The Maneete:I want to elaborate a little bit on something we talked about last week when we talked about how fish navigate. We had briefly discussed that fish are able to sense changes in water pressure and water currents because of their lateral line. The lateral line, if you'll remember, is a line of small holes that runs horizontally along a fish's body. Each of these holes is connected to a canal that sits just under the fish's skin and within the canal, there are these small sensory hairs that move back and forth when they're stimulated by changes in water pressure from water entering the canal. This sensitivity to water pressure allows the fish to detect changes in currents, which helps them to navigate, to make their way through the environment and I bring this up because you need to understand it for today's discussion, which is actually about how the manatee navigates. You should be familiar with manatees. They're large marine mammals that are found in warm water, coastal and river ecosystems; places where salt water and fresh water meet. In North America, they can be found in Florida and the Caribbean. The manatee's habitat is often characterized by dark, murky water. As a result, it's very difficult for manatees to see in this environment. It's difficult to see any distance. It's difficult to see any objects. Manatees don't have very good vision anyway and unlike other marine mammals, such as whales and dolphins, manatees don't use echolocation. Echolocation's when animals produce really high-frequency clicks and then detect the echoes of those clicks that bounce off objects in the water. It allows animals like whales and dolphins to sense how far away objects are and to navigate. So, manatees cannot echolocate and their habitat makes visual orientation less than ideal. So, how dothey navigate? Well, manatees have an unusual characteristic. They have these very tough hairs that are spaced more or less evenly all over their bodies and about a hundred years ago, one scientist, well his instinct was and don't ask me how he came up with this, was that this might have something to do with manatee navigation. His opinion was that these were tactile hairs. Tactile has to do with the sense of touch and tactile hairs are so-called because they allow animals to feel what's going on in their environment. They're different from other hairs because of the hair follicle sinus they sit in. The hair follicle sinus is just like a small sack within which a single hair sits in the skin of the animal and importantly, the sinus is attached to lots of nerves; more nerves than other kinds of hair follicles. So when the hairs touch something or move, the nerves sense the movement and send a signal to the brain. Now, here's what was a little peculiar about the scientist's proposal. Other mammals have tactile hairs, but they're usually restricted to the facial region. An example of this is the whiskers on cats and dogs, so what this scientist was proposing, just based on an instinct, was kind of unusual, but if his instinct was correct, that these were tactile hairs, then it's possible these hairs do constitute a system that enables navigation, something similar in function to what fish have. Anyway, that was a hundred years ago, but all of this came to light again recently when a researcher analyzed some magnified images of manatee hair follicles. He found out that indeed these are sinus follicles and the hairs in them are indeed tactile hairs, so together these hairs form a sensory system for manatees. What he also found is that on manatees, these hairs are spaced far enough apart that they don't touch each other, so that they don't overlap and interfere with each other. In other words, so the manatee doesn't sense itself. So this research is all very interesting, but the big question is how similar manatee tactile hairs and fish lateral lines are. What information is the manatee receiving from the tactile hairs? Like, can tactile hairs allow manatees to detect stationary objects such as rock formations or riverbanks? See, there are patterns of flow in the water and stationary objects disrupt that flow. Fish perceive these kinds of disruptions because of their lateral lines and the research is ongoing, but preliminary findings seem to say that yes, manatees have this ability. Let's take a look now at one particular experiment.
