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A Rose:Good evening. Im Alexander Rose the executive director at the Long Now Foundation. As many of you know we start these talks with a long short. A short film that in some way exemplifies long term thinking and often we cheat and use things like time lapses. Tonight its a little different but before I introduce that, I just wanted to mention there is a whole other series now going on that Long Now is producing. At our smaller venue the interval, this Friday we have a 5PM kind of a social hour talk with Rachel Sussman who formerly spoken the series on her project photographing organisms that have lived longer than 2000 years all over the world and her book is just now coming out and will be hearing another talk from her as well as she will be doing a book signing that is Friday in Fort Mason and afterwards you can go to get your dinner at off the grid from all the trucks and Tuesday we have Violet Blue speaking about her newest book Smart Girls Guide to Privacy and she has all kinds of good tips for not let your digital data go out into the world. So tonights Long Short is actually by someone who has, I believed agreed to give a talk in the series when he walks by in about 5 years and he started his walk out of Africa a little over a year ago. This is a description of his project right before he left. He emailed us from Israel where he is now and gave us permission for this video and they are actually soliciting support for their effort and there is a URL at the end to help them get him through walking the entire out of Africa track down through the America over the course of 7 years. Enjoy. Movie:(whistle) Next year I'm taking a long walk retracing our ancestors first great migration across the planet starting in our birthplace the Rift Valley of East Africa and walking north through the Labont and then eastward across the great plains of Asia to Arctic Siberia from where I have a boat to the America and rumble down the western plank of Patagonia the last corner of the world where our ancestors ran out of horizon. I'm a journalist and I'm trying really hard to return a more human phase of storytelling and not just getting in and out of assignment but walking with people digging deep into crucial stories that we missed because we are all moving too fast to listen. I'm as worried as anyone about the troubles we faced the next century ahead. Climate change, resource shortages, mass migrations, war. Our ancestors also forecame huge obstacles in their primal journey across the world whether it was ice ages or massive epidemics or famines. My long journey will be difficult and I'm not so nave to believe that the world can't kill you in an instant. It can. But in my experience when you slow down, people tend to open up to you. The world its home after all. [applause] S. Brand:Good evening I'm Stewart Brand from the Long Now Foundation. The Long Now Foundation adores desert I think its because the Long Now adores deserts because when you go into the desert you step out of biological, you step out cultural time, you step out of biological time and you are stuck into geological time and things in deserts since the water isnt there anymore, are incredibly well preserved part of it because there is no water there rotting them and there is kinds of traffic to wear them down. Further because humans dont go there anymore because the water is not there. If you want long view of long horizon, the desert has large quantities of that. Our speaker tonight has been dealing with the best of all various deserts, the Sahara. It is bigger than anything if you look at earth from the space and big events are Antarctica, the oceans and big brown amazing of that of North Africa. Everything is south of the Mediterranean all the way down to central Africa is a single immense unexplored uninhabited event that has been an event with various times in human history and there is again a various respects. And our speaker looks at things out there and a very few explorers go there and look at things out there. They are often looking at things that nobody has looked at or thought about in thousands of years. Thats what geological time is like, to experience, to examine and to dissect and analyse and then think about it. And he is best at that, our resource speaker Stefan Kroepelin. S. Kroepelin:Thank you steward. Hello everyone does the sound work? Okay, thank you because this one out of my pocket. So I'm going to talk tonight on my favourite subject, the Sahara, and particularly on the mysterious desert cradle hidden in the deep Sahara. The Sahara is, Steward just mentioned is the largest desert on earth it covers almost about the size of the United States 9 million square kilometres so one lifetime is not good enough to know at least a part of it and of course the Sahara doesnt exists as many Saharas is like a big difference between the Canadian border and Florida and the east coast states in California and the same applies to the Sahara of course. So I'm focusing on the eastern Sahara which to the present day probably is the least explored part of this big desert and even 100 years ago it was particularly completely unexplored as you see on this atlas from 1922. And so its a big opportunity for geologist and archaeologist like mine of wrinkling still these days on research frontiers and thats part of the sites I have been working to in the past 35 years so each red spot can stay for a few days but it can also stand for a few months of field work and this was only possible within the scope of several large scale long term research projects called collaborative research centres which provide as a logistics and the possibilities to work in this remote places. This is an outline of what I'm going to talk. So first of all, talk about the bits on the working conditions which are a bit different from geological work from other places on the globe and then I will provide a few examples of outstanding sites but its just a very short selection of sites I could promote in an hour and finally I will try to condense everything into a short synthesis and conclusion on the origin. So going to your study area sometimes take weeks and months and there is no tracks because the eastern Sahara is practically devoid of wealth and near surface ground water. There is no bed winds as in the central western part of the Sahara that means there are practically no tracks and you always have to find your own way especially during the pre GPS period that was sometimes a bit complicated. You have to carry everything you can and for example this a few cabibish bed winds were the only people we met during the first 10 years of field work in the eastern Sahara where the last prehistoric people left some 5000 years ago and most places you go, you are the first human homosapiens to return to these sites and sometimes you have to drive down quite steep slopes, sometimes you have to climb up a couple of hundred meters which takes sometimes a whole day just to get 2 meters up building your own road using sand ladders. Sometimes you have to shovel away half a dune and prepare your own road to find a decent down and escarpment in some places well thats daily sports, this is taking out your vehicle which is particular difficult in soil to marsh deposits which is near surface ground water sometimes the whole fleet got sank like Kian the great sensi of Egypt were sometimes the cars stuck 50 times in a row and in the evening you know what youve done that is certainly no research these days, and even worse if you have 26 to un trunk get sunk in them a sort of muddy salt deposits and you can go on it for some while until it breaks down and unloading 18 tons of payload and getting three week out of it made our day off the last day of 1983. So sometimes you have to build your own road just to get down from plateaus into the fall end without knowing whether you will make it down again because sometimes if for example, well it gets plucked and your down with the cars and you have a serious problem and sometimes it gets dusty, most people dont like it, we like it because these are sort of paleo like deposits so called fish-fish deposits and the second later you wouldnt see the car anymore. Sometimes you have kind of mechanical problems like in this case where the back exits of our unimog was cut like with a laser beam 100 km away from the Nile and what we could do is use backhoe shovel as a force wheel and make it walk the last 50 miles back to the Nile. Sometimes visibility is quite that like for a few years ago when we have that one week long dust storm which is much more difficult than sandstorms because sand, normally if it doesnt fly as in 2 meters above ground so in a Kemlon top of the car, you're easy while driving for a week with such visibility of just a few yards poses some problems especially if you have to cross dune fields. The biggest problem in the past few years since our paradise our foods, where we stayed up to 6 months in a row in one year, we saw meeting a single person today of course insecurity and normally you only find art buried in the last minute but since for example is a detachment, official detachment of the Chaldean army and not rabbit. If this would have been robbers or bandits I might not be