An asteroid wiped out dinosaurs – did it help birds flourish? | Hacker News Reader

An asteroid wiped out dinosaurs – did it help birds flourish?

nytimes.com

41 pointsgardenfelder31 comments

Link to more pnas text, as usual it doesn't match the times copy very closely.

https://www.pnas.org/doi/10.1073/pnas.2319696121

Seems strange that people still don't think of birds as dinosaurs (just going off the title)

Why does that seem strange? People who are interested will know or course, but to 99.99% of people, “dinosaur” specifically means lizards (often huge) that lived millions of years ago. Even the name means “terrible lizard” and a lot of people might remember that. They’re conceptually so far from birds that the relationship is naturally relegated to a tangential factoid.

Conceptually they are very different than sparrows or robins, but if you get up close to a Cassowary one has the distinct impression of meeting a modern Utahraptor.

They're actually utahraptors hiding inside bird skins. They snuck out of the armageddon in costumes and they just wander around trying to act natural now.

I mean, we don't think of ourselves as lobe-finned fish either.

That's because we aren't lobe-finned fish... But birds are a type of dinosaur

Birds aren't just a "type" of dinosaurs, they're literally defined as the surviving dinosaurs and their closest extinct relatives. For all intents and purposes, what we call "birds" are simply dinosaurs.

So looking at the timeline of DNA diversification in birds, the biggest spread occurred 10's millions of years before the asteroid mass extinction, and net there was not so much after the asteroid hit itself. Makes sense to me as I imagine birds were hit with devastated ecosystems and had to adapt, though I imagine their greater range made them more resilient.

We will have to wait for fossils to confirm this.

Did an asteroid wipe out the dinosaurs? I think it was blood borne viruses transmitted by biting insects across the large surface area of the dinosaurs bodies. They had no immune system, short opportunity to adapt, only the smaller types lived.

Yes, the short answer is, it was an asteroid and the effects after that killed the (large, non-avian) dinosaurs. Other hypotheses do not have the same explanatory power and may only account for a minuscule and much slower influence leading up to the asteroid extinction. Survival after the impact was greatly influenced by the simple ability to acquire food, but also other adaptations such as the immune system and ability to fight off fungal infections. Flying birds in particular had an advantage because they could forage for seeds over a vast distance while other terrestrial species run out of food (the article's cited study may broadly agree with this as an advantage, but suggests not as much post-chixculub diversification as believed before, and shows pre-chixculub modern bird form examples)

There is a good YouTube documentary on the matter, but it is long: https://www.youtube.com/watch?v=6DHgkMYgp7w

You shouldn't be down voted. While that hypothesis is outside the scientific consensus and based on very limited, circumstantial evidence it isn't completely impossible. There could have been multiple contributing causes.

https://press.princeton.edu/books/hardcover/9780691124315/wh...

This computational model doesn't match the fossil record which suggests the flaw is in the model, not the evidence.

They used the fossil record to fine tune the baysian phylogenetic model. So no this is not correct.

I think this might be wrong. The article ends with quotes from Jacob Berv. It says:

> Jacob Berv, an evolutionary biologist at the University of Michigan who was not involved in the study, said that it illustrated state-of-the-art methods for crunching huge amounts of genetic data to reconstruct evolutionary history. But he did not agree with its conclusion.

> If the new study was right, there should be fossils of all major groups of living birds from well before the asteroid impact. But almost none have been found.

> “The signal from the fossil record is not ambiguous,” Dr. Berv said.

> Dr. Berv suspects that the correct story comes from the fossils, and that most major groups of birds emerged after the asteroid impact. The potential problem with the new study, he said, is that it assumes that the bird DNA accumulated mutations at a steady rate from one generation to the next.

I'd suggest reading the article which quotes experts in the field explaining that the fossil record does not fit this model.

>“The signal from the fossil record is not ambiguous,” Dr. Berv said

The fossil record says the asteroid had a big impact on bird evolution. A fancy new computer model trained on DNA data says it didn't. The computer model's results are surprising and not supported by the fossil record.

I know where I'm placing my bets.

The fossil record could be incomplete, and both could be true. I've seen other studies hinting at bird evolution happened older than we thought

The fossil record is certainly incomplete, but it's also certainly more reliable than a new DNA model reporting conclusions that make no sense (the impact didn't impact bird evolution? There's no way that passes the smell test)

Yes, I had the same thought. The DNA data is completely uncalibrated. From the NYT article, it looks like they've beaten the DNA data until it supports their hypothesis.

[stub for offtopicness]

Just because there was genetic diversity before the asteroid does not mean it did not affect things. A human builds a shack in the woods and that has measurable impact in terms of ecosystem disturbance decades even centuries after its a ruin. An asteroid is going to do something.

I feel like I caused this problem by replacing the article's title with "The asteroid that wiped out dinosaurs didn't impact bird evolution: new study". I wanted something less baity than the article's own title, in keeping with the site guideline: "Please use the original title, unless it is misleading or linkbait" - https://news.ycombinator.com/newsguidelines.html.

The problem is that it is too easy to object to. "Didn't impact" is too strong. Everything impacts everything, as you say—especially asteroids. But now we're in generic tangent territory, driven by a bad title rather than anything interesting (or indeed, anything at all) about the study. Since the edit made things worse, I'm going to drop it. Sorry.

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.

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)

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 now the common wisdom is that birds are dinosaurs -- what's left of them.

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