before the last ice age great mammals ruled the plains of North America woolly mammoths and saber-toothed cats and other extraordinary animals I can't see anything like it today but then suddenly they disappeared and nobody really knows why it happened so fast did humans kill them all man probably came to North America as a super predator or was their fate more like the one we face today with our climate in crisis we need to know how our planet responds to such events or was it something from outer space now a new theory has blown the question wide open it would have been hell on earth been a very very bad day and scientists are fighting over the meaning of startling new discoveries you need extraordinary evidence and I haven't seen that yet Nova wayde's into the thick of this controversy in hopes of finding the answer this is a this is this to me is a Mona Lisa image this is science in action the stakes are high the outcome uncertain right now on Nova go inside the investigation to solve the mystery of this last extinction thirteen thousand years ago the Earth's climate was not unlike ours today but then suddenly it changed radically it was mysteriously thrown back into the Ice Age and some of the greatest animals that ever lived vanished enormous creatures including the woolly mammoth but a modern elephant with thick fur and huge tusks and the saber-tooth cat vicious predator built more like a bear than a lion these magnificent animals dominated the earth for more than 100,000 years then like the dinosaurs some 65 million years earlier disappeared across North America in what is a geologic instant but unlike the dinosaurs nobody really knows why there was an incredible diversity of animal life an incredible diversity with it you can't see anything like it to date Gary Haynes an archaeologist at the University of nevada-reno studies the remains of these animals and their modern relatives to try and figure out what happened to this incredible diversity of animal life we had several kinds of mammoths mastodons we had big predators and we had a lion is even bigger than the one in Africa today very much looked like it we had saber-tooth cats probably the most memorable animal of all it looks like a huge cat but it's got these funny fangs some of these dates are big arcing teeth that looked just like the saber or dagger blades in all there were between 15 and 35 types of large mammals that went extinct suddenly including giant sloths it could be as tall as a giraffe with a girth of an elephant there were some wonderfully odd creatures - like the glyptodont imagine an enormous armadillo with a big armored cover while these are well defended against predators you don't see anything like that today sometimes they'd probably reach the size of a Volkswagen Beetle there was such a rich assemblage of animals come in here we go to Africa on Safari well that was what it was like in North America all these animals were wandering out great diversity of large animals beautiful animals and they were lost in an instant it seems geologist James Kenneth is also fascinated by what killed off these animals and several of the discoveries throughout his career helped illuminate the mystery it is such a long-standing passion that he in fact wrote about it in his very first scientific textbook at age 11 I was going to be a geologist when I was just 11 years old and I wrote some books and ones on paleontology there's a picture of a saber-toothed cat here's my rendition of the woolly mammoth obviously it must have been interested in what knocked these animals off because having explained what this megatherium is as giant ground sloths for South America it says having no protection the caveman killed it off because of its stupidness but there is nothing stupid can it says in trying to figure out why these large mammals disappeared especially today when humans worry about changes in our environment so much happened so quickly was a sad day that these were lost he was of Lawsons lost so suddenly the extinction of these animals has perplexed scientists for centuries but today there is a controversial new theory that might just explain it Allen West is digging for the evidence a former geophysicist for the mining and oil industry West is now using his expertise to investigate this mystery millions and millions and millions of mammoths mastodons saber-toothed cats an American camel American horse they all were happily grazing across North America and they disappeared right at this boundary they vanished exactly at this point this extinction boundary plainly visible in this riverbed in southern Arizona near the Mexican border shows up right under an ominous dark layer of Earth formed by decayed plants and algae it is called the black map what I've done here is remove some of them sediment that's above the black mount and then I'm removing the centimeter so the half-inch that's right below the mat and this is where the mammoth would have walked so this is the action zone right there the beauty of this mat is this is an extraordinary snapshot into the past it's so rare in any kind of geologic record to be able to point to a spot and say here's where something happened very suddenly in the past three years West has dug into his retirement savings shipping boxes of dirt to colleagues around the world trying to solve the mystery West has become his very own FedEx hub of ice age dirt in a tantalizing early discovery the team found traces of iridium one of the rarest elements in the Earth's crust that discovery meant that they could be onto something really big in the late 1970s a Nobel Prize winner named Luis Alvarez and his son Walter also found iridium in geologic layers from 65 million years ago the time when the dinosaurs got wiped out it is a stunning find while there are mounting found on the surface of the earth there in tiny quantities they are however in high