Quick and dumb question about dinosaurs

[Flying Spaghetti Monster]

REcently it was confirmed that an asteroid wiped out teh dinosaurs. Of course that tehory has been around for maybe thirty years, but recent findings seemed to all but confirmed that idea.

So if the dinos were wiped out in one swoop how did birds evolve?

Thanks!

 

[PlixTixiplik]

Birds had evolved in the Middle/Late Jurassic, about 100 million years before the extinction of the non-avian dinosaurs.

 

[Jadzia]

The modern idea is that there were two asteroid strikes, since that is what the sediment layers show (high temperature fused materials, and large concentrations of some of the rarest metals appearing in sediments dating from that time are found all over the globe)

The closer to the present, the less variety of fossils are found as well as the less total number of fossils. When the second asteroid hit, all life on earth appeared to have already been in a steady state of decline. Many species were dying out.

It's believed that dinosaurs were already on the way out too, and that the second asteroid really just made that ending come a lot quicker. All creatures with large body mass would have been unable to thrive. Perhaps the best survivors would have been those who lived in the ground and oceans consuming rotting vegetation.

Many people believe that birds are the evolutionary descendants of the dinosaurs. The evidence points roughly in that direction. Birds have a physiology quite unlike mammals and insects, and a skeletal structure reminiscent of dinosaur skeletons. Birds (like a chicken) also have repressed genes that suggest their ancestors had a toothed jaw instead of a beak.

Then there was a late species of dinosaur called the archeoptrix, that is the first creature known to have evolved feathers.

 

[RoJoHen]

I think the question being asked is: If birds evolved from dinosaurs, and the dinosaurs were wiped out, how did birds evolve at all? What dinosaur(s) managed to survive the extinction to allow birds to evolve in the first place?

Or, if birds already existed, how did they survive the asteroid?

 

[PlixTixiplik]

The modern idea is that there were two asteroid strikes, since that is what the sediment layers show (high temperature fused materials, and large concentrations of some of the rarest metals appearing in sediments dating from that time are found all over the globe)

No, there was only a single impact at Chicxulub - the claims of a double impact was by people who don't understand sedimentology - in regions near the crater there are two layers (proximal ejecta and stratospheric ejecta) separated by a tsunami deposit.

The closer to the present, the less variety of fossils are found as well as the less total number of fossils. When the second asteroid hit, all life on earth appeared to have already been in a steady state of decline. Many species were dying out.

It's believed that dinosaurs were already on the way out too, and that the second asteroid really just made that ending come a lot quicker. All creatures with large body mass would have been unable to thrive. Perhaps the best survivors would have been those who lived in the ground and oceans consuming rotting vegetation.

There is no evidence for a gradual decline in diversity in any group prior to the K/Pg boundary, including dinosaurs. People used to think that, but it's simply a reflection of the imperfections of the fossil record (something called the Signor-Lipps effect). When confidence intervals are placed on the stratigraphic ranges of groups like ammonites or dinosaurs their extinction is in fact abrupt and coincident with the boundary clay layer.

Many people believe that birds are the evolutionary descendants of the dinosaurs. The evidence points roughly in that direction. Birds have a physiology quite unlike mammals and insects, and a skeletal structure reminiscent of dinosaur skeletons. Birds (like a chicken) also have repressed genes that suggest their ancestors had a toothed jaw instead of a beak.

Then there was a late species of dinosaur called the archeoptrix, that is the first creature known to have evolved feathers.

Archaeopteryx is actually the earliest known bird (perhaps, depending on whether a new taxon Pedopenna is actually a bird or a dinosaur). However, it is not the first species to have evolved feathers. Downy feathers appeared fairly early in the theropod lineage and even vaned flight feathers (and flight itself, most likely) predate birds. Here's a picture of non-avian feathered dinosaur Anchiornis (with actual true colors).

And here's a cladogram showing the appearance of various flight-related characters in non-avian theropods and stem-group birds.

 

[PlixTixiplik]

I think the question being asked is: If birds evolved from dinosaurs, and the dinosaurs were wiped out, how did birds evolve at all? What dinosaur(s) managed to survive the extinction to allow birds to evolve in the first place?

No non-avian dinosaur survived the extinction, but that's irrelevant since birds first evolved 100 million years before the extinction of non-avian dinosaurs. There are more than 50 species of Mesozoic birds known.

 

[Silvercrest]

I think the question being asked is: If birds evolved from dinosaurs, and the dinosaurs were wiped out, how did birds evolve at all? What dinosaur(s) managed to survive the extinction to allow birds to evolve in the first place?

Or, if birds already existed, how did they survive the asteroid?

The other aspectthat a lot of people miss is this:
People talk about the extinction of the dinosaurs as if it was targeted specifically at them. It wasn't. The asteroid took out a helluva lot of other species, not just dinosaurs. Some birds and mammals (which had already evolved) happened to be among those who weren't wiped out. That's all.

 

[Robert Maxwell]

I think the question being asked is: If birds evolved from dinosaurs, and the dinosaurs were wiped out, how did birds evolve at all? What dinosaur(s) managed to survive the extinction to allow birds to evolve in the first place?

Or, if birds already existed, how did they survive the asteroid?

The other aspectthat a lot of people miss is this:
People talk about the extinction of the dinosaurs as if it was targeted specifically at them. It wasn't. The asteroid took out a helluva lot of other species, not just dinosaurs. Some birds and mammals (which had already evolved) happened to be among those who weren't wiped out. That's all.

And water-dwelling creatures fared much better. There are still some species (such as crocodiles) who haven't changed much since the dinosaurs were wiped out.

 

[RoJoHen]

I think the question being asked is: If birds evolved from dinosaurs, and the dinosaurs were wiped out, how did birds evolve at all? What dinosaur(s) managed to survive the extinction to allow birds to evolve in the first place?

