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What Really Killed the Dinosaurs?
- tocomment 14y agoI never understood why small dinosaurs wouldn't have had the same likelihood of survival as small mammals? Also why didn't dinosaurs living in the sea survive this? I've always had the suspicion there was something more going on to wipe out an entire animal kingdom at once.
- tokenadult 14y agowhy small dinosaurs wouldn't have had the same likelihood of survival as small mammals? A good question. Of course one category of small theropod dinosaurs (clade Aves, commonly known as birds) did survive the extinction of the rest of the dinosaurs, as the article points out. It's a greater puzzler to figure out why the sea-going groups of clade Reptilia (NOT dinosaurs), like the mososaurs and plesiosaurs, became extinct. An extinction event that brings an end to life forms both on land and at sea is quite a major extinction event. http://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event http://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_ex...
- Nursie 14y ago"I never understood why small dinosaurs wouldn't have had the same likelihood of survival as small mammals?" Maybe they did have the same likelihood, as in mathematicl probability, but the specific circumstances just worked out this way. A little like the anthropic principle - if it hadn't, we wouldn't be in the world we observe. Maybe some proto-rat-creature-mammal-things just lucked out.
- arbitrage 14y agoThe anthropic principle, and this type of stochastic lottery argument, are terribly unsatisfying. They may be right, but then again, they may not. They're eminently unfalsifiable, and shouldn't be given any more credence than a typical appeal to divinity.
- Nursie 14y agoI vehemently disagree with it being equivalent to an appeal to divinity. I haven't anywhere said 'this is what happened'. If you want to say it's equivalent to an answer of 'I don't know', then that's fine.
- arbitrage 14y agoI'm sure you didn't, but either way the outcome is the same. You throw your hands up in the air and walk away, seemingly content to look no further. The anthropic principle and its ilk are a dead end for investigation, and ultimately useless to invoke.
- Nursie 14y agoWho said I was content not to look further? Does "this is what I guess, as far as I know" imply I don't wish to know any more?
- svachalek 14y agoThe question is "why didn't some other outcome have the same likelihood?" and the answer was, perhaps it did. We don't know what the most likely outcome of the extinction was, only which one occurred.
- jug6ernaut 14y agoMammals are more adept to adapting to climate change. Reptiles on the other hand have a very hard time dealing with even a few degrees of temperature change from there norm.
- Steuard 14y agoSure, but dinosaurs were closer to birds (and thus also warm blooded, as I understand it).
- jug6ernaut 14y agoBirds are not strictly "warm blooded" as mammals are, but yes they are not strictly cold blooded ether. They are able to generate their own body heat to some extent yes, but are still fare more susceptible to climate change then a mammal would be.
- Amygaz 14y agoI don't know about birds during these "dark" times, but todays birds are pretty resilient to wide change in temperature even on a daily basis. They are capable of generating and circulating fair amount of body heat. Their average temperature is typically much higher than mammals. They are also well insulated, more than humans, apes, dogs, cats...
- JanezStupar 14y agoIts also easier for birds to migrate than for land based creatures.
- run4yourlives 14y agoExcept that birds did quite well during the extinction event, all things considered; more so than mammals.
- tocomment 14y agoBut plenty of reptiles survived just fine. It's as if there were something special about dinosaurs. Could there have been some major virus that wiped them out and left other species untouched?
- nickgully 14y agoThey did, they're called birds. Small mammals just grew into more large animal locations.
- edanm 14y agoI know next to nothing about dinosaurs, so someone correct my ignorance: Don't we define Dinosaurs, in some sense, as "animals that were alive then and aren't alive now?". Obviously, some of the Dinosaur species were related, but aren't there lots of different families of Dinosaurs which aren't connected? Had the wolves died too, wouldn't they also be considered as just another family of Dinosaur? (Again, I don't really know if this is how Dinosaurs are defined or not. One argument against is that people talk about "birds" being descended from Dinosaurs).