quantities and meteorites and other cosmic material so if you find a peak in iridium in a particular layer then the first suspect is was there a cosmic event as the evidence mounted the verdict seemed inescapable an asteroid from outer space wiped out the dinosaurs the era of giant beasts that had ruled the earth for millions of years ended with a bang so do elevated levels of iridium just below the black mat mean that the giant land animals of the Ice Age shared a similar fate Allen West and James Kenan a part of a growing team of scientists that are analyzing this new evidence and now propose the 12,900 years ago a comet slammed into the earth this cosmic catastrophe would have devastated the great land animals it's hard to comprehend the disaster one of the closest things we have to picturing it is the impact of a nuclear bomb or perhaps several of them if you imagine multiple nuclear explosions occurring over wide areas generating major pressure waves flash heat waves knocking down forests and this led to wildfires over wide areas major destruction of the vegetation the burning over broad areas of the continent would have destroyed the food resources for many of these animals and we suggest that is why the larger animals preferentially became extinct the larger the animal the more devastating the effects of this would have been there would have been hell on earth been a very very bad day surely such a bad day would leave behind obvious evidence like this impact crater from 50,000 years ago but so far no crater has been found and that means the impact team needs to find other compelling proof and they are now going to the ends of the earth to do so including here at the Greenland ice sheet Pole Majewski from the University of Maine has joined the team and is particularly well equipped for the job he is one of the world's foremost glacier experts and has traversed more of Antarctica than anyone else there is any evidence sealed away in this magnificent glacier of a comet that killed off the great animals Majewski wants to find the reason he might be able to is that this ancient ice is not only beautiful but it is also an exquisite frozen library of information about the Earth's history these icebergs have captured within them a remarkable story trapped within every single year's worth of snow is an amazing archive of what the environment was like at that time these glaciers are like giant computer hard drives filled with icy data including ancient microscopic dust the snow itself holds all of the little dust particles chemistry that comes out of volcanoes from forest fires of meteorite impacts somewhere in the enormous Greenland ice sheet is the very snow and dust that fell when mammoths walked the earth and possibly the chemical trace evidence of a cosmic impact that wiped them out but how can you possibly find that specific layer of ice during the brief Greenland summer Nova brought Paul Majewski here to take up a challenge my F ski brought with him his colleague Andre curve atop an expert in analyzing glaciers for microscopic particles is key and curva table will be looking for evidence of the impact sealed away in the ice particularly extraterrestrial materials like iridium the clue that helped solve the dinosaur extinction the first step though is the daunting problem of finding the exact layer of ice from twelve thousand nine hundred years ago in the vast ancient Greenland ice sheet we can will not move those two dates because we have an eclipse happening and that is why Majewski is working with JP Steffensen Danish scientist who knows this glacier as well as anyone in the world if you look here you can actually see there's this white line between the two black ones and that's the last layer of this ice HS and right here the ice start moving the layer of ice they're looking for is located between two distinct features caused by ice age conditions glaciers preserve snow and annual layers it can be clearly visible much like tree rings at the edges of the Greenland ice sheet these layers get exposed it's similar to the way layers of earth are exposed at the black mat and there is another parallel just as the black Matt in Arizona appears right where the animals went extinct here in Greenland there is a visual marker of this time as well ice from the last ice age is gray in color because the arid climate during an ice age erodes the soil puts a lot of dust into the atmosphere that gets trapped in the ice these bands of color alternating between gray and white can be clearly seen in this aerial photograph the ice from the time the mammoths died off should be right between those bands of gray and each year during the short Greenland summer the glacier is not covered in snow these color differences are visible on the surface of the ice this stark ice is what we call velvet ice because it has such a velvety rollin soft way of running and then you see in the background you have much more bumpy and whitish ice comes up you can see almost the other incision up there to the hill Steffensen has analyzed this area and found evidence of ice from this mysterious period using these color differences he zeroes in on a slope with both colors of ice this is a promising spot but then again as you know Paul in science you have to try and hope you're right but that would be my my best guess right now this is science in action well and also a very long way to come on a guess even an educated one I want to make sure to sample the upper part but confirming if this is indeed the right spot we'll take a sophisticated molecular analysis it can only be done back in the lab for now the job is to collect the samples and hope they're in the right spot just try the youth jiggle Majewski and kirby tov cut a 17 metre trench down the hillside into these exposed layers from the more recent ice to older ice deep into the Ice Age samples are taken in 15 