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cc >> Hello, thank you for watching Wednesday Nite at the Lab this evening. I'm Cassie Immel from the UW Biotechnology Center. This evening we have John Doebley, who's a Professor of Genetics and a member of the Plant Breeding Faculty at the University of Wisconsin-Madison. John and his laboratory group are working to understand the genetic basis of morphological evolution in plants, which is a fundamental challenge for evolutionary biologists. He grew up in Philadelphia, Pennsylvania, and he holds a bachelor of arts in Anthropology from West Chester State College in Pennsylvania and a PhD in Botany from the University of Wisconsin-Madison. As part of his PhD research, he and his collaborators discovered a new species of teosinte which, unlike maize, is a perennial plant. He received postdoc training in statistical and molecular genetics at North Carolina State University under the guidance of Professors Major Goodman and Ronald Sederoff. He then worked as a faculty member at Texas A&M for three years, followed by 12 years at University of Minnesota as a full professor before joining UW-Madison in 1999. And without further ado, let's welcome Dr. Doebley.

APPLAUSE

>> Well, thank you for that welcome. This is something of an unusual treat for me because mostly I'm used to talking to people who are about 40 years younger, and tonight I'm talking to a group of people who are about my age. So I'll have to enjoy that moment. I'm going to pass around, sorry for the folks at home, you don't get to participate, but some cups with teosinte seed. Teosinte, I'll talk to you about tonight, is the ancestor of corn, and you're free to take a few seeds. Take them home. You can try to grow them in you garden. This seed is very old; it may not grow. Don't worry about it becoming and invasive species because it really can't actually complete its life cycle in Wisconsin. And so you can get an idea of what teosinte looks like. And here's another bottle I'll pass around too just in case that one doesn't have enough seed to satisfy everyone. I'm going to try to talk about this remarkable happening in human history in which a wild plant called teosinte was domesticated about 10,000 years ago to become our modern crop corn. And it's just a truly phenomenal series of events over the past 10,000 years. I'm going to kind of break it up into sort of three different processes. The domestication process, the beginnings of how wild plant was converted into a cultivated crop. Then the diversification. After that crop was, teosinte was converted into maize, the domestication, maize then spread throughout the Americas, and then after European contact with the new world, maize was spread throughout the world. And it diversified to a large number of different varieties and forms over that period. And then much more recently, you could say probably starting in 1930, about 1930, corn has become industrialized. So it's a much different crop today, especially here in the Midwest, than it was back even in the 1800s in the Midwest and certainly than it was over most of its history. Okay, so here, this is teosinte. That's an ear of teosinte, and what you have in those cups I've passed around are what happens when teosinte matures. This is its ear while it's growing, and it's all these little units that are kind of attached together, and each of those units contains a single seed. That single seed is inside a hard casing, and when it matures, this little stalk or ear of teosinte fractionates or breaks up, shatters into little bits, each one of those bits then contains a single seed, and that's how it disperses itself. So it's a wild plant. It needs to disperse its seeds. For teosinte, probably the way this was done or continues to be done is animals would graze and eat the whole the plant. So it would eat all the leaves and stuff, but tucked in the leaves would be these hard little grains, each inside hard covering, and they could pass through animal, like a deer, and then be distributed around the countryside to start a new plant in a new location. So this is, this ear of teosinte is the structure that gave rise to the modern ear of corn. And a series of genetic changes selected by ancient plant breeders converted that ear of teosinte into that modern ear of corn. That's actually what I work on in my laboratory is the genetics of that transformation of teosinte into corn. I'm not really going to talk very much about that today, but that's what we do upstairs on the fifth floor here. So what are some of the differences between teosinte and corn? I just want to explain a few of those. Here, again, is a ear of teosinte. You can think of it like a stick of bamboo, which is a more familiar object. It has a series of nodes and internodes. This would be like a node and then an internode and a node and an internode. And each of these internodes is hollowed out so it forms a little cup. And inside that cup is where a single kernel sits. And here you can see the silk that goes down into there, and the silk, of course, is the pathway through which the pollen tube grows to carry out fertilization and fertilize the seed inside. So teosinte has silks just like maize. And here's the ear, but the ear just has a small number, usually 10 or 12 kernels in it, where a modern ear of corn has somewhere around 500, up to 500 kernels in it. The other thing I want you to notice about this, there's silks that come off to this side and silks that come off the that side. So teosinte actually only has two rows of kernels. It has a row of kernels that faces out to this direction and a row of kernels that faces out to that direction. All those kernels are in the protective casing or fruit case that you can actually feel when that gets passed around. This ear shatters into little bits like that when it comes mature, and each of those carries a single kernel to disperse and start the next generation. So that's what an ear of teosinte looks like. To think about that, human selection being converted to a modern ear of corn is pretty amazing. Now, the plant of teosinte also looks pretty different from modern corn. Here's a teosinte plant. It's a big plant. So it can be as big or bigger in terms of plant height than modern corn. So here's a modern corn plant. But the teosinte plant is much more branched. So it has lots of branches like this. And here's modern corn plant. It has a single ear, sometimes two ears and there are varieties with even a few more, and those ears on the tip of a side branch. If you've ever pulled an ear of corn off a plant, you'll see what we call the shank underneath, and all those husks on that shank are actually leaves and those husks surround that ear. Well, teosinte has branches on the side too and leaves along those branches, but at the tip of the branch it has a tassel. So what happens in corn is instead of having a tassel at the tip as teosinte does, you have an ear at the tip. All the leaves that are along that branch actually then get wrapped around the ear, and the internodes along that branch, instead of being greatly elongated as they are in teosinte, are all kind of telescoped down. So if you look at the shank of an ear of corn, you'll see a bunch of very short internodes all telescoped down. So that's how the whole structure of the plant of teosinte relates to corn. So in addition to really remarkably changing the structure of the ear, you've also changed the structure of the entire plant. Now, teosinte is native to Mexico and Central America. It's just actually been discovered in Costa Rica just within the last year. Several years ago in the 1990s it was discovered in Nicaragua. And so it's actually still not entirely known. You can say what it's exact range is so that there's lots of new discoveries going on in Latin America in very remote areas. I had the good luck of