Please answer a question about the following article about Affirmative action in the United States:

During a panel discussion at Harvard University's reunion for African American alumni during the 2003–04 academic year, two prominent black professors at the institution—Lani Guinier and Henry Louis Gates—pointed out an unintended effect of affirmative action policies at Harvard. They stated that only about a third of black Harvard undergraduates were from families in which all four grandparents were born into the African American community. The majority of black students at Harvard were Caribbean and African immigrants or their children, with some others the mixed-race children of biracial couples. One Harvard student, born in the South Bronx to a black family whose ancestors have been in the United States for multiple generations, said that there were so few Harvard students from the historic African American community that they took to calling themselves "the descendants" (i.e., descendants of American slaves). The reasons for this underrepresentation of historic African Americans, and possible remedies, remain a subject of debate.

What did two prominent black professors point out at the panel discussion?
an unintended effect of affirmative action policies at Harvard