The Rite of Spring:Today I'd like to look at an important piece of music of the 20th century. It's a ballet, so you might imagine graceful melodies and dancers, refined and beautiful, but this traditional view of ballet was challenged and altered one evening in Paris in May of 1913. The theater was reopening after extensive renovation and the audience was impressed when they saw the newly restored elegance. The first piece that evening was a very traditional ballet with unremarkable music, but that could not be said about what followed: the premiere performance of The Rite of Spring by Igor Stravinsky. The Rite of Spring opened with some very high notes played by the bassoon, normally a deep-toned instrument. Such strained, pinched notes that many in the audience had no idea what instrument was playing then another instrument came in playing a different melody with a slightly different rhythm, one that didn't really mesh with the opening bassoon. Gradually, more and more instruments came in, each playing a perfectly beautifulmelody, but none of them really making sense with what the other instruments were playing. It sounded (chaotic), but then things really went crazy when the curtain went up and the audience saw the dancers. They were wearing rough costumes and weren't poised elegantly like traditional ballet dancers and when they started dancing, I should mention here that the choreography was created by Stravinsky's collaborator, Naginski, and Naginski, in the words of an eye witness, Naginski had the dancers repeat the same gestures a hundred times. They stamped in a place he said, they stamp, they stamp. Well, very soon noise started to build in the audience and it quickly became clear that there were two different camps, supporters and detractors. Members of the audience began to shout at each and soon people were actually fighting in the aisles. The lights were even turned on so the police could escort some of the offenders out of the building, though that didn't really seem to help much. In fact, it's amazing that the performers actually made it through the piece, but when it was over, while applause broke out from some who were ecstatic about what had happened, and angry shouting from many others who were shocked and appalled by what they felt to be a complete betrayal, a breakdown of traditional ballet. The chaos that evening was a great disappointment to Stravinsky. Ironically though, the producer of the program that night was not at all upset. He was overjoyed that everyone in Paris would soon be talking of nothing but this, well what many were calling, and this terrible scandal. Then as now apparently, producers like almost any kind of publicity. Even notoriety sells seats, they say. it was less the music than the staging that outraged so much of the audience. staging=dancing=choreographymusic dancers with dancers performing totally newsteps，a modern classic. So, that's what happened at that first performance of The Rite of Spring. What's not quite so clear is why what set off this huge uproar? Was it that Stravinsky's music was such a break from the past? The retelling of the events of that evening certainly created the popular impression that this piece marked the dawn of a new, modern age in orchestral music. That helped establish the piece's reputation as an important, even revolutionary, milestone in musical history and I'd say this reputation is pretty well deserved, but that's actually a different question from the one we were trying to answer. As to what in fact caused the near-riot, well consider this: after the first few minutes of the performance, there was so much shouting in the audience, that Stravinsky's music could hardly be heard. I'm hardly alone in concluding that it was less the music than the staging that outraged so much of the audience. Ballet lovers were so shocked by Naginski's choreography in many cases, that the music, well let's just say it didn't get a fair hearing. It was only when the work was performed in concert without any dancers about a year later that Stravinsky finally felt it a true success, but that was just on the eve of World War I and so it wasn't performed as a ballet again for seven years. After the war, when The Rite of Spring finally returned to the stage as a ballet, Naginski's choreography was abandoned and with dancers performing totally new steps, the work went on to become a modern classic. Today I'd like to look at an important piece of music of the 20th century. It's a ballet, so you might imagine graceful melodies and dancers, refined and beautiful, but this traditional view of ballet was challenged and altered one evening in Paris in May of 1913. The theater was reopening after extensive renovation and the audience was impressed when they saw the newly restoredelegance. The first piece that evening was a very traditional ballet with unremarkable music, but that could not be said about what followed: the premiere performance of The Rite of Spring by Igor Stravinsky. The Rite of Spring opened with some very high notes played by the bassoon, normally a deep-toned instrument. Such strained, pinched notes that many in the audience had no idea what instrument was playing then another instrument came in playing a different melody with a slightly different rhythm, one that didn't really mesh with the opening bassoon. Gradually, more and more instruments came in, each playing a perfectly beautiful melody, but none of them really making sense with what the other instruments were playing. It sounded (chaotic), but then things really went crazy when the curtain went up and the audience saw the dancers. They were wearing rough costumes and weren't poised elegantly like traditional ballet dancers and when they started dancing, I should mention here that the