Evidence Of Cleaner Air, Hidden In The Drawers Of A Museum

9:27 minutes

field sparrows, soot coverage
Field Sparrows from The Field Museum’s collections, with gray birds from the turn of the century and cleaner birds from more recent years when there was less soot in the atmosphere. Credit: Carl Fuldner and Shane DuBay, The University of Chicago and The Field Museum

If you’re looking for evidence that policies like the Clean Air Act are working, look no further than the the drawers of the bird collection at The Field Museum in Chicago. A study published in the Proceedings of the National Academy of Sciences analyzed specimens of the Horned Lark collected in the early 1900s, at the height of the Industrial Revolution. The soot on the birds’ feathers allowed them to trace the amount of black carbon in the air over time, and found that the air at the turn of the century was even more polluted than scientists previously thought. Popular Science Senior Editor Rachel Feltman joins us to discuss. Plus, scientists uncover how the durian fruit got so stinky.  

[Why don’t banana candies taste like real bananas?]

Segment Guests

Rachel Feltman

Rachel Feltman is Science Editor at Popular Science in New York, New York.

Segment Transcript

JOHN DANKOSKY: This is Science Friday. I’m John Dankosky. Ira Flatow is away.

Later in the hour, we’ll talk with primatologist Dr. Jane Goodall about her revolutionary work with the chimps in the Gombe Stream Research Center over 50 years ago, and we’ll chat about what issues are most pressing for her today.

If you’ve got a question for Jane Goodall about her work, you can call us. Our number is 844-724-8255. That’s 844-SCI-TALK. You can always tweet us @scifri.

But first, ever wonder if environmental policies like the Clean Air Act are actually working? Well, look no further than the Field Museum in Chicago, home to a collection of songbirds from the early 1900s. In a new study, researchers say the soot captured in these birds’ feathers provides a picture of the air quality around the Industrial Revolution that’s much worse than scientists originally thought.

Here to tell us about that, as well as other short subjects in science, is Rachel Feltman, science editor at Popular Science. Rachel, welcome back. Good to see you.

RACHEL FELTMAN: Yeah, good to see you too.

JOHN DANKOSKY: So tell us about what researchers learned about air pollution from studying this old bird collection.

RACHEL FELTMAN: Yeah, so basically they were just able to analyze how much soot had been in the atmosphere over a span of about 135 years, because they had this collection of the same species of birds that had been collected from the same part of Illinois over that entire period.

And it’s really cool, because it’s a reminder of how important natural history museums are. A lot of people don’t realize that the vast majority of the collections in the Natural History Museum aren’t on display. They’re in unmarked boxes, or, at best, labeled drawers, somewhere in the bowels of the museum. And researchers are, these days, really poking around a lot to see what old specimens that have been ignored for a long time might teach them. So this is just a great example of that.

JOHN DANKOSKY: What gave them the idea to do this, though, to pull off soot from the birds’ feathers?

RACHEL FELTMAN: As far as I know, they just had this whole span of birds to look at, and it was really apparent that the birds from 1906 were filthy. They had just been put away covered in soot, because that’s how all the birds looked at that time. The difference is so striking that you would think that there had just been some evolutionary change in coloration, but they were just filthy.

So it was just that when looking through their drawers of dead birds, because natural history museums have those, it was just such a striking spectrum of color that they decided to try to use them for this purpose.

JOHN DANKOSKY: I just have to quickly ask, how do they know that these specimens were clean, I suppose, in that they weren’t treated with chemicals or washed off? I mean how do they know that this was a real sample?

RACHEL FELTMAN: Well, that’s a good question. I guess it could be that they were even filthier before they were put in, which would mean that their estimates were actually conservative for how sooty the air was in the early 1900s. But generally there are pretty good records, especially if we’re just talking about a century ago, for what people did to the specimens before they put them away.

JOHN DANKOSKY: It’s so interesting.

OK, so our next story, I’ve got to tell you, it kind of stinks. Scientists say they can explain how durian fruit got so stinky. Do I even want to know the answer to this?

RACHEL FELTMAN: Yeah, it’s actually very cool.

So scientists decided to sequence the genome of the durian, which is notoriously smelly. People say it smells like rotting animals or garbage but it tastes delicious. I wouldn’t know, but I’ve been told.

And they sequenced its genome and found that it’s actually very closely related to cacao, which is where we get chocolate and obviously smells very nice. The main difference is that the durian had what’s called a genome duplication event, which is what it sounds like. At some point a plant mutated and just copied its genome and then had two copies.

The reason that that’s beneficial, especially to plants, is that it gives you an extra set of genes to play with. You can imagine the one set carrying out the functions those genes have to carry out for the plan to survive. The other set can play around with all different mutations. Obviously some of those didn’t pan out, but the ancestor of the modern durian is the plant that happened to evolve stinkiness. Like, really strong stinkiness.

