Thoughts on this conversation about extinction?

[Jesuslover340]

Picked up a book from the local library called Hunting Dinosaurs by Louie Psihoyos. In it, he (the author) had a conversation with Bob Bakker about Bakker's ideas as to what causes extinctions. I'm including a couple of photos...just easier to show than to type it all out. I think he brings up some good points...piqued my curiosity. What are your thoughts?

Also learned from this book that Edward Drinker Cope is the elected type specimen for Homo sapiens (I knew Cope wanted to be the holotype, but his bones had been put away in a museum in Philadelphia instead because they had syphilis, which, as a result, were deemed unfit to be the type specimen for our species). The author worked with Bakker to make Cope the lectotype. Consequently, our registered type locality for humans is Philadelphia, where Cope lived.

[jpc]

Bakker was not a fan of the asteroid theory 20 plus years ago when that book came out. He was an advocate of the germ theory... that microbes killed of the dinosaurs. I don't think that theory has had any other proponents. I'm not sure where Bob stands now. There are a few paleontologists who still don't buy in to the asteroid theory. My thought on it is that contrary to what Bob says in this modern amphibians... frogs esp... have been suffering form population crashes and even extiction all over the world, and it took science 20 yrs to figure out why. These are population crashes we can actually see in real time, and we had a hard time understanding it. We may never know the actual reason for dinosaur, mosasaur and ammonite extinction, but we can throw out a bunch of theories, and slowly eliminate them. But he is right, ewhen thinking of these thngs it is not enough to consider why they all went extinct, but why did delicate things like frogs survive.

btw... great book with great pix.

Edited November 24, 2015 by jpc

[Ridgehiker]

As a geologist I dismiss the asteroid theory completely. I believe it is oft-repeated baloney (not very subtle in my opinion).

I personally have only known one vertebrate paleontologist who thinks there is something to it. Like a lot of theories it has worked itself into the public media and culture.

I'm in the Phil Currie camp... 'I don't know, but neither does anyone else'.

If I had to guess there were multiple variables. Contrary to public opinion, the Dino's did not occupy a plum Eco niche but were relegated to survival on the surface at the macro level. 99.999 % of life thrives in a smaller state in the ground or water. I 'think' that they were slowly out competed at the macro level by more intelligent and evolving mammals....just like orders of mammals have out competed each other. But...in the end...'I don't know'.

[jpc]

Interesting... most vert paleo folks I know do seriously consider the asteroid theory as at least partially responsible.

[Ramo]

I'm in the Larson camp on this.

[Jesuslover340]

Very interesting....certainly makes one think. And yes, the book is certainly a worthwhile read!

Ramo:

[squali]

I'm not a paleontologist and I don't know what happened to the dinosaurs. What kind of evidence is there for mammals out competing dinosaurs?

Microbes are an interesting theory but lack evidence. Mass die offs? From what I have read I think most paleontologists agree that there were many factors involved with all extinctions.

Meteorite impact on one side of the Earth, Dekka Trapps on the other side.? According to some calculations 1000 miles away from the meteor impact there would be a 450 mph blast wind

That would ignite everything. That's an enormous area of complete devastation. Like most theories that have a limited amount of proof, more evidence can only strengthen or weaken.

Lets say you discovered a poker room abandoned with a pair of twos and a pile of money at one seat and a pair of 3's and no money at another seat. All of the other cards are scattered around the room. There is no sure way of knowing how the guy with the two's won without more information. But he did win

[Malcolmt]

Larson is the best......... my favorite cartoon of all time was by him titled "I am Blind and my dog is dead"

[ynot]

The problems with the microbe theory are many in My opinion.

It does not account for the multitude of other things that went extinct alongside the dinosaurs.

Diseases are usually very species dependant, rarely, if ever, infecting a whole ecosystem.

When an infectious disease runs through a population it does not (usually) have a 100% mortality. This would not allow for the microbes continued existence, and that is the purpose of life-- to continue its existence through the propagation of descendants. This becomes untenable when You destroy the environment You need to survive! (Something Our species needs to learn really quick.)

The smart mammal theory is also lacking. They may have contributed to the dinosaurs demise, but how did they affect the things in the oceans? (I do not believe that the mammals were that good at fishing.)

I do not know if the meteor was responsible for the dinosaurs demise, but I do think it had some contributions to the mass extinction that took place 65 million years ago.

Tony

[sdsnl]

Maybe it hard to do with oxygen levels? When it's a lack of oxygen, bigger animals would die first. I've had a shrimp and snail tank, at one point the snail were growing really fast and the shrimps reproduced a lot, and they started to have a lack of oxygen especially at night when the plants also need oxygen. The shrimps often came to the surface to breathe, and the snails would stick this tube out of the water to get air. Soon the big shrimps died, then the medium ones. Only the smallest ones survived.

[jpc]

The bottom line in my book is that there are many theories out there...someone once said there are as many theories as there are dinosaur paleontologists. Of these many theories,only the asteroid impact has any geological proof. I like it, but it also seems that the dinosaurs, were on a low swing, biodiversity-wise, not sure about ammonites, but I do know,that like the dinosaurs, there was a peak in biodiversity several million years before the extinction.