centimeter sections that way any change in the levels of extraterrestrial materials like iridium will show up many different samples are needed especially clean bottles are used to collect ice to analyze for the presence of iridium to do it other samples are collected to test for oxygen isotopes that can help determine the exact age of the ice and finally chunks of ice are taken to see if there are other trapped clues that could be the fingerprint a cosmic catastrophe the stakes are high only when these samples are analyzed will my Eskie know if this trip was a waste of time or if it could yield the smoking gun proof that earth was slammed by an object from outer space only twelve thousand nine hundred years ago an object big enough to blast up to 35 kinds of animals into extinction truly an extraordinary claim it's not impossible that you could get an event like that that recently it's just extraordinarily improbable and when you're making an extraordinarily improbable claim you need extraordinary evidence and I haven't seen the extraordinary evidence physicist mark boslough analyzes impacts of comets and asteroids he says one way to evaluate if such a devastating impact occurred is to calculate the statistical probabilities of it happening the odds don't look good you have in probability stacked upon in probability we're talking about something that may happen only once in the entire age of the earth and I have a hard time accepting something like that happened at recently Vaz Lowe uses some of the Department of Energy's most powerful supercomputers to model the physics of various cosmic impacts and midair explosions in this simulation I bring in an asteroid a small asteroid about thirty thousand miles an hour and it explodes three miles above the surface and is able to show clearly their devastating power at ground zero temperatures as hot as the surface of the Sun and this vortex is moving at supersonic speeds so it's like a ultra white-hot tornado and this is one of the most extreme events I think that could ever happen on the surface of the earth baaz lo says that while an event like this would certainly devastate the environment and the great animals he thinks there are far simpler explanations you know Occam's razor the simplest explanation is probably the best one and there are other hypotheses that to me don't seem as extraordinary it seems a little far-fetched there's a lot of species that did not become extinct which would be hard to explain why weren't they affected of all these other large mammals were why weren't deer and elk and bear affected why did they survive could there be a more down-to-earth explanation for these mysterious extinctions possibly and to understand them it is important to investigate what the earth looked like at that time and that is the work that Vance Haines a legendary archaeologist from the University of Arizona has done one day in the 1960s walking through this riverbed hain Sawbones lodged into the canyon wall they turned out to be from a mammoth his ensuing investigation of this site has given us one of the best pictures of life here some 13,000 years ago that picture is hard to imagine looking at Arizona today instead of sprawling cities were valleys full of animals and instead of the retirees and golfers who flock here there were other immigrants the first well-documented humans in North America the Clovis people the Clovis people appear to have arrived in this area just before the black mat is formed a little information we have about them comes from their beautifully engineered stone tools at spear tips called Clovis points they're essentially functional art this can be used both as a as a knife as well as a projectile point but the basic function of this is for killing a game but yet they took the trouble to get very nice symmetry these sleek stone weapons were a major advance in hunting technology I think from seeing their stone technology they were very sophisticated people these were probably on a spear that was used for either thrusting or for throwing with a spear thrower so the idea was once they penetrate an animal this would come off this would stay with the animal but they would then have another one sort of reload and be ready to go again Keynes's excavations at the black mat prove that the Clovis people hunted the mammoths and other animals here right up until they disappeared and this is where these animals just came to a sudden yet we've repeatedly dated this level right here at twelve thousand nine hundred years ago my bottom line is something happened twelve thousand inode years ago that we don't understand efforts to explain this mystery have led to some very peculiar clues the value of this evidence held under lock and key in the basement archives of the Arizona State Museum is no BS but the evidence itself is exactly that an ancient piece of poop giant sloth poop yes you heard that right giant sloth poop it is not classy science working with this stuff in the lab it smells like you know what Jim King the former director of the Carnegie Museum of Natural History says the sloth dung is a goldmine of evidence about how these animals lived and possibly died fossilized done is fabulous because this in my hand is the evidence of what these animals ate to see all these fibers little bits of twigs much of this will be Joshua Tree fiber the manure discovered in a cave piled five feet high is high in carbon therefore makes for perfect radiocarbon dating the last maneuver in this cave dates to around twelve thousand nine hundred years ago the time the black mat appears not long after the stone artifacts show the arrival of the Clovis people scientists use that coincidence to support a theory that these early hunters were responsible for killing off the great land animals man probably Kim's North America at that point as a super predator with an IE fauna that had no idea