participating in the discovery of a new species back in the late 1970s when we found this new perennial type of corn growing in Mexico. But here's its distribution map. It gets as far north as the state of Chihuahua, and then all the way down as we now know to Costa Rica. There's a bunch of different types of teosintes. The different ones in different areas are slightly different one from the other. Now, if you go down to some parts of Mexico, as I have, and collect teosinte, this is what it might look like. This is a hill in Mexico and all of these plants you see here are teosinte plants. They just cover that hillside. It doesn't quite show it in this picture, but that's a really high hill. It took us several hours to climb to the top of it, and it's covered with hundreds of thousands, maybe millions, of plants, of teosinte. When you get up to the top and you look out over the landscape, all you see is hill after hill after hill covered with teosinte. It's like a major prairie plant would be in the Midwest hundreds of years ago. That's how teosinte is in some parts of Mexico today. A point I'd like to make here is what you can well imagine is that would be a tremendous resource for ancient people because each of those plants is producing hundreds of grains. If they could collect those grains and then make bread or tortillas or whatever out of them, they would have a remarkable food source all of which is grown by nature for them. Now, teosinte grows in lots of different places in Mexico. We actually can find it along streams and tropical forests like that. So this is a little patch of teosinte growing along the stream within a tropical forest. And today it actually grows sometimes as a weed in the cornfields of the highlands or central plateau of Mexico. This is in the valley of Mexico. That's a cornfield. And teosinte has invaded these fields as weeds, and it's a bit of a problem for the farmers. And they try to weed it out, but it's nice for us botanist because if we go to Mexico City, then it's very easy to just go out to the cornfields and collect some teosinte. And then it can grow in even somewhat deserty areas. This is all teosinte here, a more slender form of it, growing right in the shadow of that cactus. And then this again in the central plateau region of Mexico. This is a cornfield and so this tassel you see here, these slide, unfortunately, are reduced in size, but this is a tassel of corn here and that's a tassel of teosinte, and the type of teosinte that's growing as a weed in this cornfield just has a more highly branched tassel. So we can just ride down the highway in our car and watch out into the cornfields, and we can spot it from a distance because of the difference in the tassel structure. >> Is teosinte used for anything these days? >> Is teosinte used for anything these days? The answer is yes, a little bit. They will feed it to animals so the animals can graze on it. The hillsides I showed you, they let their livestock go into those fields in the fall and eat it. I've heard, I don't think it's very common, but in some of the poor regions of Mexico they may even collect seeds of it for human consumption in bad years when the corn crop fails. >> Does it cross-pollinate with the corn? >> It can cross-pollinate with the corn. There are some genetic factors that inhibit that from happening. There's also some things such as flowering time. The teosinte can flower a little later or earlier. And then, also, where teosinte grows in wild places, there's no corn so it won't cross-pollinate there. But there is a certain level of cross-pollination. The problem is the hybrids are not favored by the farmers because they're no good for the farmers, and they can't survive in the wild. So the hybrids have a very dim future. So the two populations of corn and teosinte tend to stay separate with very little cross between them. And the person who actually works on one of the genetic factors that keeps corn from crossing to teosinte is my colleague in this building, Jerry Kermicle. So, what I was going to tell you in this slide, in teosinte you can see how different looking it is from corn. So this is Carl Linnaeus who was the first to give Latin names to our plants and animals. And he was one of the first people himself presented with corn, and he gave corn its Latin name. Zea mays was made up by Carl Linnaeus, and maize is actually the word maize is actually a word that comes from a Cuban Indian named for corn. And Columbus, on his way back to the old world, stopped in at Cuba. That's where he got corn, he got their name for corn, and then he took that name back to Europe. But when the botanists first started looking at it, they didn't realize that teosinte, when teosinte was brought back to Europe they didn't realize that it had much to do with corn. First they thought it had something to do with rice because it looked so different from corn. Then a little later on they thought, well, they switched it around taxonomically and said, well, maybe it has something to do with another grass called foxtail. And if you're a corn farmer in Wisconsin, you might know foxtail. Then a little later on, they finally realized, yes, it has something to do with corn. They put it into the same group of plants as corn, but they kept it as a separate species. So they didn't consider it exactly corn, but they realized it was more closely related to corn than it was to rice. >> Where did corn originate? >> Well, corn is just generally the European word for grain. Right? So, in England corn would be wheat or barley could be corn. And in the US, because maize was the predominate form of corn, we've generalized corn just for maize. But Europe, especially in England, they would use corn for wheat or barley. So, the taxonomy continued to change. One of the things they realized, someone asked me this question, is corn and teosinte can hybridize. So here's a teosinte ear and here's a corn ear, and these are ears of F1 hybrids, crosses between them. So you can see they can hybridize, and you get these F1s. If two things can hybridize, then you know they're very closely related. So they began changing the taxonomy. In 1890, they really called it close to maize, they put it in the same taxonomic group but kept it as a different genus. They called teosinte the genus Euchlaena and maize the genus Zea. In 1904, they had to give up on that. They said, you know, they can cross, we'd better put them together in this same genus. So, in 1904, they made teosinte Zea mexicana and left maize as Zea mays. And then finally, in 1972, Hugh Iltis in the botany department here at Madison said listen, if they can cross, they're the same the biological species, let's call them what they are. And he made them both different forms of a single species, Zea mays, Zea mays subspecies mays for corn and Zea mays subspecies mexicana for teosinte. So, basically saying, they're so closely related we can't keep them as separate species. And that makes good sense. If there's only 10,000 years separating them one from another, they're not likely to evolved far enough apart to be considered separate species. Consider modern human populations, we trace back to something like 120,000 to 150,000 years ago when modern human populations started to separate, yet we're all quite obviously one species. Now, I've been making this point that corn and teosinte are remarkably different, so what's made it such a great story is other crops aren't like that. So here is a wild tomato. It looks pretty much like a cultivated tomato except it's different in size. This has a very small little berry which is perfect for birds to eat and they get to digest all the pulp and the seeds pass through them. And here's a great big giant tomato which is perfect for us to eat, and we digest all the pulp and then we go back to the garden store and buy another packet of seeds.