here for this lecture today and even worse are the land mines which are widely distributed in the exit zones two hour study areas in the central Sahara usually remains bad, remains from the Libyan war we chart for example where you're not supposed to leave one check and me going in front thats one of the rare occasions where all my colleagues are really following in my track directly which is also normally not often the case if you're unlucky then you hit an anti-tank mine to cut the long story short the two person just run across it was a miracle but a few minutes later nothing of this brand new Mercedes car were just some liquid aluminium and going there of course you have to find a camp site every night because usually geologist are bed wind so we move, normally we get our walk weekly done so I prefer camp sites in the downwind side of this large ????? which can weigh up to 100,000 tons which are transported by the winter a couple of meters up to 8 meters a year so still not well understood physical features and of course everybody knows its quite hot Sahara sometimes plus more than 50 degrees in the shade. Of course the east little shades so if you forgot to take your foot and then used a car and then you got heavily sunburned within minutes on the other end much worse of the cold nights which including a chain effect which can cool down in the winter season and thats the only of the year when you can walk to minus 20 degree Celsius, I dont know that exactly in Fahrenheit but believe me its cold. And thats our kitchen if there some sand storm and we forget to close our kitchen and then there is a room for some cleaning up in the next day. So enough with it, that would take up a high percentage of our work in the Sahara, so when I was young I thought well one day, a preparation is needed for one hour of serious field work sometimes in between I got it one week is necessary from writing proposals down to getting the permits and customs and transport and so on for one hour, but anyway thats a very low relation between the work you have to put on logistic just to get to this remote areas. Our field masses, I'm not talking about left masses, this would be another lecture but and we are studying more than 50 different proxies as we say to find our payload climate but the most our favourite time is sticking holes either using such small mechanical excavators like this one and then digging a few yard deep holes where you can take the samples and look for archaeological remains etc., which is much better than taking course and if not possible then just digging a whole and go in and look what you find at the base thats geology sometimes. We already dug a 6-7 meter deep holes and that was what Ive seen the whole day taking a section it was just a hole in the top thats in the central Sahara and other interesting more of easier work so I'm taking up stratigraphy this means layers of deposits of former our long extinct lakes and rivers and prior lakes and this is one of the sites For the archaeologist, a lot of time has to be spent for surveying or for mapping any sites and thats a lot prehistoric site where at first I have few people who would think that there is anything left. Archaeologist excavations are extremely time consuming like Kian the great sea of sensi where sometimes you need a couple of weeks just to excavate a few square meters but every excavation means destruction, that means to have to resort to speak parcel of the kind of artefacts which have been produced at the site and to tell who did it what skills did he have in which direction was the wind blowing and so on. You have to take this time not to lose any possible information to your best of conscience. Excavating one new listed grave for example can also take one week for 4-5 archaeologist the same applies to remains like this elephant jaw embedded in paleo-like deposits which is also its not just taking it out and sampling it but getting all the information possible so now why all these kind of work and the first replies of course, academic, its first of all to say well to the ocean, ocean course and the ice course from the polar region tells the whole story for climate change on the continents and thats in the end where people are living, used to be living and will be living in the future and as a man is neither a fish or a penguin, the important information has to come from terrestrial paleoclimatology and there are as many things for example which where that the whole scene, the post glacier period of the past 11,000 years was considered based on polar research at the most stable period as you will see in the Sahara the opposite whereas the case. Another hypothesis which was based on ocean course taken by my good friend Peter Demenocal from Lamont in New York, was that he was claiming by analysing or interpreting ocean course that the onset of the green Sahara happened within decades within one generation and is the same thats what he claim was his desiccation of the entire Sahara of what he call the African humid period happened also in a few decades and that was while which it didnt go along with our data which has been collected and of course that general approach is to see how climate and environmental change, changed the socioeconomic way of life of the prehistoric dwellers in what is today a hyper area desert and whether that included cultural change and whether that or that has brought some evolution which is important to the present today. And so paleoclimatologist always more amazing thats why I asked my friend Craig Reddit put it on the leading text book on paleoclimatology once humans are in. Paleoclimatology without humans is a bit let exciting and of course I recently stumbled on this quote from Stewart, the oceans keep displacing the important in our daily lives and that made me think why on earth or why someone likes me who goes into the desert for more than 40 years spend their a couple of months every year, there must be some hidden motivation if not probably you wouldnt do it and some people only go once and never again. And there are many things which come to my mind. I mean, first of all, in your camp site in the night we have a 360 degree horizon around you and you hear the blood in your veins, from blood veins say you can even listen to your bones and you hear the meteorite if you have some meteorite going down in the night you hear the sound. When there is no wind, theres an absolute quiet. Of course, you stop being a consumer like in the western world that consuming ancient more or less because there is nothing you could buy and so on the same as money loses any importance because the only thing thats good for when you stay months without meeting any people is may be to light a fire. Of course, there is no internet and so thats the whole existence which in one way loses any importance under this hotel of a million stars which you have any night when there is no sandstorm and staying outside so listening, thinking about daily problems like finding a parking a lot they sound so absurd once you are in a place you have 9 km of parking lot available and its difficult to explain that to some a few remaining local people there and on the other end, your own existence gains a lot of value because any single drop of water is a miracle more or less. And in the morning you have a sympathy when there is a slight defrost a scorpion crawling out under your sleeping bag so you would never had the idea to kill it because he survived, you survived another cold night or stormy night and he is trying to do his life as you do as well as there is a sort of sympathy which may sound crazy to you but thats really one of the of the motivations you have. So of course deserts are timeless and fairly also I am the one at Long Now subject its probably to state its a fate of the planet every single become desert like the surface of Mars and so on so its with our time and, again before I start we sit before it become too, get too philosophical thats really, I think its no wonder that most religions originated in deserts where you confront yourself. And now I'm showing a few examples one comes from the Gilf Kebir peak sandstorm plateau in the south western corner of Egypt falls of the great sensi of Egypt and you have this almost 1000 mile long longitudinal views up to 100 meters high which run into the sandstorm plateau and some may know it you have seen the film, the English Patient which goes back to one of our tradition, the English Patient in fact was Laszlo Almasy to whom we still have a lot of direct relation and of course the film the English Patient wasnt taken or shot there close to the Libyan border but in Hollywood in Tunisia in some easier places but there I left what was brought on the movie of the English Patient called the swimmers cave where you have depictions of apparently swimming people in the middle of the desert where today there is less than 2 mm of rain fall on an average which from spot of the rock art in this cave. And on this radar image you can see that its in fact of a really fluvial system drainage patterns existing during the period of first half of the hall of scene 11 to 5000 years ago more or less which originated directly at the foot of this cave of the swimmers and recent just a few years ago some