

What Really Killed the Dinosaurs? - tokenadult
http://www.slate.com/articles/health_and_science/animal_forecast/2013/02/dinosaur_extinction_was_an_asteroid_the_only_cause_of_the_cretaceous_mass.html

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abcd_f
The 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
_it'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>

as interpreted by the Hacker News welcome message

<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>

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-
ancesto...](http://www.usatoday.com/story/tech/2013/02/08/mammal-ancestor-
dinosaur/1900207/)

and "Rat-Size Ancestor Said to Link Man and Beast"

[http://www.nytimes.com/2013/02/08/science/common-ancestor-
of...](http://www.nytimes.com/2013/02/08/science/common-ancestor-of-mammals-
plucked-from-obscurity.html)

about scientific investigation into the most recent common ancestor of
placental mammals.

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3minus1
I'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
Why 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
What 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.

------
c3d
One 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 ;-)

~~~
fasteddie31003
There is a Star Trek Voyager episode on the idea of dinosaurs leaving earth.
<http://en.memory-alpha.org/wiki/Distant_Origin_(episode)>

It is one of my favorite Voyager episodes.

~~~
mixmastamyk
They 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?

------
veryOdd
This 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>

~~~
spoiledtechie
I would like to know why the system was Under Stress.

------
SeanDav
The 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
The 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
It'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>)
However, while habitat destruction is often blamed for man of those
extinctions that's just another name for human intervention.

~~~
Scriptor
> 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.

------
thaumaturgy
I 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.

------
tocomment
I 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.

~~~
jug6ernaut
Mammals 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
Sure, but dinosaurs were closer to birds (and thus also warm blooded, as I
understand it).

~~~
jug6ernaut
Birds 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
I 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
Its also easier for birds to migrate than for land based creatures.

------
achalkley
Dinosaurs 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.

------
Ntrails
_This 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
It doesn't even have to that high of an entity - there was the Archaeoraptor
scandal: <http://en.wikipedia.org/wiki/Archaeoraptor>

------
agrona
This 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
The Deccan lava flows started about three million years earlier, see for
example <http://www.ias.ac.in/jessci/jun2001/1352.pdf>

------
bad_user
Judging 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
This sounds like one of those "just-so" evolutionary stories without much
evidence to back it up.

------
pjungwir
Since 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?

~~~
jcastro
I 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_fro...](http://www.ted.com/talks/jack_horner_building_a_dinosaur_from_a_chicken.html)

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.

~~~
Steko
Isn't the lesson from the movie that the park would just need better security?

