First up this week, highly pathogenic avian influenza is spreading to domestic flocks around the globe from migrating birds. Why don’t many countries vaccinate their bird herds when finding one case can mean massive culls? Staff News Writer Jon Cohen joins host Sarah Crespi to discuss the push and pull of economics, politics, and science at play in vaccinating poultry against bird flu.
Next up, a crazy method of reproduction in the yellow crazy ants (Anoplolepis gracilipes). Hugo Darras, an assistant professor in the Institute of Organismic and Molecular Evolution at Johannes Gutenberg University, talks about how males of this species are always chimeras—which means their body is composed of two different cell lines, one from each parent.
Read a related perspective.
This week’s episode was produced with help from Podigy.
0:00:05.7 Sarah Crespi: This is the Science Podcast for April 7th, 2023. I'm Sarah Crespi. First up this week, Highly Pathogenic Avian Influenza is spreading to domestic flocks around the globe from migrating birds. Why don't many countries vaccinate their bird herds? Staff news writer Jon Cohen, joins me to discuss the push and pull of economics, politics, and science at play and decisions to vaccinate against bird flu. Next up, a crazy method of reproduction in the yellow crazy ant. Researcher Hugo Darris is here to talk about how males of the species are always chimeras, which means their whole body is composed of two different cell lines, one from each parent.
0:00:52.6 SC: Around the world, particularly in the US, Latin America, and Europe, Avian flu, Highly Pathogenic Avian Influenza is on the rise. Even one case at a farm can trigger a cull. In 2022, 58 million farm birds were killed to contain the infection. The virus is next to impossible to eradicate 'cause it's carried by wild birds. If you look up the recent cases, you're gonna see Canada Goose, Bald Eagle, American Crow. Any one of these birds can carry the flu and give it to livestock birds. And beyond birds, humans can actually catch this infection sometimes, but luckily for now, it doesn't spread person to person. This week in science, staff writer Jon Cohen, asked, "Why aren't we vaccinating, or why aren't most farms vaccinating birds against this flu?" Hi, Jon.
0:01:42.6 Jon Cohen: Hey, Sarah.
0:01:42.6 SC: What is the scale like now for the Highly Pathogenic Avian flu in 2023? Is this problem still growing?
0:01:49.3 JC: It's kind of at a steady state. Growing is kind of funny because it sometimes explodes overnight. [chuckle] We haven't had a Highly Pathogenic Avian Influenza in the United States since 2015, and this one showed up in February of 2022, and it hasn't left. They're called HPAI for short, Highly Pathogenic Avian Influenza, or they're called High Paths. They're usually seasonal. They show up with the migratory birds. The birds leave. The poultry farms are okay. These High Paths usually burn-out in the migratory birds. They get the susceptible ones, and the other ones are immunized. Some of them don't get sick from them, and that's that. But this one has evolved into a really fit Avian Influenza. And it's alarming because it's spreading into poultry, but it's also alarming because it's spreading into mammals. And it's not clear that there's mammal to mammal transmission, but it's giving the virus more and more opportunity to adapt to mammals.
0:02:53.3 SC: And that's just one little scary step towards, if mammal to mammal, then we start to worry. It goes to humans, and then it goes humans to humans. And we have another flu pandemic.
0:03:03.5 JC: Yeah. I wanna roll the clock back to pre-January, 2020.
0:03:08.0 JC: There's no COVID. Okay?
0:03:09.8 SC: Me too.
0:03:10.8 SC: Jon, I definitely wanna do that.
0:03:12.2 JC: Okay. So let's just take a little time machine. Go back to December, 2019.
0:03:16.9 SC: Great.
0:03:16.9 JC: The world was worried about a Influenza pandemic, not a coronavirus pandemic. Influenza's always been at the top of the list of worries for virologists, immunologists, public health people. It has created mayhem in the world many times before. So that's always been the biggest worry. And all of the human pandemics with flu that have occurred, appear to have jumped from avian to humans.
0:03:44.1 SC: We definitely paid a lot of attention to it before the Corona pandemic. This was something that came up so many times on the pages of science, what was going on with the different strains and how people were studying it.
0:03:53.6 JC: Yeah. And Sarah, the WHO, the World Health Organization has set up over the last 75 years, an enormous influenza surveillance system. We didn't have that for Coronaviruses.