Italian tourist explorers found another cave nearby which is probably the single most richest single brick in the all of the Sahara where you have more than 10,000 single depictions ranging from 2 mm to more than 2 meters depicting some monster like features and also depicting some swimming people, person apparently and all kinds of other details which tells a story about the prehistoric life in this remote place when the Sahara or Rolls rolls rasa Sabana in the desert and you have seen many paintings and engravings which may be connected to the much, much later art during their very unique empire on the other end there are still lots of rumors, speculations and do you normally prefer to get some firm evidence before venturing to much demanding hypothesis on the origin. There is a book which our ????? institute edited recently its 5 kg couldnt bring it, but its probably the largest work art documentation of a single site to my knowledge. So not too far away is Wadibacht and usually we give our own names because there is no better you could call for local names so we always term most of the sites ourselves. This is a playa lake like in south western states of today which once had acquired impressing water surface which was born because the water blocked by a form of dune which closed the entire well and only some 7000 years ago that dam of this dune then broke and froze to a natural gap of the water drained and since then there was no more accumulation of deposits which are the only basis for climate reconstruction geologist have and thats one of the sections and where you see, that you have each and every single major rain fall event recorded in some tiny sand layers and if you get radiocarbon dating you will get a more detailed information on the distribution of actual rain events over the millennia in this hyper arid core present day hyper arid core of the eastern Sahara which had rainfall up to 150 mm per year compared to less than 2 mm today and all these deposits are connected to the change in the prehistoric life and economy. So another interesting point is which I would just mention shortly that its not the average rainfall per year which is important but rather the distribution of the rainfall, that means someone sooner summer daytime rainfall has much less impact on the growth of vegetation than absence very light winter night time rains which occur during the later period which provided for much grassland and much more pasture than in the earlier date. That means sometimes the date of frontieology and archaeology are contradictory until you resolve the puzzle. So now as an example is what was once the largest palaeolake in the eastern Sahara what we call west Nubian palaeolake and what you see here is not the backbone of a gazelle but the backbone of a Nile perch which used to live in this place where today no scorpion can survive with a length of almost 2 yards and some places are not covered by windblown sand and with only land for one data we had for there was practically nothing to be seen, but it used to be a very large lake with full of bones that means within 5 minutes you could collect such a collection of fish bones and crocodile bones and diplo bones etc., etc., and also we found some tortoises in this tortoises have been the last proofs that probably what we rediscovered and called it west Nubian palaeolake in fact corresponds with totally it means marshes of the tortoises which are recorded in the written sources by Bartholomew and where the geology, present day geology could also locate these lakes which are well not known before and this what looks like today must should have look like present day Chad today a very large, but very shallow fresh water lake and of course once there is water, there are prehistoric settlements and what looks like these today including a cattle barriers and all kinds of archaeological features probably looked like this when the early cattle were used by the people living around this lake and again, very short sometime settlement sets only after the maximum lake extension has gone because who likes to settle in a marsh which is infested by crocodiles and malaria or mosquitoes and so on that usually only once these lakes, if palaeolake become smaller that people approach while the surrounding environments were no more good for living so they were approaching this remaining lakes until they finally disappeared. For as example, this one which is to the present day practically the least explored part of the Sahara if not of Africa and this is in the extreme north eastern corner of what is today a Republic of Chad only one has a name they tried to cross it riding in front of his caravan on a white horse but he was guided of course by the guides from Kufra as a Libyan oasis ????? and then you crossed it but he was riding at night so there is practically nothing left of his first transacted through this area and he would have died of thirst if the year before wouldnt have been a rainy one exceptional rainy one and so they found water and thats the way they made it into a sub Saharan Africa but that was one trip we did in 2005 on this El Dimar which is as a known, there seems to be a plateau which I have been showing before was 120 years ago that means there was never ever been any scientific research or any other research to the written knowledge and its a high escarpment, these are escarps for a scale where you first have to find your way up even there google doesnt help too much. Sometimes you are driving again on apparently a sandy surfaces which in fact just a small windblown cover on wet fluvial and lake, former palaeolake deposits and this is a dust wits in the end ????? Amazonian rain forest because this dust which originates in Czech today is transported over the Atlantic and provides all the minerals necessary for this arrival of tropical rain forest and that typical landscape its like the surface on Mars town into detail really from many metres to tens of kilometres scale its very similar so this is probably the best analagon for the land forms on Mars on planet earth. And there are some in the north east parts exists like this where you could have a 360 degree view which would look all the same and at this specific position, 19 half degrees north 23 degrees east is what used to be the triangular junction between the 3 empires of France, England and Italy and that was why the small stone can was erected by the only known merits soldier, two soldiers who was sent there to mark the border of the 3 European empires in 1937, so we didnt find it we found it later but they did a very good job in its many kilometres away from the GPS position of course and I was showing this to show that place is like the Eldima tube where there is practically nothing there are almost no prehistoric settlement side. There are no palaeolake that means this plateau must have been what it is still today because Eldima means the enemies country and this has been also depicted like that since history writings and even today if you would run into someone and probably you could still stay for there so many years without meeting a single person but if then for sure these would be bandits or rebels while surrounding of the Eldimar you have this machine in sites which consists of these grinding tools and many many other archaeological material and thats for sure not even any bed wind has passed at this location during the past 5000 years because it would certainly would have taken this Mohakas grinding tool for his wife a ????? for regular daily use. That was my team of this first scientific exploration of this part of the world and now I'm taking you to another part of Chad, in north eastern Chad the energy plateau which is a triangular scape, sandstone plateau. Its like a big labyrinth. So 90% are completely unknown to the present day and probably will still take a generation to explore all these thousands and thousands of miles of box canons hidden in this plateau the size of Switzerland more than 30,000 sq km or may be one day must hire robots who will do the job and first mention of this site was by Gustav Nachtigal one of the early German explorers who did the basic research in Chad but Nachtigal inspired his 5 year travel didnt make it there but he collected all the information by the local people at that time and was inscribing it quite well the surrounding escarpment looks like this in many places. You have real labyrinths which to me are really the origin of the tales of one thousand one night with the labyrinth where Kermit can hardly go through and so on and drew the detail and this is the recent view from a clip we prepare for UNESCO recently where you see that you really can get lost if there is a dust storm, the GPS doesnt work because it dont have a satellite access. You can really die of thirst if you lose yourself inside so even today, you have to take care and some places resemble very much to the monument really but they are much more distributed and much bigger. You have some of the highest rock arches on the globe. You have for example this mushroom rocks which indicate a former land surface and this is evidence of millions of sandstorms have taken everything and they lower 2 meters away. You have all kinds of interesting sandstone pillars, etc., and you