Presently the greatest number of riders with horse burials on the territory of Sambian-Natangian Culture was discovered in the Aleika-3 cemetery. The appearance of this burial custom falls on the beginning – the middle of the second century. The rite appears in Sambia in the completed manner. Horse equipment of Aleika-3 cemetery has numerous analogies in the Danube region, this fact enables to suggest that its appearance in the region follows German-Sarmatian contacts during the Marcomannic Wars. The custom to bury horse to a rider reaches Western Balts with the Germans who took part in these wars. The grave furnishings of Aleika-3 riders in practice do not differ in contents from the tackle of Germania Liberia riders. The abundance of the Roman imports found in Aleika-3 cemetery including the luxury items and clearly expressed relationship with Welbark Culture are the result of the fact that the multiethnic society oversaw the beginning of the amber trade in this region and probably controlled it. Archaeological evidence of Aleika-3 cemetery enables to conclude that the beginning of the process of clan system degrading is fixed in the second century. This process was conditioned by penetrating of the German ethnic component involved into amber trade.