choreography was created by Stravinsky's collaborator, Naginski, and Naginski, in the words of an eye witness, Naginski had the dancers repeat the same gestures a hundred times. They stamped in a place he said, they stamp, they stamp. Well, very soon noise started to build in the audience and it quickly became clear that there were two different camps, supporters and detractors. Members of the audience began to shout at each and soon people were actually fighting in the aisles. The lights were even turned on so the police could escort some of the offenders out of the building, though that didn't really seem to help much. In fact, it's amazing that the performers actually made it through the piece, but when it was over, while applause broke out from some who were ecstatic about what had happened, and angry shouting from many others who were shocked and appalled by what they felt to be a complete betrayal, a breakdown of traditional ballet. The chaos that evening was a great disappointment to Stravinsky. Ironically though, the producer of the program that night was not at all upset. He was overjoyed that everyone in Paris would soon be talking of nothing but this, well what many were calling, this terrible scandal. Then as now apparently, producers like almost any kind of publicity. Even notoriety sells seats, they say. it was less the music than the staging that outraged so much of the audience. staging=dancing=choreographymusic dancers with dancers performing totally newsteps，a modern classic. So, that's what happened at that first performance of The Rite of Spring. What's not quite so clear is why what set off this huge uproar? Was it that Stravinsky's music was such a break from the past? The retelling of the events of that evening certainly created the popular impression that this piece marked the dawn of a new, modern age in orchestral music. That helped establish the piece's reputation as an important, even revolutionary, milestone in musical history and I'd say this reputation is pretty well deserved, but that's actually a different question from the one we were trying to answer. As to what in fact caused the near-riot, well consider this: after the first few minutes of the performance, there was so much shouting in the audience, that Stravinsky's music could hardly be heard. I'm hardly alone in concluding that it was less the music than the staging that outraged so much of the audience. Ballet lovers were so shocked by Naginski's choreography in many cases, that the music, well let's just say it didn't get a fair hearing. It was only when the work was performed in concert without any dancers about a year later that Stravinsky finally felt it a true success, but that was just on the eve of World War I and so it wasn't performed as a ballet againfor seven years. After the war, when The Rite of Spring finally returned to the stage as a ballet, Naginski's choreography was abandoned and with dancers performing totally new steps, the work went on to become a modern
The Disappear of Giant Mammal:Now, one of the things I like to do from time to time in this class is looking at how the knowledge we've gained from studying earth's geology has been applied to questions outside our field. Take the mass extinction that occurred around 13,000 years ago when most of the giant mammal species of North America vanished from the geological record. Creatures like wholly mammoths, saber-toothed cats, giant sloths, beavers, and camels. So, what caused these animals to suddenly disappear? One possible answer lies at the start of a period of sudden climate change called the Younger Dryas. Let me back up a minute. Just before this extinction, Earth was coming out of a long ice age. Glaciers were beginning to recede, but then temperatures in North America suddenly plummeted again, setting off this frigid thousand-year period known as the Younger Dryas. North America became so cold, that glaciers started expanding again and one theory is that this sudden change in climate would have made it difficult for these large beasts to survive. Of course, there's been other climate changes, some even more extreme and longer-lasting, yet with no evidence that they triggered any extinction events, so maybe not the strongest theory, which means we need to look elsewhere, maybe space. I mean, we're all familiar with how impact events can affect life on earth like it's now generally agreed that a meteor triggered the extinction of the dinosaurs. Of course, since that theory's been widely accepted it's tempting to look to space to explain all extinction events. A large meteor crashing into the earth would scatter osmic debris and cause massive firestorms and that's the theory proposed recently as an explanation for the large mammal extinction. Researchers who support this theory claim to have found evidence of a meteor impact at a site in the state of Arizona in a layer of sediment called the Younger Dryas Boundary. The Younger Dryas Boundary, or YDB, is a very thin layer of sediment that was laid down across North America at the beginning of the Younger Dryas period, and what's particularly significant about this 13,000-year-old layer is that under it, we find lots of fossils of these large mammals, but above it, that is after the YDB was laid down, well, not a single one. So, what happened here? Although the researchers suspect a meteor event, they didn't find any evidence of an impact crater, but they say they did find evidence of several types of particles commonly associated with meteor impacts, including nanodiamonds and high concentrations of certain magnetic particles. Nanodiamonds are small particles that can either originate in space or be formed in the extreme pressure of an intense explosion like the impact of a meteor for example. The magnetic