The LWb blood group as a marker of prehistoric Baltic migrations and admixture

Archaeological findings and historical records indicate frequent migrations and exchange of genetic material between populations in the Baltic Sea are a. However, there have so far been very few attempts to trace migrations in this area using genetic markers. We have studied the Baltic populations wi th respect to exceptional variations in the frequencies of the Landsteiner- Wiener (LW) blood group. The frequency of the uncommon LWb gene was high in the Baits, around 6% among Latvians and Lithuanians, very low among the ot her western Europeans (0-0.1%) and apparently absent in Asiatic a nd Africa n populations. From the Baltic region of peak frequency there was a regular decline of LWb incidence (a descending dine) in the neighboring population s: 4.0% in the Estonians, 2.9% in the Finns, 2.2% in the Vologda Russians, and 2.0% in the Poles. Thus the distribution of LWb suggests considerable a nd extensive Baltic admixture, especially in the north and northeast direct ion. In Southern Sweden with an LWb frequency of 0.3%, the Baltic influence appeared slight, while in the population of the Swedish island Gotland in the middle of the Baltic Sea there was a significantly incrased LWb frequen cy of 1.0% compared with that of Western European countries. The distinctio n of codominantly inherited LW antigenic forms, LWa and LWb (previously Ne- a), is known to be due to a single base substitution. Based on our populati on data, it is plausible that the expansion of this point mutation occurred only once during human history. Furthermore, our data indicate that the ex pansion of the LWb mutation occurred in Baits and that LWb can be considere d a 'Baltic tribal marker', its presence in other populations being an indi cator of the degree of Baltic genetic Influence.