LAUGHTER

But the change is not so great in the sense that if you look at those two, it's easy to think that selection by people could have bred this into that. But you can't think that way with corn and teosinte. It seems much more hard. And here's also for wild wheat and cultivated wheat. So they're very similar in structure so it's easy to imagine one is the ancestor of the other. But the idea that teosinte is the ancestor of maize is very controversial. One of the reasons that it thought that it couldn't happen, here again is a teosinte ear, is these grains are locked up in those little cases. So, how are you going to eat them if they're in those hard little cases? How are you going to get them out of there and actually eat the grain? So that was one of the arguments made for saying that teosinte could not be the ancestor of corn.

Hugh Iltis put it this way

teosinte is a very unpromising grain source because the grains are locked up in those little cases. And I happen to think that even though it seems to us, modern Americans or modern people anywhere around the world, that this is an unpromising grain source, I think 10,000 years ago those folks were a lot smarter than us on how to get food out of wild plants. I'm just going to read you a quote from an ethnobotanist from 1874, and this is taken from work with the native peoples in the southwestern United States. And he was a botanist, so he's interviewing all these native peoples in the southwest and figuring out what they know about nature. And he says, "But it is not for a moment to be supposed that the Indian is a superficial observer. He takes careful note of the forms and qualities of everything that grows on the face of the Earth. As his perceptions of individual differentiations is nice and minute, so his nomenclature is remarkably full. I assert without hesitation that the average intelligent Indian, even if not a medicine man, knows a far greater catalog of names than nine-tenths of Americans." Probably like 99.99% of Americans today.

LAUGHTER

Hugh Iltis put it this way

"Nothing escapes him. He has a name for everything and indeed there is a reason. In times of great scarcity, they are driven by the sore pangs of hunger to test everything the soil produced if, per chance, they may find something that appeases the gnawing of appetite." So I think when we look at that, we think unpromising. I think when they looked at it, they thought child's play. We can get that grain out of their and eat it. So I think they were much more knowledgeable and inventive than we might imagine today. Now, there was this big difference so it was very controversial. There was a huge controversy surrounding the origin of maize. Basically, there were two camps. There was the camp that said teosinte is the ancestor of corn, and that was led by this fellow right here. His name if George Beadle. If you're a geneticist, you'll know that name because he won the Nobel Prize for the theory one gene-one enzyme. He was president of the University of Chicago. And he was in the camp that teosinte is the ancestor of maize. And this was another famous geneticist. His name was Paul Mangelsdorf. He was a professor at Harvard University, and he said no way teosinte could be the ancestor of maize. Well, this was a photo taken after a conference and confrontation that they had at Harvard University, and the consensus is that Beadle won on that particular day. Today, it is broadly accepted. Although, like the theory of evolution or anything else in science, there always is a fringe of people who try to keep the controversy alive.