- jcastro 14y agoNo, dinosaurs are a distinct kind of animal; - http://en.wikipedia.org/wiki/Dinosaur http://en.wikipedia.org/wiki/Dinosaur - http://en.wikipedia.org/wiki/Archosaur http://en.wikipedia.org/wiki/Archosaur Animals species that used to be alive are classified "extinct", as opposed to being around today which is "extant". Wolves wouldn't have died off at this time, large mammals hadn't evolved yet.
- fhars 14y agoNo, we define dinosaurs "as the group consisting of Triceratops, Neornithes [modern birds], their most recent common ancestor, and all descendants" (Benton, via http://en.wikipedia.org/wiki/Dinosaur http://en.wikipedia.org/wiki/Dinosaur). And to answer the GP: yes, many small dinosaurs did in fact survive until today. You can hear them singing in the big blue room behind your office window in spring and summer.
- jcastro 14y ago> Also why didn't dinosaurs living in the sea survive this? The entire ecosystem of the planet collapsed, lots of things went extinct (including some mammals), the classic "dinosaurs" are just the most famous ones.
- ufo 14y agoPrecisely. So many things went extinct that is probably better to ask "why did this group survive?" instead of "why did this group go extinct?".
- 3minus1 14y agoI'm no scientist, but I do think it's interesting that the theory of a massive asteroid destroying the dinosaurs arose in the age of nuclear weapons. The article mentions a newer theory involving climate change, which seems to befit the present day.
- jug6ernaut 14y agoWhy do you find it interesting that this theory arose in the age of nuclear weapons? The "age of nuclear weapons" has been some 60 years now, a lot of new information has come within these past 60 years. Unless your implying that nuclear weapons somehow lead them to this idea. I would argue that the 110 mile crater would be a bigger influence but that's just me.
- run4yourlives 14y agoWhat he is saying is that it looks like we are explaining the unknown based on our greatest fears - coming to a conclusion and then finding evidence to support it - rather than by looking at the evidence. It doesn't mean the conclusion is wrong, just that it is always worth remembering how our ability to analyze data points is always done through a haze of our own experiences.
- mikeash 14y agoIt also arose in the Space Age, when knowledge of space was increasing dramatically. It only seems reasonable that theories would find wider applications. Knowledge of climate change has greatly increased in the past couple of decades, and it's not as if there's something that only restricts that knowledge to being applied within a few centuries of the present.
- ufo 14y agoTo be fair, knowledge of everything else was also expanding dramatically... And the impact theory only really solidified in the 90s after they found the crater.
- fhars 14y ago
- veryOdd 14y agoThis is very odd. Just today an article was published in Science that reinforces the theory that the Chicxulub impact was responsible (although the system was "under stress" before): http://www.sciencemag.org/content/339/6120/684 http://www.sciencemag.org/content/339/6120/684
- spoiledtechie 14y agoI would like to know why the system was Under Stress.
- deleted 14y ago[deleted]
- Ntrails 14y agoThis idea was punted around for a long time and gained momentum during the “dinosaur renaissance” of the 1970s. By 1996, paleontologists had begun to find fuzzy, fluffy, feathery dinosaurs that confirmed what had been proposed on skeletal grounds—birds are just an offshoot of the dinosaur family tree. There is a part of me that wants this to be the result of a mischievous entity watching from on high and thinking "oooh, I should probably hide some bones to match that theory, why didn't I think of it when I put the dinosaurs there in the first place..."
- yread 14y agoIt doesn't even have to that high of an entity - there was the Archaeoraptor scandal: http://en.wikipedia.org/wiki/Archaeoraptor http://en.wikipedia.org/wiki/Archaeoraptor
- bad_user 14y agoJudging by current-day mammals and comparing them to current-day reptiles and birds which have a lot in common with dinosaurs, mammals may have been smarter and more fit to survive in general, especially to changing conditions.
- ufo 14y agoThis sounds like one of those "just-so" evolutionary stories without much evidence to back it up.
- deleted 14y ago[deleted]
- abcd_f 14y agoThe best theory I heard to date is this - The moon is getting slowly away from the Earth. If we extrapolate backwards, it's obvious that at some point in dinosaur times it was mere meters away from the Earth surface and that's what kill the dinosaurs - they were knocked off by the moon.
