Bicicleur, I don't think anyone has proposed that the bringing of plague was the only cause for the advance of the steppe people into Europe. I certainly haven't and wouldn't propose any such thing. It would be just one of many factors, as the bringing of measles, mumps, small pox and other diseases to the New World wasn't the only factor in the success of the Europeans. I don't think anyone could deny it was a huge factor however. I also don't know why you would expect lots of remains from people who died of disease. Half of Europe died of plague in the Middle Ages but the remains in the known plague pits don't equal that number of victims, and many of the pits are only being discovered now. Plus, the same argument could be made if the farmers died of starvation caused by climate change or were killed by the newcomers. Where are those mounds of skeletons? Yet it's clear that something dire happened to a lot of the farmers, whatever the cause. Furthermore, could you provide me with the dating you're using for the first contact between the farmers and the people of the steppe, and what particular group of farmers and the date you're using for the collapse?From David Anthony:" people from the steppes migrated to the fringes of and even into Old Europe, just before it collapsed. So there was a phase of intense interaction that involved people from the steppes immigrating into territories that had been occupied by Old European farmers. These steppe people seem to have been enriched by the contact, but we don’t know exactly how. They could have been looting; they could have been raiding. But the work has not really been done to answer that question in detail. What has happened is that we’ve been accumulating radiocarbon dates, but we need a lot of radiocarbon dates to answer this question. The great mass of radiocarbon dates now available have clarified the suddenness of the shift. But an explanation for the shift is going to depend on whether it was a sudden change or whether there was a slow evolution toward a new pattern. Those two different possibilities have been unresolved and argued about until recently, when we’ve collected enough radiocarbon dates so that, at least as far as I’m concerned, we have the evidence to say it was a sudden collapse."He's not mentioning the opposite movement, which was the movement of farmers onto the fringes of the steppe, which has been well documented. This is just one such interface:"Both hunter-gatherers and early farmers were attracted to the forest-steppe. They came face to face in the forest-steppe of the East Carpathian piedmont, northwest of the Black Sea, about 5800–5600 b.c.It was a meeting that utterly changed both ways of life because it provided the means for humanity to profit from the Eurasian grasslands: domesticated cattle and sheep. Cattle and sheep were grass processors. They soon spread into plains that formerly were grazed only by wild horses and antelope, and they converted grass into leather, milk, yogurt, cheese, meat, marrow, and bone—the foundation for life and wealth. The steppe region began to witness the emergence of societies committed to stock-breeding while the forest-steppe northwest of the Black Sea remained the home of increasingly prosperous and productive mixed farmers. An economic-cultural frontier formed between them. It remained the most clearly defined and contrastive cultural frontier in prehistoric Europe for about twenty-three hundred years, 5600–3300 b.c."
http://www.encyclopedia.com/humaniti...uthern-steppesAs for my comment about the steppe people fleeing from the disease, that was my speculation presented for discussion, not something proposed by Krause.I do think, though, that it's more than possible that the steppe people carried this disease with them wherever they went. The map of spread of the forms and the dates make that rather incontrovertible. It may not have been as virulent for them. Again, the history of the New World is a parallel. The Europeans carried smallpox with them, for example. It was fatal for many of them, but it was far more fatal for the native peoples. In certain areas the latter were totally wiped out. It's true we don't know how the earlier variant of plague was spread. That requires more research. If it was pneumonic, that is even worse than the bubonic version. Plus, even the bubonic form was present in the steppe by around 2000 BC.