The problem with modern avocados — and the ancient solution

NATE ROTT: Hey, Nate Rott here. Before we get into this episode, a quick ask for you to lift that finger and press the Follow button on your app. We love telling you all the latest cool science out there. And following us helps you make sure that you never miss any new science stories coming from us and have smarter, more informed conversations with all of friends. We all want that, right? OK, PSA over. Here's the show.

ANNOUNCER: You're listening to Short Wave from NPR.

ROTT: Hey, Short Wavers. I'm still Nate Rott.

HANNAH CHINN: And I'm Hannah Chinn.

ROTT: With our biweekly science news roundup featuring the one, the only, the exquisite Ailsa Chang, of All Things Considered.

AILSA CHANG: Nate Rott, you're very exquisite, too. Thank you so much for having me again, guys.

ROTT: Happy you're here. OK. So this week, we've got a few discoveries that help us better understand this wacky world that we're all living in. The first is a discovery about ancient avocados, which are my favorite kind to eat, that could help us keep slathering our chips with guacamole today.

CHINN: And the next one looks at the mummified remains of Egyptian princesses and upends some of our assumptions about how they lived.

ROTT: And the last study takes a global look at birdsong. Trust me, Hannah, and Ailsa, it's going to be "trilling."

CHANG: Get it?

ROTT: Yeah, a pun. All Puns Considered. You're listening to Short Wave, the science podcast from NPR.

[RELAXING MUSIC]

ROTT: All right, Hannah and Ailsa. We've got a lot to get into.

CHINN: Let's start with ancient avocados.

CHANG: Is my avocado toast in danger here?

CHINN: Well, not yet. So when you pick up avocados at the grocery store, or when you get guac in your burrito, chances are that it's from a single type of avocado. It's called the Hass avocado.

CHANG: Right.

CHINN: And, Ailsa, this type of avocado makes up more than 80% of commercial avocado production.

ROTT: Which is, you know, kind of convenient, because it means that our avocados tend to be, like, consistent in their size, shape, flavor wise. But because they're all genetically identical, they're all susceptible to diseases in the exact same way.

CHANG: Oh, like farmers are putting all their eggs-- ha, ha-- or avocados, shall we say, in one basket here? So are there other varieties of avocados that we could grow so there's sort of like, genetic variation?

CHINN: Yeah, there are. And a lot of them look very different.

KEVIN WANN: They're bigger. They're whiter. They're glossier, less bumpy, usually, like, lighter green, sometimes come in different shapes and sizes. And on the inside, they tend to be less fatty.

CHINN: So this is archaeobotanist Kevin Wann. He's a fellow at the Smithsonian National Museum of Natural History and a PhD candidate at Texas A&M doing avocado research, even though, up until a couple years ago, he'd never tasted one.

WANN: I was going to see if I could go my entire PhD studying avocados without ever having eaten one or eaten guacamole.

ROTT: But what Kevin wanted to know is how much genetic diversity he was dealing with. So he collected DNA samples from a bunch of different avocado varieties in Mexico and Central America, mostly from local farmers or home gardens.

CHINN: Yeah. And he sequenced the genomes of these avocados to compare them, to each other and also to an existing archive of avocado varieties, kind of like a 23andMe or ancestry.com test but for avocados.

CHANG: That's kind of cute. OK. So what did they find?

ROTT: So he found a lot of genetic diversity and a few varieties of Nicaraguan avocados that were super genetically similar to those in South America, which suggests they were brought there by ancient farmers and then hybridized with native species. Kevin published a paper on these findings this past week in the scientific journal Plants, People, Planet.

CHINN: Then I talked to anthropologist Amber VanDerwarker She's at UC Santa Barbara, and she wasn't involved with the study. But she said Kevin's research really reveals this genetic diversity that has been preserved over the past thousands of years by these intrepid ancient farmers. And she told me, it's important for us to keep this diversity alive, right, so avocados stay sustainable into the future.

CHANG: Totally. But I am still dying to know-- did Kevin ever eat an avocado?

CHINN: He did.

WANN: When I was interviewing that farmer in Nicaragua, he picked off one of the avocado fruits and said, here, try this. And I couldn't say no.

CHANG: No, you couldn't.

CHINN: Exactly. And, Ailsa, you'll be happy to know that Kevin told me he eats avocados and guacamole almost every single day now.

CHANG: Good for him.

ROTT: Good man.

CHANG: So let's move on to Egyptian princesses. Tell me more.

CHINN: Yeah. So maybe what I love most about this story is that it came from an effort to unclutter a basement.

ROTT: Yeah. So that's what the Egyptian Museum in Cairo was doing when they rediscovered this box with the mummified remains of six members of an ancient Egyptian royal family that had been excavated and stashed more than 100 years ago.

CHANG: Yeah, totally normal thing to find in one's basement.

ROTT: Of course.

CHANG: So who was this family?

CHINN: It was five princesses and a king who lived thousands of years ago, around 1800 BC.

