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This is a very strange argument. I don't see how you can say the asteroid had no impact. There were entirely new niches that opened up after the mass extinction

by TSiege 3y ago

This is a very strange argument. I don't see how you can say the asteroid had no impact. There were entirely new niches that opened up after the mass extinction. Birds by definition had to evolve into them after the impact since ~75% of species went extinct. I can believe that birds evolved before the impact, but to say it didn't impact bird evolution is like saying mammal evolution wasn't impacted by the impact because mammals pre-existed before then. Who knows if birds would be as dominant as they are today had the impact never have happened. Today there are almost twice as many species of birds as there are mammals. I think both can easily be true > When searching for fossils of the major groups of birds alive today, scientists have found almost none that formed before the asteroid hit. That striking absence has led to a theory that the mass extinctions cleared the evolutionary arena for birds, allowing them to explode into many new forms. But the new study came to a very different conclusion. “We found that this catastrophe didn’t have impact on modern birds,” said Shaoyuan Wu, an evolutionary biologist at Jiangsu Normal University in Xuzhou, China.

bluGill 3y ago
Scientists find lots of fossils in places where they are likely to form, which is mostly wetlands. We have much less evidence for what the rest of the world was like just because those area didn't leave evidence behind. It may be that birds and mammals dominated the earth - except for wetlands where dinosaurs lived (probably not, but we don't have much evidence)
b112 3y ago
That striking absence has led to a theory that the mass extinctions cleared the evolutionary arena for birds Just thought of something, which others may have considered, but I had not. When taught this, and when reading about this, my takeaway was "lots of dinosaurs and other animals died, leaving free "tree of life" positions for mammals and birds to fill. EG, if a "fox like dinosaur" dies, something mammalian can move into that niche. But what if the truth is, all the birds species survived, but as the dinosaurs died out, many of the now "missing' bird species were unable to live, for they subsisted in the realm of the dinosaur. Think of specialized birds eating seeds out of sauropod manure. Birds eating ticks and other such creatures off of larger dinosaurs, birds cleaning their teeth, essentially birds hyper-specialized to live in the 'realm of the dinosaur'. These birds would be secondary die-offs, not primary, and would open up niches for other birds. Here's an example. 20 years ago, there were no woodpeckers on my rural property. Then the ash borer and other pests infested all the local trees. Soon after, within 2-4 years, woodpeckers started to arrive. This is a well known phenomenon, the min/max cycle with prey/predator. The prey increase in numbers, so the predator follow. Then? The predators eat so much prey, that the prey population crashes, and so does the predator. Anyhow my point is, the woodpeckers ran out of food. And I noticed them literally "pecking" at the ground, using their long beaks, to get grubs from my lawn. I believe they are not well suited to this, and that grub supply is too small, but are starving, and are using this, and their beak specialization as a way to get whatever food they can. (Also note that they are competing with skunks, voles, and crows. Also also note that crows use HF vocalizations to detect grubs in the rain!) Now imagine such backup strategies being employed post-asteroid. The primary method of food gone. Backup methods used. Slowly such specialists dying off. Anyhow. Just rambling thought.

by TSiege 3y ago

bluGill 3y ago

Scientists find lots of fossils in places where they are likely to form, which is mostly wetlands. We have much less evidence for what the rest of the world was like just because those area didn't leave evidence behind. It may be that birds and mammals dominated the earth - except for wetlands where dinosaurs lived (probably not, but we don't have much evidence)

b112 3y ago

That striking absence has led to a theory that the mass extinctions cleared the evolutionary arena for birds Just thought of something, which others may have considered, but I had not. When taught this, and when reading about this, my takeaway was "lots of dinosaurs and other animals died, leaving free "tree of life" positions for mammals and birds to fill. EG, if a "fox like dinosaur" dies, something mammalian can move into that niche. But what if the truth is, all the birds species survived, but as the dinosaurs died out, many of the now "missing' bird species were unable to live, for they subsisted in the realm of the dinosaur. Think of specialized birds eating seeds out of sauropod manure. Birds eating ticks and other such creatures off of larger dinosaurs, birds cleaning their teeth, essentially birds hyper-specialized to live in the 'realm of the dinosaur'. These birds would be secondary die-offs, not primary, and would open up niches for other birds. Here's an example. 20 years ago, there were no woodpeckers on my rural property. Then the ash borer and other pests infested all the local trees. Soon after, within 2-4 years, woodpeckers started to arrive. This is a well known phenomenon, the min/max cycle with prey/predator. The prey increase in numbers, so the predator follow. Then? The predators eat so much prey, that the prey population crashes, and so does the predator. Anyhow my point is, the woodpeckers ran out of food. And I noticed them literally "pecking" at the ground, using their long beaks, to get grubs from my lawn. I believe they are not well suited to this, and that grub supply is too small, but are starving, and are using this, and their beak specialization as a way to get whatever food they can. (Also note that they are competing with skunks, voles, and crows. Also also note that crows use HF vocalizations to detect grubs in the rain!) Now imagine such backup strategies being employed post-asteroid. The primary method of food gone. Backup methods used. Slowly such specialists dying off. Anyhow. Just rambling thought.