The men of evil responsible for human sterilization, racial sociological science, master race planners, artificial human fertilization, animal and human cloning, modifications of the frequencies of human genes, state laws of mandatory vasectumy and castration operations targeting the mentally ill, mentally defective, mentally retarded, and the "feeble minded", racially driven genetic counseling in the 1970's, and the human genome project extending to the present day.

     "The facts," Professor Thorndike wrote, "are easily, simply and
completely explained by one simple hypothesis; namely, that the nature
of the germ-cells--the conditions of conception--cause whatever
similarities and differences exist in the original natures of men, that
these conditions influence mind and body equally, and that in life the
differences in modification of mind and body produced by such
differences as obtain between the environments of present-day New York City public school children are slight."
     "The inferences," he says, "with respect to the enormous importance of original nature in determining the behavior and achievements of any man in comparison with his fellows of the same period of civilization and
conditions of life are obvious.
     All theories of human life must accept as a first principle the fact that human beings at birth differ
enormously in mental capacities and that these differences are largely
due to similar differences in their ancestry. All attempts to change
human nature must accept as their most important condition the limits
set by original nature to each individual."
     Meantime other investigators, principally followers of Karl Pearson in England, were working out correlation coefficients in other lines of research for hundreds of different traits.
     It was found, no matter what physical or mental trait was
measured, that the coefficient of correlation between parent and child
was a little less than .5 and that the coefficient between brother and
brother, or sister and sister, or brother and sister, was a little more
than .5. On the average of many cases the mean "nature" value, the
coefficient of direct heredity, was placed at .51. This gave another
means of measuring nurture, for it was also possible to measure the
relation between any trait in the child and some factor in the environment. A specific instance will make this clearer.
     Groups of school children usually show an appalling percentage of
short-sightedness. Now suppose it is suggested that this is because they are allowed to learn to read at too early an age. One can find out the age at which any given child did learn to read, and work out the
coefficient of correlation between this age and the child's amount of
myopia.
     If the relation between them is very close--say .7 or .8--it
will be evident that the earlier a child learns to read, the more
short-sighted he is as he grows older. This will not prove a relation of
cause and effect, but it will at least create a great suspicion. If on
the contrary the correlation is very slight, it will be evident that
early reading has little to do with the prevalance of defective vision
among school children.
     If investigators similarly work out all the other correlations that can be suggested, finding whether there is any regular relation between myopia and overcrowding, long hours of study, general economic conditions at home, general physical or moral
conditions of parents, the time the child spends out of doors, etc., and
if no important relation is found between these various factors and
myopia, it will be evident that no factor of the environment which one
can think of as likely to cause the trouble really accounts for the poor
eyesight of school children.