This started out as a comment to Adrian, but I it got so long it may as well be a post on its own….
The significance of racial labels is not in identifying the genetic makeup of individuals. The significance is in how the labels were used to enforce segregation long before the American Revolution. Before slaves in the United States were freed in 1865, defining who was Black was to identify who was eligible to be held in slavery and have ownership of property. There were grave concerns about mixing owners and slaves resulting in slaves gaining their freedom, especially once capturing them from Africa was no longer allowed. Defining race was about control then. Even in the more than one hundred years after the slaves were freed, defining who was Black was about control. Instead of who could be forced into slavery, the definitions of who is Black identified who could be excluded from power. The fear was mixed people using the laws to somehow get access to power. Only since Affirmative Action has it become in any way beneficial for others to have less than pure European descent.
Adrian remarked many of us have ancestors which keep us from being purely from one or another group. Chatting with George and Lorenia yesterday, George pointed out even in Europe, southern Spain and Italy confounds the stereotype. Our increasing understanding of genetics and culture invalidates race as a useful means of describing individuals. Individuals have genetic markers linking them all over the globe. We are one species. My favorite example PBS show indicating the women described as Amazons moved to western Mongolia.
“The earth is but one country and mankind its citizens.” – Baha’u’llah