Keeping transgenic corn sustainable, and sending shrunken heads home
36:58 Share

This is the Science Podcast for February 28th, 2025. I'm Sarah Crespi. First up this week, freelancer Kata Karat talks with me about a complicated effort to identify traditionally prepared shrunken heads or sansas in museums and collections around the world.

and potentially repatriate them to Ecuador. Next, genetically modified BT corn has helped farmers avoid serious crop damage from insects. But planting it everywhere all the time can drive insects to adapt to the bacterial toxin made by the plant. Researcher Christian Krupke talks about the economics of planting BT corn and the ways farmers could save money and extend the lifetime of this form of pest control.

This week in science, freelance journalist Kata Karat wrote about shrunken heads or sansas, a project to study them and maybe one day repatriate them. Hi, Kata. Welcome to the Science Podcast. Hi, Sarah. Nice to meet you. Thank you for having me here. So, Kata, you're from Hungary, but you've been working in Ecuador for almost seven years. And this is a topic very close to you. This is the origin of the shrunken, most of the shrunken heads that are out there in the world now.

Exactly. That's why it was so cool for me to be able to research this story because I could go anywhere that the story required me. When did you first encounter a shrunken head? I think I ran into one in Peru, like staying at a hotel which had displays up and one of them was there. Where did you first see one?

That's a very good question because by now I've seen so many. But I think the very first ones were ironically in the Celestian Museum called Abia Yela. It's like a small ethnography museum founded by Catholic Celestian missionaries that have been living and working in Ecuador since the previous century.

But like by now, I feel like I'm not entirely sure if those ones are ceremonial or commercial sansas. Right. Yeah. So this is something if anyone listening has ever seen a sansa, chances are it's not one that was probably created with the original ritual and intention. There are lots of imitation ones in museums, in collections. Exactly. You can have...

a human shrunken head, but it's still fake in a way because it was not created through the indigenous Shuar ritual, but it was created for trade, for commerce. The ones that were not created for commerce, the ones that came out through the ritual, can you talk about where they came from and who was making them? I have to point out that most information that we have about shrunken head or tsantzas come from secondary sources.

like missionaries or anthropologists or maybe settlers,

So we have to take them with a grain of salt. I did try to read as many variations in Spanish and English as I could, even like old ones from like the 20th century, the beginning of it. As far as we know, the indigenous Shuar people were the ones who mainly created sansas, even though some sources also point to neighboring tribes. But they all agree that the main creators for the indigenous Shuar people put this day

They live in the Ecuadorian and a little bit in the Peruvian Amazon region. And they are the second biggest indigenous group in Ecuador with more than 130,000 people. It varies why they made it, but it boils down to basically preserve the energy, the power of the slain person and transfer that energy into the winning warrior.

as well as the potential leadership knowledge of the slain person.

So that's the main reason that we know that they did it. And some other sources like current Shuar people also say that sometimes they did it as a tribute to different deities like Arutan for the rain and the sun and the good produce and hunting. And even sometimes the Shuar themselves offered their bodies to be turned into a Tzantza. Right. And what are some of the reasons that we are only able to...

to speculate. Even the people that still exist to this day, it's their history, but it's just not, it's not very clear what was happening back then. As the main character in the story, Jefferson Lucky, points out, it's colonization. Because settlers came and they started to encroach into the land of the Shuar and they brought the missionaries and the missionaries tried to convert the Shuar into Christianity and had territories

the Shuar children in boarding schools and obviously slowly but surely alienated them from the culture. All the knowledge that we have from Shuar people today, it's not monolithic. Some say this information, some say other information, and they have trouble remembering it because at the time when the settlers came to Shuar,

didn't have written sources. So it was an oral tradition how it passed down. So with the missionaries taking away the children, there were no one left to pass it down and the elder people passed away. And the other thing I wanted to ask about was, you know, we've made this distinction between, you know, the traditional sansas prepared by the shuar.

And then imitation ones that are still human heads, but not necessarily made in the same way. Why are there so many imitations? And how did they get to England, to the British Museum, to all these different places? Basically, the researchers pointed out to me that it was the demand from European and American museums that fueled imitation.

the creation of these commercial sansas because at the time, at the end of the 19th century, in the beginning of the 20th century, all of these famous museums were founded and they wanted items for their collections. And they loved to exoticize foreign cultures and install very problematic and often racist theories about savagery and stuff like that. And this is how shrunken heads became so popular.

