At https://www.eurekalert.org/pub_releases/2017-04/fos–smt040217.php … the period, 2300-2000BC was not just one of turmoil and upheaval, with evidence of site destruction far and wide, including earthquakes and perhaps atmospheric explosions of meteors, it was also one of migration and plague. This is too early for most books on historical epidemics to mention (they usually begin with the Bible or Roman records) but we have seen previously that plague or epidemics were a feature of the period around 3000BC also. The story in this instance is the result of Swedish research (by Kristian Kristiansen of Gothenburg University and Eske Willerslev of the University of Copenhagen). A major influx of people from the Russian and Caspian steppe zone affected India and the Middle East (spilling over the Caucasus) and Europe too (and possibly even China in the east). What might have sparked such a migration must be linked to whatever occurred to destroy civilisations to the south, east, and west, as there is apparently good evidence of a drastic decline in the population of Neolithic Europe.
In the case of Europe the invaders came from the Yamnaya Culture and it culminated in a blend of Neolithic people and steppe pastoralists – giving rise to the Corded Ware culture. This influx has recently been shown to be a reality by DNA analysis. Kristiansen claims to have evidence via genetics, strontium isotopes on diet and mobility etc (from the teeth). The Neolithic people were responsible for the big stone chamber tombs (megaliths) he says, who practised collective burial (he says). In contrast the newcomers. They had arrived ultimately from the Caspian steppe zone using wagons as mobile homes and their economy was based on meat, dairy products, and fish – but did not till the land. They built family barrows in lines to mark seasonal routes and people were interred individually. They were able to establish a foothold in Europe as a result of a decline in the Neolithic population (which Kristiansen thinks was due to an epidemic of some kind). In fact, he even mentions plague on the steppes as the driving force behind the invasion – which is all make believe, made up solely to explain the long distance migration. Catastrophism is out of the question – plague is one of those things people can't argue with as we just don't know, but suspect, it occurred often in the past. One can expect to read the plague event as dogma shortly – after it is repeated a few times. This is how urban myths are born.