The Gypsies: migrations of yesterday and today
The Gypsies, a young trans-national founder population spread across many countries, illustrate the genetics of recent human migrations, where small groups of people change their traditional geographic and social environments to form new ethnic communities in the midst of established societies. The 8-10 million Gypsies dispersed throughout Europe form a complex mosaic of culturally, linguistically and genetically divergent groups, often separated by complex rules of endogamy. Their lack of written history has led to multiple hypotheses, none supported by unequivocal evidence, about origins, timing of migrations, number of migration waves, and current structure. Genetic research has provided answers to many of these questions, characterizing the Gypsies as one of the most interesting genetic isolates in Europe.
Genetic variation in the Gypsy population has been studied in nearly 2000 subjects, representing different parts of Europe and Gypsy groups. Slowly evolving polymorphisms, which define Y chromosome and mtDNA haplogroups and reflect ancient human history, used in comparison to global diversity data, traced the origins of the major Gypsy lineages to the Indian sub-continent. Markers of higher mutability, such as Y chromosomal microsatellites, the minisatellite MSY1 , and mtDNA sequence variation, showed very limited diversity of the predominant lineages, pointing to a small group of related founders. Disease-causing founder mutations and their surrounding haplotypes suggested a single migration wave out of India around 1,000 years ago and provided strong evidence that the sequential splits giving rise to the current population structure occurred after the arrival in Europe and continued until very recently. Small founding populations and limited gene flow rapidly transformed Gypsy groups into genetically differentiated sub-isolates, sharing a common primary founder effect yet showing distinct features in allele frequencies and haplotype evolution.