Dinosaurs extinction caused by more clever predators?

[Myuncle]

I read on science news that their extinction wasn't probably caused by asteroid impact. http://www.sciencedaily.com/releases/2011/09/110919144042.htm

If it was caused by any asteroid why anyway they didn't pop up back after that?

Can we consider the croc as a small dinosaur survived only thanks to water?

Is it possible that dinosaurs, being as clever as chickens, they have been wiped out by more clever predators?

Edited September 20, 2011 by Myuncle

[the asinine cretin]

I read on science news that their extinction wasn't probably caused by asteroid impact.

This strikes me as a major overstatement. That research refers to the asteroid family thought to be a major candidate for the source of the killer asteroid, the hypothesis does not rest on that detail.

 

 

If it was caused by any asteroid why anyway they didn't pop up back after that?

Can we consider the croc as a small dinosaur survived only thanks to water?

Is it possible that dinosaurs, being as clever as chickens, they have been wiped out by more clever predators?

Is there a shred of evidence for such a scenario? And what might have predated on the top-of-the-food-chain dinosaurs? Long story short, I think if you were familiar with the basic evidence for the cretaceous-tertiary extinction event this question would thereby be resolved.

 

[Myuncle]

Or maybe the T-rex killed every big dinosaur until there was no meat enough for them to survive so they turned to cannibalism until extintion...

[the asinine cretin]

The impact event hypothesis explains much more of the data than could such an overkill hypothesis. If the extinction revolved around species that were possible prey of T. rex it might be a good hypothesis, but good luck actually accounting for plants, marine life, microbial life, and explaining other data such as the K-T boundary. Assuming multiple causes, is there any evidence whatsoever that implicates T. rex on some level? Even if there were suggestive evidence it might be difficult to establish cause. For example, there is evidence of cannibalism among T. rex but was this a normal behavior, a result of overkill, a result of external forces lowering prey populations, etcetera? But anyway, I doubt the niche that T. rex filled could have such a substantial impact and your ideas would need to be based on the preponderance of evidence. Armchair speculation doesn't count for much.

[Myuncle]

The impact event hypothesis explains much more of the data than could such an overkill hypothesis. If the extinction revolved around species that were possible prey of T. rex it might be a good hypothesis, but good luck actually accounting for plants, marine life, microbial life, and explaining other data such as the K-T boundary. Assuming multiple causes, is there any evidence whatsoever that implicates T. rex on some level? Even if there were suggestive evidence it might be difficult to establish cause. For example, there is evidence of cannibalism among T. rex but was this a normal behavior, a result of overkill, a result of external forces lowering prey populations, etcetera? But anyway, I doubt the niche that T. rex filled could have such a substantial impact and your ideas would need to be based on the preponderance of evidence. Armchair speculation doesn't count for much.

 

If the asteroid impact explains their extintion, then why the dinosaurs didn't pop up again after this impact? If they were the strongest animals on the planet, evolution should have brought them back following the same genetic mutations that allowed them to appear before this impact.

[the asinine cretin]

If the asteroid impact explains their extintion, then why the dinosaurs didn't pop up again after this impact? If they were the strongest animals on the planet, evolution should have brought them back following the same genetic mutations that allowed them to appear before this impact.

 

Obviously they weren't the most robust in terms of surviving that particular mass extinction event. Evolution is not deterministic and there is no reason why it should have brought them back. The dynamics of gene pools are pretty stochastic. Also, following the catastrophe one would expect it would be easier (i.e., quicker, simpler) for surviving species to fill whatever niches had been occupied by dinosaurs (largely by mammals as it turns out) than that dinosaurs would evolve anew.

[Laurens]

From what I hear the asteroid impact seems the most likely explanation - it explains the sudden extinction found at the K - T boundary, and the high levels of iridium. Plus we have the Chicxulub Crater... For me these all provide strong evidence for an asteroid impact.

 

How does the predation hypothesis account for these observations?

