It is evident that strictly endogamous marriage customs could never be upheld in tribes which have any intercourse with their neighbours if the social institution were not supported by a real psychological aversion to outsiders. It has therefore been congruous with the advantages of society to promote in the youth the feeling that any man or woman outside the tribe is a being with whom no emotional exchange is to be thought of. To make this feeling possible, on the other hand, it is necessary that everything which is connected with the foreigner should be held up to contempt. Their dress, their language, their manners, and so on, have thus been considered as something to be kept at a distance. It is needless to point out that marriage systems are not alone responsible for the development of this feeling. Religious differences, so important in primitive communities, have undoubtedly often given rise to the common notion that people outside one’s own tribe do not, properly speaking, belong to the human species. Continual war induces a feeling of contempt, which in the stronger tribe is mingled with pride and in the weaker with bitterness, and which in both cases extends to the smallest details of physical appearance and behaviour. And apart from all regard to these social causes, the primitive man, in civilised as well as in savage nations, is always apt to look upon everything unusual with a feeling of scornful disdain. No doubt such a disdain can even be coincident with exogamous marriage customs. But it seems evident that it must everywhere have strongly influenced sexual selection during those unknown endogamic periods in which the racial and tribal differences were developed and fixed.[306] And it may even now be observed among living tribes of man to how great a degree antipathy to every detail in the outward appearance of foreigners precludes union between members of different tribes. The national and parochial dresses of modern peasants no doubt exercise a great influence on the love-life of the respective boys and girls. The most telling example that could be quoted in this connection is the case of Savakot and Äyrämäiset in Eastern Finland. When examining a Savakko youth as to the reason why none of his tribe had ever chosen a wife from among their neighbours, Ahlqvist[307] received the characteristic answer: “Se kuin on heillä Äyrämäisillä niin hirveä vaatteen manieri niin siihen ei meidän pojat uskalla puuttua”—that is, As these Äyrämä girls have such horrid dresses, our boys do not dare to approach them.