Since 2014, further studies have refined the picture of interbreeding between EEF and WHG. In a 2017 analysis of 180 ancient DNA datasets of the Chalcolithic and Neolithic periods from Hungary, Germany and Spain, evidence was found of a prolonged period of interbreeding. Admixture took place regionally, from local hunter-gatherer populations, so that populations from the three regions (Germany, Iberia and Hungary) were genetically distinguishable at all stages of the Neolithic period, with a gradually increasing ratio of WHG ancestry of farming populations over time. This suggests that after the initial expansion of early farmers, there were no further long-range migrations substantial enough to homogenize the farming population, and that farming and hunter-gatherer populations existed side by side for many centuries, with ongoing gradual admixture throughout the 5th to 4th millennia BCE (rather than a single admixture event on initial contact). Admixture rates varied geographically; in the late Neolithic, WHG ancestry in farmers in Hungary was at around 10%, in Germany around 25% and in Iberia as high as 50%.