particles can also come from space and the ones found inthe YDB are very similar to particles associated with other meteor impacts. Recently, however, a new group of researchers tried to replicate these findings and while they also found nanodiamonds and high concentrations of magnetic particles at the Arizona site, these researchers wondered whether the presence of such particles might be accounted for in other ways. So, to test whether the magnetic particles were unique to the YDB, they analyzed dirt from the rooftop of a researcher's house, and in fact, they found magnetic particles in the rooftop sample too. Turns out that these particles are not just the result of impact events. They can have many origins, including the ash from nearby coal burning, electrical power plants, or even cosmic dust that originate in space and then falls to earth. Ok, but then how to explain the elevated concentrations of the magnetic particles in the sample from the YDB. Well, these samples had come from a riverbed where rainwater would have carried and deposited the particles and in fact, additional samples taken from outside the riverbed contained only normal concentrations of the magnetic particles in the YDB. As for the nanodiamonds, while a group of meteorite or comet fragments colliding with earth would certainly provide the high temperatures and pressures needed to create such nanodiamonds, there might be other ways to explain their existence. It turns out, they're also commonly found in cosmic dust, which could explain their presence not only in the YDB but also in the rooftop sample. So, if there's no strong evidence for a meteor impact or for a sudden climate change, then we need some other explanation for the disappearance of so many large, North American mammal species during the Younger Dryas.
Printing Shop Music:In our discussions of Renaissance music up till now, we've established that when music was copied and distributed to others, it was all written by hand. You can imagine the tedious nature of that work, right? Today though, I want to turn our attention to printed music; music that was published through the use of a printing press and we will see that the printing of actually changed the audience for it and therefore changed music itself. Let's start with a man named Ottaviano Petrucci. Music printer Ottaviano Petrucci printed his first publications around the year 1500. (2)These were gorgeous publications and they were very expensive to produce, mainly because they required a lot of time and a great deal of precision. Printed music became, in short, a luxury object for the upper class. We know from existing records that for the price of one Petrucci print of music, you could purchase several, yes several, volumes of literature. The revolution in music printing came around 1520 with a French printer named Pierre Attaingnant. The first thing Pierre Attaingnant did was to get an assurance from the king that he would be the only one who could set up a music printing shop in all of France. This is understandable since it was such a risky enterprise, but I mean, let's be realistic, with no competition, how could he have failed? Anyway, Attaingnant used a new, less expensive way of printing music than Petrucci did. Admittedly, the prints weren't as attractive as Petrucci's prints, but they were much, much cheaper, and therefore, they actually got used. They weren't just for collectors to display on a shelf and since they got used, the paper itself degraded and so we don't have nearly as many Attaingnant prints as we have Petrucci prints. S1: How is the music Attaingnant printed used? P: Well, Attaingnant printed lots of songs and people were singing them for their own entertainment in their own homes and this use, this amateur sort of domestic performance meant that the musical arrangements needed to be less complex than the arrangements professional musicians would use. This gave rise to a new genre called Parisian chanson. Chanson is a French word for ‘song.' Although the genre was popular throughout Europe, it came to be known as Parisian chanson because so many of the songs were printed in Attaingnant's shop in Paris, and here is a key feature of Parisian chanson. Imagine you're standing around a dinner table with three friends getting ready to sing a song that has four different vocal parts. Well, in the printed music book you have, you see only your line of music, only the part that you'll personally be singing in front of you. S1: Oh, that makes sense. Then you won't be distracted or confused by everyone else's parts, right? P: True, but actually having only your part could make it a bit more challenging because you might not know what everybody else is about to sing or even who's supposed to sing first. Like, think of an orchestra with different instruments. Not all of them start playing right at the beginning of the song. Maybe just the violins start and then the trumpets come in later and so on,but an orchestra has a conductor to tell the musicians when to start, but there's no conductor in your dining room, so the composers of Parisian chanson worked around this by having all four voice parts start at the same time and in the same rhythm. Now, as the song progressed the rhythms, melodies, and harmonies did get more difficult, more varied, but these songs always had everyone singing the same pattern at the beginning. So, this is a very interesting moment in music history where it's very clear that the business side of music, that is to say, the selling of printed music by Pierre Attaingnant and those who followed, the business end of music shaped the artistic end. The technology that allowed Attaingnant to produce inexpensive prints affected music itself by leading to the creation of an entirely new genre of music.