have lots of vegetation especially in its western wells because of the higher elevation which collects some monsoon rain still coming from the gulf of Guinea and traversing a big part of sub Saharan Africa to reach there so thats why its been called the garden Eden of the Sahara which is a sort of relic area which is a good comparison for the situation during the green Sahara 11,000 to 5,000 years ago. We also have some very small trenches to go to which sometimes open up to cathedral like structures where you find trees and birds and water and so on and you have the famous ????? where it is still the last remaining crocodiles in all of the Sahara. The last remaining crocodiles which have arrived 5,000 years of heredity which once came from the Nile going along the Buddy Hower to reach the end of mountain and the last population now is 7 and there is against all the forecast of all biology, there is a new born crocodile one which got out of an egg last year. So even sometimes a minimum population is good enough for proliferance, if thats the right word. So from here you probably see nothing at all but if you look closer you will find these two Barbara sheep, mouflon which are still living in this plateau which are extinct in most places of Sahara. You will also still find lots of other animals which are completely extinct anywhere else in the Sahara and we met people who have never seen a white person in their life, never seen a western or European in their life who live in very remote places on top of the plateau and once they got to know that we wouldnt do them any harm, they were very friendly. That happens through the present day. In the Sahara, people have never seen any white person and most famous of all is the rock art of sanity which in my view is a part of any other rock art sites of which are a few in the Sahara including the Tasali achea in the uncounted breeze and caves there and some which give a very clear almost photographic impression of prehistoric life in this mountainous area during the time and you can already can see some details as it is but once youre applying from color enhancing message and you see much more and you can really find details on the dress that women had, the type of dance when they went out for party or whatsoever taken from into details on the hut, how their hair dressers etc., many, many other details which are hidden there and which really give direct insight in this prehistoric way of life. 9,000 to 2,000 years ago more or less and this is all natural colors which survived uncounted hours of insulation, heavy insulation and sandstorms and so on and they are still there. But the most important any male depicted where the cows which are apparently at a much bigger significance to prehistoric people, than elephants or giraffes or hippos or rhinos and so on. And in the later period during their iron age you had typically the sort of horse rider until the camel people arrived around 2,000 years ago because Kamestra introduced into the Sahara only about 2,000 years ago after the Persian invasion of Egypt and there you see all the first snakes coming up and normally this camels are painted overlay earlier rock art such as this horses or the cattle and sometimes on top of these camels which are the more recent historic appeared just in find to Utah pick up with some collection cup attached on top and this is the most recent drop out dating from the 1950s when there was the onset of modern cars in this part of the Sahara. We might even have found the first comic but thats big enough for another one but depending whether you read it from left to right or vice versa tells a different story and so we go to another to Buddy Hower which once was the largest ????? to the Nile from the Sahara linking for central Chaldean basin of lake Chad which the Nile well in a westerly, easterly direction so it was a large river up to 10 km wide and the lower part was 500 km long and had really a superrich importance of all these south eastern Sahara and thats how it looks today if you're lucky and you find some windows with some exposed river deposits and you even find people who drown in this deposit, thats not a burial apparently today it was practically 5 or 20 mm of rainfall there were people drowning in this deposits like this gentleman which was dated to around 7,000 years ago and this place, once you looked into the deposits which looks like this today has looked into detail like a site in northern corner to find a western dafo as it looks today and everything you see on this picture from the deposits to the bird bones we found in the deposits in this place and thats how it looks in some other places where you find in such places high energy freshwater oysters which you will find today in the Chad tracts along the Nile well it certainly no more anywhere in the Sahara or jaws of elephants or exotic minerals like this realistic volcanic rock which indicate that there was a long, long range fluvial transport until a few thousand years ago and you have probably the most ancient rock at it all at least in northern Sudan where you find these herds of rhinos which are normally solitarily living animals which was peaceful, with peaceful people in between. Now this is to me really some sort of impression from this early of early paradise which is depicted at this single rock art site near Buddy Hower and of course archaeologist its a nightmare you have square miles large sites which have a culture layer up to 1 meter in depths that means it takes a few weeks just to excavate a few square yards not to think of square mile that means these are the largest prehistoric sites which even more expanded to any prehistoric site along the Nile well it was certainly never ever be excavated and every single piece you find here consists of pottery or bone remains because on top of the dune whereas for physical reason there is not any other material to be expected. So we also found the largest and only big construction we ever found during the past 40 years which is a fortress a diameter 150 yards with some walls up to 8 meters and as we know today it probably dates back 3,000 years once in a pattern a period but to the present day its purpose is not well known. Why? To step yourself in such a big fortress 100 km away from the Nile and probably of course to impress people coming from the south so controlling any traffic transport may be of cold and so on, but this puzzle hasnt been solved yet. So just one few, what we can show from the different region in the eastern Sahara thats how the environment changed from a rich with lots of lakes and temporary rivers and then there is the Palaeolake dried out until people had to shift to places with surface ground water where they could stick walk in wells so as a rider strategy to survive until even that ground water fell too deep and thats to either to move or to die. So the most important example for the reconstruction paleoclimatology on younger lakes to the present day in a hypocontinental position very far from the nearest ocean coast and the first exploration happen here in 1916 by some French military geographer and thats in fact the state of the art we had when we took up the research in the late 90s because the north of Chad was no more place to go there but to go there is take some time and just to get them the material and the vehicles there and doing the field work at the site so far already took almost 1 year of field work and thats why well, I was lucky to do this field work or the other were lucky not to take this venture. But going there is worth any trips so you must imagine you cross the Sahara which sometimes takes 1 week or 2 weeks depending where you come 3 weeks and then you go without seeing a single piece of grass and then you arrive at this spot and you at once in just 1 meter or 2 meters and then you have this site of this inner of the largest lake surface in the Sahara of today and while you have still islands in this lakes and all kinds in the very rare moments where there is no wind, you have all kinds of reflections and thats another speciality we have fresh water lakes which are paradox on to any arid place because you know freshwater gets salty within a few years or decades at best and these are lakes which for where you find today in toads and living molluscs which are in a direct genetic line from the molluscs which are exposed in the old lake beds and you also find fish and these freshwater lakes occur only because of a unique natural mechanism which consists and form a big lake which once was of course much, much later was dissected by encroaching dunes which made several lake chambers so to say and the ground water and of course this lake is 100% supported by fossil ground water by rainfall which fell in the early Holocene and 100% again measured evaporation of more than 6,000 mm a year which makes it another natural extreme and the ground water which goes into this peripheral lake is transported through the dune bodies into the central salt lake which works like a gigantic evaporation pump and keeps this mechanism going and thats why you have fresh drinking water you can use in a place where its not supposed to be there. There are other lakes in the western part but they are all highly saline and the most important