It is probably the more unusual African American that has no white or Native ancestry anywhere on their 400 year(of slavery) old tree. And I would imagine that those white Americans who proudly claim Mayflower or other very early American ancestry, would be unusual not to find an African or Native ancestral family member. I hear many of these people proudly claiming Native ancestry, but one of them became VERY angry with me when they told me of a grandfather whose ancestry they could find no information on, may have actually been from an African American family that 'hopped the fence'.

As for what to call yourself, I too am tri-racial, I call myself black. I've had to argue with people who don't feel I should call myself that. Consequently, I am a firm believer in your right to call yourself what every you like.