 I'm interested in the origin of our species, Homo sapiens, in Africa, the emergence of Homo sapiens outside of Africa into Eurasia. In particular, I'm interested in the timing of the movement of modern humans out of Africa and also the roots or the carters that they took. So there's a big question as to whether or not they took coastal roots all the way to Australia or whether they used inland terrestrial roots. The traditional theory has been that modern humans speciated in Africa and they moved out of Africa in one wave around 60,000 years ago and they rapidly moved across Eurasia at 60,000 years ago to reach Australia by around 50,000 years ago, employing coastal roots. Our research has actually challenged that traditional theory and in fact some of the field work that we have been doing in the southern route that is in Arabia and places like South Asia show that in fact we have archaeological sites and even fossils that are older than 60,000 years ago and lo and behold they are found in inland terrestrial settings suggesting that coastal roots were either used rarely or not at all. This is an important question in human evolution because we really want to know of course about the history of our species, but we also want to know about our abilities, how did we become what we are as a species today all around the earth. I personally was interested in this question because there were big gaps in our knowledge with respect to out of Africa and so I have done large field projects in places like Arabia and India over the last 30 years to try to fill in a lot of the gaps that we have in the archaeological record. So we start our work employing satellite imagery for example. We map places like Arabia and Africa and in doing the satellite imagery work we have seen that in the past there were many rivers and lakes and those rivers and lakes were interconnected so we can actually trace rivers and lakes from Africa into the Sinai and then into Arabia. We start with that satellite imagery and armed with it we go to the field and conduct archaeological survey first of all to verify if in fact our satellite images are correct. In the field work that we have performed to date we have seen that our mapping is mostly accurate in fact there are rivers and lakes on what are today desert environments in desert environments so we know in the past these places were very wet when we find the rivers and lakes we go about doing archaeological survey in search of archaeological or paleontological sites and lo and behold when we've done our surveys we can see that there were many sites in the past associated with the rivers and lakes and then after we verify their archaeological sites we want to know something about their age of course so we go about doing very careful and precise excavations. Well our excavations have been really rather remarkable. We have actually shown that along the edges of the freshwater lakes we even have the bones of hippos for example so hippos are dependent on deep freshwater lakes so we have proven that we had drinkable water with findings of hippos and we even have freshwater shells and we have fish bones and along the edges of the lakes themselves we actually have stone tools and these stone tools are very similar to the stone tools that we find in Africa so we think that populations moved from Africa into Arabia using very similar stone tool technology. All of this together is very important because we're showing a very close association between freshwater lakes and paleontological sites as well as archaeological sites. Now we've gone about dating these archaeological and paleontological sites and we have ages on these sites going back to 200,000 years ago. The sites are not only 200,000 years old but they represent multiple phases of wet episodes so we have sites for example 200,000 years old, 125,000 years old, 100,000 years old and 80,000 years old and lo and behold all of these archaeological sites which we think represent Homo sapiens itself are much older than our traditional theory of 60,000 years ago for the emergence of modern humans out of Africa. Now the other importance of these very old sites in Arabia is that they're in inland terrestrial settings along the edges of rivers and lakes and these are places in deserts today so they were previously human environments and so we know these early hunter-gatherers were moving across Arabia inland terrestrial settings. This is very far from the coasts. Now the coasts were traditionally thought to be the root of expansion of modern humans out of Africa. And we have proven that modern humans were actually using inland roots as well as potentially coastal roots. Not only do we have the stone tools of what we think are modern humans but we also have recently found the fossil remains that represent Homo sapiens itself. And we have found that the bones of Homo sapiens in Arabia date to also 90,000 years ago, far earlier than the 60,000 year old hypothesis for the movement of modern humans out of Africa. Our findings are relevant because first of all it challenges the traditional view about the movement being only 60,000 years ago. So we have multiple dates of course from 200,000 years ago on upwards and this challenges the idea that there was a single migration. So in fact we think there were multiple migrations out of Africa, not just 60,000 years ago. Our findings are also relevant because we have found many hundreds of archeological sites in the interior zones of Eurasia including Arabia. And that means that coastal roots might have been used but we also know that inland roots for the migration of humans took place in terrestrial settings. And so all together we think the traditional theory of 60,000 years ago and coastal roots has been shown to be wrong by our research. Now what's really important to consider here is the role of climate change as a driver of out of Africa migrations. So during warm and wet intervals we find plentiful archeological sites along rivers and lakes. But however during dry intervals when deserts expanded we no longer find paleontological or archeological sites. So this means that fluctuations between warm and wet intervals and dry intervals is very important to consider when we think about out of Africa migrations. So it led to either the expansion of humans during certain periods but it may have even led to the demise of humans in certain parts of Eurasia when things got bad. And this of course is very relevant to us today because we are very interested in the role of climate change and what effect does it have on society today. And so these lessons from the past can be very important in thinking about people today. Well I've been spending about 30 years on doing surveys and excavations and what we call the southern route out of Africa and looking at places like Arabia and South Asia. However northern territories in places like Russia and China have been under explored. And so I think it's very important to be doing a lot of field work in places that we know very little about. So we have major geographic gaps in our knowledge about many parts of Asia. We have started new research in terms of northern routes out of Africa. We've begun to map some of the territories up in the north in northern latitudes and in fact we've even started some field work. So we have a team in Mongolia looking for caves and looking for ancient lakes as well as archaeological sites in order to show that modern humans were not only employing southern routes out of Africa but also using northern routes to get across high latitudes. If we can understand the southern route combined with new knowledge obtained about the northern routes this will tell us something about obviously the movement of modern humans out of Africa and it will tell us a lot about how did they cope with environmental change. It'll tell us something about their adaptations through time and this will lead to revisions of out of Africa theories. And so all of this is very important because it tells us something about us as a species and it tells us something about us and our ability to cope with environmental change now and the future.