 In each case, racial population naturalism encounters problems in trying to demarcate discrete boundaries between different biological populations. If discreteness is indispensable to a human racial taxonomy, then mismatches can only be avoided, if at all, through human intervention. But as noted above, biological species are also not genetically discrete, and thus boundaries between non-human species must also be imposed through human intervention. And just as the demarcation of non-human species is justified through its scientific usefulness, so too are human racial categories justified. For instance, Andreason contends that a cladistic race concept that divides northeastern from southeastern Asians is scientifically useful for evolutionary research, even if it conflicts with the folk concept of a unified Asian race. In turn, the concepts of genetically clustered and socially isolated race may remain useful for detecting and treating some health problems. Ian Hacking provides a careful argument in favor of the provisional use of American racial categories in medicine. Noting that racial categories do not reflect essentialist, uniform differences, he reiterates the finding that there are statistically significant genetic differences among different racial groups. As a result, an African American is more likely to find a bone marrow match from a pool of African American donors than from a pool of white donors. Thus, he defends the practice of soliciting African American bone marrow donors, even though this may provide fodder to racist groups who defend an essentialist and hierarchical conception of biological race (Hacking 2005, 102–116; Cf. Kitcher 2007, 312–316). Conversely, Dorothy Roberts emphasizes the dangers of using racial categories within medicine, suggesting that it not only validates egregious ideas of biological racial hierarchy but also contributes to conservative justifications for limiting race-based affirmative action and even social welfare funding, which supposedly would be wasted on genetically inferior minority populations. In effect, race-based medicine raises the specter of a new political synthesis of colorblind conservatism with biological racialism (Roberts 2008, 537–545). However, Roberts’ critique fails to engage the literature on the statistical significance of racial categories for genetic differences. Moreover, she herself acknowledges that many versions of colorblind conservatism do not rely at all on biological justifications.