LAUGHTER

Hugh Iltis put it this way

So, what did Beadle propose to make teosinte into corn? So, Beadle said that there could be as few as five gene changes that can convert teosinte into a primitive type of maize. And he did a little experiment to prove that or to test that hypothesis, and my lab has actually been following up on that. We've sort of cloned three of those big genes. So we actually know at the molecular level what they are and the molecular nature of the changes in those genes to make teosinte into corn. But here's Beadle's experiment. Beadle applied basic Mendelian logic. And he just said, so, if you cross maize and teosinte and you get their hybrid, what geneticists call the F1 hybrid, this isn't showing up very well, but then at any particular gene, a fourth of the plants would have two copies of the maize version of the gene, a fourth of the plants would have two copies of the teosinte version of the gene, and half of the plants would have one teosinte copy and one maize copy. So that's Mendelian principles right there. So, if there were one gene that made all the difference between teosinte and corn, then if you looked at the second generation of hybrids, what geneticists call the F2, you would see a fourth of the plants would look like maize, a fourth would look like teosinte, and half would be somewhat in between. If there were two genes that explained all the differences between maize and teosinte, a sixteenth would look like teosinte, a sixteenth would look like maize, and the rest would be somewhat in between. So Beadle grew out a large population of these second generation hybrids, and he found that it was somewhere around one in 500 looked just like maize and one in 500 looked just like teosinte. And so he said it was somewhere between four and five genes that makes the difference between the basic architecture of teosinte and the basic architecture of maize. And so that was his argument was that because you get back any second generation hybrids, plants that look pretty much like maize and plants that look pretty much like teosinte, then the genetic differences must not be too complex. So what are some of those genes? I'm not going to go into any detail about that. My lab has cloned and characterized a few of these. One of them is called teosinte branch gene, and it controls this difference. This is a long branched teosinte plant, and this is a teosinte plant into which we inserted the maize version of this teosinte gene. It still has branches, but they're very short and they have a little ear on the tip. So it does just what maize does as a short branch with an ear, and that we get by substituting in the maize version of this gene. Here's another one. This is a teosinte ear and we found the gene we call teosinte glume architecture and that takes this hard fruit case and blocks it from fully developing so now the kernel becomes partially exposed. So this is pure teosinte and this is teosinte with this maize version of this glume architecture gene inserted into it and what you'll see is that the kernel becomes partially exposed. So this would be a great step in maize domestication because now the problem of having the grain locked up in that hard casing is solved. There the grain is visible on the ear. And there's another gene that affects the shattering. So instead of the ear of teosinte falling apart, it all stays intact. And there are other genes, instead of getting just two rows, you get multiple rows of grain and so forth. So it's probably, definitely it's more than five genes as Beadle had suggested, but it's not such a large number that it's impossible to think how it could have happened. And so you could by putting all these genes together, start with teosinte and start substituting a few individual changes and end up with a very small, primitive ear of corn. So, basically, what you're doing is you're stopping, opening up the fruit case, now, this one the grains are partially exposed on the outside, you're making the internodes a little bit shorter so they're more compacted together, they're closer together, each of the kernels, and then you're just forming these kernel-forming units not just on the two sides but all the way around to finally get the full ear of corn. And, basically, the way I like to put it is maize domestication was like turning the teosinte ear inside out because here the grain is on the inside and we've got all this fruit case structure on the outside. All these structures and tissues that are on the outside form the cob of maize. So you, in a sense, turned it inside out. So now the fruit case forming tissues are on the inside making the cob, and the grain forming tissue goes from the inside to the outside for easy use by humans. Now, how did all that happen? Well, there are two ways it may have happened. One, and I really like idea so I want to present it to you, is the idea that part of it may have been unconscious. People study origins of agricultural called unconscious selection. So this is like a trial about collecting grasses or something. Let's imagine the trait of shattering. So the wild grass needs to shatter and have its seeds dispersed around, but people want the seed to stay on the plant so when they go there to harvest it, they don't want it to fall off. They want the seed to stay attached to the plant. Now, let's say you go into a field and there are a mix of plants, some of which shatter and their seed falls to the ground and others that don't shatter and the seed stays attached to the plant. You don't even have to think about it, which type of seed are you going to get? You're going to get the ones that have the genetic mutation to stay attached to the plant. So even without thinking about it, unconsciously you would domesticate that plant if all you did was harvest and save some seed to plant the next year. So by having a sowing and reaping cycle, you automatically domesticate crops by unconscious selection. That's not to say it's entirely unconscious because people very well understood everywhere you go around the world, every society, everyone understands that like begets like. And they have different ways of explaining it. The Greeks thought semen contained little babies which were incubated inside the woman, and that the woman's contribution was just to sort of be an incubator but the male actually provided this tiny little fetus directly into the woman. And, of course, now we know that's not true. The Hopi Indians had a really nice thing for corn too. They believed that the Gods lived in the Earth and that the corn seed was a message to the Gods. So if you put a blue grain of kernel, a blue kernel into the ground, the God would see the blue grain and understand that you would want blue corn, and they would return to you a plant that would grow blue corn. If you put a red kernel into the ground, the Gods would see they want red corn and give you back a plant that grew red corn. They had a perfectly good testable hypothesis which they verified year after year that said what a corn seed really is is a message to the Gods. And it worked. So I want to ask-- Another question then was, where was maize domesticated? So here's distribution. It goes all the way down to Costa Rica. And we kind of looked at that, too, using genetics. Because what we could