 Hello and welcome to NewsClick. Today we have with us Professor David Reich who has worked on whole human genome sequencing. His work is well known. We are going to discuss the methodological issues. What does the whole human genome sequencing, which is what you and your group has been one of the pioneers, how has it helped the study of ancient migrations? Well, if you can obtain whole genome sequences of similar quality to people living today from ancient bones and from ancient teeth from known archaeological contexts where you know the types of pots people made, you know the types of buildings they were living in, archaeologists have studied the similarities or differences amongst cultures. You can then ask the question, were the people who lived in these sites related to people who lived in other sites that may or may not have similarities to them into people living today. So we can ask the question how do people, ancient people relate to each other and to people living to get today and we can ask the question, is the connection in material culture due to movement of people or is it just due to sharing of ideas and that's what it makes it possible to answer. So a lot of the fertile crescent agriculture seems to have been both movement of people but also movement of ideas? I think so. I think that it's certainly in the case of the development of agriculture, it's clear that multiple groups that were quite different from each other spread. So for example, some of the first farming starts in Anatolia and present-day Turkey and the people there genetically are quite different from the people in Western Iran who are in turn quite different from people in the Levant, present-day Jordan and Israel and yet all of those groups seem to have expanded along with the spread of farming and domestication has potentially occurred in multiple places there. So it doesn't seem to be a single group developing agriculture but instead a kind of multi-ethnic world where agriculture is developing and there's spread of people and there's also spread of ideas and technology that's independent of the spread of people or that's beyond the spread of people. Some of the spread of the agricultural products in that seeds and so on seem to have taken place without migration of people at least in large numbers. So you would see that this is more technologies being and knowledge being transferred rather than in this particular case. I think you see both things occurring. You see both things occurring. So for example, the place where we know this best is in Europe and the Near East but especially in Europe where we have lots and lots of whole genome sequences now from before and after the transition to agriculture and from before and after the transition, other transitions that happen later and we can see that the arrival of agricultural lifestyle coincides with an arrival of new people. It's a one-to-one mapping. It's a perfect mapping initially in many places and so whether that might not, this new way of life is coming with new people. So this is the expansion that takes place from Anatolia to Europe. That's right. So it comes in from Anatolia, agriculture spreads from Anatolia or maybe from Cyprus or it's not totally clear where but genetically the data from early farmers from Anatolia from eight and a half and nine thousand years ago is extremely similar to early farmers from Europe from a little bit later and it's consistent with the idea that that's the source population. And in Levant as well as Anatolia as well as Iran, Zagros Mountains, this you see the spread of agriculture but not really the spread of populations in the same way. No, you do see that also. So after the initial period of the development of agriculture you see all of these groups mix into each other. So for example in Iran you actually see a lot of Anatolian ancestry and in Anatolia you see a lot of Iranian ancestry and in Levant you see a lot of Anatolian and Iranian ancestry. So you see all of these groups mixing into each other in different proportions in different places but it's not one group pushing out the others it's rather multiple groups mixing with each other interacting with each other in ways that enrichly you know interact with the archaeological knowledge and so it's allowing us to quantify the process those processes. So this is the agriculture part we're not discussing South Asia because your papers are under review and they have not been yet published so there's a I believe an embargo talking to the press on that. So let's focus more on the European publications or European migrations that took place from Asia. The second migration which is also that you have worked on is the in the European speakers or horse shall we say riding people coming into Europe. So what would that where would that location be roughly in your according to your studies? Right so one of the things that we and others have documented with ancient DNA beginning in 2015 is that after this mass movement of people into Europe from the Near East via Anatolia probably after 9000 years ago there's another large-scale movement into Central and Western Europe that comes from a different source population that is we think is very likely to be or maybe the sources the this particular archaeologically defined group of people that's often called Yamnaya that lived in the steppes north of the Black and Caspian seas. It's not clear that they were riding horses there's a debate about whether they rode horses at all and for example but they certainly used domesticated horses very intensively for at least for pulling things and maybe for milking things and maybe for eating until chariots and not definitely not yet that's that's much later. So the first chariots are also from from the steppe but they're a thousand years later and so and the these people expand to the to the west and to the east and leave a very profound demographic impact on Europe. So these are the two major demographic impacts of the European stock as it were one is from the Anatolian agrarian people and the other is the steppe's people may or may not be horse riding but associated with horses. It's not even yes or associated horses is just not clear to what extent horses are important in their expansion or not but and then the third component of ancestry in Europe is the indigenous components the hunter-gather component that mixes in a substantial way with these other three but Europeans today are for the most part a mixture of these three source populations first farmers from Anatolia probably local indigenous hunter-gatherers and steppe storilists who come in after five thousand years ago and it's a mixtures of those three sources and different combinations that contribute most to the variation in ancestry in Europe today. So the Demic expansion theory or model that was proposed by different historians and also demography demographers and so on so that seems to hold good for agriculture but if you come to the steppe's population and language then the European speak Indo-European speakers are probably associated not with agricultural expansion but with the steppe's people. I think it's highly likely that Indo-European languages track at least some extent with the expansion present day spoken Indo-European languages that's tracked to some extent with Yamnaya steppe pastoralist ancestry and the reason is is that the spoken languages its source Yamnaya ancestry is a kind of tracer dye for the for for for Indo-European languages and so Indo-European languages are not spoken very much in the Middle East and the Near East and there there's very little steppe ancestry and we see it spreading into Europe at a time that well after the spread of agriculture making a massive impact it's hard to imagine that that spread was not accompanied by language transition and other lines of evidence also make the steppe a plausible source for the spread of Indo-European languages. There are Indo-European languages that are attested in the texts Tokarian and Hittite and in particular it's quite possible that Hittite which is ancient language of Turkey and other early Anatolian languages don't have Yamnaya ancestry so this is not a statement about the ultimate homeland of Indo-European languages but rather late proto-Indo-European the languages that are spoken today. Okay thank you very much Professor Reich to be with us thank you and we hope that you have a nice visit stay and discussions in Jaipur. Thank you thank you for your thank you for your interest in my work thank you for coming to talk with me.