David Reich: evaluation

Transcript context

…Let's jump forward then, since you mentioned this. Agriculture was developed in the Middle East like 10,000-12,000 years ago. Later, the population of Native Americans declined because of disease. One of the hypotheses that you talk about in the book is that potentially this happened with respect to people in Europe by the Yamnaya with the bacteria that causes the bubonic plague, Yersinia pestis. The question I'm trying to ask is going back a bit. James Scott, who I think just died a couple of weeks ago, wrote his book, Against the Grain. The whole book is like, “Agriculture sucked but we were forced to adopt it because it allowed some humans to organize nation states that were very abusive. But it did allow them to get the barbarians and co-opt them because they needed the labor to do this monotonous activity.” One thing I didn't realize until I read that book is just how new most of the diseases that afflict humans today are, everything from cholera to typhus to tuberculosis if you just go down the list. It might have been because of agriculture: domestication of animals and the density that was created. The theory he talks about in the book is that potentially the reason the hunter-gatherers, the “barbarians,” couldn't fight back against these early nation-states was because they were getting killed off by the diseases. I don't know how much evidence there is for this. Basically, the question I'm trying to ask is about the way in which Europeans encountered Native Americans in the New World. Did that just happen again and again throughout history? If you go back to Europe 9000 to 5000 years ago, is that just what human history has been like? That wasn't a one-off event? There's an amazing book by Kyle Harper. It's called The Fate of Rome. He's a Roman historian. It's a history of three major plagues in the Roman period, two of which are really not even very well known. It argues that the decline of the Roman empire is due to just weakening as the result of plagues and other climatic, biological, climatological worsening events. There is a lot of reason to think that some of these events have been recurrent throughout history. It's not just a difference between farmers and hunter-gatherers, but it’s actually a lot of different types of interactions that are occurring. The example that you mentioned is something that's been a big shock from the ancient DNA revolution. This is now maybe eight years, nine years old. The first large number of DNA sequences—from people who lived 6000 to 4000 years ago in the steppe north of the Black and Caspian Seas and in Europe—were being published around 2015. This group in Denmark, led by Eske Willerslev and Kristian Kristiansen and colleagues, looked at their DNA. They discovered in their sequence, from the 100 or so humans they sequenced, that there was also pathogen DNA. In 5-10% of the random people they sequence from around 4000-5000 years ago, there was Yersinia pestis, the agent of the black death, but actually without the plasmid that contributes to bubonic plague. That's required for flea-rat transmission. So it must have been pneumonic plague with an aerosolized transmission or something. 5-10% of random deaths means that the percent of people who were dying must have been even higher, because they weren't detecting everything that was there. There’s a study by another group, Johannes Krause and colleagues, of people in plague pits in London from the 1300s epidemic. They found that when you apply this method to people we know died of black death, you only find a quarter of the people. So the rate was even higher. If people are bacteremic when they die, if they have bacteria in their teeth, they almost certainly died of that agent. A paper just came out a few weeks ago in Scandinavia. It was looking at these tombs from about 5000 years ago of farmers who were just on the verge of encountering people from the steppe. A huge fraction of them have Black Death when they die. They're buried in tombs and normal and they have rates that are even higher than 5-10%. It’s this whole pedigree with many, many generations. It's not all at the same time. It’s like the parents and generations and generations with a very large fraction. Well more than 10% have Black Death and have Yersinia infection. So it looks like this particular agent has been killing people for 4000-5000 years in western Eurasia. In fact, it’s killing a scarily large fraction of the population. As the quantitative person I am reading this literature, I think people are embarrassed by the implication. The implication is that a quarter to a half of deaths in this entire period are from this. . As the quantitative person I am reading this literature, I think people are embarrassed by the implication. The implication is that a quarter to a half of deaths in this entire period are from this. It's so unbelievable and so ridiculous that such a high proportion of people over such a long period of time are dying from this one agent. People don't even say it. They just publish one paper after the other, publishing more sequences. They just don't think about the implications of such a high rate of death. Yet it's really hard to imagine that people have bacteria in their blood and they're not dying of these things. It doesn't seem that people are selectively picking tombs. These are tombs that are buried properly. They're not grave pits. The implication seems to be that this one agent we happen to be able to detect is killing a very large fraction of people in western Eurasia over this period. So what's the implication of that? One thing is that it seems to be coming from steppe rodents, probably. Maybe the people on the steppe—I mean, they are still dying of it—are somewhat more protected from it. Then it spreads into farming Europe, maybe 5000 years ago, which is when we start to see it. Maybe this results in disorganization of the population, giving such a high rate of death. Maybe it creates a type of situation that the Europeans encountered when they got to the Americas, where societies were disrupted. In the last few years, we had Covid-19. It killed a half percent of the world population or something like that. It was so disruptive. This thing is killing a third of people or half of people randomly. It’s randomly killing people with cultural knowledge, randomly ripping into structures. Was it Montezuma who died or one of his parents, resulting in civil wars? You have the Inca when the Europeans encountered them, just disrupting the cultures that were there. Maybe this would have created a situation where there was disruption in the old ways of life. Maybe combined with other things, or even just by itself, it could have created an opportunity for people to move in from elsewhere, even though they were not as densely spread. There’s a big observation we haven't talked about. It's something that we as an ancient DNA community have been looking into again and again now and keep making progress on. About 5000 to 4500 years ago in Europe, there's a radical transformation in the ancestry of Europeans. An example of this is what happens in Britain. About 4500 years ago, the farmers who are there arrived there 6000 years ago. They build Stonehenge. The last big stones of Stonehenge go up 4500 years ago. Within 100 years, 90% of them are gone. They're replaced by migrants from the continent bearing prop majority ancestry from the steppe north of the Black and Caspian Seas. This is one place where we know what happened very well, but we see it all over Europe. We see it in Spain. We see it in Portugal. We see it in the Netherlands. We see it in Germany. We see it in Czechia. We see it in Italy. We see it in Switzerland. We see it everywhere. This wave of people from the east arrives.…

Stored transcript either side of the excerpt. The highlighted words are the published quote; the surrounding text is unedited source, never generated.