CHANG: Wow, a girl dad.

CHINN: Yeah, exactly.

ROTT: Yeah. But one of the things that confused the archeologists when they found these remains was that the women were all buried with weapons, like daggers and maces and bows and arrows, which archeologists typically associate with men.

CHANG: Of course.

ROTT: So the assumption was the princesses were buried with these weapons for symbolic reasons.

CHANG: Symbolic? Wait, hello! Have these people not ever heard of Xena, Warrior Princess? Because women do carry weapons sometimes, OK?

CHINN: Exactly. And that's what the person who helped find these remains wanted to figure out.

ROTT: Yeah. Her name is Zeinab Hashesh. She's a bioarchaeologist at Beni Suef University in Egypt. And she says, you know, we all have this assumption that princesses are like Disney characters.

ZEINAB HASHESH: That they are fluffy, they are wearing beautiful dresses and very beautiful jewelry.

CHINN: When Zeinab looked at these bones, she noticed that these skeletons had really strong muscle attachments.

CHANG: These women were buff.

CHINN: Exactly. And she did a deeper analysis of the bones, and she found these women were, yeah, buff. They were really strong.

HASHESH: Strong forearms and shoulder. And also, for example, Princess Noub-Hotep, her right second hand bone shows a [INAUDIBLE] curve.

ROTT: And that curve, Ailsa, likely came from the repeated use of a bow and arrow.

CHANG: Wow. Wait, so these women literally were warrior princesses?

ROTT: Well, Zeinab says it's unclear if these findings, which are published in the journal Frontiers in Environmental Archeology, prove that they were actually like warriors, in the sense that they fought. That's also what I heard from another Egyptologist who wasn't involved in the study. But he says it does show that their lives weren't as relaxed as we might have thought, that they did real work.

CHANG: They were shooting bows and arrows! All right. Our final topic is birdsong. What are you gonna tell me about singing birds?

ROTT: Yeah. So this study analyzed more than 116,000 bird songs from perching birds, which include, you know, robins and thrushes, warblers and crows, and on and on.

CHANG: Cool. OK. So what were the scientists looking for specifically in all of these bird songs?

ROTT: Yeah, so they were listening for how the pitch of songs were changing over time to try to find patterns. "Acoustic motifs" is the technical term.

CHINN: And they found that for all the variety there is in these birds worldwide, they're all trying to communicate basically one of two messages-- either attracting mates or claiming territory. And they use these eight basic motifs.

CHANG: OK, so what are the eight different motifs?

ROTT: So there are three different types of trills. There's a slow trill, sung here by a Northern cardinal, recorded outside of Minneapolis.

[BIRD TRILLING]

[LAUGHTER]

CHINN: And an ultra fast trill.

[BIRD TRILLING QUICKLY]

CHANG: Whoa. Was that the ultra fast I just heard?

ROTT: Ultra fast.

CHINN: Yeah. And that one's sung by a Bohemian waxwing in the Canadian province of Newfoundland and Labrador.

CHANG: That's amazing. It was almost like-- I don't know, like a drill.

ROTT: The most appropriate use of the word "ultra" you can imagine. Yeah. And it's worth noting that all these recordings were collected from a public database where birders uploaded songs.

CHINN: And we don't have time to cover all eight of them, but another pattern that's maybe worth knowing is the flat whistle.

[BIRD WHISTLING]

ROTT: That's sung by a three-wattled bellbird in Costa Rica. And the reason it's worth knowing that call is the researchers on this new study found that in the dense, loud tropical forests all over the world, birds have independently evolved this type of call.

CHANG: Wait. So that flat whistle call, does that give them some kind of advantage?

CHINN: Well, it's simple, and it's loud, so it can be heard in a wide area. Here's the lead author of this study, Quentin Bacquelé. He's a PhD candidate studying bioacoustics in Paris.

QUENTIN BACQUELÉ: So that's really impressive to see that nature found the same solutions for the same constraints, but across different parts of the world.

ROTT: So in other words, Ailsa, birds separated by oceans and continents all landed independently on the same types of acoustic patterns to communicate.

CHANG: That is so cool!

ROTT: Well, Ailsa, thank you so much for geeking out with us this week. Come back anytime.

CHANG: Oh, always. It's so fun to hang with you guys.

ROTT: You can hear more of Ailsa Chang on Consider This, NPR's afternoon podcast about what the news means for you.

CHINN: And for more science stories just like this one, follow Short Wave on whatever app you're listening to.

ROTT: This episode was produced by Berly McCoy and Jordan-Marie Smith. It was edited by Lauren Gonzalez, Rebecca Ramirez, and Christopher Intagliata.

CHINN: Tyler Jones checked the facts. Annlie Huang, Robert Rodriguez, and Peter Ellena were the audio engineers. I'm Hannah Chinn.

ROTT: And I'm Nate Rott. Thanks for listening to Short Wave, the science podcast from NPR.

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