Social Evaluation:Now when the last class ended, we were talking about how we evaluate other people, how we look at other people and determine which people are likely to be helpful to us and which people are likely to hinder us as we go through life and we noted that the ability to distinguish between these two kinds of people, to perform what we call social evaluations, is critical to our survival. Yes, Karen? S1: Is that a learned ability or something we're born with? P: Well, there've been studies that suggest that we are born with a certain capacity for social evaluation, that infants as young as six months are able to make social evaluations. David? S2: I don't doubt that that's possible, but at six months, babies are still preverbal, so… P: That's a good question. One of the studies I'm referring to consisted of two experiments done by researchers at Yale University. In both experiments, the researchers looked at a group of six-month-olds. To prepare for the first experiment, the researchers constructed a little stage and on that stage, they constructed a little hill, ok? And then they got three wooden blocks: one in the shape of a circle, one in the shape of a square, and one in the shape of a triangle, ok? And on each of these blocks, they glued a pair of eyes, little circles with black dots in them that looked like eyes, ok? (2-1)So in the first phase of the experiment, the researchers showed the infants a series of brief scenarios. In every scenario, one of the blocks, let's say the circle block, played the role of a climber trying to get to the top of the hill, ok? So the circle block was the climber. At first, the climber block would appear by itself and start climbing up the hill, but it would be struggling. Then in some of the other scenarios, one of the other blocks, let's say the square, would appear and would always help the climber block get to the top of the hill; gently nudge it up the hill, ok? So you had the square block always helping the climber block and in the rest of the scenarios, the other block, let's say the triangle, would appear and would always hinder the climber block. It would always block the climber's path and force it back down the hill, so the triangle block was always hindering the climber block. Ok, so that was the first phase. Then in the second phase of the experiment, the researchers placed the helper and hinderer blocks in front of each infant and they noted which block each infant reached for. S2: And the idea was that they'd reach for the helper block? P: That's right and that's exactly what happened in almost every case. Karen? S1: I’m wondering how you could be sure that they're choosing based on the social evaluation. I'm mean; maybe they just like circles better than squares or maybe they just like to see things going up the hill more thanthey like to see things coming down the hill or something. P: Excellent question, which is what the researchers were obviously wondering as well because, as I mentioned earlier, they did a second experiment. They took another group of six-month-olds and showed them scenarios very similar to the ones in the first experiment, ok? Only this time, the climber block didn't have eyes and it never moved by itself. It only got pushed up the hill by one block, very gently, very smoothly, and down the hill by the other block very gently, very smoothly. S1: So in the second experiment, the idea was that the babies wouldn't perceive the climber block as a living thing and it wasn't trying to do anything, so it couldn't really be helped or hindered. P: Exactly. S1: So then there wouldn't be any social evaluation involved. P: Exactly and this time, when the researchers offered the infants the wooden blocks they didn't have a clear preference. S1: That's very interesting. P: Yes and what's considered most significant about these studies is not so much that the infants were able to make social evaluations, but that they were able to evaluate interactions between unknown individuals; interactions that had nothing to do with themselves. That's pretty sophisticated. S1: Especially for a six-month-old
Student Housing:Narrator: Listen to a conversation between a student and a Department of Housing employee S: Hi, I'm a first-year student and I've lived in student housing for the past 6 months. A classmate just told me that I might have missed the application deadline for the next academic year. I didn't know I had to apply again so early. I thought I'd better stop by. Um, has that deadline passed? Employee: Well, housing is a three-stage process with a few different deadlines. One of them is approaching soon, but none of them has passed yet. So you're fine. S: Great! Oh, that's a relief! Could you tell me then about what I need to take care of? Employee: Sure! For stage one, you only have until the end of this week to do two things. First, you need to go to the university home page and complete the housing re-application online. And secondly, if that gets approved, you have to pay the $1,000 non-refundable housing deposit. S: Uh oh, I mean the $1,000 is not a problem, it's the non-refundable part that… Employee: Well, what do you mean? S: (2)Well, it's just that I don't know yet precisely where I'll be next year. I applied for the university's study abroad option, but they won't make their decision for a few more months. So I do really need to plan for both possibilities, but if the $1,000 is non-refundable… Employee: Well, you still have to meet our re-application and deposit deadline to remain eligible for any future guaranteed housing. Otherwise, you'll always be put on the waiting list. (3)However, the study abroad program is an exception to our non-refundable