The ethno-linguistic affiliation of the Bastarnae was probably Celtic, which is supported by the earliest historians. However, later historical sources imply a Germanic or Scytho-Sarmatian origin. Often they are associated with the Germans, or the peoples "between the Celts and the Germans". The most likely scenario is that they were originally a Celtic tribe, originally resident in the lower Vistula River valley. Around 200 BC, these tribes migrated, possibly accompanied by some Germanic elements, south-eastwards into the North Pontic region. Some elements appear to have become assimilated, to some extent, by the surrounding Sarmatians by the 3rd century.