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An asteroid killed dinosaurs in spring, which might explain why mammals survived

arstechnica.com

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Re: An asteroid killed dinosaurs in spring, which might explain why mammals survived

#31

Post by mstipetic »

hvs wrote: post #28
throw_m239339 wrote: post #26

Earlier quoted context omitted.

> Some 66 million years ago, a catastrophic event wiped out three-quarters of all plant and animal species on Earth, most notably taking down the dinosaurs. The puzzle of why so many species perished while others survived has long intrigued scientists. More importantly, it means that even if we annihilate our specie because of our stupidity, life has great chances going on and in millions of years perhaps, the earth…

If we wipe ourselves out within 100,000 years, I'm not sure "intelligence" is a particularly advantageous trait, evolutionarily-speaking.

For long term survival you need to get off your planet, for which you probably need intelligence. Earth has around half a billion years left until it starts feeling serious issues with our sun. If our evolution took something like 10 percent longer things would be tricky

Re: An asteroid killed dinosaurs in spring, which might explain why mammals survived

#32

Post by marcosdumay »

hvs wrote: post #28
throw_m239339 wrote: post #26

Earlier quoted context omitted.

> Some 66 million years ago, a catastrophic event wiped out three-quarters of all plant and animal species on Earth, most notably taking down the dinosaurs. The puzzle of why so many species perished while others survived has long intrigued scientists. More importantly, it means that even if we annihilate our specie because of our stupidity, life has great chances going on and in millions of years perhaps, the earth…

If we wipe ourselves out within 100,000 years, I'm not sure "intelligence" is a particularly advantageous trait, evolutionarily-speaking.

Well, it's more like 300,000 years.

Anyway, even if that always happens, that seems a bit too large a hill for evolution to notice it's not a global peak and route around. Unguided genetic evolution is scarily efficient, but not that much.

(Funny thing that memetic evolution may be able to make that decision, but if you are right, it's the problem by itself, so it couldn't fix it.)

Re: An asteroid killed dinosaurs in spring, which might explain why mammals survived

#33

Post by londons_explore »

caymanjim wrote: post #29
Flatcircle wrote: post #11

One thing that isn't talked about as much as it should be, there's a possibility that 65 million years ago during the time of the dinosaurs, the earth's atmosphere was very thick. All these Dinosaurs with their extremely long necks and bodies couldn't support their own weight if wandering around the earth today. The mass extinction event may have occurred simply because the atmosphere changed and these giant beasts u…

The cretaceous atmosphere had a higher oxygen concentration (roughly 50% more oxygen than today). It was denser, but the idea that it provided structural support for large animals is ridiculous. Part of the reason animals could be larger then (from "giant" insects to genuinely-giant dinosaurs) is that the extra oxygen meant smaller lungs (or better absorption for non-lung-havers) required to support higher energy use…

But at say 10 bar of pressure, flight would be much easier...

Is there any evidence for or against the surface pressure of earth being higher in the past?

Re: An asteroid killed dinosaurs in spring, which might explain why mammals survived

#34

Post by marcosdumay »

Flatcircle wrote: post #15
Flatcircle wrote: post #11

One thing that isn't talked about as much as it should be, there's a possibility that 65 million years ago during the time of the dinosaurs, the earth's atmosphere was very thick. All these Dinosaurs with their extremely long necks and bodies couldn't support their own weight if wandering around the earth today. The mass extinction event may have occurred simply because the atmosphere changed and these giant beasts u…

Can't believe the downvoting. There's several major issues with the current dinosaur theory RN. Four areas of scientific incongruities regarding these animals’ large size are 1) insufficient muscle strength, 2) insufficient bone strength, 3) unacceptably high blood pressure within the tallest dinosaurs, and 4) the paradox of pterosaurs having grossly insufficient power to fly in atmospheric conditions similar to the…

Most of those incongruities were solved as soon as people stopped trying to model dinosaurs after lizards. The pterosaurs one was solved when they stopped modeling them after birds.

I'm not sure the blood pressure one was solved, but given we have current animals with features that could solve their problem, it's not too much to expect that it's not a fundamental problem and we will find how it was solved when we get a detailed enough picture of their necks.

Re: An asteroid killed dinosaurs in spring, which might explain why mammals survived

#35

Post by lazide »

londons_explore wrote: post #33
caymanjim wrote: post #29

Earlier quoted context omitted.

The cretaceous atmosphere had a higher oxygen concentration (roughly 50% more oxygen than today). It was denser, but the idea that it provided structural support for large animals is ridiculous. Part of the reason animals could be larger then (from "giant" insects to genuinely-giant dinosaurs) is that the extra oxygen meant smaller lungs (or better absorption for non-lung-havers) required to support higher energy use…

But at say 10 bar of pressure, flight would be much easier... Is there any evidence for or against the surface pressure of earth being higher in the past?

Hah, while that could help a bird (if ACTUALLY 10 bar, which is insanely high - 145 psi, compared to 14ish now), it wouldn’t help as much as you would think. At STP, air is 1.3kg per cubic meter, and at 10 bar, it’s still only 11kg per cubic meter. Water is 1000kg/cubic meter.

