Dinosaur Survival Disputed

[Mighty_Emperor]

Dino 'survival' claim disputed

By Paul Rincon
BBC News Online science staff

The idea that dinosaurs survived for some time after the asteroid impact blamed for wiping them out 65 million years ago has been dealt a blow.

Dinosaur egg fragments dug out of rocks in China seem to postdate the dramatic extinction event popularly believed to have extinguished the creatures.

But new data suggests the egg pieces got mixed up in later deposits through the action of mud and debris flows.

Details of the latest findings are published in the Journal of Geology.

We actually have no idea what's happening anywhere else in the world
Dr Norman MacLeod, Natural History Museum

Dinosaurs survived until the end of the Cretaceous Period of Earth history. But by the beginning of the Tertiary Period, about 65 million years ago, they had apparently vanished.

Egg discovery

At numerous sites around the world, a clay layer separates rocks laid down in the Cretaceous from those deposited in the Tertiary. This is known as the K-T boundary.

The boundary contains high concentrations of the element iridium, commonly found in meteorites. Researchers have proposed that a meteorite impact which produced a huge crater at Chicxulub in Mexico, could have been responsible for the demise of the creatures.

Discoveries of dinosaur egg fragments in deposits from Nanxiong Basin, southern China, which contain Tertiary animal remains and pollen, suggested dinosaurs there could have survived until about 62 million years ago.

But US and Chinese researchers now dispute this.

They claim the egg pieces originated in Cretaceous deposits and were swept up in mud and debris flows during the Tertiary. This jumbled material was then re-deposited.

Dr Brenda Buck of the University of Nevada, Las Vegas, US, said she came upon the idea while examining palaeosols, ancient soils that have been buried and later exposed in Nanxiong.

"During the dry season you had these big open cracks," she explains.

"Mudflows would come down and fill in those cracks. All those mudflows are in the [rock] sections where the flora and fauna are mixed."

Dr Buck suggests the presence of several iridium layers at Nanxiong supports a view that Cretaceous rocks were reworked in the Tertiary.

Multiple claims

There have been other claims for the survival of dinosaurs into Tertiary times at sites in Montana and New Mexico in the US, in Bolivia and in India.

All of these claims have been questioned by other researchers.

"The only really well documented dinosaur remains are from the American west. We actually have no idea what's happening anywhere else in the world," Dr Norman MacLeod, keeper of palaeontology at the Natural History Museum in London, told BBC News Online.

"We know that they lived on other continents, so there's no particular reason to suppose that that western US population was the last population.

"It could well be that they went above the K-T boundary in other parts of the world, especially parts that were remote from the Chicxulub impact."

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/3458651.stm

Published: 2004/02/05 10:31:59 GMT

© BBC MMIV

 

[Anonymous]

Why is it they never consider new evidence just ways to dismiss it? It is supposed to be science which is supposed to question everything. If you have dogma you are religous not scientific.

 

[Mighty_Emperor]

gl5210: I think things are more complex than that - as well as finding new evidence old evidence has to be reconsidered and re-evaluated. What you have to watch out for are people re-assessing the evidence in an effort to eliminate it but as there is rarely one theory that is supported by every scientist people can make whole careers rebuffing each others evidence

Emps

 

[Anonymous]

people can make whole careers rebuffing each others evidence

Emps

And yet, you do it here for free

 

[Mighty_Emperor]

And yet, you do it here for free

The first one is free the rest cost

[edit: Removing a # ]

Emps

 

[Anonymous]

Emp I agree in some cases. I just get frustrated with out of hand dismissals. Let us look at all of the evidence. How can you ask the right questions if you eliminate any contadictory evidence to what you already think. I guess that I like astronomy more, they seem more open to the questions, they admit that based on available evidence we believe this______. I find the biologists and anthropologists much less open to inquiry and debate. Plus studies often contradict one another why not a probe into why and who knows a whole new idea might emerge. My father-in-law was a research scientist for many years and we often talk about these things.

