Close affinities between Neolithic cultures in the Horn and North Africa

The widespread continental distribution of related Caucasoid peoples is further supported by the close affinities between the main Neolithic cultures in both the Horn and North Africa. In other words, one can find cultural commonalities between both regions extending back thousands of years, just like the still extant genetic, skeletal and linguistic affinities between both areas. This is because the makers of those industries were of the same ancestral Hamitic(Cushites, Berbers, Egyptians, Ethio-Semites) stock:

source: http://www.sciencedirect.com/science/article/pii/S096098220902065X

The map above, depicting the African climate, vegetation and culture in the early Holocene, is by the anthropologists Michael C. Campbell and Sarah A. Tishkoff and part of their study titling "The Evolution of Human Genetic and Phenotypic Variation in Africa". A quote from their study regarding this map:

Following a period of dramatic increase in rainfall around 10.5 kya, the expansion of both rainforest vegetation in the Congo Basin and woodland savanna farther north and south of the rainforest belt, as well as the expansion of tropical steppe and grassland vegetation into the Sahara region took place. New lakes also appeared, while old lakes grew in size along the southern edges of the Sahara [6]. Between 10.5 and 8.5 kya, several key demographic events occurred among culturally distinct ancestral African populations, including the migration of Nilo-Saharan-speakers from their homeland in Sudan northward to the dry tropical steppe vegetation of the eastern Sahara where they practiced agropastoralism [6]. Northern Erythraites (Afroasiatic-speakers) also lived mainly in the Mediterranean climate of the northern Sahara where they engaged in herding and wild grain collection [6]. The distributions of these cultural groups, among others depicted on this map, roughly correspond to the present-day distribution of major linguistic groups in Africa (Figure 1). The shift from dry to wetter climatic conditions in the early Holocene likely provided an opportunity for ancestral Africans to develop cultural traditions, such as agriculture and herding, in a more favorable environment leading to further technological developments in Africa [6]. Adapted from [6].

The anthropologist Christopher Ehret on these early Northern and Southern Erythraites which form the common ancestors of the modern day Berbers, Egyptians, Ethio-Semites and Cushites:

source: http://books.google.de/books?id=0K0p8wC

Variation among the Cushitic speakers of the Lowlands

The Eastern Aethiopid (Somalid) type (see here) is the most dominant type among the Cushitic speaking tribes (Somali, Ogaden Oromo and Afar) which reside in the dry and plain lowland regions of the Horn of Africa.
Besides this very prevalent type, there can be seen a spectrum of other types and influences: 
robust cromagniform or cromagnoid variants, orientalid influenced variants, real proto-negroid-caucasoid transitional variants and individuals with recent Bantu negroid input.

However these types occur in a rather low frequency (less than 20% fall into this spectrum).

Here a random collection of six Somali males showing the usual and typical phenotype variation among their people:

1. Eastern Aethiopid(Somalid)

2. Eastern Aethiopid(Somalid)

3. Eastern Aethiopid(Somalid) with slight infantilism 

4. Robust Cromagnoid variant of Eastern Aethiopid type

5. Robust Cromagnoid type with an overall negriform deviation

6. Eastern Aethiopid with stronger infantilism and with probably a proto-weddoid? strain

Nasal index of Hamites

http://maxwellsci.com/print/crjbs/v4-1-3.pdf

“Cephalic and nasal index are very useful anthropologically to find out racial differences and medical management (Shah and Jadhav, 2004; Porteret al., 2003; Ochi and Ohashi, 1983). Cephalic index is used to measure the size of the head which is done by determining the ratio of the maximum head breadth to the maximum head length (Kelly et al., 1999). There are three classifications of cephalic index which can be used to describe the human head; these include dolicocephaly, mesocephaly and brachycephaly (Golalipour et al., 2005). Nasal index measurement can be utilized in the analysis and classification of fossil remains as well as the study of living populations (Alex et al., 1996). Studies have shown that the Negroid race mainly of African descent have the platyrrhine nose type (Carleton, 1989)[...]