So there was a demand from collectors and museums all around the world. We don't know if these so-called commercial shrunken heads were made by the shuar without the ritual, or maybe it was made by other people who were not shuar.

who didn't know how the ritual was done, but they tend to contain mistakes that doesn't align with ceremonial shrunken heads. Like the cut at the back of the head is at the wrong place, like on the side, like one of the heads that we feature in the story has the cut around the right temple.

which is entirely incorrect. Or they're like overdressed with crowns that are not typical wear of the shuar or the eyes are not sewn in from the inside or neither the mouth, or they have different amount of stitches or the stitches is not correct.

The trouble is that without a trusted shore source, we don't know anymore. So the best bet the researchers and the shore people have is to examine as many sensors as possible and talk to each other. Even the shore talk between themselves and try to reach out to elders that maybe live in more remote communities and find out. We're kind of at the center of the scientific part of the story where I think we're going to touch most on the science.

There is this effort to analyze all of these shrunken heads, figure out how they were created, and also to take a look at what can be genetically determined about this tissue. And this is the first project, the first scientific project of this type that the Shuar have been involved in. Can you talk a little bit about the people behind the project? The main researcher behind the project is anthropologist Maria Patricia Ordonez from the University of San Francisco de Quito.

and her team. And of course, the Shuar leaders, Jefferson Leckie, David Tancamash, and from the Petrievers Museum, Laura von Brockhoven, and staff from the Guayaquil Municipal Museum, Joaquin Moscoso. So this is a bunch of people

What's great about this project that is mostly led by Ecuadorians, both mestizo and shuar people. What are the first steps that they are trying to accomplish right now? Even though they know that there are possibly hundreds and hundreds of shrunken heads outside of Ecuador, they don't know their exact location. Just some of them, because many of the places might not even have them on display or they might have a couple on display, but they have much more.

in storage, and obviously there are a lot of private collections. So one of the goals is map them and reach out to both public and private institutions and connect them with the Shuar and also ask them for DNA samples and CT scans, if it's possible. The CT scans can reveal the inside details because these are basically soft tissues. There's no skull in them.

This way, they can check it without physically modify it. So they can see the stitching, the cut. They can even check the fibers a little bit with the DNA. First of all, they can see if it's a human or not. And then they can see if it's a man or woman. And then they can even try to get down to haplogroups, basically genetic ancestry.

Now, that's not easy because there has been a lot of treatment of this tissue. It's had chemical exposures. It's had boiling. It's not the easiest thing to get DNA out of this. It's very hard, in fact. And they're mostly managing to get mitochondrial DNA, so they're most confidently able to

check the maternal ancestry. With nuclear DNA, they have more trouble, especially getting any variants from the chromosome Y. That's why they haven't even published any results on that, because they were not able to sequence consequently those variants, and they didn't want to publish anything confusing. Now, one thing that I hadn't thought of before reading this story was that if you're talking about a

A lot of museums are avoiding or starting to take human remains off display and repatriating things to their descendants. In this case, you could repatriate or send home a shrunken head to the descendants of that person, the relatives of that person, or

or to the people who made that ritual item? Well, I've never met such a complicated issue with repatriation for several reasons. Right. But basically, there are no international laws that oblige museums to repatriate ancient human remains. And then it comes down to the individual ethics of museums or universities or whatever. And it's

all over the place. The level of engagement, some museums like a Pitt Rivers Museum take it very, very seriously and they definitely want to hear all stakeholders. So not just the Chouards,

but the possible descendants of the victim, even if it's not directly, but at least in the indigenous group they belong to. But others just want to give it back to the Ecuadorian government as soon as possible, and then they don't care what happens with it afterwards. So it's very complicated, especially because the DNA cannot at this point

distinguish between the different indigenous groups, not just because of sequencing difficulties, but also because there are not enough South American or Amazonian indigenous DNA samples in databases to be able to match them and come down to individual haplotypes. Their best guess is always, okay, so this is a human, a male or a woman.

