According to the theory of degeneration, a host of individual and social pathologies in a finite network of diseases, disorders and moral habits could be explained by a biologically based affliction. The primary symptoms of the affliction were thought to be a weakening of the vital forces and will power of its victim. In this way, a wide range of social and medical deviations, including crime, violence, alcoholism, prostitution, gambling, and pornography, could be explained by reference to a biological defect within the individual. The theory of degeneration was therefore predicated on evolutionary theory. The forces of degeneration opposed those of evolution, and those afflicted with degeneration were thought to represent a return to an earlier evolutionary stage. This can be seen socially when mixed race marriages started becoming more frequent as the 19th century progressed. Such mixed marriages, all but unthinkable in 1848 but now on the rise among Indo-European and even full-blood European women with native men, were attributed to the increasing impoverishment and declining welfare of these women on the one hand an "intellectual and social development" among certain classes of native the other. The issue, however, was rarely addressed since the gender hierarchy of the argument was contingent on assuming those who made such conjugal choices were neither well-bred nor deserved European standing. As more people  began to mix with a race or people that was seen as lesser, degeneration theory became intertwined with development in a racial and colonial sense and more of these examples became common.