Oladipo et al. (2007) conducted a study on the morphometric analysis of the nasal parameters of Igbo, Ijaw and Yoruba ethnic groups of Southern Nigeria. The results obtained showed that an average Igbo had a mean nasal index of 94.1±0.37, Yoruba 89.2±0.30 and Ijaw 96.37±1.06. Thus the Ijaws had a significant higher nasal index (p less than 0.05). Fawehinmi et al. (2008) reported a mean nasal index of 98.5±0.93 and 94.1±1.18 for male and females of Kalabari ethnic group of Nigeria. The Somalia people in East Africa have a nasal index similar to that of European Caucasoid of 69.90 or less, which is of leptorrhine nose type (Porter et al., 2003; Carleton, 1989). The nasal index of African-American women is 79.70, Bantu speaking negroes and the bushmen of Africa as well as the Australoids of Australia are platyrrhine having a broad nose and a nasal index of 85.00 or more (Mulchand, 2004)”

http://ispub.com/IJBA/3/2/7314

Lacking prognathy among Hamites

Hanihara et al. (2005) examined facial flatness(prognathy) in many global populations, both modern and old, including ancient Egyptians:

"In the present study, the frontal and facial features of 112 populations from around the world are compared in terms of frontal and facial flatness measurements. Univariate analyses and canonical correlation analysis were applied to six indices representing flatness of frontal and facial bones. The deep infraglabellar notch, marked prognathism, and flat frontal bone show distinctive Australian/Melanesian characters among recent populations. Very flat faces in the transverse plane are the most common condition in eastern Asians. Some subSaharan Africans share similar characteristics with Australians in terms of marked prognathism and flat frontal bones in the sagittal plane on the one hand, and with eastern Asians on the other hand, for flat nasal and zygomaxillary regions. These results are not necessarily inconsistent with the evidence for regional continuity. The examination of relationships between frontal and facial flatness through canonical correlation analysis reveals a significant association between morphological features such as a deep infraglabellar notch, prognathism, flat frontal bone, and flat faces in the transverse plane. In this context, together with the generalized features of the late Pleistocene fossil record, the features of Australians having transversely projecting faces and of eastern Asians showing weak infraglabellar notches, ortho-/mosognathism, and rounded frontal bones can be interpreted as a differential retention of ancestral traits of anatomically modern humans. This may allow us to suppose that the frontal and facial flatness features treated herein can be explained by the hypothesis of a single origin of anatomically modern humans."

http://www.ncbi.nlm.nih.gov/pubmed/10618591

It found out that Somalis are the least prognathic population on earth, lesser than all modern populations examined. 

For prognathy see the M40/M5 mean column:

All populations lower than the Somalis (Cyprus, Greece/Rome, Spitalfields, Ensay, Morocco) are pre-modern ones, and "Morocco" is for the Guanches. 

Somalia=94.0
Sweden=95.1
Norway=94.9
Modern Italians=94.3
Ancient Italians=93.0
Modern Greeks=94.4
Ancient Greece=93.0
Turkey =96.5
Palestine=95.7
Early Nubia=94.8
Recent Nubia=98.5
Spain=94.5
West Africa=102.6

Afghanistan=97.7

The whole study: http://www.femininebeauty.info/hanihara.flatness.pdf

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 111:105–134 (2000) Frontal and Facial Flatness of Major Human Populations TSUNEHIKO HANIHARA

Morphological relationships between many different populations in North, Horn and East Africa

According to Billy (1988). It compares the morphological relationships between many different populations in North, Horn and East Africa, as well as some groups in Southwest Asia. Here is a dendrogram from the study, with the geographical sources of the samples shown below it:

As can be seen, the northern Horn groups in general, including the northern Somalis, form an immediate cluster with the Yemeni and coastal Libyan samples, before ultimately tying up with the other North African and Southwest Asian groups. A central Oromo sample and the southern Somali/Sab sample, on the other hand, cluster with Afro-Asiatic-speaking groups in southern Ethiopia that have a very large, dominant Sub-Saharan component (such as the Geleba/Daasanach and the Maji/Dizi); the Kikuyu sample also belongs to this cluster due to some admixture with neighboring Cushitic groups (per Wood et al. (2005), about 19% of them are E1b1b carriers).

