From the anthropologist’s point of view, two groups of facts militate against this belief: the wide diversity of Jews with regard to physical characteristics, and their similarity to the Gentile population amidst whom they live. Both are reflected in the statistics about bodily height, cranial index, blood-groups, hair and eye colour, etc. Whichever of these anthropological criteria is taken as an indicator, it shows a greater similarity between Jews and their Gentile host-nation than between Jews living in different countries.
To sum up this situation, I have suggested the formulae: Ga- Ja< Ja- Jb; and Ga- Gb ≈ Ja - Jb. The obvious biological explanation for both phenomena is miscegenation, which took different forms in different historical situations: intermarriage, large-scale proselytizing, rape as a constant (legalized or tolerated) accompaniment of war and pogrom.
The belief that, notwithstanding the statistical data, there exists a recognizable Jewish type is based largely, but not entirely on various misconceptions. It ignores the fact that features regarded as typically Jewish by comparison with nordic people cease to appear so in a Mediterranean environment; it is unaware of the impact of the social environment on physique and countenance; and it confuses biological with social inheritance.
Nevertheless, there exist certain hereditary traits which characterize a certain type of contemporary Jew. In the light of modern population-genetics, these can to a large degree be attributed to processes which operated for several centuries in the segregated conditions of the ghetto: inbreeding, genetic drift, selective pressure.
The last-mentioned operated in several ways: natural selection (e.g., through epidemics), sexual selection and, more doubtfully, the selection of character-features favouring survival within the ghetto walls. In addition to these, social heredity, through childhood conditioning, acted as a powerful formative and deformative factor.
Each of these processes contributed to the emergence of the ghetto type. In the post-ghetto period it became progressively diluted. As for the genetic composition and physical appearance of the pre-ghetto stock, we know next to nothing. In the view presented in this book, this “original stock” was predominantly Turkish mixed to an unknown extent with ancient Palestinian and other elements.
Nor is it possible to tell which of the so-called typical features, such as the “Jewish nose”, is a product of sexual selection in the ghetto, or the manifestation of a particularly “persistent” tribal gene. Since “nostrility” is frequent among Caucasian peoples, and infrequent among the Semitic Bedouins, we have one more pointer to the dominant role played by the “thirteenth tribe” in the biological history of the Jews.