This section is from the book "Principles Of Sociology With Educational Applications", by Frederick R. Clow. Also available from Amazon: Principles of sociology with educational applications.
Nevertheless, hereditary capacity and incapacity really exist and lie at the basis of the well-to-do classes on the one hand and the poverty-stricken classes on the other. This has been pointedly illustrated by the contrasted histories of the "Jukes" family and the Edwards family, and still more pointedly by the account of the two branches of the "Kallikak" family.
. . . Just before attaining his majority, the young man joined one of the numerous military companies that were formed to protect the country at the beginning of the Revolution. At one of the taverns frequented by the militia he met a feeble-minded girl by whom he became the father of a feeble-minded son. This child was given, by its mother, the name of the father in full, and thus has been handed down to posterity the father's name and the mother's mental capacity. This illegitimate boy was Martin Kallikak, Jr., . . . and from him have come four hundred and eighty descendants. One hundred and forty-three of these, we have conclusive proof, were or are feeble-minded, while only forty-six have been normal. The rest are unknown or doubtful. Among these four hundred and eighty descendants, thirty-six have been illegitimate. There have been thirty-three sexually immoral persons, mostly prostitutes. There have been twenty-four confirmed alcoholics. There have been three epileptics. Eighty-two died in infancy. Three were criminal. Eight kept houses of ill-fame ... in spite of the fact that they mostly lived in a rural community where such places do not flourish. . . .
Martin Sr., on leaving the Revolutionary Army, straightened up and married a respectable girl of good family, and through that union has come another line of descendants of radically different character. These now number four hundred and ninety-six in direct descent. All of them are normal people. Three men only have been found among them who were somewhat degenerate, but they were not defective. Two of these were alcoholic, and the other sexually loose. . . . There have been no feeble-minded among them; no illegitimate children; no immoral women. . . . There has been no epilepsy, no criminals, no keepers of houses of prostitution. Only fifteen children have died in infancy. ... - God-dard, The Kallikak Family, pp. 18, 19, 29, 30, 68.
Here is the caste principle clear enough. The present generation of the bad branch of the family are what they are, not so much because one thirty-second part of their blood came from that feeble-minded girl, but rather because the successive generations of her descendants have lived in a certain social current, mating with persons like themselves and bringing up their children to ways like their own. Likewise the descendants of that wife have been respectable and prosperous because they have mated with their kind and brought up their children in an atmosphere of respectability.
In cases of this kind the interest of society calls for encouragement of the caste principle. When the defective classes mingle freely with other people they become the tools of the criminal classes; unable to make a living honestly, they try to do it dishonestly. In neighborhoods where these people collect we often find the worthy poor living alongside of them because it would cost more to live anywhere else; occasionally also we find persons of the highest character and intelligence - some of the whitest souls on earth - bound there by affection or some necessity. But the combination of feeble-minded, criminals, and the poverty-stricken makes the lowest stratum of society. The social mind of it must be described in negative terms: low intelligence, low standard of living, disregard of law of all kinds, degrading rather than refined pleasures, lack of high ideals, little energetic effort. Cooley does not rank the poor as a class because they lack the energy to develop a current of thought of their own, which would be still more true of defectives. But nature abhors a vacuum, and human nature has enough low impulses to occupy the mind of any social group in which the higher impulses remain undeveloped. There are always enough criminals and demagogues to exploit those who lack initiative. It is the opinion of those well informed on the subject that this bottom class as a whole owes its existence largely to hereditary feeblemindedness.
At the same time we must not forget that defective children come from all classes of society, from the homes of the rich and talented as well as of the poor and criminal. Heredity is not the only cause: vicious living, disease, and accident play their part as well. But the defective child in a well-to-do family is sheltered from evil influences, given such education as he is capable of (though not always wisely directed), and provided with a suitable occupation when he grows up. This saves him from falling into the criminal and poverty-stricken class described above.