And it's Amazonian indigenous. That's the level they can come down with the historical records. What about the shuar who are involved in this project and helping navigate these issues? What is their take on it? In their eyes, since they are the makers, they claim to be the only ones being the makers of santas. They are the owners, so they want them back all. And meanwhile, the achuar, I only managed to talk to one, but he was authorized by the

the Ashuar Nation's president to talk to me. He said they don't want to do anything with them anymore. They're another indigenous group that was likely a source of a lot of these heads? Exactly. They are the main indigenous group. All sources, including the Shuar, point to as the main victims. They're called the Ashuar. Sounds like the Shuar would welcome the shrunken heads that have been made according to their rituals.

that they know of, that they would prefer to have them back. But as you write in your story, the actuar, they don't want to revive old hostilities with the shuar. And, you know, they're...

much more interested in this need for indigenous peoples of the Amazon to work together to conserve lands. Yes, yes. The other tribe is not interested. Meanwhile, the shore is very much interested. Actually, they're demanding them back. But there are so many levels of bureaucracy in different countries and different museums that it's not that easy. And usually these negotiations last years, even if they come back to Ecuador.

According to Ecuadorian laws, they belong to the Ecuadorian government. They are human remains that tend to be more than 100 years old, so they're considered to be ethnographic or archaeological. And that's why, even though the shark culture and nation is well and alive,

Joaquin Moscoso, who is an expert in cultural heritage laws, told me that they know and they're working on renewing it. And they hope this research project help all stakeholders to talk to each other. And probably if the Ecuadorian government talks with the Shuar, there are possibilities in individual cases to be repatriated directly to them. What would they do with

them then at that point? What's the ultimate goal there? So that's the other big issue that they don't have a museum. Their big dream is to have their own museum

build on their own cosmovision, their own worldview, and have them exhibited there. They do have shrunken heads. They have like 11 locked up in a safe in the Federation's headquarters, but they have been there since the 1990s and they never managed to get enough funding to build their own museum. So now they are trying to find funding for that, either from the government or other sources.

I have to say there are so many levels of not conflict, but things that are fraught, that are controversial, that require delicacy, considering all angles. You know, one thing that I'm actually part of the visuals team, even though I do audio, it just happened to be that I work most closely with those folks and they have to put together, you know, a visually appealing, informative story with photographs of humans

human heads. And it's not an easy thing to do when we are, when they are very sensitive to whether or not they're going to show human remains, whether or not people are going to look at this for purient reasons or just, you know, this is, this is something that's, again, very sensitive. So, you know, how was it to go through that process of like getting photos of these things? I mean, that must not have been easy either. I,

tried my best to look up any possible way to understand what would be the most respectful way according to the Shuar point of view but obviously the most important point was securing their permission because

because we discussed it with all the different editors that first we need to secure the permission. I asked them if they prefer any kind of framing or they have any kind of creative ideas for it, but they were not really interested in commenting on that.

So I got the permission and then I had to get the permission from the museum as well. And then we had this very, very long discussion of how to show them without showing them. Because I understand that these are human remains and they have appeared in pop culture as well so many times, like Harry Potter or the latest Beetlejuice. So we didn't want to fetishize them either. Right.

When I look at the article, I think it turned out well. We ride the line between showing human heads and pointing out the details that are important to the research. Thank you so much, Kata. This has been really interesting to talk about. Same as well. Thank you so much, Sarah. It was a pleasure meeting you. Kata Karat is a freelance journalist and documentary filmmaker based in Ecuador. You can find a link to the story we discussed at science.org slash podcast.

Stay tuned for lessons from BT Corn for slowing pest resistance. Farmers have been planting genetically modified corn, and we're talking in this case about BT Corn, which is maize that produces bacterial protein harmful to insects. Farmers have been planning this to fight off pests for decades. But just like with pesticides or herbicides that you apply to the fields, resistance in the pest can accumulate. One way to combat the rise of resistance is to plant

the BT corn strategically. But resistance is a global problem, and farming is more of a local concern. So there might be more coordination required to combat resistance. This Week in Science, Christian Krupke and colleagues wrote about farmers in the U.S. corn belt, their history of planting BT corn, and how much individual farmer needs and the needs of the group may overlap. Hi, Christian. Welcome

Welcome to the Science Podcast. Hi, Sarah. Thank you. I want to do some groundwork before we kind of get into the nitty gritty of the study. So we need to tell people, for example, that BT corn has changes in it that allow it to express the bacterial protein that is toxic to the body.