do is we could take modern corn and we could ask which type of teosinte is it most closely related to. So modern corn would be genetically more similar to some types of teosinte than it is to others, and the types of teosinte that it's most similar to would be the ones that it should be ancestral from. And so we did that using molecular methods. We've done it multiple times. We make something like this. It's called an evolutionary tree. An evolutionary tree. And here's all different forms of maize, and these come from all over the world. I shouldn't say all over the world. All over the native distribution of maize. So everywhere from Chile on up to Canada which is where the native peoples of the new world grew corn prior to contact. So we have, from the Andes Mountains in South America all the way up to Canada, all the different types of corn that were grown before Europeans arrived in the new world. We make an evolutionary tree and we see which type of teosinte they come out closest to, and they come out closest to these forms here, which are shown in green, and particularly those forms with the little asterisk at the end of the branch. And that's a type of teosinte. It has a fancy botanical name or Latin name called Parviglumis. And this comes from a particular area in Mexico, and that's where we think corn was domesticated from. So on that tree, those types of teosinte that are closest to corn come from this area. That's in southwestern Mexico. If you kind of make out, this would be like the Caribbean over here and this is the Pacific. Mexico City is right here. So just southwest of Mexico City in a part called the Balsas River drainage. It's where we believe corn was domesticated about 10,000 years ago. And so the earliest archeological evidence for corn, the earliest archeological cob is about 6,000 years ago. So there's a bit of a gap. We think it probably happened about 10,000 years ago, but the archeological record is not all that rich. Corn ears do not preserve as well as we would like, and then of course there's the limited amount of archeology that has gone on in Mexico. But there are some ears that are 6,000 years old, and they're really, really tiny. Just about the size of the type of your little finger. They have about 35 kernels attached to them. So the first ear of corn had only about 35 kernels. But if you go to this archeological site and through time you can see there's a gradual increase in the size up to about 600 years ago, the time of European contact, they full sized modern ears of corn just like we have today. And if you look at the archeological dates on the types of corn, the oldest ones are from southern Mexico, which is where our genetic data say teosinte was transformed into maize. And then the more recent archeological dates, so about 2,500 years ago it made it into the eastern United States, and about 1,500 years ago it made it into the southern Andes, and it's hard to see but there's kind of a speckling and that shows the distribution of corn agriculture prior to Europeans coming to the new world. Now, when corn spread all over those areas, it diversified it. It had to adapt to the conditions everywhere it grows. So this is maize in Guatemala. The plant reaches about 22 feet in height. This is in the mountains in Guatemala. That's Hugh Iltis from the botany department. He's about my height. So he's about six feet tall. He's standing on the ground right next to this plant. You can't see, but he has his hand on the stalk. So he's about six, keep going up the stalk, there's the ear. It's probably somewhere around 12 to 15 feet off the ground. Try to drive a tractor through that field and harvest that corn. And then you have to go another, I don't know, 10 or 12 feet above the ear to get up to the tassel of that plant. So in a tropical rain forest, we've got a lot of heat, a lot of moisture, a lot of sunlight, plants are growing wildly, you've got to grow fast in order to keep your place in the sunshine, so everything gets really big, and the corn there is really, really big. The stalks on it are tremendously strong. You can use them for fence posts, building material, anything you want. Now, another extreme. This is in Arizona. This is on the Hopi Indian reservation. They grew corn there too. It's adapted to the desert. Now, there's not very much moisture in the soil, so they have to put the plants very far apart so they can spread out their root system and they don't compete with each other for moisture. They also plant the seed very deep into the ground because in the desert, the heat bakes off the moisture in the upper layers of the soil, but deeper down you go, the more moisture there's going to be. So that's a cornfield in Arizona. Probably farmed 1900 to late 1800. It's out of a book. And here's, I think it's Francis Collins, not Francis Collins. He's a modern geneticist. Another Collins. A USDA agricultural scientist standing in one of these Hopi fields. You can see how short it was. So you don't have a lot of moisture, and so you want to be very short. And so it's just about three feet tall, but it's rather productive. So if you strip off all the leaves, it has a nice set of well developed ears of corn for food. >> How large are they? >> I've got some of them here. They'd be something like this. Yeah. They get a lot there. They actually, the cob on them is really thick too, and it may have worked like a water storage organ. So the cob is thick and spongy to help keep some moisture in the plant. >> Are those annual or perennial? >> It's annual. All of corn is annual. There's a wild teosinte or a couple wild teosintes that are perennial, but corn itself is all annual. So Collins did this experiment. He saw that they had, the native peoples in Arizona had adapted it to grow deeper. So he did a little test. He took three types of corn, one from, I think it's from Boone, North Carolina, another variety that's called Chinese in his figure, it's probably something like from the US that was carried to China in trade, and then the Navaho Indian corn. And he plants them at four centimeters into the soil, and they all come up. He plants them at different depths, and what you'll see when you get down to somewhere around here, 20 centimeters into the soil, all the sudden the Chinese variety is no longer coming up. When you get down to around 30 centimeters, so that's a foot into the soil, only the Navaho corn can grow that full depth. And he goes down to 40 centimeters, so that's well over a foot, so you can take a seed of Navaho Indian corn, put it a foot and a half into the ground, and it will grow all the way up through that and start a plant. And that's how they adapted it to grow there by making it so it would germinate and grow deep into the soil. So they also had kept a lot of diversity. So you might think I went to a whole series of farmers' markets and collected one ear from each plant. No, this is out of a single farmer's corn crib in Mexico. So in a single field you have all that diversity. So there's just a lot of diversity in the native varieties of corn that some groups grow. Of course, other groups had a much more archetypal view of corn. They had one variety that they bred to be a certain way. But in some places they did this. They have tremendous diversity within a single variety.