0:04:05.1 SC: No, we did not.
0:04:05.7 JC: Yeah. Now things have changed, but this influenza surveillance is the best surveillance for any virus. That's why we're picking up all of these birds. Also, they're getting reported everywhere.
0:04:17.0 SC: So we can see it. Do we have to do something about it is the next question. We talked a little bit about culling. So if you have a bird that's suspected to have this High Path version of the virus, you just kill the flock.
0:04:29.5 JC: Yeah. So there's a history here. The first Highly Pathogenic Avian Influenza hit the United States before we even knew what the influenza virus was in 1924. What did we do if your farm had a bird that was sick, kill all the birds, and we stopped the transport of birds from places that had sick birds. That became more sophisticated over the years with biosecurity. But culling and biosecurity have remained the cornerstones and education of preventing these High Paths from taking root and becoming endemic parking themselves into our poultry flocks. And we have been able every time since 1924 to get rid of them. With that system. So that's the reason why there hasn't been a lot of interest in vaccines until now.
0:05:20.9 SC: So now we're looking at a different situation where these culls, biosecurity is not preventing it from sticking around over multiple seasons.
0:05:28.5 JC: So Europe and the United States have had a similar culling elimination program. Let's eliminate the virus whenever it shows up. Get rid of every High Path. While China in 2005 decided let's try and vaccinate all our flocks.
0:05:44.0 SC: It's a lot.
0:05:44.9 JC: Yeah. Billions of birds. And China did that because you may remember in 1997, there was an H5N1 that killed humans.
0:05:57.4 SC: That's a kind of influenza it's one of the High Paths, right?
0:06:00.9 JC: Right. It's one of the High Paths. Basically, influenza viruses are designated Hs and Ns to describe their subtypes, which are the surface proteins on the virus, hemagglutinin and neuraminidase, and they mix and match. Influenza has this ability to swap genes. So if a bird becomes infected with two different subtypes, it can take an N from a different H5N, whatever and swap it into its H5, or it can swap Hs out.
0:06:29.5 JC: Going back to 97, there's an H5N1. That H5N1 goes into humans. It surfaces in Hong Kong, it moves to China. Causes a huge problem in Vietnam in 2005. So it's in Asia really making progress in hurting humans. Not clear whether it's really good at human to human transmission. It doesn't seem to be, but it's hitting poultry farmers hard and they're getting sick. So China says, "Let's vaccinate all our birds." And they have continued that from 2005 until 2023. And they have evidence that it's done great good to their flocks and to humans.
0:07:09.7 SC: As you say, these viruses update all the time. So they must have to have a way of updating their vaccine over this time.
0:07:16.3 JC: Yeah. So the H5N1 vaccine, they have, they've updated 10 times since introducing it in 2005, but then China got hit really hard by an H7N9 that was really killing a lot of humans infected more than a thousand. So they went whole hog into an H5, H7 bivalent vaccine.
0:07:42.2 SC: Okay. So more than one antigen.
0:07:44.7 JC: Yeah. And they shut down transmission to humans of a dangerous virus. It's a really remarkable success story.
0:07:52.4 SC: And now are some people considering, taking China's approach and vaccinating poultry on farms against the High Path that's around now?
0:08:02.3 JC: Yeah. There's a lot of movement toward it in Europe and the United States. There's a big push to consider it. But as one veterinarian, I quote in my story says, "There's science and there's political science."
0:08:16.4 SC: Yeah. What are some of the political cons here?
0:08:19.8 JC: One of the cons is, it's theoretically possible that if you vaccinate a flock, a virus will get in and you won't know it. And there will be silent transmissions. Now, if you're doing good surveillance, that wouldn't happen. But there's a kind of a tradition of looking for a sick dead bird and then saying, oh, let's test the bird. Oh look, we've had the virus. This would challenge that system. Is that science? A lot of scientists shrug at it and say, "No, so there's something else going on." So what is that something else? The Emu in the corner, if you will.
0:08:57.4 JC: Is that there's a trade concern. Countries do not want to import poultry that has been vaccinated.
0:09:06.8 SC: Even if it's meat at that point?
0:09:08.9 JC: One might wonder why that would be a concern, because there's no evidence that a frozen chicken... [chuckle]
0:09:15.1 JC: Right.
