[HN Gopher] An asteroid killed dinosaurs in spring, which might ...
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An asteroid killed dinosaurs in spring, which might explain why
mammals survived
Author : thedday
Score : 110 points
Date : 2022-02-24 15:36 UTC (7 hours ago)
(HTM) web link (arstechnica.com)
(TXT) w3m dump (arstechnica.com)
| jedberg wrote:
| > Three-dimensional rendering of the partial paddlefish fossil,
| _with googly eyes added for reference_.
|
| I'm glad to see even serious scientists can have fun sometimes.
| imwillofficial wrote:
| Another wildly speculative claim that they will contradict in a
| few months. Headlines like this are effectively worthless
| clickbait.
| ghaff wrote:
| It is speculative but it is also a paper in Nature. It's hardly
| some random blog.
| imwillofficial wrote:
| Exactly, I hold them to a higher standard.
| feoren wrote:
| That's standard pop-sci title inflation. The article is about
| how evidence from analyzing fish buried in debris tsunamis
| indicates that the impact happened in Spring (in the Northern
| Hemisphere). That _is_ a genuine contribution to understanding
| what happened. You 're right that the hibernation thing is
| pretty speculative -- but it's also a falsifiable hypothesis
| that other evidence could shed light on later, so it's not like
| we shouldn't talk about it.
| Flatcircle wrote:
| 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 used to this exotic
| thick atmosphere could no longer support their own weight.
| caymanjim wrote:
| 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. It isn't
| because the atmosphere literally stopped them from falling
| down. It's still a gas, and gravity hasn't changed.
| londons_explore wrote:
| 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?
| lazide wrote:
| 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.
| 988747 wrote:
| >> 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.
|
| Earth's atmosphere is constantly being blown away by
| solar wind[1]. I guess after 65 millions years this would
| add up. But I'm still not convinced if it's possible to
| loose enough air this way to lower pressure 100 times.
|
| [1] https://www.sciencealert.com/earth-loses-hundreds-of-
| tons-at...
| caymanjim wrote:
| A thicker atmosphere would provide more static lift, but
| flapping wings in thicker atmosphere would require larger
| muscles and use more energy. There are scholarly writings
| out there on this topic, but I'm not familiar enough with
| any of them to have an opinion. I know there's a school
| that argues pterosaurs couldn't fly today solely due to
| lower atmospheric density, and a school that argues they
| could. I think the lower oxygen levels would still be the
| primary barrier due to energy requirements.
| Flatcircle wrote:
| No it's not ridiculous at all, pressurized gas can act like a
| liquid. And at sea level, thick atmosphere would certainly be
| pressurized.
|
| smaller lungs aren't relevant to the issue that comes up
| regarding extremely large dinosaurs.
|
| Because it's not an issue of lung capacity, or oxygen supply
| per liter of blood.
|
| We're not talking about animals that are comparable to modern
| day elephants.
|
| Have you seen the size comparisons of dreadnoughtus to blue
| whales? They are enormous. The physics start to come into
| question. Just the sheer weight of skin and muscle hanging on
| bone. Even if the bones are hallow and even if the muscle is
| somehow more efficient due to increased oxygen in the blood.
|
| Like a whale plopped on dry land, they'd collapse under their
| own weight standing up. Much less, hunting, mating, and
| fighting.
|
| furthermore the thick atmosphere theory helps solve another
| tricky mystery which is the, Mesozoic Paleoclimate Paradox
|
| During the Mesozoic era a remarkably homogeneous flora of
| tropical and temperate plant species covered the Earth.
| Plants such as ferns, laurels, palm trees, and Magnolia that
| could not withstand freezing, thrived at 70 degrees north and
| south latitude. Many of the same plants that existed near the
| equator were also thriving at the Polar Regions of the Earth.
|
| For decades paleoclimatologists have tried to explain the
| Mesozoic paleoclimate paradox. If they matched the vegetation
| of the lower and middle latitudes then their climate models
| were too cold at the higher latitudes. If they matched the
| warm temperatures of the Polar Regions then their models
| projected an unrealistic hot sauna for the rest of the planet
| that again conflicts with the geological evidence.
|
| The reason their climate software models fail to match the
| Mesozoic climate is because perhaps the paleoclimatologists
| make the incorrect assumption that the Mesozoic atmosphere
| was the same thickness as the present. As stated earlier, the
| variation of temperatures around a planet whether it is day
| or night or according to latitude, is a function of the
| thickness of a planet's atmosphere. Planets or moons with no
| atmosphere will have the most extreme difference in
| temperatures, planets such as the present day Earth and Mars
| that have relatively thin atmosphere will still have these
| differenced in temperatures but much less extreme, while
| extreme thick atmosphere planets such as Venus and the
| Mesozoic Earth show almost no temperature difference at all
| according to latitude.