 

[Mighty_Emperor]

gl5210: I understand but I don't think they have dimissed things out of hand. Taphonomy (the science of site formation) has made great leaps forward in the last few decades and sites are constantly being re-examined in the light of evidence from new studies, etc. From what I read in that BBC report their explanation seems reasonable - huge numbers of sites have been found to be more a mix of layers than clean and sealed strata this only makes the news because of its important implications.

As well as mudlfows there has been a lot of work done examining the effect of animals (from insects and earthworms to nesting cave bears and hyaenas) churning up the ground and mixing things together. Cryturbation (things like frost heave) are also a problem in notherly climates.

The fact that no case is closed is a good thing - if we are going to understand things then we need to be able to trust the evidence and in geology and palaeontology there are a vast range of factors that can affect the specific site you are examining. Its not that someone somewhere has said "we don't like this evidence of dinosaurs surviving the KTE so go out and sling some mud" but for such important things like this the evidence has to be rock solid (sorry for the puns) and so they will be under scrutiny.

There are a number of competing theories for the extinction of the dinosaurs from the boli impact to a more gradual decline in their numbers (with possible survival past the Maastrichtian) and so if this study has been a little dismissive then someone else will certainly be happy to say so (the problem is that retrations are less newsworthy).

Emps

 

[Anonymous]

I remember when I was growing up we were taught not only the impact hypothesis but others as well, but look at textbooks now a paragraph about other ides and a chapter devoted to impact. I guess I am just nitpicky. I don't like the indoctrinization. I guess I would just like them to say based on this evidence we think this___. I get irritated with the whole we have all of the answers and your to stupid to understand. Teach kids the way to think critically and examine evidence and form their own ideas. I had a wonderfull teacher growing up ( that I completely did NOT appreciate at the time) but he challenged us to look things up and come up with our own ideas. He made defend what we thought and I guess that is what is lacking the idea that people can look at all the competing theories and who knows maybe look at differntly and point out something new that noone has noticed before.

 

[Mighty_Emperor]

I remember when I was growing up we were taught not only the impact hypothesis but others as well, but look at textbooks now a paragraph about other ides and a chapter devoted to impact. I guess I am just nitpicky. I don't like the indoctrinization. I guess I would just like them to say based on this evidence we think this___. I get irritated with the whole we have all of the answers and your to stupid to understand.

Isn't that what theya re saying above:

"The only really well documented dinosaur remains are from the American west. We actually have no idea what's happening anywhere else in the world," Dr Norman MacLeod, keeper of palaeontology at the Natural History Museum in London, told BBC News Online.

"We know that they lived on other continents, so there's no particular reason to suppose that that western US population was the last population.

"It could well be that they went above the K-T boundary in other parts of the world, especially parts that were remote from the Chicxulub impact."

Teach kids the way to think critically and examine evidence and form their own ideas. I had a wonderfull teacher growing up ( that I completely did NOT appreciate at the time) but he challenged us to look things up and come up with our own ideas. He made defend what we thought and I guess that is what is lacking the idea that people can look at all the competing theories and who knows maybe look at differntly and point out something new that noone has noticed before.

Your concerns aren't really the fault of science but are more due to the fact that education (esp. in school) has, by and large, got to be fairly simplified - if you go into everything with "well this might be true but so might this, etc." thn it could end in a mess. I've found that it is really onl when you go to University that they try and instill critical thinking and examination of evidence and competing hypothesises (you'll find similar simplification in a lot of reporting (although that Beeb report isn't an example of it) as your article would rapidly become a book - also simplfying the reporting makes announcements seem much more clear cut rather than the more vague things they actually are).

I had a great teacher when I was doing my geology degree who told us to come up with theories to expalin a certain formation because no matter what we came up with he had evidence to disprove it. He reckoned he had an idea about it but he also had evidence which disproved that too. All we can do is build modls and test them against data - sometimes we ar wrong and somtimes we get a little closer to what may have happened.

Emps

 

[Anonymous]

I really enjoyed geology I find it fascinating and found I did better in astronomy because of it. I am not strong in math and did not follow it further. But I would like to take follow up classes in both. I like both of these subjects better than biology. They do more about open inquiry and dialogue. The geology class I took was and internet class and there were professors from all over the country that contributed to the lectures that I watched on video it was fascinating. I think sometimes when you take a class from one person you get only their perspective on that subject and their interpretation of the info in the textbooks. My astronomy Professor was especially brilliant, he taught right out of the book, but his excitement for his subject was infectous. He had only recently begun teaching and had been part of research before which made him very inquisitive. Great subjects. I need to follow with some more reading in both of these areas I have been on a more historical and classics tangent in my studies the last year or so.