to many insects. We're going to focus on rootworm, which is something that I'm assuming attacks the roots of the corn? That's correct. The larval stage of rootworms, which are beetles, their larval stage feed on corn roots. If the roots are consumed, there are two things that can happen. The plant can fall over or partially fall over, which makes it hard to harvest. And

And the other thing, of course, is this plant now is not able to take up water. And if it's a dry year, a drought year, then it gets really concerning. So it is the number one insect pest of corn and has been for decades. When the corn gets decimated by a pest, farmers lose money, food goes away, all of that stuff. Corn for food, for feed, for the many purposes we use corn is our number one use of arable land in terms of agriculture in the

in the country. And the vast majority of that corn, the overwhelming majority, over 80%, is expressing some of these Bt toxins against pests. So when you drive by corn, see corn, think about corn, it's almost always Bt corn. Yeah. So when I'm reading this paper, what I see is this hybrid, that hybrid was planted. Why is everything called a hybrid when we're talking about the different kinds of corn that are being planted? With corn, you have a male and a female parent. And we're taking these two parents

parents and we're crossing them. They both have these desirable traits. We're crossing these two plants to get a hybrid. The hybrids are chosen based on these genetic characteristics of plantability, drought tolerance, nitrogen use, et cetera, et cetera. So that's where a lot of innovation and a lot of research and a lot of work happens in what we call classical breeding is developing these hybrids that are

efficient, durable, and do well under a variety of conditions. These plants aren't just engineered to be good at growing in these conditions. They have all of this background from like intrabreeding and then you get the good seeds and then you sell those good seeds with those genetic changes as well as those inherited traits. One question that you're asking here is basically if everybody plants BT corn with this protein in it, resistance will come about faster.

But is it bad for farmers to change their practices and plant less Bt corn in certain circumstances? Is that kind of the main thrust here? Yeah, one of the main thrusts is to see that since we have introduced these particular Bt hybrids against rootworms in 2004,

How has this pest responded to that in the U.S.? How has it evolved, adapted, become resistant to the technology and doing that region by region? Because we know that this pest in particular can get resistant to anything we've thrown at it. Every insecticide we've used, and in this case, BTs as well, they become resistant to everything. When and if they become resistant determines how long you get to keep the technology in place.

That's the first part of the question. The second part is, what is the background population? How many of them are out there? So in 2004, for example, where I am in Indiana, virtually all of the state could benefit from BT corn versus rootworms because we had such severe infestations. It's very different now. It's a very different system. It's very hard to find that high pressure from the pests.

And that's kind of the question we're hoping to untangle. Is there still utility, the same as there was 20 years ago, in using these hybrids everywhere we're using them? Right. So you're saying the pest pressure has changed. That's how much of this pest is there just standing by, ready to attack your corn if it doesn't have Bt in it? Bt or some other protection. What is the background population and how has that population changed in terms of

how able it is to overcome those Bt toxins. So you had to measure pest pressure in this study and also find out what people were actually planting on their farms, which was kind of harder than I thought it would be. That was always going to be the difficult component because we knew anecdotally what farmers that we talked to were doing.

And then what was sort of the magical missing piece is an introduction that one of my co-authors, they had access to this proprietary data that shows where these seeds, where these hybrids are planted. And so now we on the entomology side had the biological data on the rootworms, on how many there are and how well they do, et cetera, et cetera. And so that was the magical missing piece. And that's what made the whole thing sort of sing is that now we know, okay, we have the economics. If

If you want to talk about anything to anybody, you got to get there pretty quickly. That's a lever that everybody kind of has at some level is that, okay, what is it costing me? Because we can talk to a blue in the face about sustainability and resistance and the future and blah, blah, blah. But where the rubber meets the road is always the dollars. And that's what let us get there.

Yeah. And so let's talk about your study population, the U.S. Corn Belt. Can you describe that? Yeah. So when we think of the Corn Belt, if you picture the United States in your mind's eye, think of the central part of the country, let's say the northern third to a half of the central portion of the country from the Great Plains states, Nebraska and Iowa. And you're heading all the way over to across Illinois, Indiana and into Ohio. And you include Michigan and Minnesota in there as well. Some of those

more northern states. It's a big swath of the country. It's a huge part of the country. And it's, of course, our biggest crop. It's a huge crop. And you did see differences between the eastern Corn Belt and the western Corn Belt in their crop

crop practices as well as how much pest pressure there was. Right. And we had to sort of arbitrarily at some point divide this up. And some people would argue and say, well, Iowa's not Western. Maybe it isn't. Those arguments are never ending. Who lives in the Midwest anyway? Yeah. Right. Exactly. We knew that in the Western part of the Corn Belt, they plant more continuous corn. So corn, corn, corn, corn, corn, year after year.

