Genetic Relationship of Parents	F	Mortality of Children (through 12 years of age)
Unrelated	0	0.082
Second cousins	0.016 ( )	0.108
First cousins	0.0625 ( )	0.114
Source: After D. L. Hartl and A. G. Clark, Principles of Population Genetics, 2d ed. (Sunderland, Mass.: Sinauer, 1989), Table 2. Original data from W. J. Schull and J. V. Neel, The Effects of Inbreeding on Japanese Children (New York: Harper & Row, 1965).