CAUCASIAN GENES IN AMERICAN NEGROES

Published estimates of the proportion, in American Negroes, of genes which are of Caucasian origin are critically reviewed. The criteria for estimating this proportion (M) are discussed, and it is argued that all estimates published to date have either deficiencies pertaining to the African-gene-frequency data used or statistical inaccuracies, or both. Other sources of error may also exist. Evidence is presented that the Fya gene of the Duffy blood group system may be the best gene now available for estimating M. Estimates based on Fya frequencies have been obtained for Negroes in three non-southern and two southern areas. The value of M is found to be appreciably greater in non-southern areas, the best estimate being 0.2195±0.0093 (Oakland, California). This estimate is still subject to some uncertainty. The value of M in the South is appreciably less. Natural selection can introduce a bias in the estimate of M. Claims that selection acting on certain genes in American Negroes have been demonstrated are reviewed, and it is concluded that they are not yet proved. The approach discussed here may be valuable in the future as a sensitive method for detecting the action of natural selection. In addition, knowledge of the amount of Caucasian ancestry may be of medical value in explaining the frequencies of occurrence of certain hereditary diseases in Negroes.