Summary of Results--Inbreeding and Evolution--Effects of Close
Inbreeding--Crossing and Variation--"Difference of
Potential"--Resemblance and Intensification--Coefficient of
Correlation between Husband and Wife--Between Cousins--Between
Brothers and Sisters--Consanguinity and Eugenics--Consanguinity and
Social Evolution--Conclusion




CHAPTER I

INTRODUCTION


The purpose of this essay is to present in a concise form and without
bias or prejudice, the most important facts in regard to
consanguineous marriages, their effects upon society, and more
particularly their bearing upon American social evolution. The
problems to be considered are not only those which relate primarily to
the individual and secondarily to the race, such as the supposed
effect of blood relationship in the parents upon the health and
condition of the offspring; but also the effect, if any, which such
marriages have upon the birth-rate, upon the proportion of the sexes
at birth, and the most fundamental problem of all, the relative
frequency with which consanguineous marriages take place in a given
community.

No thorough and systematic study of the subject has ever been made,
and could not be made except through the agency of the census. The