Or, if birds already existed, how did they survive the asteroid?

The other aspectthat a lot of people miss is this:
People talk about the extinction of the dinosaurs as if it was targeted specifically at them. It wasn't. The asteroid took out a helluva lot of other species, not just dinosaurs. Some birds and mammals (which had already evolved) happened to be among those who weren't wiped out. That's all.

Sure, I understand that. I guess the part that interests me is what advantages did the surviving species have that allowed them to, ya know, survive.

Underwater creatures I can understand. It's the above-ground creatures that I wonder about.

 

[Robert Maxwell]

I think the question being asked is: If birds evolved from dinosaurs, and the dinosaurs were wiped out, how did birds evolve at all? What dinosaur(s) managed to survive the extinction to allow birds to evolve in the first place?

Or, if birds already existed, how did they survive the asteroid?

The other aspectthat a lot of people miss is this:
People talk about the extinction of the dinosaurs as if it was targeted specifically at them. It wasn't. The asteroid took out a helluva lot of other species, not just dinosaurs. Some birds and mammals (which had already evolved) happened to be among those who weren't wiped out. That's all.

Sure, I understand that. I guess the part that interests me is what advantages did the surviving species have that allowed them to, ya know, survive.

Underwater creatures I can understand. It's the above-ground creatures that I wonder about.

One advantage I can immediately think of regarding small mammals is their low caloric intake and ability to hibernate. Large dinosaurs had to eat constantly and required warm, humid climates (I think, someone can correct me). A small mammal that can hide underground has the advantages of not requiring a lot of food, having fur to stay warm, the ability to burrow (again, to stay warm), and to hibernate (read: reduce caloric intake for an extended period.)

Likewise, I think most of the early birds survived by being carrion eaters. And there were a lot of dead things to feed on after the asteroid impact.

 

[RoJoHen]

Likewise, I think most of the early birds survived by being carrion eaters. And there were a lot of dead things to feed on after the asteroid impact.

Mmm, I hadn't thought out that.

I generally try not to think about eating rotten carcasses.

 

[Silvercrest]

I tend to dismiss the size/caloric thing as a too-easy answer, because it doesn't explain why the small dinosaurs died... and why other land reptiles lived.

I tend to think that it was just luck of the draw that some species survived and some didn't. I'm sure a lot of birds and mammals were also exterminated by the strike, or the aftermath. The dinosaurs all just happened to fall on the wrong side of the coin. I'm sure there could be a more scientific explanation.

 

[Robert Maxwell]

I tend to dismiss the size/caloric thing as a too-easy answer, because it doesn't explain why the small dinosaurs died... and why other land reptiles lived.

I tend to think that it was just luck of the draw that some species survived and some didn't. I'm sure a lot of birds and mammals were also exterminated by the strike, or the aftermath. The dinosaurs all just happened to fall on the wrong side of the coin. I'm sure there could be a more scientific explanation.

By all accounts, it must've gotten very cold after the asteroid hit--all that dust and debris blocking out the sun. Creatures without some kind of covering to protect them from the elements didn't have much of a chance. Scales just don't cut it, you need feathers or fur.

Nothing is universally true on this subject, as there are obviously larger lizards that survived, but being small, agile, and furry confers a lot of advantages.

 

[Silvercrest]

All true. But I think RoJo is looking for something that's universally true, and there may not be one.

 

[Myasishchev]

It's important to recall that a lot of dinosaurs were feathered, and still died out.

But I agree that for terrestrial animals size was the biggest determinant of failure.

 

[Christopher]

REcently it was confirmed that an asteroid wiped out teh dinosaurs. Of course that tehory has been around for maybe thirty years, but recent findings seemed to all but confirmed that idea.

According to one paper. Other scientists still disagree. In fact, I find the claim of "confirmation" rather disingenuous, because there's no dispute that the Chicxulub impact happened, merely question over whether it and it alone killed the dinosaurs. The theory I gather was gaining ground was that mass extinctions are a combination of two factors, a long-term stressor that renders the population vulnerable (such as disease) and a sudden traumatic event that finishes them off.

So if the dinos were wiped out in one swoop how did birds evolve?

As stated, birds came along well before the K-T extinction. Evolution isn't a ladder, but a tree; new forms don't come after old forms in a neat line, but branch off and coexist with them.

The key is that in extinction events on land, it's the largest, most dominant forms that are the first to go. The biggest critters need the most food, so if a climatic catastrophe makes food scarce, it's the gas-guzzlers that die out while the little critters that can get by on less survive. Also, the smaller critters breed faster, so they can evolve faster. If it takes, say, twenty generations for a useful adaptation to arise, a creature that has a new generation every year can adapt to an abrupt environmental change within two decades, whereas a larger creature that takes fifteen years to reach sexual maturity would need three centuries to catch up, by which time it would've already gone extinct.

This is why mammals and birds survived the K-T extinction and the big, dominant order of life, the non-avian dinosaurs, died out. It's because the mammals and birds were smaller. The meek literally inherited the Earth. As with any revolution, the folks at the top of the pecking order are the first against the wall, while the great mass of little people just carry on with their lives beneath the radar.

 

[O'Dib]

Why would the large water reptiles have suffered as well?

 

[Silvercrest]

Or the small dinosaurs, as I said before?

 

[Robert Maxwell]

Why would the large water reptiles have suffered as well?

Or the small dinosaurs, as I said before?

All forms of life suffered. All of them! Some were just more resilient than others. Obviously, not all small reptiles died out, or we wouldn't have any today.

 

[Finn]

Sometimes, we just have to settle with "They just didn't survive. Other survivors managed to over-compete the smaller dinosaurs that may have survived the mass extniction event.