| feoren wrote:
| I've heard that oxygen levels are lower now than they have been
| in the past (this seems to change a lot on geological
| timescales), and that high oxygen levels may help allow
| megafauna's existence. I wouldn't think it's so much the
| buoyancy as it is about all the other biological machinery that
| can operate more efficiently at higher oxygen levels. Oxygen
| levels are largely driven by algae and plant levels, which of
| course could have been dramatically affected by the impact.
|
| It's also possible you'd be better received espousing an
| alternative to conventional science if your handle didn't sound
| like a reference to Flat Earth Theory.
| [deleted]
| Flatcircle wrote:
| 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 present
|
| Today there are no reptiles capable of generating the power
| needed to fly, and yet during the Mesozoic era reptiles grew to
| be the largest flying animals that ever existed. The largest of
| these pterosaurs was the Quetzalcoatlus. It had a chest size as
| large as a horse and stood as tall as a giraffe ... [Y]et some
| paleontologists continue to insist that there is no scientific
| paradox regarding how the pterosaurs could have flown ...
| [P]terosaurs could not have flown in today's atmospheric
| environment. The application of aerodynamic equations show
| pterosaurs falling far short of meeting the requirements for
| obtaining flight in today's atmosphere, and the experimental
| efforts using RC models provide physical evidence confirming
| these conclusions. It should be alarming to all scientists and
| science educators that some paleontologists continue to claim
| that they understand how pterosaurs flew when the evidence is
| so overwhelming in refuting their claim ...
| onychomys wrote:
| 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
| swagasaurus-rex wrote:
| 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.
| Flatcircle wrote:
| The examples you listed, the giant Sloth, the Mastodon, and
| the giant Armadillo are all actually smaller than a modern
| elephant so you're not really making your point with those
| links.
|
| The giant sauropods are thought to have been 10 times
| heavier than an Elephant.
|
| Ten times heavier! That's enormous.
|
| And the wandering albatross you linked to is said to have
| existed 50 million years ago in the article.
| lapetitejort wrote:
| Similarly, people may not realize that the largest animal
| to have ever lived is alive right now:
| https://en.wikipedia.org/wiki/Blue_whale
| marcosdumay wrote:
| 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.
| margalabargala wrote:
| Are you suggesting that this is the cause of the extinction
| event, rather than an extraterrestrial impact? Or something
| more like the impact may have caused a significant change in
| atmospheric composition?
|
| This would not explain the myriad other, much smaller species
| that also perished, not to mention all of the marine animals.
| zardo wrote:
| I would love to see a scientific paper on the bouyant dinosaur
| theory.
| Flatcircle wrote:
| lol, why the downvoting? I didn't say it was a fact, I said
| it was a possibility.
|
| https://dl.icdst.org/pdfs/files2/abe347ca228406be4720d5554a6.
| ..
| Flatcircle wrote:
| https://www.researchgate.net/publication/26553081_Atmospheri.
| ..
| feoren wrote:
| I'm not great at evaluating the quality of Journals
| (Chemical Industry and Chemical Engineering Quarterly is at
| least peer reviewed), but that article has been cited 0
| times, and its abstract reads like a YouTube video trying
| to convince me Bush did 9/11.
|
| > how can a giant dinosaur such as an apatosaur pump blood
| up to its brain (more than 13 m above its heart) when
| animal energetics and physics say that in no way can it do
| it. Do we have to change the laws of physics and biology? I
| don't think so.
|
| The "Science says it's impossible! Either we have to change
| the laws of science, or <my one pet alternative theory out
| of 10 million other alternatives> must be true!" is just
| really characteristic of that style.
| robbedpeter wrote:
| We don't have soft tissue or a specific understanding of
| internal organs. Maybe they had multiple hearts with
| multiple vascular systems, or maybe the rate of blood
| flow and chemistry of energy production differed from
| animals we do understand. All we know for sure is that
| the brontosaurus was way too big for its biology to be
| understood by similarity to any extant creatures.
|
| Maybe we'll be able to simulate dna, protein, and
| evolution at some point such that we can sample huge
| spaces to see if we can reconstruct creatures with
| similar features.
| zardo wrote:
| 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
| lazide wrote:
| 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.