of which is lake Yuan which is the largest body of water in the Sahara because of its depth of 27 meters it has a diameter of only 2 miles but because of the depths which is again fully 100% depending of fossil ground water and the evaporation on this lake is equal the consumption of all European town with one million inhabitants permanently and all these tremendous loss of more than 6 meters of water column is completely recharged by fossil rainwater and that makes it so exceptional. By the way, you can subscribe to this magazine freely and then in their present edition there is also an article on it and the most important thing for science is that when I went there for the first time in 1999 with a small rubber boat and not even knowing the depths of the lake and it begot deeper, deeper and deeper and then it took a gravity call and what you can see here that when I took the core out you have had what we called a raft layering that means you have one layer for summer, one layer for winter, one layer for summer, one layer for winter etc. and thats the best you can have as a paleo climatologist because such sediments give very precise data and information on climate change abound to a sub end well chronological scale and to see thats the top of the cords completely undisturbed and consisting of only algae which drizzling down while we are here together the sedimentation grows on and provides a new record for the mystery for the last years and this was good enough for science to cover story and to cut the long story short, the analysis of pollen data and several other data were clearly indicating that there was a very great real desiccation of the Sahara during the past 6,000 years from a fully developed savannah vegetation over some sort of shilling type vegetation to the present day to some desert vegetation until even this disappeared and there is nothing left but some oasis flora around the lake and this is in clear contrast to the assumption of my friend Peter who was claiming that this area desiccation of the Sahara happened very quickly within decades and the detailed analysis of this core has showed that there is really not a single year missing in this record and thats why we return in 2010 with some heavier equipment and working for a long time in a quite high temperature to extract the longest core, not only of the Sahara or in Africa but probably on earth where you have 60 meters of the sub annually laminated deposits which I consider some sort of Rosetta stone for paleoclimatology of the Sahara and there is a lot of publications in the pipeline so there is hardly any ever comparable site on this and of course these lakes were up to 100 meters higher than today because there is from a lake deposits on top of the surrounding table here which give information of the former extent which for example you can see in lake Yuan was much, much bigger than whats left today and apart from science, usually our counterparts in Africa they are less interested in paleo climate than mineral deposits or in that case, you know initiative I took 15 years ago to get this lakes listed as a world heritage site and this is what happens thats why I got to my colleague decorated as knights of Chad by the Chad president and all the local people and the local hierarchy are very happy because nobody even most Chadeans have never heard about these lakes. Nobody ever went there and now they are the first world heritage natural site in one of Africas largest country and there is already lots of improvement for the daily life of the people the way which we did. So a short example because I have been mostly talking about climate environmental change I will also give one example on from archaeology and thats one site we call Chara. Its a cave in the central Egyptian plateau where such kind of artefacts are of knives were produced by the prehistoric people, really pieces of arts which later 500 to 2,000 years occur in the Nile really. And if you have such the former collection of these artefacts which were excavated 100 years ago in the Nile really and you put the samples of the artefacts from the Sahara over and you see they really fit in them completely but only they were a couple of 100 years or 500 years or 1,000 years or 1,500 years older and thats same applies to some sort of typical pottery which form on a black rim and so on which also occurs 100 of years earlier than the first time in the Nile really. And there is also a lot of other evidence on even links into the later period between that the last ecological niches remaining in what became more and more a desert for desert as we know today with the Nile really including, no time for that, but possible origins of hieroglyphic writing even deep in the Sudanese desert. So now you almost made it and make a short time travel through the last 11,000 or 15,000 years. Thats how it looked like say 15,000 years ago. The eastern Sahara you dont see a single prehistoric site, there was absolutely no occupation or in 35 years we would have overlooked it but there is really many reasons to believe that the entire size of this equals the size of western Europe more than 2 million square kilometres not a single site, while all were able all known prehistoric sites are along the Nile really of course because thats one rescue Nubian salvation paying there better study to you than here but there is not a sight anywhere outside until apparently from 11,000 years, the Nile really became too over crowded at least thats one explanation because there are graveyards where you still find arrow heads and individuals which were apparently killed by arrow heads by tribal fights and so on. So suddenly, apparently the Nile really which was receiving much lesser rainfall than during the later period was no more a perfect place to live. And this change relatively rapidly not within decades or within generations but say between 500 to 800 years when monsoon rain coming from the south might went north from where it is today changing, that was once a completely unoccupied subcontinent into a savannah. That means there was no more desert in a strict sense it was certainly arid, to semi arid with rainfall below 150 mm or worst against the evaporation of 6000 mm by today but you see thats the green Sahara and what is clear that you hardly have any site left along the Nile really where all the occupation site are in what is today the Egyptian Sahara and to have a couple of site in the northern Sudanese Sahara but not in the part which received most of the rainfall and again, best explanation is that it was just too humid too dangerous, too unpleasant for daily living that people, prehistoric people would certainly arrive from the south move north where there are open savannahs which are good for raising for hunting games etc., etc. and a much better place to live than along the temporary river infested all kind of unpleasant animals. In this situation, states there around 2300 years when there was a development not only and even previously of pottery which is may be which is a sign of a so called Neolithic revolution which is probably until may be the electronic revolution recently was the biggest step forward in mankind because this is a sign of sedentary living with lots of implication later, domestication of rains and especially domestication of cattle which is of pastoralism which is a way of life which still is the most important one for the rural areas of sub Saharan Africa. But anyway, people we are living all around and thats a face where only in the north were some influence the introduction of goat and cattle where our goat and sheep while probably cattle was an autonomous invention from the green Sahara period. In this situation a change of 5300 years BC when you see that there was first of all a shift of settlement sites into the south what is today the northern Sudanese desert. People were surviving only on ecological nicious beat in the plateau in nicious like on the Gilf Kebir plateau oh and their old impression but in the vast spaces of the eastern Sahara, there was no settlements and especially what you see the 3500 you have hardly any settlement site left, any settlement left in what is the western desert of Egypt today and you have complete corridor of settlement along the Nile really and some remaining settlers for the south in the Sahara and you see that this was really the decisive states 7000 years or around 7500 years ago when there was really the onset of the desiccation of the Sahara which went on until probably very recently another interesting subject the importance of the desert to the pharaoh on a period but this would be good for another talk when there was a fourth trend Saharan expedition sent by the Pharaohs with a lot of most recent and unpopulous discoveries during the past few years. So again, the old picture the Sahara once was, well at least one quarter largest than it is today so in spite of 9 million square kilometres it was probably 12 million kilometres so covering much more than 1/3 of the continent a relatively sudden onset of the green Sahara relative stable period of 2 thousand years and then a very great results were retrieved of the desert margin to the situation where it is today and again if you will see if you will to thousands of archaeological