- tokenadult 14y agoit's obvious that at some point in dinosaur times it was mere meters away from the Earth surface Is there some particular reason under the Hacker News guidelines http://ycombinator.com/newsguidelines.html http://ycombinator.com/newsguidelines.html as interpreted by the Hacker News welcome message http://ycombinator.com/newswelcome.html http://ycombinator.com/newswelcome.html that this is the top comment under this thread? This prompted me to look up other comments by the same user. http://news.ycombinator.com/threads?id=abcd_f http://news.ycombinator.com/threads?id=abcd_f AFTER EDIT: Just as an example of what I think is a helpful link to share in a Hacker News thread, here are new journalistic reports, "Mammal ancestry expanded after dinosaurs died off," http://www.usatoday.com/story/tech/2013/02/08/mammal-ancestor-dinosaur/1900207/ http://www.usatoday.com/story/tech/2013/02/08/mammal-ancesto... and "Rat-Size Ancestor Said to Link Man and Beast" http://www.nytimes.com/2013/02/08/science/common-ancestor-of-mammals-plucked-from-obscurity.html http://www.nytimes.com/2013/02/08/science/common-ancestor-of... about scientific investigation into the most recent common ancestor of placental mammals.
- SeanDav 14y agoThe article kind of contradicts itself. First saying that the asteroid impact theory is pretty outdated and then not really coming up with anything other than maybe it was asteroid impact and/or volcanic activity and/or changing sea levels.
- Scriptor 14y agoThe impact theory is outdated in that people used to think it was by far the largest cause of the extinction. What the article is saying is that scientists now agree it was far more balanced between impacts, volcanoes, and sea levels. Exactly how much each of those contributed is still debated.
- Retric 14y agoIt's still generally considered the root cause. Consider, it's hard to see how sea level changes could be a cause of such a wide spread extinction event. (~75% or more of all species were wiped out) However, it's possible that an asteroid impact could lead to both volcanic activity AND sea level change. That's not to say sea level change was not a contributing factor, just it's most likely part of the overall cascade caused by the impact. PS: People have caused a significant die-off in what is almost a geologic instant. (http://en.wikipedia.org/wiki/Category:Extinctions_since_1500 http://en.wikipedia.org/wiki/Category:Extinctions_since_1500) However, while habitat destruction is often blamed for man of those extinctions that's just another name for human intervention.
- Scriptor 14y ago> it's possible that an asteroid impact could lead to both volcanic activity It could lead to local seismic activity, sure, but I don't think it'd be enough to cause enough volcanic activity. I may be wrong, though.
- mturmon 14y agoI noticed the same problem. Sympathy for contrarian stories is a known tic of Slate magazine. Maybe most concisely illustrated by their "you're doing it wrong" series on cooking standard dishes like pancakes, but see also http://www.economist.com/blogs/democracyinamerica/2009/10/contrarianisms_end_1 I think it came from their founding editor, Michael Kinsley, who has a taste for this kind of thinking.
- deleted 14y ago[deleted]
- pjungwir 14y agoSince birds are dinosaurs, I wonder what the evolutionary history is of the big birds like emus and dodos. Did they come from medium-sized dinos?
- Nursie 14y agoLooks like that is still very much an open question (from a quick scan of wikipedia) - http://en.wikipedia.org/wiki/Ratite http://en.wikipedia.org/wiki/Ratite --edit-- though not dodos, pretty sure they were a type of pigeon... or I could be making that up.
- albemuth 14y agoCurrent bird size has nothing to do with their ancestors really since all birds share a common ancestor, all variance came after they branched off.
- pjungwir 14y agoThat's sort of what I suspected; too bad!
- userulluipeste 14y agoThe size doesn't matter :) All feathered creatures must have been evolved from a single one (that first got that feather-mutation), like Archaeopteryx or something older, but the difference in their sizes may be something that occured later.
