Historically birthright citizenship was from common law traditions ( Germanic / Anglo Saxon law). When Britain established colonies this came over as well. In America it was also useful when dealing with the massive numbers of newly emancipation slaves who did not have clear birth records.
In contrast bloodright citizenship was historically from Latin traditions. In Roman society there was large groups of conquered foreigners who the Roman’s were reluctant to incorporate into their society, as being a Roman citizen came with many advantages they did not want to give to everyone.
Most modern countries incorporate elements of both into their immigration systems.
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