And where I am in Indiana, certainly parts of Illinois, Ohio, Michigan, we tend to rotate almost always with soybeans, one to one. So that's a big difference in how much you're exposing the pest, how much you're showing your hand, so to speak, to these pests. Like if only one year out of every two, you show them, hey, I've got this BT. Can you get resistant to it? Versus every year.

Yeah. Yeah. You're like, how about some more BT this year? And how about next year? And then you end up with... Right. You're going to push that evolution. You're going to push that adaptation. Exactly. And we knew all that. That's nothing new to this paper. But what we didn't know is that in the East, we have driven those populations of rootworms down farther and faster than we have in the West. So here in the East...

the utility of BT corn or anything else, any insecticide or anything else for rootworms is much, much less because our pressure went down. Okay. So just to repeat that. So there is less of the pest. So you don't need to buy BT corn, which is more expensive. Exactly. Than other hybrids. You don't have to have as much of that. So you could save money. You could save a lot of money. What about the other side? On the other side, it was more aligned because...

because those rootworms are exposed every year, they've become resistant more quickly. There are more of them. They are, so to speak, evolutionarily stronger and have been more exposed to these toxins than the pests in the East. So we get these reports of resistance. Most of them originate in areas with more consistent planting of corn, more continuous corn is one of the predictors, as you would expect, how quickly the pest will get, will

will get resistant. The point is that this resource is finite. Eventually the pests will figure out a way to evolve resistance to these approaches. And we knew that from the beginning. It's been proven out over many locations over the last 20 years or so. So there's kind of one question here is even though we know the pest pressure is

is reduced on the eastern side. So these are the people who are rotating their crops. They have a slower buildup of resistance in their pests. They're still planting almost completely the same amount of BT corn as the western half. They're still

buying this and planting it. Why are they doing that if we know that it costs more money? Our study looked in detail as far as 2016. And then for a few sites, we went up to 2020. I'm not talking about 2025 data here at this moment. So your question, why are they still doing it? And one of the reasons is that the way corn hybrids and many products are sold

is with bundling with, if you want this, you get that. If you want ESPN, you have to get oxygen. You got to bundle the cable channels together. The history channel. Exactly. It's very much like that. There's an economy of scale to that, which, you know, we can't have every conceivable option available to everyone. That's not practical for any business to run that many different lines of any product. But one of our points is that it

It was way off. It was skewed, especially in the Eastern Corn Belt. None of the Eastern Corn Belt states are the number one or number two state, but it's still a lot of what we produce. So what we found that the disconnect was so large that this is an easy and a relatively achievable change to make. The problem is that when you want, let's say, an elite hybrid, you want the top, top corn. It very often comes with the top, top traits and all of them.

them. Even though you don't need it and it might be kind of counter to your interest in the long run to plant BT. We all have products that we buy that are bundled in that way. Yeah. How much money are we talking about here? Like with the mismatch between what they needed to do and what they actually did in the Eastern Belt?

99 million a year. You get one year of benefit of $99 million and lifetime benefits, we estimate as $1.98 billion because you're not burning up the technology. You're only using it as needed. The point is, I mean, these are huge numbers that in some way become abstract, but the point is that this is a measurable, quantifiable opportunity cost here. Reducing planting in Eastern states would have saved 99 million a year.

Yeah, it's a lot of money. And part of it is there's two reasons behind it. One of them is how much corn we plant, how many millions of acres every year, 90 to 100 million acres. And the other part is those tech fees that you pay for these traits are

are not insignificant. It's a real cost. And that's the one cost we looked at. The other one is the down the road cost of, okay, if you erode that susceptibility, if you look at that as a resource, a declining balance, you only get so many kicks at the can with this pest, that has a cost too that can be monetized and that we do monetize.