- pjungwir 14y agoYes, but it's kind of interesting if some big birds had big ancestors running around with the dinosaurs. "Later" could mean "after someone got feathers" but still be before the mass extinction.
- jcastro 14y agoI recommend reading Jack Horner's "How to build a Dinosaur", he talks about this sort of thing, namely that you can take an existing flightless bird, give it teeth, a tail, and flip the arms around and you've basically got a dinosaur. The creepy part is people are actually messing around with chicken genes and can turn on things like "grow teeth" and "grow a tail". - http://www.ted.com/talks/jack_horner_building_a_dinosaur_from_a_chicken.html http://www.ted.com/talks/jack_horner_building_a_dinosaur_fro... You'd think the guy who was the dinosaur adviser for Jurassic Park would actually learn the lesson from the movie, so if we all get eaten to death by chickens, here's your guy.
- achalkley 14y agoDinosaurs are still alive today. Birds are avian dinosaurs. What I like to see are those dinosaur shaped chicken nuggets in the supermarket and thinking about how you're really eating dinosaurs.
- c3d 14y agoOne thing I've always wondered about is what would remain of anything humanity built in 65 Myrs. If there had been a species of very smart dinosaurs populating the Earth for, say 100kyrs, and having a nuclear-capable civilization for say 200yrs... would we even see it? I keep toying writing a book around the idea that a spaceship full of dinosaurs returns to Earth, having aged very little (Langevin's paradox), and find the planet populated by the offsprings of these pesky tiny egg eaters. Kind of like Planet of the Apes in reverse. Oh well, if only I had time to write more than HN comments ;-)
- paganel 14y agoAs a "Planet of the Apes" fan myself this sounds like a very cool idea, honestly
- fasteddie31003 14y agoThere is a Star Trek Voyager episode on the idea of dinosaurs leaving earth. http://en.memory-alpha.org/wiki/Distant_Origin_(episode) http://en.memory-alpha.org/wiki/Distant_Origin_(episode) It is one of my favorite Voyager episodes.
- c3d 14y agoThanks so much for the pointer. Will be looking at it right away!
- mixmastamyk 14y agoThey were quite powerful given that they had a 65MY head start. I hoped they might have brought them back for a visit to handle the borg/dominion. Geeky enough for ya?
- ajross 14y agoIf they were nuclear-capable, we'd probably know about them. Even long after the concrete had crumbled into dust and the steel had rusted into minerals, the isotope makeup of the spent fuel would be unmistakable. See: http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor for a really interesting story. In Oklo, the reactor was critical 1.7 billion years ago and it's still easily recognizable.
- agrona 14y agoThis is the first I've heard of the Deccan Traps. Interestingly, they're "almost" on the opposite side of the globe from the Chicxulub impact (21'N 90'W to 17'N 77'E). I wonder if their formation or activity might have been caused by the impact?
- fhars 14y agoThe Deccan lava flows started about three million years earlier, see for example http://www.ias.ac.in/jessci/jun2001/1352.pdf http://www.ias.ac.in/jessci/jun2001/1352.pdf
- thaumaturgy 14y agoI read an interesting comment on Reddit recently that the higher oxygen content of the atmosphere is what primarily supported massive life forms (and that seemed to be proven at least plausible by a recent experiment where researchers were able to grow larger dragonflies in an oxygen-rich environment). Given the current descriptions of the environment at the time -- higher volcanism, an asteroid impact, global wildfires -- is it reasonable to conclude that this had a huge impact on the oxygen content of the atmosphere? And, if so, couldn't that have simply led to a tremendous selection pressure on species, where larger animals were constantly oxygen-depleted and smaller, more efficient ones were able to continue thriving? Think about it: a Tyrannosaurus would require an immense amount of oxygen to be able to maintain an active hunting pattern; if the oxygen in the atmosphere were depleted by even just a few percent, it would find things like running nearly impossible, and long-distance travel would require frequent rest breaks. I'm not sure how this half-assed notion would fit into the oceanic species' extinction, but it makes a lot of sense for why so many of the larger species died out over a period of time while the smaller ones survived.