I am convinced that in the next century millions will cut each other's throat because of 1 or 2 degrees more or less of cephalic index.

European expansion overseas, therefore, set the stage for racist dogmas and gave violent early expression to racial antipathies without propounding racism as a philosophy. Racism did not get its currency in modern thought until it was applied to conflicts in Europe – first to class conflicts and then to national. But it is possible to wonder whether the doctrine would have been proposed at all as explaining these latter conflicts – where, as we have seen, the dogma is so inept – if the basis for it had not been laid in the violent experience of racial prejudice on the frontier.

Generally speaking, there has been an ethnic succession in all areas of crime, beginning with the Irish, who were the first identifiable minority to inhabit urban slums. In the 1860s Harper Magazine observed that the Irish “have so behaved themselves that nearly 75 percent of our criminals are Irish, that fully 75 percent of the crimes of violence committed among us are the work of Irishmen…” Speculation as to the causes of the alarming rate of crime among the Irish centered on ethnic traits, especially the intemperate disposition of the Irish “race.”