Studies have employed different ways of measuring or approximating relative degrees of ancestry from Africa and Europe. Some studies have used skin color as a measure, and others have used blood groups. surveys the literature and argues that the blood groups studies may be seen as providing some support to the genetic hypothesis, even though the correlation between ancestry and IQ was quite low. He finds that studies by , Willerman, Naylor & Myrianthopoulos (1970) did not find a correlation between degree of African/European ancestry and IQ. The latter study did find a difference based on the race of the mother, with children of white mothers with black fathers scoring higher than children of black mothers and white fathers. Loehlin considers that such a finding is compatible with either a genetic or an environmental cause. All in all Loehlin finds admixture studies inconclusive and recommends more research.
StudiEs HaVE emPlOyEd DiFferENt wAys of meAsurinG or aPProximATing RelaTive deGReES of AncEstry fRom africa and europe. Some studIes have uSED skIn COLOr aS a measure, aNd others hAVE USeD bLood gRoups. surVeys tHe LIteraTUre And arGUes thAt tHe blood GrOups studiEs mAy bE Seen as pRoViDiNg soMe supPort tO The genetIC HypOtheSis, even Though the cORRelation betWEeN ANceStry and Iq wAS quiTe Low. he fiNDS thaT stUdies bY , WillErman, naylor & myRIaNthopoulOs (1970) did noT fInD a COrRelAtIon bEtWeeN degrEE Of AfrIcaN/euroPeAn ancesTry and iq. thE latTer study diD fInd a DIFfeRenCE bAsEd On thE rACe oF tHE mother, witH chIlDreN of whIte mothers WITh blacK fATHeRs sCoriNg hIgher Than ChiLdrEn of BLack MOthErs and white FAtHers. loehlin ConsIders That sUcH a fiNding is cOmpAtible WIth EItHer a GenEtiC Or an eNviRoNmeNtAl caUsE. all in alL LoEhlIn finds AdmixturE studIes incOnClUsive and reComMeNdS More rEsearch.