I'd like to hear your thoughts in more detail, Canadawest. I am open to revisit this topic.

[RJB]

A very interesting read this thread. JP, love your first post here. For me, I don't care. they are gone. Gunna concentrate on my tomato garden for next year and prep a rock or two.

RB

[FossilDAWG]

I also would be curious about Canadawest's opinion on the matter.

As far as I am aware, there is a pretty general consensus that a comet/asteroid impact played a significant role in the end-Cretaceous mass extinction. There is still considerable discussion about whether or not there was one single giant impact, or perhaps it was preceded by a series of lesser impacts. In some sections there appear to be smaller iridium anomalies below (earlier than) the big one that closed out the Cretaceous. Also there is discussion about whether this group or that was on the way out anyway, with the impact being merely the straw that broke the camel's back. It seems to me that people who advocate this are focused on a single animal group, especially dinosaurs, and choose to ignore the fact that the extinction occurred simultaneously in terrestrial and marine ecosystems. Also any group of animals will have periods when they are increasing in diversity and periods when they are in decline. Sometimes the decline in diversity may reflect the evolution of a small number of very efficient species that out-compete a larger number of less efficient species, as may have been the case with predatory dinosaurs. A more accurate way of assessing the success of any animal group may be to look at total biomass or total numbers of individuals, but that is hard to assess in the fossil record. Similarly, ammonite diversity was lower at the very end of the Cretaceous than it was in the Jurassic or Lower Cretaceous, but work by Peter Ward and others proves that these species were widely distributed and were maintaining constant populations right up to the extinction event.

I do not see any reason to assume (as Bakker seems to) that every mass extinction in the history of the Earth has to have the same cause. Frankly that notion seems counterintuitive and completely without logical foundation to me. We know that some mass extinctions were gradual, some occurred in steps (such as the end-Permian extinction, the largest in the fossil record), and some (the end Cretaceous) appear to be virtually instantaneous. How could these all have exactly the same cause?

After the asteroid impact hypothesis was advanced, some paleontologists ridiculed it as a return to catastrophism over gradualism. This seems absurd to me. We know that asteroids and comets exist, we know their size distribution and some are fairly big, and we know that they sometimes impact the Earth and other planets and moons. There is a pretty good collection of impact craters on the Earth, and the moon presents a good record of the history of impacts. The moon is right beside us, why would it be hit so often and the Earth rarely or never? It's not "catastrophism" to say sometimes we will get whacked with a really big one, it's a statement of statistical inevitability.

Of course there will be lots of little mysteries about an event that happened 65 million years ago. Why did some groups survive unscathed and others were rendered extinct? I think a lot of that can be sorted out by considering position in the trophic chain; larger predators and large herbivores may well have been unable to survive absence of food for even just a few years. However there would have been a lot of detritus around, lots of seeds left over from just before the impact, lots of fungi feeding on dead material (there is a huge spike in fungal spores after the impact). Omnivores and animals with less specialized diets would have had an advantage. Also we don't know the exact season when the impact occurred; if it happened in winter when some animals were dormant the long-term effect could have been very different from a summer impact. This could be reflected in what groups survived and what didn't in the northern and southern hemispheres.

Ynot has offered some good ideas (which I agree with) about why the disease hypothesis does not stand up. I have not heard any other ideas that are convincing as a cause of world-wide extinction in a very short stratigraphic interval (time frame) for so many animals at many tropic levels. I think it is telling that all the top-tier predators and all the large herbivores dropped out, on land and in the oceans, at the same time. What could cause such a massive environmental collapse? I think the comet/asteroid impact could do it, and I haven't heard a more convincing suggestion.

Don

[Auspex]

There is much in Peter Ward's writings on extinction events that resonates as true for me, and most of it comes down to something(s) upsetting the atmospheric applecart ("atmosphere" here including the oceans, which to my mind are inseparably part of the atmospheric system).

[Mike Pocock]

Very interesting thread, I think with what I have read over the years that a meteor did strike and that caused a chain reaction that activated some volcanic action around the planet, this combination then in turn caused a change to the atmospheric conditions around the world, and was the major contributor to the extinction event. Also with so much dead plant and animal debris about who is to say that then some very nasty microbial spread, this may be why so many divergent species went out at the same time.

Thanks for the thread very interesting

Regards

Mike

[bcfossilcollector]

An asteroid the size of Mount Everest striking the Earth at terminal velocity would release such unimaginable amounts of energy that a mass extinction would not be out of the question. If the Chicxulub crater is indeed the result of an end Cretaceous strike the global impact of such an event would have been catastrophic. Consider the recent high altitude explosion of the Chelyabinsk meteor over Russia. The mass of this asteroid was in the order of about 14000 tons and exploded with a force at least 20x that of the Hiroshima bomb. Luckily the atmosphere absorbed much of the impact. If the asteroid that struck the Earth 65.5 mya was as big as estimated it mass would have been measured in the billions of tons. It boggles the mind to think that anything could have survived such an event!

[The Goatlady]

Ground squirrels survived inside the blast zone from the eruption of Mount St Helens.