 

[Mighty_Emperor]

gl5210: Good to hear.

Anyway it seems like the smoking gun (crater) might be too young - I've always been more a fan of flood basalts (they are better explanations for some of the other big extinctions and the Deccan Traps are a good candidate in age for the KTE):

Tuesday March 2, 02:33 AM

Were dinosaurs really wiped out by asteroid?

By Maggie Fox, Health and Science Correspondent



WASHINGTON (Reuters) - Scientists probing a vast crater off Mexico's Yucatan peninsula have questioned a popular theory about dinosaurs, saying the collision that formed the crater happened too far back in time to have caused their extinction by itself.

Much evidence points to the idea that an asteroid or comet gouged the Earth around 65 million years ago, triggering volcanic and climate changes that eventually wiped out the dinosaurs.

When the huge, mostly underwater crater was found off Yucatan, it seemed the perfect candidate.

"Since the early 1990s the Chicxulub crater on Yucatan, Mexico, has been hailed as the smoking gun that proves the hypothesis that an asteroid killed the dinosaurs and caused the mass extinction of many other organisms at the Cretaceous-Tertiary (K-T) boundary 65 million years ago," the researchers write in this week's issue of the Proceedings of the National Academy of Sciences.

But they said a core drilled out of the middle of the crater suggests it dates back more than 300,000 years before the K-T boundary and "thus did not cause the end-Cretaceous mass extinction as commonly believed."

The researchers, led by Gerta Keller of Princeton University and including experts from Germany, Switzerland and Mexico, studied a sample that extends 5,000 feet (1,500 metres) below the current surface, in the middle of the more than 125-mile (200-km)-wide crater.

Other samples have included tiny pieces of glass-like rock that could have been melted during an asteroid impact, and which seem to date to the 65-million-year point, give or take a few hundred thousand years.

But their core sample showed fossils that suggest the crater was blasted out 300,000 years before the K-T boundary. Magnetic evidence also suggests it is older than previously believed.

ALTERNATIVE THEORY

This finding would support an alternative theory that the dinosaurs and other forms of life were wiped out in a series of disasters that changed the Earth's climate, Keller's team said.

They noted there are other craters dating to around this time. None is big enough to have caused world-altering changes by itself.

But the meteors or asteroids hit at the same time of a busy period of volcanic activity known as Deccan volcanism, as well as when greenhouse-type atmospheric warming and major extinctions occurred.

"The Chicxulub impact occurred at a time of massive volcanism which led to greenhouse warming," Keller said in an interview conducted by e-mail.

The name Deccan comes from an area of what is now India where a massive amount of molten material surged up from near the Earth's core 65 million years ago.

It would have brought vast amounts of carbon gases to Earth's surface, causing a warming effect that would have wiped out many species of plants and animals.

"This finding suggests that the K-T boundary impact (and volcanism) may have been the straw that broke the camel's back, rather than the catastrophic kill of a healthy thriving community," the researchers concluded.

Now they need to find the actual crater left by whatever made this final blow. Perhaps one known as the Shiva crater in India, dating to around the same period, is the one, they suggested.

"There is evidence for a third impact, which occurred about 150,000 years after the K-T mass extinction," Keller said.

This impact may have made it harder for plants and animals to recover from the worldwide effects of the blasts from space and from within the planet.

http://uk.news.yahoo.com/040302/325/enev0.html

I'm glad to see the article illustarted with a picture of a dinosaur - so thats what they looked like.

Emps

 

[Anonymous]

Why is it they never consider new evidence just ways to dismiss it? It is supposed to be science which is supposed to question everything. If you have dogma you are religous not scientific.

I agree 100%, simple to say that its not science. True science has already shown us that creatures like the coelocanth, cephalopods, and frogs have survived numerous extinctions, and they are supposed to be very sensitive to their environments.