0:09:15.5 JC: Is gonna transmit the virus. But there are trade concerns and the trade concerns have a history and they're mixed up with politics that might not have a whole lot to do with science.
0:09:28.0 SC: Say we do go ahead. Say it actually happens. Who would be making this vaccine and how would it be updated and kind of shared across all these different farmers?
0:09:37.6 JC: There are commercial companies that make animal health vaccines. It's an enormous market. The companies that make your pet vaccines, make poultry vaccines and make vaccines for all livestock.
0:09:48.0 SC: Right. So birds do already get vaccines. It's just not for...
0:09:51.2 JC: Birds get a ton of vaccines. The question that these companies are asking is, where's the marketplace? Well, the USDA regulates approval of vaccines in the United States. Why would a company make a vaccine that the USDA won't use? If the USA doesn't give a green light and say, "Hey, we need these vaccines." The companies aren't gonna make them. It doesn't make sense. In 2015 when we had a High Path outbreak, the government decided to put High Path vaccines into what's called the National Veterinary Stockpile. But there are now no avian flu vaccines in the National Veterinary Stockpile. And they haven't put any proposals out there for the companies to say, Hey, we wanna invest in this. And the companies are like pulling their hair saying, are you kidding? Pay us. We'll do it. We have a stockpile for human vaccines. Right? And we have, we have H5N1 for humans in the stockpile. There's something else we haven't talked about that's important. And that's the division within the poultry industry.
0:10:55.7 SC: Is this Turkeys versus chickens?
0:10:57.6 JC: It's more complicated than that.
0:11:00.2 SC: Okay. [laughter]
0:11:00.8 JC: So broilers are chickens that we eat. They in the United States, are only alive for about eight weeks, which shocked me to learn that. And the eight week turnaround for the bird creates a question of, well, is it really worth it?
0:11:16.3 SC: That is a short window to get a vaccine on the bird and...
0:11:19.3 JC: But there's something else. Broilers are 18% exported.
0:11:24.0 SC: Okay.
0:11:24.6 JC: So the broiler industry is hugely sensitive to the notion that their trade would get shut down. That's the broiler industry. So their chicken council has opposed vaccination, but the layers that are doing eggs, those birds stay on farms for a year or even longer. And in a backyard farm, those birds can live for eight years. They want the option for vaccines. And then there are Turkey farmers, another huge industry in the United States. Turkeys live for five to six months, and they're really susceptible to High Paths. They get sick really easily. Then there are ducks. Well, ducks often don't get sick from High Paths. So each one of these industries has a different agenda and a different marketplace.
0:12:12.3 SC: So it sounds like a watch this space type situation at this point to see which concerns went out.
0:12:18.1 JC: I think something we've learned during COVID is that we have cycles of panic and neglect.
0:12:23.9 SC: If the panic rises high enough, everybody's gonna say, "Oh no, why don't we have vaccines?" [chuckle] It's gonna be like... There's this old scientific saying that, at first no it can't be and then that moves onto, well it might be, but probably not. And then it becomes, we knew it all along.
0:12:44.6 SC: Yep.
0:12:45.0 JC: Right now where it maybe, probably not. If this keeps devastating poultry farms, we're gonna move into, we knew it all along. The timeline from USDA for a vaccine coming to market is two to three years. Now We know with our Human Influenza Vaccines that we update every year.
0:13:05.2 SC: Right.
0:13:05.7 JC: That it doesn't take two to three years to produce tests and approve. Why is it taking so much longer for Poultry vaccines? They do have a system where they can do something similar to our emergency use authorization. So that could happen. There's a possibility but the official line from USDA in writing to me is two to three years.
0:13:29.6 SC: Wow.
0:13:31.3 JC: Yeah. That's a pretty big wow. [chuckle]
0:13:31.8 SC: That is a big wow. I mean, that's like, we're gonna see where this goes no matter what then if they stick with that timeline.
0:13:37.4 JC: Yes. And one veterinarian, I quote in my article says, "She's seen this before, this discussion with the panic. And she said she doesn't think it's gonna lead to vaccination this time around, but it's preparing the future for vaccination".
0:13:53.5 SC: Laying the ground worth. People are getting their ducks in a row, if you will.
0:13:57.6 JC: Yeah. Yes, that's right. [chuckle] It's hard to avoid the puns.
0:14:01.2 SC: Oh my gosh, I love poultry puns. So John, you actually visited a chicken farm for your reporting and brought us some chicken noises too.
0:14:09.1 JC: We have a chicken farm about a half hour drive from my house without traffic. And I went there and the farmer was wonderful. His grandfather started the farm. He let me hang out with him all morning and he has 30,000 chickens.
0:14:23.3 SC: 30,000 chickens. [laughter]
0:14:26.5 JC: That's a small farm. That's a small farm, and California changed its law so that you have to have cage free birds now for layers. What cage free means surprised me.
0:14:45.7 JC: What it means is that he has three barns each divided in half. So there are 5,000 birds in each portion that is separated from the other birds. And they're crowded together like people on a big city subway car at rush hour.
0:15:01.1 SC: So wing to wing.
0:15:02.3 JC: Yeah. They can jump around, they have tiers and they can go up and down. It's, there's more freedom to move around than being in a cage. But I looked at it and I said to him, "Wow! This is a dream for a virus."
0:15:13.4 SC: Oh yeah.
0:15:15.2 JC: And he said, "Yeah, I've had to increase my vaccinations against different diseases because of it." And then I spoke with his vet and she said that's happening with all of her farms in California. So I don't know a lot about the industry, so please understand, but I imagine cage free birds running around in the field and...
0:15:35.1 SC: Just 30,000 birds in the backyard. Right.
0:15:37.5 JC: Just frolicking around. Yeah.
0:15:39.4 SC: Yeah.
0:15:40.4 JC: Well that's not cage free [chuckle] That's beyond cage free. And so I asked the farmer, you have a lot of land here. Have you thought about doing free range? He said, I have a lot of coyotes here.
0:16:00.4 JC: And the Coyotes get onto the land and come to the barn. He goes, look at all the plywood I have on the barn here that's to keep the coyotes from reaching in and grabbing my chickens. [chuckle] He said, "If I let them out here on the range, do you know how many coyotes I'm gonna have?" [chuckle] And so it was just a real eye-opener about what the business is.
0:16:20.2 SC: Oh yeah. Thank you so much, Jon.
0:16:22.8 JC: Yeah, you bet.
0:16:23.5 SC: Jon Cohen as a staff writer for science, you can find a link to the story we discussed at science.org/podcast.
0:16:31.4 SC: Don't touch that dial or touchscreen. Next up is researcher Hugo Darris. We talk about the first animal that appears to always be a chimera.
0:16:45.3 SC: In your standard run of the mill, Sexual reproduction a male sex cell with half a compliment of chromosomes fuses with a female sex cell, also with a half the number of needed chromosomes. They combine and you get a full set, a whole new genome. From there it's plain old cell division and the making of a new individual, Each cell a genetic copy, a clone of the original product from the two parents. Of course there are always exceptions in nature and some use social animals like ants. Females have that two copy of each chromosome thing going on in every one of their cells, one from each parent, but the males arise from unfertilized eggs and only have one set of chromosomes in each cell. But of course, things can get even weirder. In this week's issue of science, Hugo Darris and colleagues wrote about a new way of making babies in Yellow Crazy Ants. Hi Hugo.
0:17:44.4 Hugo Darris: Hi Sarah. Thanks for having me.
0:17:46.5 SC: Oh sure. This is a really fascinating study. I always like it when we find out that animals are doing something that we never thought they could do. [chuckle] So let's first get to the subject of your study. These species, the Yellow Crazy Ants, I guess they are kind of yellow looking, but why are they called crazy.
0:18:06.3 HD: It's because when you disturb their nests, the workers go outside and move in all direction. It's in erratic movements.
0:18:14.4 SC: So they kind of go into a frenzy. Yeah.
0:18:16.5 HD: Yes. [chuckle]
0:18:17.5 SC: Why did you think there might be something unusual going on with the way Yellow Crazy Ants reproduce?
0:18:24.1 HD: It's a long story. So this species is very well known because it's one of the worst invasive species in the world. So people have been studying it for a long time. Back in 2008, people were starting using genetic markers to study the dynamic of populations and they realized that there was something rare with the males in this species. When you do genetic on the males, instead of finding only one copy of each Chromosome as you expect in, of ant species, as you said, they operate normally. People always find two copies of each chromosomes.