and geological radiocarbon data, again you will see in this graph which is a line from north to south are relatively simultaneous onset of settlement and then you had this period where what we call the formation period where people did a big cultural and socioeconomic steps and then of 5300 that was the onset of the arid desiccation of the Sahara and then later period only an ecological niche there was room for survival or you have to move south that means, stay and die or may be develop some survival strategies for some generation then you have to move or die and thats what people did during all this time. And again, this is may be synthesis of this, all this decades of field work where again you see the north trend relatively simultaneous onset of settlement all over the Sahara and the great well desiccation of the desert and that goes along with what we always call Egypts desert roots and while you have all kinds of desert traditions which made it into the pre dynastic period and later even into dynastic time and this by my friend and colleague Ruth Cooper was our guiding line of our research all since late 1970s and probably no more time to read all through these who wants to know better can stop the stream also on but eventually thats what I said, again in a few line and now concerning the desert origins of the dynastic civilization that was I mean, the traditional few was always that the origins of Egypt, of the Egyptian civilization all came from southwest Asia and were introduced by some sort of a superior culture but I think this notion is more and more given up except by some very traditional Egyptologist and there are lots of proof that it was a really big step into human evolution from hunters and cattle raisers to sedentary people living more or less way of life who still do today with invention of the, the biggest invention which was pottery at the period which provided the preservation of food and other things. This was clearly happening completely independently from what was happening in the Labont in Palestine and so on. And the more and more evidence shows that there are many technological cultures, socioeconomic traditions which were invented in the west what is today the western desert of Egypt in which were introduced into the prehistoric and pharaonic cultures in the Nile well and now again, unless you claim the coincidence of the state of roughly 3500 BC when there was absolutely no more room not even one niche, existing niche where you could survive in the desert and this was exactly the time the origin of the Egyptian civilization then you will probably see some climate impact on it and may be a climate control which doesnt work everywhere. So it does make a big difference if you are in Somalia and there used to be 300 mm rainfall, today is 200 mm of rainfall. That doesnt make that much but when you are in region where you had 150 mm and later you have none, this makes a big difference and thats why we all formerly believe that this every desiccation of the Sahara which was terminated 3500 at the same time gave rise to the origin of the Nile well civilizations not only in the Egypt but also in Sudan in the Nubian civilization and thats why we shorten up. So Egypt is not only at least a gift of the Nile it already have a daughters but at the same time a gift of the desert and now I thank you for your enduring to this many slides and after, I hope for a discussion. I hope you have a good way back. [applause] S. Brand:My leg one is asleep I'm not having a stroke or anything. I think about an hour of thinking about that would be an order at this point. Okay, quick easy question from Jim Spalding, Why dont you helicopter into these places rather than grinding your way across an impossible surface. S. Kroepelin:Well it seems too far away and even the most modern Egyptian army helicopter they couldnt make it one way not to be back. On the other hand, theoretically all the place where we live, where we do our research is protected military area that mean getting a helicopter there even for this is impossible and even very good US colleague from selected staff in spite of year long waiting they never got the permit just to take research aircraft to fly over the western desert for this is certainly no option and if you have lots of time then may be army type rescue mission could make it but then you certainly would need to wait for weeks and so far never ever most of these places a helicopter has been to present day. S. Brand:Where have you been over the last couple of days and why? S. Kroepelin:Where? I have been to Chad a few days ago before just changing the plane for San Francisco Ive been in the capital of Chad and NDjamena the hottest African capital we have temperature of 45 degree Celsius and in the beginning rainy season that makes permanent sauna and there the objective was to push forward another world heritage project to work with, hopefully next year at least one year later that any deep plateau will be elected as a second world heritage site of one of Africas largest countries. S. Brand:That sounds great. Say a little more reassure to some of the stuff of that plateau. Because the world has already decided does it then become a place that some of us can go and visit and see some of those incredible box cannons and monument valleys and see the rock art and the rest of it, what happens when it becomes a world heritage site? S. Kroepelin:Well sure, well if I mean, there is of course very strictly guidelines for any world heritage site and for all the host countries because this is world heritage and not just national heritage so they otherwise to follow it and usually taking its relatively easy to control the relatively few visitors who will go there during the next years and decades provided that the security situations remains stable because in contrast to practically all of history knows on Chad is now is the only the tranquil quiet island within the Sahara while all the other Saharan states are practically no more place to go at least not into the desert unless you want to do some adventure or travel. S. Brand:So are other scientist following your path and one of the questions had to do with this, why is there arent so many particularly interested in this part of the world in your journey as a scientist. After you are gonna let them cycle and do some scientific tradition and have forge the way into some amazing areas and amazing kinds of discovery. Are other scientist following now and pursuing this past research? S. Kroepelin:Well, its getting more and more difficult to find students who are ready to go into the field for months beside lake stream. S. Brand:Why whats wrong? S. Kroepelin:Its because its an extreme road condition like on a space shuttle there is no way to have a beer one day, you're practically in the night you can take your sleeping bag and go away from the camp fire walk up a hundred meters we are living on 5 liters a day one gallon a day which we hardly use except when it really gets hot everything included in the night its very cold, day time its very hot, you can't take a shower for months, you are separated from your family or friends for a month so fewer and fewer students are ready to take this, just to do the research so we are still, we are sort of out dying species of this type research, you have to wait some Mars type robots who will take the follow up and usually it is still sometimes possible to find students who go along once to right for diplomacy and so the PhD and so no, but right after they switched remote sensing Let, work etc., so. Its shocking yes. S. Brand:The younger generation of explorers are reserves. I would expect, you make this adventure look so tough and incredible that you of anybody would be attracting people who would be coming up after trials like this, saying okay I'm changing my life I want to go the hardest most exciting places in the world, where really original discoveries can be made. You dont have a lot of people being inspired to go off and do that for years? S. Kroepelin:No I have a long, long list of so called amateurs of laymen of people save me rock art, hunters who are interested in rock art or adventurous and so on, I felt really tired generals, doctors, I have long, long, long list of people who is just one call or one email and I can take along 50 on one trip, the problem of this is not covered by the German research council and I need to take scientist or students to do this kind of research and of course you need some training and thats a problem. So I mean, there are lots of highly enthusiastic people who would pay even a lot just to follow it because we are really going to last unexplored, places which you can't order with some two operator but unfortunately we need too specialist and they are difficult enough to get and also its all you need. Normally, its impossible to find, to get a good team because first of all most important is you have to have a team which gets along for a specific time of period of time in extreme group condition. Of course you need a very good field researcher then you need at the same time say a good writer who puts its all, there is a paper work then you need someone who knows about lab analysis which is very important and then you need one who does cooking, who