"Blood quantum might sound like an action movie, but to the country's Native Americans it's all about identity.
First introduced in colonial Virginia in the early 18th Century as a means of restricting the rights of anyone deemed to be more than 50% Native American, the term only became widespread after the Indian Reorganization Act of 1934.
By then, it had become a mechanism for calculating the amount of federal benefits a tribe could expect to receive, based on its population.
Over time, different tribes have adopted different levels of blood quantum.
Florida's Miccosukee Tribe is among a handful which require members to have 50% tribal blood - or the equivalent of one full blood parent.
At the other end of the spectrum, some Cherokee and Apache tribes require just 6.25% blood quantum. The largest number of tribes, however, require 25% or 12.5%.
Some, including the bulk of the Cherokee Nation, have abandoned the strict criteria of blood quantum in favour of simple ancestry, based on rolls drawn up by a congressional commission in 1893."
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Blood quantum influences Native American identity
(BBC News 7/11)
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