Edited September 20, 2011 by Laurens

[the asinine cretin]

From what I hear the asteroid impact seems the most likely explanation - it explains the sudden extinction found at the K - T boundary, and the high levels of iridium. Plus we have the Chicxulub Crater... For me these all provide strong evidence for the an asteroid impact.

 

How does the predation hypothesis account for these observations?

 

You've essentially restated the first half of post #4.

[ajb]

Don't predator prey populations oscillate about a fixed point viz the Lotka–Volterra model?

 

I would expect that some other mechanism would be needed to dive the system off this oscillation. So, after some climatic event or disease etc. the predators could have done very well at first eating the ailing prey. And then later they would have started to starve.

 

I think the idea that the predators had a big impact on the overall dinosaur population is very creditable, but only after something upset the balance.

 

(But go ask your local palaeontologist before taking my opinion too seriously! )

Edited September 20, 2011 by ajb

[Laurens]

You've essentially restated the first half of post #4.

 

Apologies, I just read and responded to the OP

[the asinine cretin]

I think the idea that the predators had a big impact on the overall dinosaur population is very creatable, but only after something upset the balance.

Agreed, but the OP was proposing something more than that; namely, that T. Rex in some sense "caused" the Cretaceous-Tertiary extinction event. Based on my patchy, amateur understanding of the science I don't think this is a valid notion.

 

 

Also, it is my understanding as well that climate change is one of the real-world factors that attenuates the modelling efficacy of the Lotka-Volterra equations. My surface understanding of predator-prey models does not concur with the notion of predation unto mass extinction. It might be interesting to discuss, but I must point out that the discussion with the OP has shifted from the plausibility of a T. rex causal relationship to the evolution of species following mass extinction events.

 

Apologies, I just read and responded to the OP

It's nice to have a concurrent voice anyway. No apologies are necessary, but thank you.

Edited September 20, 2011 by Ceti Alpha V

[ajb]

Agreed, but the OP was proposing something more than that; namely, that T. Rex in some sense "caused" the Cretaceous-Tertiary extinction event. Based on my patchy, amateur understanding of the science I don't think this is a valid notion.

 

At best I think T. Rex could have caused some local damage to an already stressed populations of prey. No way could simple predation by a single species be responsible.

 

My surface understanding of predator-prey models does not concur with the notion of predation unto extinction.

 

Typically the populations oscillate about some fixed point. They may settle down in the long term.

 

 

It might be interesting to discuss, but I must point out that the discussion with the OP has shifted from the plausibility of a T. rex causal relationship to the evolution of species following mass extinction events.

 

Ok, so we all agree T Rex did not eat all the other dinosaurs!

Edited September 20, 2011 by ajb

[the asinine cretin]

At best I think T. Rex could have caused some local damage to an already stressed populations of prey. No way could simple predation by a single species be responsible.

Agreed, and in the question of causation and the mass extinction event I would see that as an expected correlating effect.

 

Ok, so we all agree T Rex did not eat all the other dinosaurs!

 

Yay! hehe.

[Greg Boyles]

If the asteroid impact explains their extintion, then why the dinosaurs didn't pop up again after this impact? If they were the strongest animals on the planet, evolution should have brought them back following the same genetic mutations that allowed them to appear before this impact.

 

There is the issue of the genetic viability of a population of any given species. In short a population requires a minimum number of individuals, and the genetic variability they possess, to avoid inbreeding as in pedigree dogs where fatal genetic flaws are unleashed through breeding between to closely related individuals.

 

An inbred population is ultimately doomed to extinction.

 

In fact it has been suggested that tasmanian devil facial tumour is a result of inbreeding within a population that has lost to much genetic diversity due to land clearing etc.

 

So the asteroid impact need not have wiped out every dinosaur immediately, merely reduced the numbers of many species to levels where long term recovery was impossible. Removal of key species would then have caused an ecosystem collapse taking down many other species that were not necessarily badly effected by the aftermath of the impact.

[granpa]

and the arctic regions were cooling throughout the Cretaceous.

[questionposter]

Dinosaurs weren't killed by just 1 thing, it was a combination of things. 1 thing was the impact, another was the climate change, and another was the lack of food. There's probably even other things ocean level changes.