can change tires, who can solve mechanism problems etc., etc., and this list is very difficult to complete and so even in a good old days it was difficult to get some teams which could get along. Because well if you have one or two in the team who hate to do it and you have, you know, they are around for the next two months you can't send them home thats with the worse what can happen and so. S. Brand:So the training part, some say, in the way that it was a hardest part, what training do you really want on the scientist that would take into a place like this What background do they need to have, what kinds of backgrounds they need to have to be useful? S. Kroepelin:Now of course most of the background in geological field work and archaeological excavations and botanical research and so and of course its, this is the profile but at the same time one has to be ready to take these conditions and I would say most of at least the German soldiers would not be ready to do this way of life for extended period of time. So its really a big problem apart from academics specifications of this kind of field research. S. Brand:Well you know, with the youtube and extreme sports and sort of the things that people show of, this is more interesting than going to Mars. In fact, its pretty cool than going to Mars, except you can actually get there. I am astonished there isnt more attraction for highly skilled, highly trained, highly courageous and highly cooperative people to find their way on to these expeditions so get with people. Question, in your 40 years of exploring the deep Sahara, have you ever visited a single location during the same time of year and found differences or is the main event that nothing changes. S. Kroepelin:Oh changes, I mean, its a highly dynamic environment all deserts and even if you go to a specific location during different time of the day in the morning, at midday in the evening you see different things because of the light which comes from different angles. Sometimes you go in the morning you find nothing but fish remains. In midday you find plenty of meteorites and in the evening you find plenty of pottery fragments all around just depending on the light which gets there and of course because of aeroshifting sands sometimes places I exposed which are covered the next day and sometimes covered for 1000 years assets which move forward for example, we found a dinosaur skeleton wind what direction of this big crescentic barchans dunes when I tried, came to some specialist 5 years later this 20 meter high barchans dunes weighing 2000 tons was covered, so it would need to have to wait a couple of hundred years until it moves its spine, so its not just a matter of returning there but you always find new things and some things you overlooked and so on. S. Brand: So, there is never discovery something in front of a barchans dune. Discovery things are being revealed by this moving on. S. Kroepelin:For example, we found of one of the tyranny explorers raft that we still got to know who died almost 30 years ago and we found for example some of his things in 1930 or so a bottle of whisky with a piece of times and newspaper and this was covered by this gigantic dune and 56 years later, we found the camp site and so we could calculate the speed of the dunes advancing. S. Brand:Alright, really? And the newspaper was readable? S. Kroepelin:It was readable, it was very dry because unless in the tropical realm so everything which is dried, there is no animals not even termites could eat it so usually what you find there its stays like it isnt until the erosion by the wind removes it completely. S. Brand:The whisky bottle, thats kind of sounds good if thats. You should kept it. So the desert is telling us long term story dissected in great detail and there is a flux and we see some of the things in the story of the ice coming and going in the north and here the rains coming and going in North Africa. Whats your sense in that for as long oscillation of the place out of the next 10,000 years do you come up with a round number that we like. S. Kroepelin:Well exactly, I mean thats not politically correct what I'm going to answer to your question. I like it. Well generally, I mean most paleoclimatologist agree that the past climate history was mostly controlled by astronomical factor that means the so called Milankovitch curves and the insulation on what is today is Northern Africa during the preceding two and a half million years when there was one humid phase more or less every hundred thousand years. That was quite regular cycle of course with some changes and for some of the preceding wet phases so called imbian or isotopic marine, isotopic age 5 that was probably much more important than the last, the early Holocene, green Sahara and it was much longer but this was his trend and so normally I would say well the last glacier maximum happens some 25,000 years ago that means we would have to wait for the next period of a green Sahara, re-greening of the Sahara some 60,000 years. This would be the natural cycle. Now, since late 88 and 1980s, I found in this remote places where there is no human use, not even by bed winds or the by the camels or goats, there is a clear trend for a very slow onset of a sort of re-greening at the southern matching of what is today the desert. Re-greening that means the grass, it has increasing rainfall which produces more grass land which then attracts camel who came first time in generations much further north and then animal and some birds arrive, mice arrives snakes arrives we even see now ostrich and so on and the gazelles are multiplying so there is really a clear trend of course we can see it once you go to places which are not used for grazing. So thats what everybody is talking about encroachment of the desert. This is only well around the big cities and now imagine for example, the food, the population of 1 million inhabitants since the 1950s now we are approaching 10 million within 60 years and of course once you approach the big cities, I mean, there is all desert land, there is no more trees, there is nothing but once you go to places which is far away there is an opposite trend and so I get insulted as some sort of climoseptic just because I say theres always winners and losers and which is where you bet for the Bangladeshi may be good to the sub Saharan as a Sahelian zone or even for the old sub desert zone of the old world, desert which we just from the Atlantic to central China and this is, I would say, if this continues as a positive trend, but again, this doesnt meet everybody has to buy a high powered vehicle just to speed up the process but trend seems to be there and well, its now for 25 years that it can't be denied less more and more sensing studies and also of the arguments which now follow this early suggestion. S. Brand:It has been going on 25 years and you showed me a photograph in the green room and showed me a photograph a piece of desert which would be the most boring place on miles, flat nothing, and then another year of the same place whereas obviously blooming with flowers with grass like stuff and so on. People do not see that, so that suggest to me that in that totally desiccated desert. There was a sea bag of plant seeds just waiting patiently for a bit of rain is that the case? How long do those seeds do you suppose, how long do they have to wait? S. Kroepelin:They can apparently wait 100 of years and of course sometimes normally the dominating winds 95% of the trade winds coming from the north but there of course some rare southerly winds which then into the present day can bring seeds so far into the desert and then it just needs some local rainfall and then you have within days and weeks, you have a coverage, and this doesnt apply only to the eastern Sahara. My Sahabi friends from the western part of the Sahara my Chadean friends in north, my Sudanese friends, I mean everybody goes here telling the same story. They can't believe it. Every year they say, it has never been that green, and the next says its never been that green but oh of course only there where is hardly any human being once its used and you just have to, you would have to make a sense around it and you would get a re-greening bell which is being done these days of trying this make this green world on the southern border of the Sahara. There is a big project which already has started quite well which one day shall make a fenced area from the Atlantic to the Red sea and to show and to first to prevent winds encroach well ascend encroachment but also to make natural green world against the desert and this is, if this trend continues it certainlycontinue. S. Brand:This is somebodys fantasy or this is a scheme of the various nations across that part of Africa or collaborating on? S. Kroepelin:Its a scheme. Theoretically all sub Saharan states are collaborating of course sometimes if other problems and not talking about increasing insecurity in the Sahara it has never been so difficult to do field work in the Sahara like today. That means our paradise have pools where we could do what we like for decade. This is gone probably forever and because nobody will take away the small arms, nobody will take away the GPS and the land mines and so on so this is there to be almost