evolution and the extinction of dinos

So here is a question that I really need an answer to:If most, if not all plant and animal life had been wiped out after an apparent asteroid collision with earth, then would that mean that life, post-extinction, would have to start from scratch, like it did billions of years ago? and if so, how would there possibly have been time to create the deiversity that we see today?

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Originally posted by quicksink:
So here is a question that I really need an answer to:

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If most, if not all plant and animal life had been wiped out after an apparent asteroid collision with earth, then would that mean that life, post-extinction, would have to start from scratch, like it did billions of years ago? and if so, how would there possibly have been time to create the deiversity that we see today?

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As I understand it, the 'nuclear winter' caused the extinction of
the larger animals, while smaller ones survived.As a cause of extinction at that time it is by no means universally
accepted though. I'm sure a little web-searching would throw up
a multitude of ideas and opinions on the subject.Personally I've never found the asteroid collision theory that
compelling so I'd like to hear more thought on this subject too.

i've deleted the cookies, i refresh the page, and those posts jsut refuse to show.

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Originally posted by Peter:
As I understand it, the 'nuclear winter' caused the extinction of
the larger animals, while smaller ones survived.

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As a cause of extinction at that time it is by no means universally
accepted though. I'm sure a little web-searching would throw up
a multitude of ideas and opinions on the subject.

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Personally I've never found the asteroid collision theory that
compelling so I'd like to hear more thought on this subject too.

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JM: Me neither as the sole cause. We do know (a) an asteroid hit the earth at about the time the dinosaurs cease to show up in the fossil record. Most likely, the asteroid was not a positive life event for those dinosaurs. We also know that the Deccan traps erupted some 3 x 10^6 km^3 of basalt at about the same time the dinosaurs stop appearing in the fossil record. That volcanism was not a positive life event for extant creatures. We also know that Dinosaurs were on the decline prior to those events (likely due to diseases resulting from the introduction of Asian stock with North American stock (see Bakker's book Raptor Red for an interesting fictional account of these events). Taken together, none of these were particularly good for the dinosaurs and the previous two were not good for other organisms. Tommorrow, we are having a departmental seminar on the subject so I'll let you know if anything new comes from that.CheersJoe Meert

"If most, if not all plant and animal life had been wiped out after an apparent asteroid collision with earth, then would that mean that life, post-extinction, would have to start from scratch, like it did billions of years ago? and if so, how would there possibly have been time to create the deiversity that we see today? "
--No, because it wasn't the impact itself that in an evolutionary time scale destroyed the dinosaurs, according to uniformitarian geologic time, it was a very fast process (in geologic time) though would have spaned many years I believe. As it was the blockage of sunlight warming the planet I would think that killed them off.
--Very simmilar to my position on the extinction of the Dinosaurs (and many other creatures ofcourse, it wasn't just Dinosaurs) an ice age that was the cause of the impacts and clouded atmosphere and a drop in climate.-------------------

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Originally posted by TrueCreation:
"If most, if not all plant and animal life had been wiped out after an apparent asteroid collision with earth, then would that mean that life, post-extinction, would have to start from scratch, like it did billions of years ago? and if so, how would there possibly have been time to create the deiversity that we see today? "
--No, because it wasn't the impact itself that in an evolutionary time scale destroyed the dinosaurs, according to uniformitarian geologic time, it was a very fast process (in geologic time) though would have spaned many years I believe. As it was the blockage of sunlight warming the planet I would think that killed them off.
--Very simmilar to my position on the extinction of the Dinosaurs (and many other creatures ofcourse, it wasn't just Dinosaurs) an ice age that was the cause of the impacts and clouded atmosphere and a drop in climate.

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The problem with your position is that you place the Ice Age right after the mythological flood,4500 years ago and thats not the analysis that trained,experienced geologists get from the evidence they gathered. I posted a web site the other day where geologists speak of for great ice ages being represented in the geological records,punctuated by short periods of warmer and cooler climates(the current climate being warmer,obviously)...those ice ages last for millions of years at a time,as the geological records indicate and the last time that the Ice retreated was nearly 12 000 years ago.

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Originally posted by LudvanB:
The problem with your position is that you place the Ice Age right after the mythological flood,4500 years ago and thats not the analysis that trained,experienced geologists get from the evidence they gathered. I posted a web site the other day where geologists speak of for great ice ages being represented in the geological records,punctuated by short periods of warmer and cooler climates(the current climate being warmer,obviously)...those ice ages last for millions of years at a time,as the geological records indicate and the last time that the Ice retreated was nearly 12 000 years ago.

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Actually geologist have noted quite a bit more than 4 ice ages. You are talking about the more recent ones. There are also Permo-Carboniferous glacials, Ordovician glacials and several episodes in the Precambrian. This is a very difficult thing for creationists to explain since glaciation span the entire geologic column. Creationists pretend they don't know about the others because they have no explanation.CheersJoe Meert

Does anyone know if there is gap in the fossil record extending from 65 million years ago to some closer time, or just dino fossils disappear? I'm not clear in that.