policy. So if you get accepted into that program, you can submit a Study Abroad Notification Form to our office. S: But what will that do? Employee: That way, we can change your status. But you'll still be eligible for future housing and the $1,000 will be credited to your account. S: Oh, okay. Employee: (4) Now, as part of stage two of the housing process, coming up in about a month, there'll be an official open house session. It'll provide students with an opportunity to visit the different student housing buildings. And also, to learn more about the surrounding communities. You know, since we're a city college, some of those areas have different attractions which give each of them a differentpersonality. Take Tremble Hall for instance, it's right next to a Weekend Farmer's Market. And there's Clark Hall, which is on the same block as the Art Museum. Lots of options to explore. S: Great! I'll plan to attend. And what about roommates? There are two friends I'd like to live with. Can I arrange that? Employee: (5) Yes, the day after the open house, submit a roommate preference card. Make sure only one person submits all the information on one card. Now, we do the best we can to accommodate groups. However, please be aware as space becomes limited, individuals in the group may be placed in different locations. S: Got it! And what's stage three? Employee: That's the final stage where you select the specific room that you'd like.
Classifying Mayan pottery:Let's review, why is pottery such an important subject in archaeological analysis? Well, pottery contains more information than we might think. Can you explain what you mean? (2)Well, ，，, like sudden changes in the style and shape of pottery might help us figure out when certain cultures might contact each other, and borrowed each other's ideas, designs, even technology. Good. Today I want to expand our discussion into the topic of classifying pottery. Classification is simply an attempt to categorize or group the pottery based on specific characteristics. We'll look at ancient Mayan pottery, which, is you know by now, is my specialty. Archaeologists have traditionally attempted to classify these vessels by using a single classification system, (3)but the complexity, the variation of ancient Mayan pottery is just too great, in my opinion, to use only one system. I advocate the use of several systems, as do some of my colleagues who've been researching the Mayan archaeological sites of Mexico and Central America. By utilizing more than one system of classification, we aren't as likely to neglect important details or lose important information. (3) So I think what you are saying is when we use a single classification system, we can't label a vessel with lots of details, but when we classify in a lot of different ways that give us a more complete picture. Yes. And if we are able to label a large quantity of pottery in several ways, we can more clearly see relationships between them. Because of having a more complete picture of each one, I mean, everybody in this class is from a different state of the country, nobody is from the exact same place. (4)So if I only classify people by where they from, I might say that you have nothing in common. (4) But, what if I add more layers. Andrew, you're a skier, Sarah is also a skier. (4)So if we have a classification for your extra-curricular activities, we find you two have something in common: snow-skiing. I get it. So we begin by determining what classifications will be possible, and what classifications will be useful. These will in my opinion, vessel shapes, surface finish, which looks at texture, and finally what we all, pastes, I'll explain pastes later. Would you limit to just three classification systems, shapes, surface finishing, and pastes. Not necessarily. When we encounter a pottery decorated with a lot of detail, we might want to add a classification system for this too, what we could call, decoration. So let's look at my first classification type: pottery shapes. We need to consider the basic proportions and size of an object. (5) But what if the object is broken? Obviously, intact pottery is the best, (5) but if all we have in front of us is a collection of pieces, as long as those pieces are of reasonable size, we can still classify shapes reliably. We just have to reconstruct the object. Even if you are able to reconstruct and then determine how to classify pottery in terms of shape, you might be unable to classify it in surface finish. For instance， with many of the potteries collections found in the archaeological site of Plaikai, too little surface finish was preserved to make a determination. Really what we need are comprehensive and accurate illustrations of ancient Mayan pottery. Having drawings of their profile allows us to compare the shapes of pottery, found in different archaeological sites. Because of course, we can't personally go to all the locations. (6)But even when archaeologists and art historians do attempt to illustrate every single piece, there are problems. Like, three different people might draw the profile of the same pot, but the drawings don't turn out exactly the same? (6) Very true. Illustrating involves some simplification of the pottery and people may have different ideas of which features are important to keep in adrawing, and which can be left out. What else? Well, drawing a profile of every single pot probably takes tons of time, so it can be expensive. Aha? But digital photography is so popular and inexpensive now, why don't we just give up on drawings and make a collection of photographs, you can't get more accurate than a photograph. That's a natural question; I'll get to that in a second.