[the asinine cretin]

Dinosaurs weren't killed by just 1 thing, it was a combination of things. 1 thing was the impact, another was the climate change, and another was the lack of food. There's probably even other things ocean level changes.

Who or what were you responding to? Just sharing?

[questionposter]

Who or what were you responding to? Just sharing?

 

So to make it clear, so I don't think "just" more clever predators killed them if that was even the case in any way, especially since there's hardly any evidence for that. Dinosaurs were dominant at the time just before they went extinct.

Edited September 22, 2011 by questionposter

[Edtharan]

The number of dinosaurs that existed was quite high. If there were super predators that could prey on all of them and drive them to extinction, then these super predators would have left fossil records as they would have to be of a large enough population to wipe out billions of individuals. Not only that, we should see the evolutionary development of such a super predator.

 

not only that, at the end of the dinosaurs, the continents of Earth were not one big land mass. This means the super predator would have to have been air born. The T-Rex (most likely in jest) was previously put forward as the super predator in this thread, however, the T-Rex was not on every continent, so could not have wiped out all the dinosaurs (say for example, the ones in Australia).

 

What is needed is a global event that is capable of wiping out not just the dinosaurs, but also many different species in many different environments (between 65% to 70% of all species), didn't leave any fossilised bones or biological traces (but might leave other traces) and can do so in a short amount of time (geologically speaking).

 

There are really 2 such events that seem to fit the bill:

1) Chicxulub crater asteroid

2) Decan Traps

 

It could also be that both of these are responsible.

[kitkat]

The evidence points to that dinosaurs were selected for extinction since so many other species survived the KT boundary with no problem. Sure we probably did have an impact, maybe volcanism going on in certain areas of the globe but the fact is dinosaur fossils are found on all continents so it would seem that at least a few of them would have survived the KT boundary.

 

There is the issue of the genetic viability of a population of any given species. In short a population requires a minimum number of individuals, and the genetic variability they possess, to avoid inbreeding as in pedigree dogs where fatal genetic flaws are unleashed through breeding between to closely related individuals.

 

An inbred population is ultimately doomed to extinction.

 

In fact it has been suggested that tasmanian devil facial tumour is a result of inbreeding within a population that has lost to much genetic diversity due to land clearing etc.

 

So the asteroid impact need not have wiped out every dinosaur immediately, merely reduced the numbers of many species to levels where long term recovery was impossible. Removal of key species would then have caused an ecosystem collapse taking down many other species that were not necessarily badly effected by the aftermath of the impact.

How many times have we heard of bottlenecking as a reason for species to persist and isn't this the scenario of reduced population?

 

There is the issue of the genetic viability of a population of any given species. In short a population requires a minimum number of individuals, and the genetic variability they possess, to avoid inbreeding as in pedigree dogs where fatal genetic flaws are unleashed through breeding between to closely related individuals.

 

An inbred population is ultimately doomed to extinction.

 

In fact it has been suggested that tasmanian devil facial tumour is a result of inbreeding within a population that has lost to much genetic diversity due to land clearing etc.

 

So the asteroid impact need not have wiped out every dinosaur immediately, merely reduced the numbers of many species to levels where long term recovery was impossible. Removal of key species would then have caused an ecosystem collapse taking down many other species that were not necessarily badly effected by the aftermath of the impact.

How many times have we heard of bottlenecking as a reason for species to persist and isn't this the scenario of reduced population?

[Ophiolite]

The evidence points to that dinosaurs were selected for extinction since so many other species survived the KT boundary with no problem.

You don't feel that may be an unfortunate choice of words? In the strict context of the sentence this has echoes of ID, which I am reasonably sure you did not intend. Are you proposing that the dinosaurs were pretty well on there way out already?

 

You say many other species survived the event, but many more did not. Moreover, some dinosaurs did survive and evolved into one of the most succesful branches of vertebrate life on the planet today.

[granpa]

hes talking about 'natural' selection and yes there is evidence taht the dinosaurs were going extinct for a million years before the final event