This divergent clustering pattern on the part of the Oromo sample and the Sab is attributable to the fact that many modern Oromo speakers actually belong to other, non-Oromo ethnic groups that the Oromos assimilated (mainly Omotic groups), and the Sab are heavily admixed with Sub-Saharan peoples (so much so that one major publication on Somalia actually suggests that they are of Bantu origin and were later assimilated into the dominant Somali culture).

This divergent clustering pattern on the part of the Oromo sample and the Sab is attributable to the fact that many modern Oromo speakers actually belong to other, non-Oromo ethnic groups that the Oromos assimilated (mainly Omotic groups), and the Sab are heavily admixed with Sub-Saharan peoples (so much so that one major publication on Somalia actually suggests that they are of Bantu origin and were later assimilated into the dominant Somali culture).

"The Somali nation comprises two main subdivisions, the 'Soomaali' and the 'Sab'. The Sab tribes form an extensive wedge of cultivators between the rivers of Somalia and separate the nomads of northern Somaliland from those of the south. The 'Soomaali', who are numerically superior, despise the 'Sab' for their sedentary way of life, for their mixed origins (Oromo and Negroid admixture is pronounced), and for their mixed genealogies. Nevertheless, Sab are included in the designation 'Soomaali' by outsiders, in much the same way as the inhabitants of the British Isles are frequently indiscriminately referred to as 'English'. Within the Somali nation, Soomaali and Sab are differentiated although there is an increasing tendency for the Soomaali/Sab cleavage to be ignored in the rising tide of Somali nationalism. Urbanized and Westernized Somali maintain that discrimination is 'old-fashioned', that it is contrary to the injunctions of the Prophet, and that it undermines the unity of the Somali people. In practice and actual social relations, however, these ideals are often betrayed, which serves to indicate how deeply engrained the traditional Somali social order is."-- Akbar S. Ahmed, David M. Hart, Islam in tribal societies: from the Atlas to the Indus, p. 129

"Somalis are comprised of two major groups: the dominant Samaale (75 per cent of the population) and the Sab (20 per cent). There exists some controversy over whether the Sab have been fully incorporated as Somalis for they have traditionally been distinguished as sedentary or semi-sedentary agriculturalists inhabiting the interriverine area, while the Samaale are pastoral nomads. The Samaale are believed to be Hamitic in origin whereas the Sab are Bantu, migrants from the equatorial lakes of Africa. It is hypothesized that the Samaale have inhabited the Horn for at least 1,000 years, driving out or subjugating the populations of the interriverine areas as slaves. However, much of the literature maintains that the two groups have been integrated through intermarriage and that they are now considered as one. Recent studies by archaeologists will provide information that may alter much traditional thought on this subject."-- Mark DeLancey, Somalia, p. xiii

Dental traits of Hamites

Hanihara et al. (2005) examined dental variation in many global populations, both modern and old, including ancient Egyptians. It found out that Somalis are the only sampled African population outside of North Africa whose tooth size clustered with circum-West Eurasian populations: http://www.femininebeauty.info/hanihara.flatness.pdf

The Somalis' atypical dental traits were also noted by the anthropologist Loring Brace. He made the following observation in his Clines and Clusters Versus “Race:” A Test in Ancient Egypt and the Case of a Death on the Nile (1993) study:

"Most of our sub-Saharan African samples fall into the “megadont” category used by Flower to indicate relative tooth size (Brace and Hunt, 1990; Brace et al., 1991; Flower, 1885), but the Somalis from the Horn of East Africa sit right on the dividing line between “mesodont” and “microdont.” Evidently the ancestors of the Somalis had long been associated with food preparation practices that reduced the selective force intensity maintaining tooth size. This is consistent with the possibility that the Ethiopian highlands were the locale of one of the ancient and semi-independent centers of plant domestication (Harlan, 1969, 1971; Harlan et al., 1976; Stemler, 1980; Vavilov, 1951)."