0:18:56.4 SC: So you wouldn't expect if a haploid ant one that only has one copy of chromosomes per cell, that they would ever have more than one allele for a gene. Right? They would always have the same version of the gene in every cell that you looked at?
0:19:09.9 HD: Yes, exactly.
0:19:11.4 SC: This is a eusocial species, so they have queens, workers and males.
0:19:17.8 HD: Yes.
0:19:18.0 SC: So the queens and workers are female and they have two sets of chromosomes. The males are haploid, they only have one set of chromosomes. So this helps determine the sex of the animal and also their role in life. [chuckle] If the number of sets of chromosomes they have. So there's a lot going on here.
0:19:38.1 HD: Yeah. [chuckle]
0:19:38.8 SC: First of all, juggling the chromosomes for these animals. So when you looked at males, you saw that they had two different sets of chromosomes in there. What did you think might be happening? So could they actually sometimes be diploid, have some diploid cell?
0:19:55.9 HD: Yeah. So that was the original reportages of scientists. This we've seen in many other ant species that sometimes you have this diploid males. But the problem here was that all the males in all colony across the range of the species were always at this diploid genotypes. So this was a really difficult to explain, how this species would reproduce with males that are always look sterile because they're diploid.
0:20:21.4 SC: Right. You did a number of experiments to test out what is going on with these male ants?
0:20:26.5 HD: Yes.
0:20:26.9 SC: The first one that I read about was this leg test where you looked at what was going on with the cells in one of their legs. What did you find there?
0:20:34.7 HD: Yes. So to understand what's going on, we decide to look at ant DNA extract from the whole individual, but look at the cell levels. Compare what's the content of the male cell versus the female cells. And to our surprise, we discovered that each male cell only contain one copy of each chromosomes. So the whole body carried two sets of chromosome, but each cells only carry one copy like you expect in an haploid individual. And then we realized that, in fact the males were collections of two different cell lines within their body. Some cells that carry the maternal genome only, and some of the cells that only carry the paternal genomes. So at the cell level, these males are haploid, but when you look at the whole body they're diploid.
0:21:20.3 SC: Right. So we're all, you and I are a collection of cells.
0:21:24.1 HD: Yes.
0:21:24.6 SC: And each one of our cells has kind of this merged genome from mom and dad. The males, like a haploid male typically would have started out as a single cell with half the number of genes we would need. [laughter] And then just clone out and become one cell line. But these males have cells, a cell from mom and a cell from dad. They don't fuse, instead they just grow together into an animal. They both divide and create a male, is that right?
0:21:55.5 HD: Yes, exactly.
0:21:56.5 SC: Okay. [laughter]
0:21:57.7 HD: These species don't produce unfertilized eggs as our species to do the males. Instead the male develop from the same type of eggs as the females, so fertilized eggs. But in the case of male eggs, the parent, the gametes don't fuse and they remain separated in the eggs and each give rise to a separate cell line. So you have individuals that develop with both a cell line coming from only the mother and a cell line only coming from the sperm that fertilize the egg.
0:22:28.4 SC: Right. Before we get into what's going on with the queen and workers, I just wanna dig a little bit longer into the males here. So they are these haploid chimera. So they have two cell lines inside their bodies, half from the mom and half from the dad. They're not fused, they don't do any crossover, nothing like that.
0:22:45.7 HD: Yes.
0:22:46.4 SC: Are they kind of randomly assorted throughout the body of the ant or are there certain tissues or areas that are from the mom and certain from the dad?
0:22:55.5 HD: Yeah. So we look at that and the distribution of the two cell line is quite viable both within males and both males. So sometimes you have an organ that would carry the two cell line. Sometime you can also have individual that have one antenna with only the genome of the mother and the other antenna with only genome of the father.
0:23:15.0 SC: Really interesting. But most importantly, what about the gametes that they make? So if it's a male, it's gonna contribute a sperm to reproduction, is it always from the father then?
0:23:26.9 HD: Some males produce gametes with the genome of mother, some males produce gametes with the genome of the father. Some males produce both. But when we look across a large number of males, what we see is that there is tend to be a bias. So the normal productive cells of the males typically tend to have morphed the maternal genomes while they're germ cells. So the sperm cells typically have morphed the paternal genomes. And this leads to speculate that maybe there could be a conflict between the maternal and paternal genome to access the reproductive cells and become transmitted to the next generation.