So yeah you could get some bigger birds, but t-Rex or brontosaurus weren’t meaningfully supported by the atmosphere in such a scenario even if they had some kind of lifting bladder, which no one has seen any fossil evidence of anyway.

The amount of additional mass required to have a 100 bar atmosphere instead of 1 bar is rather incredible, and there is so far no plausible method known for such mass to disappear.

If it was somehow subducted, then hey maybe. But we also don’t know of any way for that to occur right now.

Re: An asteroid killed dinosaurs in spring, which might explain why mammals survived

#36

Post by dividedbyzero »

enlyth wrote: post #30
hvs wrote: post #28

Earlier quoted context omitted.

If we wipe ourselves out within 100,000 years, I'm not sure "intelligence" is a particularly advantageous trait, evolutionarily-speaking.

That's an interesting thought, when you think about long term survival of a species, how much does all this technology help? If you think about humans surviving the same asteroid impact that killed the dinosaurs, I think we would have a good chance, some people would stay in underground bunkers and eventually repopulate the Earth, but the majority of the population would probably die, and a lot of technological progr…

There's also the possibility that knowing early enough we might be able to prevent an impact altogether.

Re: An asteroid killed dinosaurs in spring, which might explain why mammals survived

#37

Post by YaBomm »

CommieBobDole wrote: post #4
cedricd wrote: post #3

Earlier quoted context omitted.

I was going to say that the landmasses could have been pretty different back then. But I took a quick look and it looks like they were broadly in the same place with respect to N / S hemispheres.

Yep, 65 million years ago was really not that far from the present, geologically speaking. https://dinosaurpictures.org/ancient-earth#66

No post body was provided.

Re: An asteroid killed dinosaurs in spring, which might explain why mammals survived

#38

Post by lazide »

zardo wrote: post #27
Flatcircle wrote: post #17

Earlier quoted context omitted.

https://www.researchgate.net/publication/26553081_Atmospheri...

Just skimming for what I was interested in, I don't see anything to suggest that a thicker atmosphere would provide support for a large land animal. That would require structures in the animal kept at below ambient pressure. e.g. heated air sacs

Also basic density calculations doesn’t favor the theory.

Even at 100bar, even with some weird composition difference (but not completely bizarre like sulphur hexaflouride) the atmosphere is on the order of 10-20kg/m^3.

Even with the most implausible ‘what a dinosaur is made of’ theories I can come up with, unless the larger dinosaurs were born carrying around 100+ m^3 balloons full of helium, it doesn’t seem doable. There literally isn’t enough space in them to have enough sacs of lighter than air gas for that to make sense.

Re: An asteroid killed dinosaurs in spring, which might explain why mammals survived

#39

Post by onychomys »

Flatcircle wrote: post #15
Flatcircle wrote: post #11

One thing that isn't talked about as much as it should be, there's a possibility that 65 million years ago during the time of the dinosaurs, the earth's atmosphere was very thick. All these Dinosaurs with their extremely long necks and bodies couldn't support their own weight if wandering around the earth today. The mass extinction event may have occurred simply because the atmosphere changed and these giant beasts u…

Can't believe the downvoting. There's several major issues with the current dinosaur theory RN. Four areas of scientific incongruities regarding these animals’ large size are 1) insufficient muscle strength, 2) insufficient bone strength, 3) unacceptably high blood pressure within the tallest dinosaurs, and 4) the paradox of pterosaurs having grossly insufficient power to fly in atmospheric conditions similar to the…

This is HN, please cite your sources. For example, the sentence starting "Today there are no reptiles..." comes from this website [0], which is run by somebody who freely admits that he's not a paleontologist and who sure seems to have some fairly...unusual views on biology.

[0] https://dinosaurtheory.com/flight.html

Re: An asteroid killed dinosaurs in spring, which might explain why mammals survived

#40

Post by swagasaurus-rex »

Flatcircle wrote: post #15
Flatcircle wrote: post #11

One thing that isn't talked about as much as it should be, there's a possibility that 65 million years ago during the time of the dinosaurs, the earth's atmosphere was very thick. All these Dinosaurs with their extremely long necks and bodies couldn't support their own weight if wandering around the earth today. The mass extinction event may have occurred simply because the atmosphere changed and these giant beasts u…

Can't believe the downvoting. There's several major issues with the current dinosaur theory RN. Four areas of scientific incongruities regarding these animals’ large size are 1) insufficient muscle strength, 2) insufficient bone strength, 3) unacceptably high blood pressure within the tallest dinosaurs, and 4) the paradox of pterosaurs having grossly insufficient power to fly in atmospheric conditions similar to the…

People forget there were mammals compare to or were bigger elephants in our recent past.

The giant ground sloth - https://en.wikipedia.org/wiki/Megatherium

Mastodons - https://en.wikipedia.org/wiki/Mastodon

Wandering Albatross - https://www.thehindu.com/sci-tech/energy-and-environment/ant...

Giant armadillos - https://en.wikipedia.org/wiki/Glyptodon

They aren't around because humans hunted them out. Except the albatross, those died out long ago.

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