Why? Early in our history, we had the "one drop rule" that decided one's eligibility to benefit from our racial spoils system. A person was deemed black if he had one drop of black blood. Some states had the one-thirty-second rule, whereby if you had one black great-great-great-grandparent, you were black. It's conceivable that genealogical and DNA evidence might be the only way that white-looking college students will be able to exonerate themselves at college racial classification hearings if charged with racial faking.
Racial faking isn't a one-way street. A study in the May 1947 American Journal of Sociology estimated that at one time approximately 2,600 Negroes became white -- "passed" -- each year. If these people married white people, and raised families, who knows how many white people today qualify as black.
It might be worthwhile for white parents to have genealogy studies as part of their children's college preparation. Colleges will have to specify just what percentage of black blood makes one black. For example, in my own case, I am not entirely black; there's a bit of Irish in me. Does that make me entitled to march in St. Patrick's Day parades?