Phytoliths :Archaeologists have many reasons to be interested in studying the remains of plants. Historically, humans have relied on plants as a source of everything from building material to food and medicine. So, identifying plant remains at ancient human sites would help us gain insight into the way of life of a culture at a given point in time, but plants decay quickly, so it's rare to find intact specimens to examine. Even such seemingly sturdy stuff as seeds don't hold up over time, so what do we do? Fortunately, some plants leave behind microscopic traces of themselves that don't decay. Pollen and starch grains, for example, have been used in archaeological studies, as have what are called phytoliths. Phytoliths are very tiny, mineral deposits, almost like pieces of hard glass, that formin the cells or between cells of many kinds of plants. The minerals originate in the groundwater that the plant absorbs through its roots. When the water runs through the plant's cells, the minerals are deposited. So, a phytolith is essentially a cast; a 3-D impression of a plant's cell or, depending on the species, of the space between cells, and when the plant dies, its phytoliths are released into the soil. Now, the plant suffers no ill effects from the phytoliths. In fact, plants can benefit from them. For example, leaves dense with phytoliths are ridged and better able to absorb the sun's rays for photosynthesis and these leavescan also deter hungry herbivores. Think about it. If you were an herbivore, a plant eater, would you prefer to chew on a nice, soft leaf or one full of hard mineral deposits? Now, researchers have been actively analyzing phytoliths for about four decades and they've proved to be extremely important. You see, in addition to the fact that phytoliths don't decay, the shape of a species' phytoliths is as unique as your fingerprints are to you, so we can tell what species left behind them phytoliths we happen to be studying and with advances in technology, like computer imaging and the electron microscope, we can even distinguish between closely related plants like wheat and barley. That incidentally is something we couldn't do until recently because the only tool we had was the standard light microscope. The electron microscope, which uses electron beams, allows us to see details we'd never see with light microscopes. Ok, so what exactly can phytoliths tell us about the past? Well, their presence in residue in vessels used for cooking and storing food lets us know what a population was eating. We can also determine when a particular plant was first domesticated. For example, we use phytoliths to distinguish between wild and domesticated maize. This is actually something researchers want to know about maize; when did people first start to plant it as a crop. So what we've been able to do is identify ancient sites of maize agriculture, take samples from different soil layers, and study the phytoliths from each layer. The deeper the layer, the older the soil is and we can date the soil layers. So far, we've been able to trace domesticated maize back nearly 10,000 years. It could be even older of course. Technology is making advances all the time. Now, we couldn't have studied the domestication of maize without phytoliths. Granted, pollen can be useful. As I said, it resists decay and it's possible to determine to some degree what plant a grain of pollen came from, but consider the purpose of pollen. It's to be carried away from the plant, right, by wind or animals. The plant contributes to the continuation of its species by spreading pollen around, so I'd argue that pollen is only a very loose sort of indicator of land use for the site where it's found, but phytoliths, on the other hand, are generally found very close to where the plant lived. They're deposited in the soil where the plant decayed. So, if you find a high concentration of phytoliths from a domesticated species of plant in one area, it could be an indication that you may have discovered a field; an agricultural field. Now, there are several databases and guides that identify the phytoliths of thousands of species. This means when we come across a phytolith, we can look it up in these resources and find out what plant it came from.
Ali Koushki
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