| egberts1 wrote:
| Only half of the Earth would be destroyed in that manner due to
| Earth Northern hemisphere and Southern hemisphere having opposite
| seasons.
|
| Go back to the drawing board.
| dlandau wrote:
| Springtime for T-Rex and dinosaurs
| digisign wrote:
| Don't see many Producers references on HN, bravo.
| illwrks wrote:
| Seconded! It gave me a good laugh. I need to watch that film
| again.
| iamthepieman wrote:
| I think it would be
|
| Springtime for mammals and marsupials Winter for dinos and fish
| Springtime for mammals and marsupials Come on humans, you've
| got your wish
| hinkley wrote:
| Winter for gerbils and plants.
| odyssey7 wrote:
| It's incredible to me that fossils can be linked to the specific
| day or so of the impact.
| BurningFrog wrote:
| It's pretty wild that all of humanity only exist because of that
| completely random spring surprise!
| throw_m239339 wrote:
| > 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 might be
| governed by another intelligent specie.
|
| https://www.sciencefocus.com/planet-earth/when-will-earth-be...
|
| > Simple computer models initially suggested this disaster
| could render our planet inhospitable in as little as 150
| million years from now. But late last year the journal Nature
| published a much more sophisticated simulation by a team from
| the Laboratory for Dynamic Meteorology in Paris, and this
| suggests we have got at least a billion years before this
| apocalypse.
| hvs wrote:
| If we wipe ourselves out within 100,000 years, I'm not sure
| "intelligence" is a particularly advantageous trait,
| evolutionarily-speaking.
| BbzzbB wrote:
| It's not like life (or species, as that's what evolutionary
| pressures act on) has (have) any hope of surviving beyond
| Earth's habitable period without intelligence, which makes
| it a quite desirable trait as far as I'm concerned, most
| important one as far as I'm concerned. Isn't it the _only_
| trait that gives life any hope of existing beyond
| geological timescales, no matter how high the chance of
| quick failure is? Without intelligence, it kind of comes
| back to "does a tree fall if no one's there to hear it".
| The universe existing at all sounds pretty bleak affair if
| all that's gonna happen are local pockets of life that show
| up on distant planets only to get boiled up in a hurry.
|
| Worst case scenario is this "great hominid experiment"
| fails, we take out other species with us (perhaps a
| spectacular amount if we go out with a bang) but life finds
| a way to cling on as it always has and returns to it's non-
| civilized state in a geological blink. After that evolution
| gets to roll the dice for some more million years until
| life disappears forever and without leaving a trace of it's
| existence beyond a handful of satellites drifting in the
| dark for eons. Better luck next time, Darwin.
|
| Best case has been (and is still) explored by sci-fi
| novelists.
| enlyth wrote:
| 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 progress would be lost.
| dividedbyzero wrote:
| There's also the possibility that knowing early enough we
| might be able to prevent an impact altogether.
| mstipetic wrote:
| 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
| nonameiguess wrote:
| We could easily seed the rest of the solar system and
| even a few nearby other solar systems with basic archaea
| and what not capable of surviving on any large object
| with water, at least guaranteeing some form of life
| escapes the death of Earth. It takes intelligence to
| figure out how to do this, but we have enough
| intelligence and the means to do it right now, but we
| aren't since we're largely concerned specifically with
| human survival, and humans are much harder to keep alive
| and transport through space.
| marcosdumay wrote:
| 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.)
| mc32 wrote:
| Spring in the Northern Hemisphere; Fall in the Southern
| Hemisphere.
| osigurdson wrote:
| The Northern Hemisphere does account for 68% of overall land
| area.
|
| https://www.worldatlas.com/articles/which-hemisphere-has-the...
| hinkley wrote:
| Did it at the K-T boundary?
| askvictor wrote:
| And perpetually tropical in the tropics
| cedricd wrote:
| 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.
| CommieBobDole wrote:
| Yep, 65 million years ago was really not that far from the
| present, geologically speaking.
|
| https://dinosaurpictures.org/ancient-earth#66
| YaBomm wrote:
| eatsyourtacos wrote:
| Ugh why does it keep turning on rotation when changing the
| dropdown!
|
| I'm trying to fix on a single point and move backwards in
| time to see the change but it keeps rotating the global
| every time... weird default functionality.
|
| edit: weird, now it seems to work fine. I was disabling the
| 'rotate global' but it wasn't taking effect before
| krick wrote:
| Display options -> Rotate globe
| erulabs wrote:
| Wow India is really headed north in a hurry.
| mcherm wrote:
| Yes it is! Hence the mountains.
| [deleted]
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