According to the researchers, these five family types could help explain the regional disparities in family size, education and wealth across Western Europe. Interestingly, the distribution of the types is almost completely at odds with the modern borders of Europe. The researchers speculate that the origin of the areas might be medieval, or even older. For instance, the prevalence of stem families in Ireland, along the western coast of Britain, in Brittany and on the northern shore of the Iberian Peninsula coincides with areas where Celtic populations settled two millennia ago. The noticeable concentration of a communitarian area in central Italy resembles the area of Etruscan civilization at its pre-Roman height, over 2,500 years ago.