what they were facing the super predator had communication it had weapons it hunted in groups had coordination it had all the things you would do if you and I were going out to try and hunt big animals more recent history supports this theory in Mauritius the arrival of the Dutch doomed the dodo and in New Zealand the first settlers killed off the MOA but could this also have happened to these great animals all across North America the data just doesn't support this it's it's it's inconceivable to me can it says the idea that primitive humans killed off these powerful animals is absurd and while it might happen in small island environments it is impossible to imagine they could wreak such havoc on a continent as vast as North America they didn't have the technology that modern humans have they didn't have helicopters and and machine guns and satellite navigation and so forth it always puzzled me how could they track down that last horse or that last mammoth or that last camel it just perplexed me it just didn't make sense if the human overkill theory as it's called cannot provide the whole answer what else can this is not the first expedition that Paul Majewski is made to these glaciers in search of evidence in the 1990s Majewski drilled into the center of the Greenland ice sheet extracted ice cores going back more than 200 thousand years to understand how the world's climate changed at the time nobody thought to test for impact markers like iridium but what they did find was remarkable the ice cores proved that the Earth's climate can change extremely rapidly sophisticated molecular analysis of the ice can reveal the temperature at the time it formed the ice from this time animals went extinct shows a very unusual change temperatures plummeted it happened so fast when you think about it it's it's unbelievable it's a complete change in the state of the climate system it would be the equivalent of going from maybe to three months of winter in in northern New England let's say to 11 or 12 months of winter throughout the year in possibly less than two years the annual temperatures in North America dropped up to 18 degrees Fahrenheit which may not sound like a lot but the last time it got that cold in what is present-day Chicago it was buried under a mile of ice throughout much of the world climates changed some places got colder others dried out causing more fires was this sudden climate change not the Clovis hunters what killed off the great land mammals there's periods in geologic history where things really go haywire and this was one of those times we were going through a major climate change well some animals just don't make that change Gary Haynes says that's true but there were other similar periods of climate change and these animals survived why would this one kill them off he believes that while climate may have played a role man was ultimately responsible we don't actually like to think of how destructive we are even a small amount of killing may have been a decisive factor with some species that were already stressed by climate change leading to eventual extinction humans have always had an impact on her environment the disappearance of the great land mammals is one of the most dramatic and recent extinction events in Earth's history the last extinction it also happens to be the time when the Clovis artifacts disappear from the record the only history we have is written in the chemistry and archaeology that remained behind and so far these clues have not adequately solved the mystery now the new theory of a cosmic impact has blown the question wide open the initial finding of iridium the black mat was a startling discovery but the levels were much lower than those found at the time of the dinosaur extinction because cosmic dust accumulates naturally on the Earth's surface the low-level iridium findings are not a smoking gun but we're a good tip-off about where to look for more clues including the black mat in Arizona there are at least 31 sites in North America and six in Europe where the impact team has collected dirt from the time of the extinctions that means there is an awful lot of dirt to analyze James Kennedy and his archaeologist son Douglas are literally up to their elbows in it to soar Allen West Jim wiki a geologist and Ted Bunch was retired from NASA and new technologies developed since the hunt for the dinosaur killer opened up the nanoscale natural world that is embedded in these samples of earth what Western team are finding in his ancient dirt he's extraordinary what in the world is that stuff okay this is a split open carbon Sphero and we know from the chemistry that these are formed from burning pine trees burning spruces if this is tree sap in effect that's been scorched burned but the thing that makes this extremely unusual in fact the thing that ties it to a cosmic impact is embedded in the ribs here that you see around one of the most intriguing discoveries so far is buried in the squirrels inside the carbon structures the impact team has found something that was as thrilling to a scientist as it would be to a young bride diamonds nano-scale diamonds to be exact all of the rims of each one of these little holes in here is absolutely laced with diamonds in some cases 30 percent of that kerbin sphere all is made up of tiny diamonds let's take a look at this other case these nano diamonds can be so small that 1 million of them could be squeezed inside a single grain of sand you know if they could get them out there's about a trillion dollars worth of these diamonds spread across the United States so but my cost you trillion to extract on xone all geology jokes aside it is an important discovery it's like looking at a Hubble image of all the galaxies out in the universe I mean there's an incredible number of these things all right let's get the coordinates on that exactly how these nano diamonds are