it wouldn’t theoretically be possible. It would be an insanely complex, multi stage process, though.
What, double frying chicken wings?
Like Icarus, you’re mad with wonder. Do not try it. Do not fly close to the sun of double crispy wings.
probably yes, if we accept the mountains of dead human babies the research would inevitably produce.
Pretty sure you can already get those you just need to have sex with enough siblings and cousins
That’s what I keep telling them!
Changing the color of your eye take so much changes that’s impossible todo it, gills is going to need so much changes, and we don’t even know what most of our genes do
Give it a hundred years or so
Have you been watching a fairly terrible late1990/early2000s tv series starring jessica alba? I’m pretty sure they had some fish-mutants.
I don’t think you can radically change a human’s environment that much faster than nature, especially not a system so critical as breathing. The whole organism (including the internal microbiome) needs to co-evolve with itself and the ecosystem it is to survive in - to function effectively as an independent organism. I don’t know how long it took cetaceans to evolve, but even they still breathe air at the surface - they’re really just big flappy hippos.
I’m sure it’s not impossible but I think you’d need, many, maybe thousands of generations for it to become something viable that can effectively provide enough oxygen to the other systems - or more likely adapt all the other systems to less oxygen. So it might have to live basically in a lab / sea-world for centuries. You might need scientists with unusual ethical standards to get to human - but an underwater rat? I’m sure you’d find a few Dr Mephestos out there eager to drown a few thousand of those.
Source: 100% ignorant opinion.
I was just thinking there’s plenty of creatures bigger than us with much more active lifestyles. And gills are kind of self-contained. Just slap them on there and away you go!
Hypothetically. 100% ignorant opinion as well.
I take lungs now, gills come next week.
Yes, but not very good ones, probably. We’re endotherms (hot blooded), and as a result we burn like 3 times as much oxygen as a similarly-sized shark. You’d need a lot of gills.
The rest of our body is also not very well suited to being underwater long-term. If you’re adding gills you might as well change our silhouette, eyes, hair and skin as well, but you might not look very human afterwards. Maybe you could manage something merperson-ish, with an extra-flexible neck for looking towards where you swim and gills all along the tail? Sanitation would also be a bit of a nightmare, because if there’s a sewage leak you get to breathe it.
The other option is just to get really good at diving conventionally, maybe enhance ourselves to make that easier, and build dry “indoor” spaces underwater. The technology to do it at a basic level isn’t new, but there just hasn’t been much interest in living that way yet.
Human embryos do have immature gills, but they are reused to create ears, jaw, tonsils, thymus, parathyroids and the large arteries in the neck and upper chest. We could add extra pairs and try to turn them into actual gills, although that would require removing the aortic arch and forcing all blood through the gills. Connecting them to the pulmonary system is not possible, as lungs and gills need different pressures (that’s the whole reason we have two circuits). Maybe we could connect them in parallel to the aorta? That would only work as a backup, but with an adequate vasomotor system could do a nice job!
Its funny I did a paper on CRISPR in highschool and was very interested in the technology and one of the possible uses I mentioned was giving people gills to live underwater.
would