0:24:04.3 SC: So not only are the males of this species different, they're haploid, but they're also chimera. They have two cell lines existing in their bodies. The queen and the workers, those are both females also have something unusual going on with their genomes.
0:24:19.3 HD: Yes. So in ants, normally the world colonies consist of females and you only have males during a short period of the year. These females are either a queens or worker. In most ant species, the queens and the workers have the same genomes that develop from the same eggs. And it's only during developments that environmental factors or maternal inputs lead to development to either a queen or a worker ant. But another surprising things we discover in this species is that the queens and workers didn't have the same genomes. They carry really different genetic makeup. So to understand what's going on, we look at genetic variations across the species range. And we discovered that there was two cryptic genetic edge in this species that we call R and W. Because they segregate differently in reproductive queens and in worker.
0:25:10.4 SC: These are kind of like the cell lives we were talking about before, R and W.
0:25:15.2 HD: Yes. So if you take a queen, no matter where you are in the distribution range of the species, they always carry only the R genomes. And these queen they store in the spermathecae, which is the organ that's in insect is used to store sperm. They carry both R and W sperm. When they fertilize an eggs with the R sperm, it's developed into a new queen. But when they fertilize the eggs with the W sperm, it's become a worker. So in this species, cast determinations with an egg develop into a queen or a worker. It's not determined by environment anymore it's determined by the genotype of the sperms that fertilize the eggs.
0:25:54.6 SC: And let's not forget those sperm come from these haploid males and so they're making either R or W sperm. The queen is taking that holding onto it and then making different worker or queen eggs from it.
0:26:08.3 HD: Yes.
0:26:08.9 SC: Oh my goodness.
0:26:11.5 HD: That's too complicated. [laughter]
0:26:15.5 SC: Woo. So we kind of have almost like three different species here, [chuckle] in some weird ways. We have the queen, which is two copies of the maternal genome.
0:26:25.3 HD: Yes.
0:26:25.7 SC: We have the workers who is a combination of the maternal and paternal, and then we have the males.
0:26:32.4 HD: Yes.
0:26:33.1 SC: You mentioned early on when we started talking about Yellow Crazy Ant, that they're an incredibly invasive species.
0:26:39.2 HD: Yes.
0:26:39.8 SC: Is there any relationship between the fact that they are such successful and powerful invaders between that and what's going on with their chromosomes and these cell lines?
0:26:51.4 HD: Maybe, maybe not. [laughter] So one thing that's special could perhaps explain the success of this species is that because workers are always produced from gametes that come from different lineage, they're always first generation hybrids. So in the worker, there's never inbreeding. Inbreeding is one of the measure challenge invasive species face when they colonize new habitat because of small population size. So in the case of the Yellow Crazy Ants, you don't see this inbreeding at all in the workers. You can start a population with just a queen and a male and they would produce first generation hybrid workers and each subsequent generations always you're gonna have first generation hybrid workers. So workers are always outbred no matter what the population size is. So perhaps this could be something that help the species thrive in colonizing new habitats.
0:27:43.5 SC: What else would you like to see worked out about what's going on with Yellow Crazy Ants. What are there questions do you think need to be answered?
0:27:49.7 HD: Well, there's so much we don't know about this [chuckle] system yet. Like why sometimes the maternal and paternal gametes fuse and sometimes they don't fuse. What's the molecular mechanisms responsible for that?
0:28:02.7 SC: Right.
0:28:03.2 HD: Also, what's the origin of the system? So now we have a snapshot of what's going on now, but how the system was formed in the first place. This we don't really understand yet.
0:28:15.7 SC: Thank you so much, Hugo.
0:28:16.0 HD: Thank you very much for having me, it was a pleasure.
0:28:18.5 SC: Hugo Darris, is an associate professor in the Institute of Organismic and Molecular Evolution at Johannes Gutenberg University. You can find a link to the paper we discussed on a related commentary at science.org/podcast.
0:28:33.7 SC: And that concludes this edition of the Science Podcast. If you have any comments or suggestions, write to us at [email protected] You can listen to the show on our website, science.org/podcast or search for Science Magazine on any podcasting app.
0:28:52.3 SC: This show was edited by me, Sarah Crespi and Kevin McClain with production help from Podigy. Jeffrey Cook composed the music on behalf of science and its publisher AAAS. Thanks for joining us.