The BRCA1 mutation . . . was originally described as a founder mutation in the Ashkenazi Jewish population. However, this mutation is also present at appreciable frequency in several European countries, which raises intriguing questions about the origins of the mutation.
We genotyped 245 carrier families from 14 different population groups (Russian, Latvian, Ukrainian, Czech, Slovak, Polish, Danish, Dutch, French, German, Italian, Greek, Brazilian and Ashkenazi Jewish) . . . and confirmed that all mutation carriers share a common haplotype from a single founder individual. . . .
[T]he mutation arose some 1800 years ago [200 CE] in either Scandinavia or what is now northern Russia and subsequently spread to the various populations we genotyped during the following centuries, including the Ashkenazi Jewish population. Age estimates and the molecular evolution profile of the most common linked haplotype in the carrier populations studied further suggest that [the mutation] likely entered the Ashkenazi Jewish gene pool in Poland approximately 400–500 years ago [1500 CE - 1600 CE].