formed is poorly understood 1:31 the team has discovered several different kinds most diamonds found on earth are cubic and have a highly symmetrical structure but one type they are finding the hexagonal diamond is not at all common the only known way to make these is through a high-pressure blast such as an impact we see a little hexagonal outline okay that's cool these are hexagonal diamonds hexagonal diamonds are not found in the Earth's mantle they do not occur terrestrially they only occur in craters in meteorites interplanetary dust etc they're all et it's very hard to explain the presence of such huge numbers of diamonds over such broad areas of the planet other than from the the production from an extraterrestrial impact but is this necessarily so I'm still skeptical because they really are invoking a large comet maybe a couple miles in diameter something that big has enough amass to carry it all the way to the ground and it would generate a big crater would make a big hole in the ground mark boslough says that we don't know enough about the formation of nano diamonds they are the indicator of an impact where is the crater 13,000 years ago is not very long ago in terms of geologic time that would be a very young crater it would be very obvious if something like that existed in North America when the dinosaur killing asteroid theory was proposed no one could find a crater either but then more than a decade later they did mostly underwater and it confirmed the early iridium findings so far no one has found a crater from the extinction of the large land animals we'll a crater eventually be found related to this event or could there be another explanation that is the question that Peter Schultz is trying to answer and he can simulate impacts on a much safer scale here with the hypervelocity gun at the NASA Ames Research Center outside of San Francisco ok a small glass pellet is used as the bullet in the gun and it simulates the cosmic projectile the pellet is loaded into this 40-foot long gun and fired into a vacuum chamber to model different possible impact scenarios as this part kills me in this test Schultz wants to know what would happen if the object from outer space or the glass bullet broke into thousands of pieces before hitting the earth an idea inspired by the 1994 Comet shoemaker-levy that broke apart before impacting into Jupiter well this could be interesting especially with any cameras I hope we get to see the spray pattern oh that is so sweet let's let's go see the let's be cameras him high-speed cameras capture the impact stop the action at up to an astonishing 1 million frames per second oh go back come on yeah yeah we have thousands millions of small fragments slamming into the surface simultaneously okay now that that bright stuff in here that's the projectile that's carrying any yridian any signature of the impact and then after hit it would have been blown all over the place and redistributed across the earth that's where the gold is that's the stuff that tells us that was an impact this is the massive crater a single impact would form pretty obvious so what size crater would show up in the same sized comet broke up into thousands of smaller objects we can actually see the individual small craters and then the wind came in and destroyed it the earth would recover from this very easily just a little bit of rain a little bit of weather and you lose the evidence a second scenario is that the comet or at least a major part of it would have slammed into the Ice Age glacier that covered a large part of North America at that time that can be simulated here with the impact gun using a large piece of ice you have this really intense temperature the critter just simply forms in the ice the ice around it cracks venge simply disappears again you lose the evidence the ice acted as this flat jacket and impact into the glacier could be another way to explain the lack of a crater the burden of proof still lies with the common theory team and their strongest evidence the nano diamonds is under attack mark Baz low believes there may be other far more likely explanations for the nano diamonds at the black man for instance tiny micro meteorites are raining down through our atmosphere low levels all the time was there some way during all the environmental changes happening at this time but they became concentrated right under the black map we have this constant rain of micrometeorites those contain diamonds so the question is can you concentrate those diamonds by some mechanism that changes when you have abrupt climate change so now a troubling new question has emerged when did these nano diamonds appear did they rain in slowly or a pure all at once fortunately that is exactly what the glaciers and their amazing library of information can answer this is a classic example of how the surface of a glacier can capture an environmental record you see dust and debris being blown onto the surface of the glacier more snow comes in and must and effectively gets trapped and then held there for decades centuries thousands and tens of thousands of years so we have an exact archive of what happened at that time a modern example of this will be smoke from the recent California wildfires this satellite picture shows how it rises into the atmosphere eventually that smoke will make its way to Greenland to be captured in the top layer in the ice sheet this glacier is in effect a safety deposit box with a date recorded of when it was sealed off the key question is can my ascii find the nano diamonds or iridium within one narrow layer equivalent to the layer beneath the black mat from twelve thousand nine hundred years ago and not above or below that would prove that this evidence did not rain down gradually over a long period of time remember how samples were taken across thousands of layers of ice history to see if there is a spike in iridium