White Croats
It is considered that the Czech-Polish Croatian tribes were related to the Croatian tribes from Zakarpattia and Prykarpattia in Ukraine. They became separated during the migration period and seemingly formed one large Proto-Slavic tribe. It is theorized that the migration of those (White) Croatian tribes in the 7th century was the second and final Slavic migratory wave to the Balkans, which is related to the thesis by Bogo Grafenauer about the double migration of Slavs. According to this thesis, although it is possible that some Croatian tribes were present among Slavs in the first Slavic-Avar wave in the 6th century, it is argued that the Croatian migration in the second wave probably was not equally numerous to make a significant common-linguistical influence, while others considered they arrived in a significantly larger number. Zdenko Vinski and argued that the double migration thesis is supported by the rare findings of objects and ceramics of Prague-Korchak culture on the territory of Croatia, Bosnia and Herzegovina, and Serbia which were dated to the end of 6th and beginning of the 7th century (indicating first wave Slavs), and did not make a continuity with Slavic archaeological findings from the 8th-9th century, indicating assimilation. The Croatian tribes are also seen as a warrior group who assimilated into already present Slavs. In the territory of present-day Croatia they also gradually assimilated with the Pre-Slavic population because archaeology indicates a significant continuity of late antiquity population which have partially withdrawn to the mountains, coastal cities and islands.
Genetic studies on Croats
According to 2014 autosomal analysis of Western Balkan, the Croatian population shows genetic uniformity with other South Slavic populations. The Croatians and Bosnians were more close to East European populations and largely overlapped with Hungarians from Central Europe. In the 2015 analysis, they formed a western South Slavic cluster with the Bosnians and Slovenians in comparison to eastern cluster formed by Macedonians and Bulgarians with Serbians in the middle. The western cluster has an inclination toward Hungarians, Czechs, and Slovaks, while the eastern cluster toward Romanians and some extent Greeks. In the 2018 analysis of Slovenian population, the Croatian population again clustered with Slovenians, Hungarians and was close to Czech. The population of Croatia mostly shares common ancestry with Eastern, Western, and Southern Europeans, and has almost no relation to isolated Sardinian and Basque population.