And so when you factor both of those costs in, the cost of today buying the seed you don't really need and the cost of tomorrow, it might not work as well when you need it, then you have the opportunity for a correction. And that's how we try to make this kind of pragmatic and useful to, you know, thousands and thousands of people that are in this industry and plant corn and use BT corn is just to say, well, there's, you know, there's an opportunity to change things a little bit here. Mm-hmm.

So how does the timeline compare here between the development pipeline for resistant plants and pesticides and the adaptation, the kind of generation of resistance? Are we going to see new approaches to combating the rootworm in any reasonable timeframe as resistance comes about? So your question is, are we developing products fast enough that we can shuffle a new one in? Yeah. Well, the short answer to that is no.

We're not. It takes a long time and a lot of money and a lot of development to get one of these approaches online and sold. We do have a relatively new one now, which is based on inserting proteins that block the production of a protein in the insect, RNAi technology. So that's a relatively new one. This isn't the last time we'll come up with something new. And so some of these lessons can certainly be applied to that to

to help it last longer and to say, okay, we want it to be here when we need it. We want that fire extinguisher to be charged up when we need to put out a fire someday, rather than have it bleed out over the next five years. What can you do then? The systems that we have are pretty durable and pretty time-tested in terms of whether we rotate or not rotate, irrigate or don't irrigate. So once we start to make recommendations, we don't focus there because then we're talking about people...

basically upending how they farm. This set of solutions that we propose here, which include, you know, have a little bit more flexibility in the seed supply, a little bit more, you know, monitoring and forethought of what your pest population is. Those are relatively low stakes and low hanging fruit, as we say, in terms of changes that people can make. But do they all apply to the eastern farm belt? Yes.

They do. Yeah. So in the eastern Corn Belt, you can monitor for rootworms, for example, and align your pest risk with your purchasing choice of an intervention. Right. Exactly. What about out west? What are they going to do? Well, out west, they have these large populations of resistant rootworms. So they're kind of in a position where they are, the stakes are higher for them. And they're more often using sets of traits that are where all of the traits are included at the

at the same time. So here are three different modes of action of Bt corn versus rootworm. One of these will stick. - Okay, so broad spectrum antibiotic. - Throwing everything at the wall and seeing what'll stick. And it's very different just a few states away in Indiana versus a place like Iowa. It's surprising how different it wound up being. And this all came out of us getting together at these annual meetings, all these public sector researchers and talking

I would say, well, I'm not seeing many rootworms. I can put out these trials. Rootworms don't show up. I can't really do this kind of research anymore. And my colleagues just a few hundred miles away were saying the exact opposite.

We're crawling with them. Right. And that's how this kind of started to germinate and to say, well, why are we all doing the same thing if we're clearly dealing with a different biological universe here? And then, like I said, once we put the numbers to it, the economic numbers, the dollar cost, these two types of types of expenses, current cost and future cost, that's when you see the disconnect. Most of us believe that these in-plant approaches for managing pests are good.

They're better for workers. They're better for all types of people that come in contact with planting the corn. They're better for non-target organisms. So it's in our interest to keep them around as long as we can. All right. Thank you so much, Christian. Thank you, Sarah. I've enjoyed it. Christian Krupke is a professor of entomology at Purdue University. You can find a link to the paper we discussed at science.org slash podcast.

And that concludes this edition of the Science Podcast. If you have any comments or suggestions, write to us at sciencepodcast at aaaas.org. To find us on podcasting apps, search for Science Magazine or listen on our website, science.org slash podcast. This show was edited by me, Sarah Crespi, and Kevin McLean. We had production help from Megan Tuck at Podigy. Our music is by Jeffrey Cook and Wen Kui Wen. On behalf of Science and its publisher, AAAS, thanks for joining us.

From April 25th to 30th, the American Association for Cancer Research will host the AACR Annual Meeting 2025 in Chicago. This meeting is the critical driver of progress against cancer, the place where scientists, clinicians, and other healthcare professionals, survivors, patients, and advocates gather to share and discuss the latest breakthroughs in cancer research. Both in-person and virtual registration options include access to live sessions,

Q&A, networking, CME and MOC credits, on-demand access to sessions after the meeting, access to the e-poster platform, and more. Learn more about the AACR Annual Meeting 2025 at aacr.org slash aacr2025 and register by March 7th for discounted rates.