Hi Peter. Small burrowing mammals survived (and lead to us among others).Birds (which are dinosaurs), mostly waterfowl survived.There was some extinction in marine life but not all. An interesting element of this is shown in the foraminifera fossil record: Geology Dept article 3

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One of the last great extinctions occurred roughly 66 million years ago, and according to one popular theory it resulted from Earth's receiving a direct hit from a large asteroid. Whatever the cause, the event proved to be the dinosaurs' coup de grace, and also wiped out a good portion of Earth's marine life -- including almost all species of planktonic forams.

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This period of mass death, which ended the Cretaceous Period, ushered in the modern chapter of biological development. Earth entered the new era, the Cenozoic, with a wide range of ecosystems virtually devoid of life, yet quite fertile and primed for repopulation.

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Like ecologists who study how wildlife recovers from a forest fire, evolutionists are drawn to such incidences of "biological vacuum" in search of clues as to how the earliest forms of life started evolving, when competition wasn't the controlling factor in the process.

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Particularly vexing are questions about what forces drive the process of natural selection -- what factors ultimately control the tempo and fate of biological struggle. But because of the traditional fragmentation of the fossil record, answers have remained elusive.

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"In most cases of evolution, we're incapable of collecting the basic facts. But here's one case where we are capable," Parker said.

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Since the foram record extends through a major extinction event (some of the samples date back nearly 100 million years), it represents the first, grand template against which a flock of pet theories on the beginnings of evolution may now be effectively measured, he said.

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"This is the great naturalist experiment," says Parker. "How often is it that you get to almost wipe your slate clean and then watch an ecosystem start up all over again?"

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Some scientists have theorized, but never been able to demonstrate, that in the absence of competition, an explosion of life takes place. The evolution of new species is greatly accelerated, and a profusion of body shapes and sizes bursts across the horizon, filling up vacant spaces like weeds overtaking a pristine lawn. An array of new forms fan out into these limited niches, where crowding soon forces most of the new forms to spin out into oblivion, as sparks from a flame.

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Other observers, perhaps following Darwin's lead, have envisioned a much more sedate repopulation sequence, with speciation occurring at an immensely slow rate. None of the species die off until their numbers begin to saturate the environment, exhausting its capacity to sustain such proliferation of life.

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As revealed by the ancient record left by the foram family, the story of recovery after extinction is every bit as busy and colorful as some scientists have long suspected.

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"What we've found suggests that the rate of speciation increases dramatically in a biological vacuum," Parker said. "After the Cretaceous extinction, the few surviving foram species began rapidly propagating into new species, and for the first time we're able to see just how this happens, and how fast."

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As foram survivors rush to occupy their new habitats, they seem to start experimenting will all sorts of body shapes, trying to find something stable, something that will work, Arnold said. Once a population in a given habitat develops a shape or other characteristic that stands up to the environment, suddenly the organisms begin to coalesce around what becomes a standardized form, the signature of a new species.

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As the available niches begin to fill up with these new creatures, the speciation rate begins to slow down, and pressure from competition between species appears to bear down in earnest. The extinction rate then rises accordingly.

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This scenario, Arnold says, suggests that the speciation process is sensitive to how fully packed the biosphere is with other species, not the number of individuals. Ecologists, in referring to a given environment's ability to sustain life as its carrying capacity, generally mean the natural limit, in sheer numbers, of individual organisms that any environment can support, as opposed to the number of different kinds of organisms.

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Enjoy.

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I was really asking what is in the fossil record between (say) 65 million years ago and 60 million years ago.Do we have small mammal, fish, birds, etc. in that time-frame but no dino's ... or no fossils at all, then no more dino's in the 60 million and 'fresher' fossils.i.e. do JUST the dino fossils suddenly stop, or is there a complete lack of fossils for some period around the 65 million year mark?

There are fossils of some sort throughout. After the K-T Boundary, the fossils are mostly smaller land organisms, such as birds and lizards and small mammal-like animals.However, since birds are descended from Dinosaurs, and cladistically, animals can't evolve out of their clades, we have dino fossils and bones through to today, In fact, a nice bright red dinosaur likes to hang out in the brush behind my house during the spring/summer months.

I thought the birds are dinosaurs thing was still contested by those pesky ornithologists and there left-toe/right-toe arguments ... but I haven't looked at that question for some time.I think that sort of answers my question though ... and I guess there must be a significant gap in the fossil record around that time for us to not have very specific examples of the speciation into modern birds -- or do we?

Archaeopteryx is a classic example. There are a lot of types of species that have been found with some dinosaur and some bird charicteristics, with varying degrees of each.In fact, some paleontologists have speculkated that feathers were quite an early adaptation of scales and that many of the dinosaurs we currently depict with scales actually had feathers over some or all of their bodies.

I had come across the feathered dinos idea a while ago ... even leading me to wonder if T.Rex's puny arms were really some form of wing-like structure.I didn't think Archaeopterix was considered an actual dino-bird transitional though ... not via any specific species in any case.

It's probably not ancestral to modern birds, if that's what you mean.In the first place, what are the odds?In the second place, there are maniraptors with uncinate processes, including, for example, Caudipteryx. But Archaeopteryx doesn't have them. But all modern birds do except the Anhimidae. (This is my own reasoning, I am neither a paleontologist nor an ornithologist. Add your own salt.)