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Hugh Iltis put it this way

Is this... no. This is all one variety, and it's classified on the basis of having kind of a conical ear shape. All of them, you may notice, are kind of a little thick at the base and kind of narrow at the tip. So they're pointy. It's called a Mexican pyramidal. So this is from up near Toluca in Mexico. >> How big are the ears? >> I'm not sure but I think they'd be reasonably large, but I'm not sure.

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Hugh Iltis put it this way

Oh, yeah, absolutely. In Latin America, I shouldn't say virtually all, but with traditional farmers, corn is primarily grown for human consumption. Now, of course, in Central Mexico, they have modern agriculture that grows corn just the way we do, to feed to their chickens. So they grow the same sorts of things that farmers in Wisconsin grow. >> In Guatemala, how did they harvest the corn being so high? >> I don't know. I'm guessing they would take a machete or something and chop it down. So I'm going to tell you a little story. This comes from a geographer named Carl Sauer. It's in his book, a very old book, Seeds, Spades, Hearths, and Herds, and Sauer noticed something not just about corn but about other new world crops. So here are beans, and what he noticed about these beans, these are pinto beans. Pinto beans are native to Mexico and native to South America, and look at all the color and diversity. Each one different from the other. Here are gourds. These are actually native to the United States. First domesticated in the US, probably somewhere like Arkansas or Oklahoma. Look at all the diversity. This is all one cultivated crop, all one species. Here's ones with these long projections. Here's ones kind of warty. Striped ones. Elongated ones. Perfectly round little ones. Tremendous diversity. All differentiated one from another. Remember that slide of the corn I showed you with all that diversity in one farmer's bin. And then if you want to look after I talk, there's a whole diversity in this little box I have up here. So Sauer notices all these new world crops have this tremendous diversity. What's going on? Is there extra radiation causing a lot of mutations in the new world or what? Because if you look in the old world, if you scour the Earth for diversity in barley, this is what you'll come up with. You'll go from a light reddish brown to dark reddish brown. This is out of the barley breeding book showing the tremendous diversity in barley.