JOHN DANKOSKY: But why evolve this extra stinkiness?

RACHEL FELTMAN: Well, that’s the question. We know that it has multiple copies of these genes that create sulfuric compounds, which is where it gets its smell. We don’t really know why. I mean, I would imagine that the smell probably attracts some animals and repels others, which would probably help protect the plant, except when it needs to get eaten and have its seeds spread around. So I think it was just beneficial on a species-wide level to have this quirk, and so it just kept happening.

JOHN DANKOSKY: It’s too bad that cacao doesn’t smell extra-chocolatey. But that’s for another study.

So let’s move on. We talk a lot on the show about the role of bacteria in the gut microbiome, but there’s a new study about the role of fungi in the gut. I didn’t know much about fungi. What did researchers find?

RACHEL FELTMAN: Oh, man. I studied mycology in college, so I’m actually a big fungi evangelist. So this is very exciting to me.

We talk about bacteria a lot. It’s a very hyped, new topic. But the microbiome includes all microbes, including fungi, and there are also viruses and parasites in there. And these aren’t microbes that are making us stick. Just like the bacteria we talk about in our microbiome, these are just a normal part of the flourishing ecosystem in there.

So researchers are starting to look more closely at how changes in our fungal microbiome can affect our health, or at least relate to our health. This research is even more in its infancy than the bacterial microbiome. We still don’t know what a healthy microbiome is. We don’t really know how to get one. But we are seeing that our health is connected to these organisms that live inside us.

JOHN DANKOSKY: And researchers are going to start looking into this more. Maybe fungus plays a bigger role.

RACHEL FELTMAN: Right. And there are definitely way more bacteria in our guts than there are individual spores of fungi. But they do live together. It’s an ecosystem. And so you would think that if we care about hacking the bacterial microbiome, we should really figure out what all the other microorganisms are doing, or we might not be able to make the interventions we want to make.

JOHN DANKOSKY: I have always wondered if we’re living in a computer simulation. I know that a lot of movies, like The Matrix, sort of give you the sense that that’s the life we live in. Has this been disproved now? Are we not in a computer simulation?

RACHEL FELTMAN: Well, the reason it’s such a fun thought experiment that comes up again and again is that it’s really hard to disprove. Because, you know, if you’re living in a computer simulation, how would you possibly know?

There is a study that kind of gives a sideways proof. They think they’ve proven accidentally that we don’t live in a computer simulation. Basically, they were trying to model a very complicated physics phenomenon known as the quantum Hall effect. I won’t get into it, but nobody’s ever been able to model it on a computer before.

They showed that they were also not able to model it. And, in fact, they believe they’ve shown that it would be physically impossible to model this on a computer that we use today, on a classical computer. That it would take more atoms than there are in the universe to store enough information to actually simulate this.

Now, presumably, if we lived in a computer simulation, it would have to be possible to simulate all of the stuff in our universe. So they say that proves we don’t live in one. Of course, that assumes that our alien overlords or whatever are using a classical computer and also follow the same physical laws as us. So.

JOHN DANKOSKY: So, that’s the thing. You seem skeptical about this.

RACHEL FELTMAN: Right. Well, it rules out the idea that we’re just some other human’s version of The Sims or something. If someone has a more powerful computer than we’ve thought up yet, or they live in a universe with completely different physical laws, then they could still be “Matrix-ing” us

JOHN DANKOSKY: OK, a last story for you. And this is one that, I think, is haunting a lot of us right now. Where is fall? Where’s the autumn? I mean, it’s not felt like fall, and you’ve looked into this. What have scientists told you about why there’s no fall this year?

RACHEL FELTMAN: Right. I talked to a lot of researchers about how hot and not leafy it is in New York right now. And basically researchers are just starting to look at how climate change is affecting fall. They used to focus mainly on spring because the changes are so much more profound and noticeable.

But fall is happening later. It’s saying warmer for longer, and the thing is that we think about leaf change because it’s pretty, but it also signals the end of a tree’s growth cycle for the year. So if trees aren’t losing their leaves as early as they used to, they might be growing for longer, and that could have implications for the amount of carbon they’re pulling from the atmosphere, the amount of carbon that’s being released in the soil. So there are a lot of aspects of fall that do seem to be changing because of climate change, and it’s worth looking into.

JOHN DANKOSKY: Looking into it at least as much as the spring, which is where people have focused an awful lot. The end of winter into spring.


JOHN DANKOSKY: Well, Rachel, thank you so much for bringing us these stories. I really appreciate it.

RACHEL FELTMAN: Thanks for having me.

JOHN DANKOSKY: Rachel Feltman is science editor at Popular Science.

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