Much depends, of course, upon the special character of the institutions and traditions that thus come into contact. Some societies are rigid and repellent in their structure, while others, like the United States, are almost ideally constituted to invite and hasten assimilation. Conquest has been one of the main sources of caste the world over. The hostile tradition it leaves may continue indefinitely; servile functions are commonly forced upon the conquered, and the consciousness of superiority leads the conquerors to regard intermarriage as shameful. A servile caste, strictly hereditary, existed even among the primitive German tribes from which most of us are descended, and intermarriage with freemen was severely punished. “The Lombard,” says Mr. Gummere, “killed a serf who ventured to marry a free woman, ... West Goths and Burgundians scourged and burnt them both, while the Saxons punished an unequal marriage of any sort with death of man and wife.”[107] The unlikeness out of which caste grows may not be original, as in the case of race difference or conquest, but may arise gradually by the differentiation of a homogeneous people. Any distinct social group, having its special group sympathies and traditions, has some tendency to pass on its functions and ideas to the children of its members, promoting association and intermarriage among them, and thus taking on a caste character. Accordingly, any increase in the complexity of social functions—political, religious, military or industrial—such as necessarily accompanies the enlargement of a social system, may have a caste tendency, because it separates the population into groups corresponding to the several functions; and this alone may without doubt produce caste if the conditions are otherwise favorable.