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Hugh Iltis put it this way

It's just not there. If you did the same thing for wheat, you'd come up with the same story. The people in the old world did not select on diversity. The people in the new world did. And so Sauer, Carl Sauer had an explanation for that. And here's rice. It's, again, it's like wheat and barley. There's just not a lot of diversity in the color. So what's different? So if you go to the old world crops, how do they plant? They have a basket, here this picture shows with a box, and they broadcast the seed. So when the seed goes into the ground, it's not like I'm going to take this one seed and put it in a special place. I'm just reaching into my bag or my box and I'm broadcasting fistfuls of seed. So I cannot watch or keep track of a single seed. And when I harvest, how do I harvest? Well, I've got a sickle. I'm just going to cut down maybe hundreds of plants at a time. I'm not looking at individual plants. If one of those plants has something unique and interesting about it, I'll never spot it, and if I did spot it, my planting system wouldn't allow me to grow it separately and make a new variety out of it. So the method of agriculture in the old world gave them no mechanism to identify and perpetuate individual unique varieties of their crops. >> Do you know where that picture was taken? >> This is in eastern Europe. Like Czechoslovakia or some place like that. So what about the new world? In the new world, the planting was done with a planting stick. You poke a hole and you drop in one seed. So the planting method allowed you to keep track of individual seeds. And how's the harvest done? Well, you go up to an individual corn plant and you take off the ear. So the harvest method allows you to spot individual interesting variants on a single plant. Yes? >> Since the new world was populated by old world people, why did the planting change at all? >> I don't have an answer to that. But the agriculture came long after the people came. The Americas were people probably 15,000 years ago or a little more, before agriculture. Then agriculture was independently invented in about seven different places around the world. It's actually quite remarkable. All at about the same time. Are you ready for that? So, in South America, Mexico, Africa, East Asia, the Middle East, and maybe some other areas, all about 10,000 years ago everybody went from hunting and gathering and switched to agriculture without getting ideas from the other groups. And the reason they think is something called climate change. Basically, there was dramatic climate change back then and the animals they were used to hunting disappeared and they had to do something else. They had to think quick. They came up with agriculture. Okay, so the new world peoples just had ways of spotting and keeping track of individual mutants, and so they perpetuated them. This is like a branched ear of corn. Southwest Indians collected these and kept them. They called them corn guardians, and they believed these had special powers. If you put one of these into the field, it would actually increase your yield, so they had magical ideas about it. These twin ears also, like this, were thought to improve a crop. So if you had twin ears, you should take some seeds from that and put them into the field and that would improve the yield of the crop. And this one has little pods around each of the kernels. This is an archeological representation of something that is both twin eared and has those pods around it. This one the southwest Indians called flying eagle corn because it was like a black dot in the middle of the kernel, and they said it's like looking at an eagle flying up in a bright sky, like a black dot in the sky on a summer day. And they had that, used that in their pottery. So if you see pottery like this, these are like corn kernels with the black dot. And this one I really like. So this one has something called jumping genes, which modern geneticist RA Brink was in this department. One of the first people ever to work on jumping genes. And, basically, there's a gene that gives red color to kernels. And you can have a jumping gene inserted into it so that it's turned off, and you just get yellow kernels. But where the jumping gene jumps out of the red kernel gene, you get stripes of red. So the jumping genes then jump all over the chromosomes and make new mutations which give you new variation. And so the people in western Mexico thought these were really special, and one of their breeding methods was to be sure to put a few striped kernels into every field because it will make the corn stronger. And what it would do actually is create new mutations which would give you more diversity. So they kind of tracked everything. Now, corn came to the US through western Mexico, initially. About 500 BC, 1000 AD, somewhere in that time period, sped up through western Mexico into the southwestern United States, across the Great Plains and then into the northeastern United States. The Spanish actually brought corn from southern Mexico into the southern United States. So, this came after contact. And they brought varieties from southern Mexico here. So you had two types of growing here. You had a type up in the New England and Canada area which came here a thousand years ago or longer, and then you had a type just that came about 1600 into the southern US. So you had these two forms of corn growing early on in the US. They have names. These were called northern flints. These were called southern dents. And over time, the two got to mix together in Virginia. And farmers would plant the field with the northern corn and the plant the field, maybe they'd plant with the southern corn first which took a long time to grow, and then they could plant a more rapidly flowering norther flint in the same field. The two might cross and they got hybrids between them. They noticed these hybrids outperformed either the southern dent or the northern flint. The crosses between the two were better fit. So they kept mixing together, and they produced a type called Midwestern dents. And when the settlers brought corn farming to the Midwest area, this is what they brought. They brought a mix of northern flints and southern dents, and that gave to, probably some of your ancestors a couple hundred years ago would have grown in Wisconsin or Iowa or Illinois forms called Midwestern dents. It was grown pretty much the way the native people grew it. In other words, a family would have their own stock of corn. They would grow it, give seed to their kids, save seed from one generation to the next. There were also seedsmen who were breeding new varieties and would sell them to the farmers. But if you buy seed from a seedsman, you just buy it once, you could just produce your own grain for several years. You didn't have to go back every year and buy more grain. But then in the 1920s a new idea came up to make a hybrid crop. And this was really a transformational idea. I would say they probably should have gotten the Nobel Prize for this, but they didn't. It really changed agriculture, particularly changed corn agriculture. George Shaw and Edward East are the two who proposed and actually demonstrated that it works. And that is, if you think about it, if you inbreed, what happens? You expose defects. We all know that. If brother/sister matings or inbreeding within small groups, it exposes defects. Each of us carries somewhere around six lethal genes. Each of us. So I have like six genes in me which I have one normal version and one lethal version. So if I were inbreeding, then there's a very good chance that my offspring would get two copies of the lethal version and go out of business. So inbreeding exposes genetic defects, so they realized hybridizing them should mask the genetic defects. So if you cross different things, you should mask defects. So what they would do is they proposed you first inbreed to remove some of the defective genes from the breeding stocks, and then once you create, by this inbreeding process, a series of inbreds, you've removed some of the defectives but not all of them, but then when you cross them, you create hybrids that should have a super allele at each gene in the genome. I can say a little more about how that works. So you start out with one of these Midwestern dent types that has a lot of variation. At any gene they're really super gene versions of the gene, weak versions of the genes, average versions of the gene, and then you inbreed them. And all the lethals will get removed from the population because you can't have two copies of lethal by inbreeding. And you'll keep around the superiors and the averages, and every now and then you'll fix this inbred line, inbred type of corn for two weak alleles. And you start out with something of very high diversity and you go to something with very low diversity. So this is the process by which they created inbred of lines from these ancestral types like the Midwest dents. So then you have two different inbred lines, one line A and one line B, and you cross them and you get a hybrid crop and you see something like this. So this inbred line is really short, really short. The hybrid between the two, very tall. Has a small ear, a small ear, the hybrid between them a very large ear. So this is the base of the hybrid corn industry. It started in the 1920s is when the idea came. This is just showing a little bit of genetics, how this works. It's due to something called dominance. Those single inbred line has a superior allele at every locus. But if you have a superior allele, let's say it gives you two units of yield, and that's dominate to an average allele which gives you one unit of yield, which is dominate to a weak allele which gives you zero units of yield. So if you take a gene, like, say, gene one, inbred one has a weak allele, inbred two has a super allele, so this gives two units of yield, this gives zero, but the hybrid, which has one super and one weak, gets two because of dominance because this is one that shows its phenotype in the hybrid. So then if you sum it up, this inbred has three units of yield, this has three, but the hybrid has six units of yield. So this is the basics of the hybrid corn industry. And this is what it did to corn yields in the US. So this starts from after the Civil War. In terms of kilograms per hectare, yield is absolutely flat. They're going nowhere. In other words, the amount of yield that you got in 1860 didn't change up to 1920. Farmers were making no gain in the amount of crop produced per acre in the US. Then hybrid corn was introduced. They did an initial type called the double cross. It started to go up. And then they did the single cross, and today we have about sixfold higher yield due to the introduction of hybrid corn industry. So that's really changed how corn is grown. Yes? >> Isn't that what the Irish potato famine is to blame on? The fact that there was all this inbreeding and I guess it gathered together all the bad genes? >> I don't want to say, I don't want to comment too much on the, I know they had a pathogen that killed off the crop and so they must have had a susceptible variety that was widespread throughout the Ireland. But we're talking about just the opposite here. We're talking about not being inbred but being hybrid, so having tremendous diversity. It's just structured diversity created by breeding process. >> How does that unit, kilograms per hectare, convert to bushels per acre? >> I could do that if I my brain were hooked up to Google, I could do that for you.

