Extinction of Dinosaurs: Consensus Reached . . . mostly

Scientist is as Scientist does. Ever the tentative bunch, scientists have reached a "final" consensus on the cause for the extinction of the dinosaurs. The final verdict?"Combining all available data from different science disciplines led us to conclude that a large asteroid impact 65 million years ago in modern day Mexico was the major cause of the mass extinctions."--Peter Schulte of the University of Erlangen in Germany, in this MSN article.So the debate ending, everlasting conclusion is that the Chicxulub impact was a "major cause".First of all, no shit. I don't think anyone has really debated that it was a factor, or even a major factor. However, this doesn't end the debate on how much other factors played in to it including supervolcanism in modern day India (the Deccan traps) or the already dwindling numbers of dinosaurs species that led up to the Chicxulub impact. So this leaves the debate right where it was before, with the Chicxulub impact being a player but also other players without a defined role.To be fair, I have only read MSN article and not the Science article. Still, I find it funny that scientists can't stop being scientists even when trying to portray certainty in a layman fashion. The big consensus? The Chicxulub impact made the dinosaurs go extinct . . . mostly.

That has always been the issue, from my limited reading on the subject. I would hazard a guess that most experts would have the Permian extinction as the #1 extinction event and there is no known impact event that correlates with the Permian die off. However, the Siberian traps do correlate. In fact, I watched a Discovery channel show (don't worry, I don't consider the Disc Channel as gospel truth) that directly correlated the Siberian traps with the Permian die off. So what do we have with the K-Pg die off? The Deccan traps.On the other hand, we are lucky to have the Chixulub crater. If it occurred in the Pacific, for example, the crater could very well have subducted and all traces gone. The K-Pg iridium layer would have still been seen world wide where the interface was preserved, but there is no guarantee that every impact will produce such a layer (e.g. icy comet).So it is very understandable why scientists are hedging their bet on this one. That's the way it should be.

That is the show I was thinking of. Thanks. Discovery, History, NGC, etc. all blend into one in my memory.

I have a strong suspicion that conclusions such as this is exactly what they were addressing with this "final consensus". From the abstract of the Nature paper:"The temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations (for example, darkness and cooling) lead us to conclude that the Chicxulub impact triggered the mass extinction."The important bit is "the temporal match". Reading between the lines they are arguing that there is not a gap between the impact and the ecological extinction signal. So they don't seem to be arguing against other causes so much as they are against a gap between the impact and the extinction event. Reading between the lines again, the phrasing "lead us to conclude that the Chicxulub impact triggered the mass extinction" in the abstract allows a lot of leg room for other causes (e.g. supervolcanism) being a factor.Edited by Taq, : No reason given.

That's what I was thinking too. Also, feathers provide nice insulation against a "nuclear winter" caused by such a large impact. Mammals were also nicely insulated and given their burrowing lifestyle may have had access to food unavailable to species living above ground. Crocodillians, being cold blooded, could shut down their metabolism in cold times and would require much less food. Could the extinction of the dinosaurs also suggest that a vast majority of dinosaurs species were warm blooded?For me, the most interesting feature of the extinction event is the way in which it favored smaller species. If memory serves, something like 90% of species who were 50 kg or larger went extinct while those 50 kg and smaller survived much better. To me, this indicates a very dramatic reduction in available food sources.

I think everyone agrees that the impact is just part of the explanation. The impact is being cited as the "trigger" for the K-Pg event. So perhaps a better analogy would be how "pulling the trigger" is an integral part of the explanation of how a bullet is ejected out the end of a gun barrel but not the complete explanation.

Actually, there are two major known causes: the asteroid impact and supervolcanism that produced the Deccan traps seen in modern day India. Scientists have been arguing back and forth over which of these causes had the most impact on the extinction non-avian dinosaur species.Also, these dinosaurs didn't change. They died. Kaput. Gone. There are organisms from the past that have no living descendants in the present. Their lineages have stopped. This is the case for non-avian dinosaur. There is not a living descendant of any T. rex anywhere on this Earth. Nowhere.And just to comment on confusing dinosaurs with reptiles . . . Dinosaurs are no more reptillian than mammals are. Both mammals and dinosaurs evolved from reptiles--different clades of reptiles, but reptiles nonetheless.

First off, they claimed that the coelacanths had been extinct for about 70 million years. Secondly, it is quite understandable that we would miss a species that spends most of its time in 200 meters of water or more. I really don't see how this can be compared to a land dwelling dinosaur, most of which were at least the size of large dogs and some quite a bit bigger. We humans tend to spend quite a bit of time on land compared to deep oceans. It turned out that when shown pictures of a rhinoceros the local inhabitants identified it as Mokele-mbembe."The BBC/Discovery Channel documentary Congo (2001) interviewed a number of tribe members who identified a photograph of a rhinoceros as being a Mokl-mbmb.[3] Neither species of African rhinoceros is common in the Congo Basin, and the Mokl-mbmb may be a mixture of mythology and folk memory from a time when rhinoceroses were found in the area."
Mokele-mbembe - Wikipedia