Carbon spherules or nano diamonds now back at my f skis climate change Institute at the University of Maine the field samples are run through different tests the first batch of samples is analyzed to answer the key question of whether or not they succeeded in finding that narrow layer of ice from the time these animals went extinct this machine can do that by analyzing the atomic structure of oxygen in the ice which can reveal the exact temperature when the ice formed my FC and team have already done this analysis on more than 100,000 years of ice from the Greenland ice cores so the results from the new sample are compared to this well-established record it's like comparing temperature fingerprints remarkably the lab results from this period show a suspected match the likelihood that we would find it was was very very small if it's worse than looking for a needle in a haystack and suddenly to see it in front of you on the screen it's pretty amazing it looks like Majewski Steffensen and kuba tov found the ice from when these large mammals vanished in the lab they test for the rare element iridium the finding that helps solve the dinosaur extinction the results show a spike right at the time when the animals disappear but not a very big one it's not that they're catastrophic ly higher they're about three times higher than background but to have a peak of that level preserved is pretty fascinating stuff this iridium is a tantalizing clue but just like it the black mat it is no smoking gun because the levels are low now it comes down to the nano diamonds which are also the hardest to process searching through samples from a 17 meter trench for evidence it is a million times smaller than a grain of sand is a very very painstaking process that job fell to Allen West pretty hard to work with a 10 micron sphere all when the meticulous work is finally done and West has managed to prepare samples for the transmission electron microscope nova asked paul Majewski to join james kennedy materials scientist chris Mercer and UC Santa Barbara to have a first look at the evidence now we can see increase magnification ok so that's that's remarkably just tons of all answers it is clearly and immediately remarkable the first sample they look at from the suspected time of the extinctions yes it consists of a large number of particles clearly rained out of the atmosphere this has huge implications there's no way you're going to get the these kinds of particles in the ice sheet unless they're raining out of the atmosphere it's amazing if these and these are diamonds and this is a remarkable a remarkable breakthrough Mercer conducts a test to see if these particles are diamonds a beam of electrons is shot into them which casts a series of rings each crystal structure scatters the beam in a unique way forming an identifiable pattern immediately a familiar pattern shows up this is odd this to me is a Mona Lisa image it's obvious Sciences guys these black specks are nano diamonds in an extraordinary concentration in this one slide the test reveals that there are different kinds of diamonds including hexagonal diamonds the clearest indicator of an extraterrestrial impact a diamond believed to have had its atomic structure shaped by massive force I've never seen anything like this perform this is exciting to me very excited I'm looking for cubics in the list and his examples coming out say hexagonal in Greenland and yet here it is alive and true in the Greenland ice sheet it's particularly phenomenal because the Greenland ice sheet contains 450 thousand plus years worth of ice we're trying to find a little layer and bang the very first slide that we look at has billions of nano diamonds in it the thing that is probably the absolute key to demonstrating that there is a swarm of comets at this time looking at this kind of material is dramatic as a well for James Kennedy this moment of discovery becomes overwhelming it's it's so excuse me very exciting well it's it's exciting because exciting is really not the word it is it's it's it's a an experience you usually don't have much in your scientific career moments of intense discovery are very emotional for scientists when scientists make discoveries that they think are a really important breakthroughs if you like Eureka moments they isn't elation there's a relation and emotion these are emotional moments the hypothesis predicts that the diamonds should have been there and they were so far the nano diamonds have been found only in the layers of ice around the time of the extinctions a clear indication that they did not rain out of the atmosphere over a long period of time every single time we find another piece of evidence like this from the ice sheet you think to yourself my goodness what else could possibly be in there they capture everything that was going on in the atmosphere and in this particular case the evidence is very very dramatic each new finding bolsters the theory that a comet wiped out the great land mammals twelve thousand nine hundred years ago it is still early in the investigation and no doubt other explanations will be suggested extinctions are very messy things and many stressors both climate change and human overkill we're altering the environment but clearly this new evidence for a massive impact is changing our understanding of the disappearance of the Ice Age animals of North America it was a sad day for North America the loss of these animals the whole landscape would have been so different in fact even the human cultural development would have been dramatically different in the last 13,000 years if these animals had in fact survived on Nova's last extinction website watch video extras examine a collection of beautiful Clovis artifacts and try your hand at identifying ancient stone tools find it on pbs.org this nova program is available on DVD to order visit shoppbs.org or call us at