forever I'm afraid and so. S. Brand:The scheme is officially what do you mean? This grand project of greening that band of Africa, there is a science fiction called Dune. Frank Herbert. It comes to mind of desert people you know taking generations to with a grand vision of how they can revitalize in case their plan, in this case I dont know area of an amazing continent. Anyway, this is extraordinary vision. And it you know a part from helping this kind of exploration and wants to wander where they used to help that scheme to, you know help the re-greening of that part of un-green Africa or may be help with restoring not only the plant life but the biodiversity that presumably goes with that plant life if its allowed to. Is that also a part of this fantasy? S. Kroepelin:It sure is so I think that really that the major problem again political and correct is exponentially population grows in sub Saharan Africa. I think with a stable population say that of 1950s I think that would already be a very positive trend recognized by all the people living there but of course this is a very sensitive subject in all relations and which is ignored but in effect many, many problems from the food to any weather they are all related to this for the lack of natural resources compared to the ever increasing population everywhere and thats the nature problem which is there is no way for any solution in the next time ahead I'm afraid. S. Brand:Well back to exploration, Arena asked you, you found so much, is there anything youre looking forward to in this region that you want to explore, that you want to find that you think are important discoveries, planes of discoveries yet to be made? What is still out there? S. Kroepelin:Oh sure. Uncountable! I mean, there is still for generation of field research, I mean, for example the northern part of Chad is I think I mentioned is as unknown as south western Egypt. This plateau was 120 years ago. I mean there is still a big, big people 100 years ago, I mean 100 years ago there was hiding vessels discovered only later means 90 years ago even the same situation as in northern Chad where you still have unhidden treasures. I mean, its no way not to find anything if you know what you're looking for in the Sahara. You says, some people who go there they said, what is archaeology is telling about all these artefacts we spent there for months we never found anything. Once you know a bit and you only see what you know, once you know it for example years we didnt find fish bone this parts of this Nile for example, once we knew to recognize we found them everywhere same applies to meteorites to some pottery to artefacts, to many, many, many other micro list, tiny things there has been no matter where your car breaks down or you have to change the tire, you get out and you find something. So even sometimes in the night, when you're looking you're always looking and I hate to sleep and write at the camp site because someone is snoring some parts moving and so on so always in the night I take my sleeping bag and my sac and go couple of 100 meters away from the camp up wind and so finally I find the site, I find the place to put my mattress and my sleeping bag and in the night I wake and I look to my right looking for my torch, what do I have in hand, a shawl and hand aches which can be 500,000 years ago. I look at the other site again, I dont find my torch I have another a shawl and hand aches and the next morning I look around the hand ache is a really concentrated at specific site where its protected from the wind by some sort of rock obstacle that means some prehistoric hunters and guess what, 500, 400, or 300, 000 years ago had the same problem of looking for camp site in the night where they didnt get their heavy chill factor and so its still unbelievable much to find. I have the biggest part of the rock art for example in the tablet I would not in this triple chunks in between Libya and Egypt and Sudan which were all trying to get to make it into a transboudary national park was discovered only during the past 10 years. I mean, and many, many other places are still unlimited scope for discoveries in these places and I didnt couldnt touch upon this ancient pharaonic trace into the Sahara which highly interesting subject is first trend Saharan highways because during pharaonic period and middle empire there were no camels of course, so any expeditions into what was already a full developed desert you amounted highly logistics kill sense on because you have to transport your water with donkeys where you need 100 of donkeys just to get the water which then could use as sort of payload and so on, and there are lots of interesting discoveries and I think this, this expedition which was sent by the pharaohs into the desert where we also already found some hieroglyphic inscriptions in a line that they were heading for the Ennedi plateau and for the Ounianga lakes which during the earlier time must have been really a huge for rich importance so certainly as the pharaohs heard about it and wanted it to get everything blooming African environment could provide. S. Brand:Okay, so here are these guys who are in the Nile a long way from those lakes, and are they heading on that direction looking for the lakes, fish on the lakes or fish and stuff, its a long way off. So is it stories that they are hearing it those lakes are, or is it an occasional individual who somehow getting across is saying that those lakes were good. How long would they know about something that far away that they would expedition toward it? S. Kroepelin:Its a very good question because of course, the Egyptians traditionally to the present day are very, very much a threat of the desert. Every single batch always comes from the desert today either be the locals or be sandstorms or be a bandits or later the Libyan so, we had some Egyptian colleague with us because the archaeologist always have to take a sort of inspector with them and when he came with us one of us for 35 years, he was never leaving the car, he was because all his colleagues say nobody ever returned alive from the Gilf Kebir, I mean we spent 1 or 2 months in the desert when we return and we hit the first treks and then we hit the first paved road, he went out praying for one hour because it was a new life, that means thats a typical standout and now imagine in the past, probably that was the same story that most of the Nile dwellers, everything bad came from the desert. Nobody wasnt the land of the dead and in many, many hieroglyphic writings it described of the place and well you wouldnt find any good. But then to send expedition there along missions which took months into a direction probably could only have where only possible with some supposed with some local knowledge by may be the last tough guys who remained anyway and anyhow in this remote desert may be some very, very last ecological nicious and so and they probably were used as guides. We never had any guides because in the eastern Sahara, there are no guides were able. Because all people left 5,000 years ago and so we always had to be our guides but to most other parts of the Sahara of course. S. Brand:But you dont used guides below 5,000 years ago. S. Kroepelin:But at the time you didnt need any guides because it was the last Sabanah. But anyway, and so probably say depended on some local knowledge from them tough guys who let them where they met them these people coming from sub Saharan Africa exchanging the goods and so on. S. Brand:One final story, tell me about the Persian army that entered in to the desert. S. Kroepelin:Well thats another of the mysteries of the Libyan desert after Alexander, there was a Persian general called . S. Brand:This is when what century? S. Kroepelin:That was some 500 BC and he what is known that he went along down the Nile really went west apparently and thats the last record that he reached. S. Brand:Presently there is Egyptians yelling, you'll be sorry. S. Kroepelin:Exactly. S. Brand:Thats all right we can handle, we are Persians, we know about desert right. S. Kroepelin: But at least he already was using camels and so that was a big advantage and so he probably made it into the Nueli and the old ???? depression west of the Nile and he was heading for the sea which was the site of Alexanders oracle and so on which was a tricky thing a friend of mine Klaus Coolman who excavated for years but another story. S. Brand:How much miles to the north? S. Kroepelin:Thats 100 miles across to the northwest seas the great sensi of Egypt which consist of this thousand kilometres long longitudinal dues up to 100 meters high which are very difficult to cross by camels. Because they have steep angles and so on anyway, he never showed up in Seeba but he left with depression. So according from different which range from 5000 to 50,000, he got drown by the sands somewhere, hit by some sandstorm, but there are some hints on this Persian armies consisting of old stone cans which we found some Persian pottery in some sites but thats all what is known and even to penetrate through tens of meters of sand you see with modern means, very difficult task so still way for exploration. S. Brand:Unsolved mystery. Its your job to find out what happen to the northern. Thank you so much. [applause]