This has been noted since at least the late 19th century:

Sonia Mary Cole and G.Brauer on ancient Eastafricans

see dienekes http://dienekes.blogspot.de/2004/09/racial-affinities-of-prehistoric-east.html

Origin of Caucasoids in Eastafrica:Coon thought the distribution of races in Africa was like before Caucasoids entered the continent from the north (via the Sinai or an Iberian land-bridge) and displaced the indigenous Capoids and Congoids towards the south. Other authorities suggest that the Caucasoids actually entered from the south, through the Bab el-Mandeb. Still others propose that they evolved locally. Sonia Mary Cole takes into account all possibilities(See below).

G. Bräuer conducted a comprehensive study in 1990 where he compared the East and North African Caucasoid crania with other specimens from the continent. He also cross-analysed key skeletal finds from West Asia and Europe. The results were consistent with Sonia Mary Cole's observations(see below) since the Capsian/Eburran fossils and the later Elmenteitan ones generally clustered with his various Cro-Magnon samples, except to some extent for the Elmenteitan B skull due to some Khoisanoid admixture.
He also found that the East African Gamble's Cave and related skeletal material grouped nearest to certain prehistoric Caucasoid remains from West Eurasia. They weren't Negroid, though some Negroid and Khoisan specimens did also coexist in the region during various periods (similar to the situation in prehistoric North Africa).

For example, in the Principal Component analysis below showing the main dimensions of the facial skeleton and other frontal measurements, note the proximity of the Elmenteitan A (ELMA) specimen to the Piedmosti 3 (PRD3), Oberkassel 1 (OKA1) and Chancelade 1 (CHAN) Upper Paleolithic European crania. Most of this clustering is also on the horizontal PCI axis, where 45.6% of the total genetic variance is contained.

That's what Sonia Mary Cole was alluding to when she wrote that the East and North African fossils closely resembled other prehistoric Caucasoid crania from West Eurasia; their culture did too.

"Before leaving Upper Palaeolithic man in East Africa, we should glance briefly at his contemporaries in Europe living during the last glacial period. The Upper Palaeolithic people who invaded Europe after the first phase of the Wurm glaciation arrived in a series of waves, probably from the direction of Palestine. First came the Combe Capelle type, makers of the Chatelperronian culture (which is similar to the Upper Kenya Capsian and to the later Capsian of North Africa). These are the earliest known representatives of Homo sapiens in Europe, apart from the Swanscombe and Fontechevade fossils. They were followed by the Aurignacians of Grimaldi and then by the robust Cro-Magnons, associated with Aurignacian and Gravettian industries. In the Cro-Magnons, Coon sees an admixture of Neanderthal blood, possibly springing from crosses as may have occurred at Mount Carmel. The Cro-Magnons are divisible into a dolichocephalic eastern or Predmost type (which is very close to Combe Capelle), and a broad-headed western type, the Cro-Magnons proper. After them came the Magdalenians known from Chancelade. All these different types may have arrived in Europe within a few thousand years.
The skulls from Gamble's Cave, the Naivasha rock shelter, and Olduvai are very similar to the large-brained Combe Capelle type. Cro-Magnon man is less modern in appearance than the earlier Combe Capelle people; he resembles the 'Mechta' type of North Africa. The conclusion is that Upper Palaeolithic peoples in Africa differed hardly at all in appearance (or in the form of implements that some of them made), from their counterparts in Europe."

 Here are the fossil specimen codes in Brauer's scattergram above:

Below are Brauer's overall classifications of the pre-historic crania in East Africa, taken from another study (http://www.ncbi.nlm.nih.gov/pubmed/113948)where he discusses the various specimens in greater depth. The Elmenteitan material, though generally classified as Caucasoid/Europid, has a question mark near it because of the Khosanoid admixture that's evident in the short-faced, brachycephalic F1 fossil which Cole described and which is pictured in the OP:

Here are excerpts of what Brauer writes on the East and North African Caucasoid crania, including the Maghreban Mechtoid fossils:

"There is a third African major race: the Mediterranean. The populations living on the shores of the Mediterranean Sea and in parts of East Africa are classified as Mediterranean or Afro-Mediterranean because of their relatively homogeneous Europid characteristics. Due to various admixtures with neighbouring Negrid populations in prehistoric and historic times, the present populations of East Africa in particular are more or less heterogeneous in appearance, especially with regard to soft-tissue morphology[...]
The Mediterranean character is clearly dominant among the Ethiopids, who include the large populations of the Amhara, the Galla and the Somali. Their skeletal features are predominantly Europid; the nose is generally narrow and prominent. However, there are also Negrid admixtures of varying degrees among the individual tribes. The Negrid character is strongest among the Sidamos in South West Ethiopia, and at its weakest among the Somali (Cole 1965)[...]
The number of sites in Algeria and Morocco belonging to the Ibero-Maurusian culture is relatively large. Especially well-known is the mesolithic cemetary of Afalou-bou-Rhummel on the Algerian coast, where in 1928-30 remains of more than 40 adults and a number of children were excavated (Arambourg 1929; Arambourg et al. 1934; Vallois 1952). Likewise linked with the Ibero-Maurusian culture is the important skeletal series of more than 280 individuals found in the Taforalt cave (Morocco) in 1951-1953 (Ferembach 1962). A late Pleistocene layer of this site has been dated to about 10,000-12,000 B.P. (Roche 1959).
In Maghreb, however, there are also numerous settlements of the North African Capsian, which are linked with huge shell mounds. The most important site of this type is Mechta-el-Arbi, southwest of Constantine (Algeria), where in 1907-1927 remains of more than 30 individuals were found in a huge shell mound (Arambourg et al. 1934). As an indication of the dating, the absolute age of another shell mound associated with the same culture (Upper Capsian) may be of interest; it has been dated at about 8,400 + or - 400 B. P., the beginning of the Holocene (Ivanova 1972). The skeletons from Dar-es-Soltan near Rabat (Morocco) also are ascribed to the Mechta type (Vallois 1951; Ferembach 1976).
The morphological affinities of all of these samples are generally Europid, though there appears to have been differentiation into two morphotypes. One is represented by tall, robust individuals with large, long and high crania, broad faces with low, rectangular sloping orbitae and heavy rugged jaws with strong chins (Briggs 1955; Ferembach 1962). The other type comprises individuals with small faces and less rugged "leptodolichomorphic" characteristics. Although both combinations of characteristics do not generally occur separately, relating to the sites, there is some evidence of a tendency (Schwidetzky 1970) for the more robust type to be more numerous in Ibero-Maurusian sites, while the leptodolichomorphic form is more frequent in those of the Capsian, as shown by the East African men of the Kenya Capsian.
The modern populations, too, can be understood on the basis of this polarity of types. The Berber populations from the Maghreb and North West Africa tend to be more robust and broad-faced than the Arabian populations and other groups from the East.
The present Egyptians are closer to the pole of the small leptodolichomorphic Mediterranean populations (Schwidetzky 1970), as evidenced by the populations of Egypt since predynastic times, and have yielded some larger series. However, Egypt had been infiltrated by groups of various populations, especially in historical times.The increase of Negrid influence is due primarily to the Arabic slave-trade. Nevertheless, Negrid influences in ancient Egypt seem to have been much smaller than in Nubia (Strouhal 1975). The present southern Nubians are tall and lightly built, but the skin colour is darker; they are probably the product of hybridization between Europid Egyptians and Negroids."

Only certain of the Mesolithic Elmenteitan skeletal remains in East Africa show some Khoisanoid affinities. The earlier Capsian/Eburran specimens from Gamble's Cave and elsewhere generally do not. This is because admixture between these early West Eurasian/Caucasoid migrants to the region and the local Paleoafricans (perhaps best represented by the Kanjera skull of Kenya) only really began in earnest later, during the Elmenteitan period.

Below are faithful reproductions of the Capsian/Eburran and Elmenteitan crania, taken from Sonia Mary Cole's seminal The Prehistory of East Africa:

Here is the phylogeny of the various skeletal remains, and below it, a map of the fossil sites: