So, a little reading turned up that there was a big back migration across the Red Sea into Africa from the Arab peninsula back some time in the stone age. I’ve seen one paper estimate the earliest back migration into Africa at 30,000 years, (of mt DNA type M).
It’s a common misconception that Europeans have a similar skull shape and facial features because Ethiopia was the presumed exit point for humans leaving Africa. In fact, if this were true, all the people of the world would look Caucasian, and they obviously don’t. The original people that left Africa would not have resembled any modern ethnic group of people, they had Mongoloid, Caucasoid and Australoid characteristics. The modern racial appearances are all relatively modern, when you go back past 40,000 years none of them exist in their modern form. The Caucasian appearance of some Ethiopians is in a large part due to their Eruasian ancestry.
Mt DNA type ‘M’ is thought to have originated somewhere in the Pakistan area about 64,000 years ago, and migrated back to Africa bout 30,000 years ago. An expansion of the Semitic speaking Neolithic farmers from about 9,000 years ago also accounts for some Caucasian ancestry. This expansion took a wide variety of near Eastern Mt DNA and Y chromosome haplotypes into the Horn of Africa. There has also been some historical population movement into the horn of Africa since the advent of Islam
Anyway, the gist of these collected DNA studies is that Ethiopians are about 40% Caucasian, and are genetically a little more closely related to Mediterranean Caucasian groups like Berbers and Arabs than Western Africans, as is shown by this twig map. The actual amount of admixture varies from one group to another, but 40% is the average of all these samples. There is a Y chromosome study here that goes into more detail.
“Notably, 62% of the Ethiopians fall in the first cluster, which encompasses the majority of the Jews, Norwegians and Armenians, indicating that placement of these individuals in a ‘Black’ cluster would be an inaccurate reflection of the genetic structure. Only 24% of the Ethiopians are placed in the cluster with the Bantu and most of the Afro-Caribbeans.”
“On the basis of historical, linguistic, and genetic data, it has been suggested that the Ethiopian population has been strongly affected by Caucasoid migrations since Neolithic times. On the basis of autosomal polymorphic loci, it has been estimated that 60% of the Ethiopian gene pool has an African origin, whereas ~40% is of Caucasoid derivation…. Our Ethiopian sample also lacks the sY81-G allele, which was associated with 86% and 69% of Senegalese and mixed-African YAP+ chromosomes, respectively. This suggests that male-mediated gene flow from Niger-Congo speakers to the Ethiopian population was probably very limited … Caucasoid gene flow into the Ethiopian gene pool occurred predominantly through males. Conversely, the Niger-Congo contribution to the Ethiopian population occurred mainly through females.*“
(Poloni et al. 1997)
Approximately 10 miles separate the Horn of Africa from the Arabian Peninsula at Bab-el-Mandeb (the Gate of Tears). Both historic and archaeological evidence indicate tight cultural connections, over millennia, between these two regions. High-resolution phylogenetic analysis of 270 Ethiopian and 115 Yemeni mitochondrial DNAs was performed in a worldwide context, to explore gene flow across the Red and Arabian Seas. Nine distinct subclades, including three newly defined ones, were found to characterize entirely the variation of Ethiopian and Yemeni L3 lineages. Both Ethiopians and Yemenis contain an almost-equal proportion of Eurasian-specific M and N and African-specific lineages and therefore cluster together in a multidimensional scaling plot between Near Eastern and sub-Saharan African populations. Phylogeographic identification of potential founder haplotypes revealed that approximately one-half of haplogroup L0-L5 lineages in Yemenis have close or matching counterparts in southeastern Africans, compared with a minor share in Ethiopians. Newly defined clade L6, the most frequent haplogroup in Yemenis, showed no close matches among 3,000 African samples. These results highlight the complexity of Ethiopian and Yemeni genetic heritage and are consistent with the introduction of maternal lineages into the South Arabian gene pool from different source populations of East Africa. A high proportion of Ethiopian lineages, significantly more abundant in the northeast of that country, trace their western Eurasian origin in haplogroup N through assorted gene flow at different times and involving different source populations.
(Toomas Kivisild et al.) Human Biology 75.2 (2003) 293-300
“Non sub-Saharan African samples are all grouped together…with…the Ethiopian Amharic sample [on the Y-chromosome]. Ethiopians are not statistically differentiated from the Egyptian and Tunisian samples, in agreement with their linguistic affiliation with the Afro-Asiatic family.”
The occurrence of E*5 212 and E*5 204 alleles in two populations of the Mediterranean basin (Turkey and Italy) but not in West Africans can be explained by taking into account that the Ethiopian gene pool was estimated to be >40% of Caucasoid derivation (Cavalli-Sforza et al. 1994). In addition, more recent phylogenetic analysis based on classical protein polymorphism (Tartaglia et al. 1996) and Y-chromosome sequence variation (Underhill et al. 2000) showed that Ethiopians appear to be distinct from Africans and more closely associated with populations of the Mediterranean basin.
Though present-day Ethiopia is a land of great ethnic diversity, the majority of Ethiopians speak different Semitic, Cushitic, and Omotic languages that belong to the Afro-Asiatic linguistic phylum. Maternal lineages of Semitic- (Amharic, Tigrinya, and Gurage) and Cushitic- (Oromo and Afar) speaking populations studied here reveal that their mtDNA pool is a nearly equal composite of sub-Saharan and western Eurasian lineages. This finding, consistent with classic genetic-marker studies (Cavalli-Sforza 1997) and previous mtDNA results, is also in agreement with a similarly high proportion of western Asian Y chromosomes in Ethiopians (Passarino et al. 1998; Semino et al. 2002), which supports the view (Richards et al. 2003) that the observed admixture between sub-Saharan African and, most probably, western Asian ancestors of the Ethiopian populations applies to their gene pool in general.
(Am. J. Hum. Genet., 75:000, 2004)
“The present composition of the Ethiopian population is the result of a complex and extensive intermixing of different peoples of North African, Near and Middle Eastern, and south-Saharan origin. The two main groups inhabiting the country are the Amhara, descended from Arabian conquerors, and the Oromo, the most important group among the Cushitic people. … The genetic distance analysis showed the separation between African and non-African populations, with the Amhara and Oromo located in an intermediate position.”
(De Stefano et al. 2002)
East African groups, such as Ethiopians and Somalis, have great genetic resemblance to Caucasians and are clearly intermediate between sub-Saharan Africans and Caucasians . The existence of such intermediate groups should not, however, overshadow the fact that the greatest genetic structure that exists in the human population occurs at the racial level.
Most recently, Wilson et al.  studied 354 individuals from 8 populations deriving from Africa (Bantus, Afro-Caribbeans and Ethiopians), Europe/Mideast (Norwegians, Ashkenazi Jews and Armenians), Asia (Chinese) and Pacific Islands (Papua New Guineans). Their study was based on cluster analysis using 39 microsatellite loci. Consistent with previous studies, they obtained evidence of four clusters representing the major continental(racial) divisions described above as African, Caucasian, Asian, and Pacific Islander. The one population in their analysis that was seemingly not clearly classified on continental grounds was the Ethiopians, who clustered more into the Caucasian group. But it is known that African populations with close contact with Middle East populations, including Ethiopians and North Africans, have had significant admixture from Middle Eastern (Caucasian) groups, and are thus more closely related to Caucasians .
Categorization of humans in biomedical research: genes, race and disease
Neil Risch,1,2 Esteban Burchard,3 Elad Ziv,3 and Hua Tang4