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Hugh Iltis put it this way

That day is coming. I figure in, like, probably before I leave the Earth I think we're going to have something where you can just screw an electrode into our brain and we'll have access to the web. But, what was I going to say? So, I don't know exactly. I'm going to say that yields today are somewhere around 150-175 bushels and acre. It varies from place to place. I've heard it said most of the loss of yield in corn is due to stress, and there are two forms. Abiotic stress is like drought and heat and things like that, and biotic stress which is diseases and pathogens. And I've heard something said that if you could eliminate all stress from the corn plants, then you could up the yield to about a thousand bushels an acre. If you had no stress. Now, so the scientists proposed to study plant stress back in the 1990s, and Bill Clinton just ridiculed them to no end about what on Earth were we doing giving money to people to look at plant stress. I'm sorry those plants are stressed, but we haven't got time to study plant stress.

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Hugh Iltis put it this way

So Clinton, of course we had the guy, senator from Wisconsin liked to give out these sorts of notices too. Proxmire, yeah. >> So, how does it taste? >> That's independent of yield, right? So, this is not tortilla corn. It's not sweet corn, but sweet corn yields have gone up as well. This is corn bred to produce feed for livestock. So the US corn. One other interesting story. All the corn in the US is yellow, and you know why it's yellow? So the yellow color is provitamin A. If you go back to the 1920s, they weren't all yellow. They had reds and blues and whites. Whites were very common. Then somebody did an experiment and showed that if you fed rats white corn and yellow corn, they were much, much healthier on the yellow corn because they got provitamin A from the yellow corn. Within a few years the entire US corn industry switched to yellow, and it's never gone back because it's better for livestock. They're trying to do something very similar in Asia now with something called golden rice because vitamin A deficiency is a real problem in some Asian societies. And so if you could have rice that's yellow, has provitamin A, you could eliminate a lot of disease. But that's very controversial because it's GMO. Okay, so we're almost done. So, what did the hybrid corn industry do? It changed everything, didn't it? I wanted to read you one more quote, and this is from a Hopi Indian. These people, so corn wasn't, like for us, corn, it's like something farmers grow. But for the native peoples it was like a central part of their lives. It was part of their culture. It was part of their religion. It was a very spiritual object to them. And that was throughout the entire new world, from Canada all the way down to Chile. And we don't have that relationship with our crop plants anymore, especially with corn. And this comes from an old ethnographic account of how they kept the corn from one year to the next among the Hopi Indians. And in the previous day, they'd harvest it and set the corn outside, and then they take the special ears, the ones that look the best, and put those aside into the corn room to save for the following year's crop. And it describes the corn maiden. And it says, "The next morning the corn matron takes a basket tray and goes to the door of the corn room. Here she slips off her left moccasin and then enters. As she passes the threshold, she looks around as though she were about to address a group of waiting friends and exclaims, 'My mother and children, how are you and how have you come unto the morning?'" So she's talking to her ears of corn. "Reverently, for she understands she is in the presence of the conscious and the benign." So, for these people, corn was really, really something. For us, it's just that stuff out the car window. And so it really has changed from this time when each seed was special and planted and each plant was special and harvested and there was this tremendous diversity, to now you have a farmer, he's in his tractor, he's staring at a set of three different computer screens. Right? So he's looking around, what's this screen tell me? What's that screen tell me? And then up here in your tractor, you never see the plant. And you don't have to see it because you're just growing it. It's the guys and gals at Monsanto and Pioneer Hi-Bred who are, actually, they don't even see the plants because the guys and gals at Monsanto are here in the lab. They're staring at computer screens. And they've got robots that are, you should go to Monsanto and take their tour. They've got this incredible robot that you put in a big box of seeds into this hopper, it puts them in one by one, takes a little slice of kernel off of them, then extracts the DNA from that little slice of kernel, genotypes it to see which genes it has, and then it sorts all the kernels into trays and it picks the ones that it wants to go to the next generation based on which one has the best genes. So it's all done by computers. And they'll give you a little demonstration you can watch. It's guided by cameras. They've got a camera trained on each kernel which photographs the kernel as it's going through the machine, and then it directs a little saw blade to come out to cut the kernel without cutting the embryo. That's really remarkable. And, of course, we have things like GMO Bt-corn, which is pretty remarkable. So corn is really a different crop today compared to what it was. I don't want to say too much about that because it's not my area, but it certainly has changed the way we as a society interact with crops compared to what the native peoples did either as hunters and gatherers or as modern agriculturalists. So, I'll stop there. That's kind of a brief history of corn, and thanks for listening.

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