this post was submitted on 15 Nov 2023
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[–] [email protected] 31 points 1 year ago* (last edited 1 year ago) (6 children)

I don't think he would last long with our current oxygen levels, there is a reason why such giant creatures don't exist anymore.

On top of that like comments said if we just waited out he would starve to dead, even if we were not provided food.

*Edit

Well looks like I was wrong, thx for clarifying that out.

Really though the reason for big animals not being as prevelant anymore was really the oxygen levels Idk where I got that from.

But then it is really weird how the evolution meta didn't evolve back to the huge beasts we see on books, someone said in the comments that it was due to the mammals success, if so it puts things really into perspective.

[–] [email protected] 21 points 1 year ago (1 children)

The largest animal we have known to ever live is alive right now, the blue whale.

[–] [email protected] 7 points 1 year ago (1 children)
[–] guylacaptivite 16 points 1 year ago (1 children)

In this particular case, it does. Whales are air breathing mammals.

[–] [email protected] 1 points 1 year ago (2 children)

Yes, but they spend most of their lives under water, only coming up briefly to breathe. Being under several atmospheres of pressure changes your air requirements.

Whether those requirements go up or down, I'm not sure.

[–] guylacaptivite 2 points 1 year ago

Change your air requirements in what way? Because the requirements don't change, the supply does. And whales are a proof that an animal much bigger than a T-rex can in fact survive in current times oxygen level. Even though it lives in the fucking ocean.

[–] [email protected] 2 points 1 year ago

I think it's a bit more complicated than that, blue whale are hyper efficient, they collapse their lungs to get all the oxygen they breath in into their blood stream, so they use the gas the breathe in many times more efficiently than a terrestrial mammal.

They also have hyper efficient heat retention, muscle use, everything. They are fully adapted for their milleaux, it's apples to oranges to compare them to a terrestrial bird/lizards that were mostly cold blooded and hollow boned.

[–] [email protected] 13 points 1 year ago (1 children)

there is a reason why such giant creatures don't exist anymore.

Such giant creatures do exist. Larger ones even.

By far the most robust theory for the mass extinction event that wiped dinosaurs out is the asteroid theory. Not there being a sudden extreme change in oxygen levels lol.

[–] [email protected] 8 points 1 year ago (1 children)

I think people get confused because afaik the reason today's bugs may be smaller due to the lower oxygen levels.

Doesn't really apply to T-Rex tho.

[–] [email protected] 4 points 1 year ago

Which has to do with how bugs breath through their exoskeletons which is a function of surface area. Lots of O2 can support larger surfaces area bugs.

[–] [email protected] 10 points 1 year ago (1 children)

there is a reason why such giant creatures don't exist anymore.

Yes, it's because of an asteroid.

Large dinosaurs were significantly larger than large mammals for basically the same reasons that birds can fly much longer and higher than bats: hollow bones and significantly more efficient lungs. Flying birds can also get much larger than bats, despite both breathing the same atmosphere.

Dinosaur lungs worked the same way bird lungs do. Their lungs are rigid, and there's separate sets of air sacs that work like bellows to pump the air through the lungs in a single direction. Much like fish gills, there's cross-current gas exchange so they cab extract most of the oxygen from the air.

Oxygen levels weren't really any higher. Dinosaurs just had some adaptations that let them both get bigger than other groups of animals and be better at flying.

The better question is why large birds haven't re-evolved. That's probably just due to the success of mammals. 10 ft tall "terror birds" evolved in the Americas, but went extinct within the last two million years due to competition from mammals. Birds could get larger than elephants, but first an elephant-sized bird needs to outcompete elephants.

[–] [email protected] 3 points 1 year ago

Damn, just got my feet wet into the so called "Terror birds" and they are really cool, to think us mammals ruined the chance of such glorious creatures rule the world feels odd.

[–] [email protected] 9 points 1 year ago

I think it's where the "enclosed" part of the challenge would come into play. I'd demand that it be air tight for the duration of the challenge.

Although a TRex wouldn't be feeling great at our oxygen levels, I'd be surprised if it would be enough to have it drop dead on it's own. I think you'd still need to fatigue the TRex, and doing anything to further deplete the oxygen in the environment would hurt you both... But the TRex proportionality moreso

[–] [email protected] 4 points 1 year ago

If I remember correctly higher oxigen levels influenced insects' size, not vertebrates!

[–] LouisGarbuor 3 points 1 year ago

Iirc oxygen levels were lower in the Late Cretaceous than they are today. Also, it is likely saurischian non-avian dinosaurs breathed more like their living bird relatives, which is a lot more efficient, thus allowing for a larger size.