Historically, the question of how and when Indo-European speech entered Europe was based on archaeological evidence for two competing theories. The first was that Indo-European speech entered Europe from Asia Minor as early as 9ky, in company with elementary farming techniques. Archaeology further provided evidence that prior to the arrival of these cultivators, Europe had been thinly populated by hunter-gatherers, and recent linguistic analysis has revealed distinctively non-IE elements in European I-E languages that are absent from Indo-European languages spoken elsewhere and could only have been absorbed from whatever language or languages the earlier hunter-gatherer population of Europe might have spoken.
 
But there was also a well-established theory that Indo-European speech was brought into Europe some 4,500 years ago by horse-riding pastoralists from the Eneolithic Pontic-Caspian steppes.  As amply documented by Professor Marija Gimbutas, these pastoralists were warlike and tended to impose themselves on the farming population already occupying most of Europe.
 
To discuss these rival claims, Professors Guus Kroonen and Bernard Comrie organized a workshop, to be entitled Talking Neolithic, at the Max Planck Institute for Evolutionary Anthropology in Leipzig, in 2013. Here the contributors would address the subject in terms of the intersection of Indo-European linguistics and archaeology. Then, during the planning of the workshop, remarkable genetic evidence of the origin and movements of the pre-Neolithic, Neolithic and post-Neolithic population of Europe came to light, and at the last moment it was decided to include this startling, new information in the workshop.
 
Based on fossil DNA, the new genetic evidence confirmed that cultivating techniques had been brought into Europe from Asia Minor by demic diffusion, and not by cultural diffusion as some theorists had earlier suggested. The DNA evidence also confirmed an invasion by horse-riding pastoralists from the Pontic steppes into central Europe. However, it was noted that while the evidence for these two demic invasions is now unquestionable, a detailed explication of the history of Indo-European speech in Europe still awaits further linguistic, archaeological and DNA research.