WHAT HEREDITY IS
General characteristics due to heredity
What heredity is and what it is not will now be considered in a practical way. It is clearly a matter of heredity that a man is born a man and not a monkey. Likewise, it is clearly a matter of heredity that distinguishes the various races of men. We could go farther and trace out and describe many of the physical distinctions which mark families, and even individuals, such as general size of frame, form of countenance, color of hair and eyes, etc.
Characteristics not attributed to heredity
Among mental traits we can safely ascribe to heredity only general distinctions. Intellectual parents are more likely to give birth to intellectual children than are parents whose natural mental faculties are less developed. There is also no doubt that certain natural characteristics of mind, such as quick temper, musical ability, etc., may be inherited. The belief, however, in the inheritance of many less distinct features, both physical and mental, is not well established by scientific investigation. Strength of muscle, control of the nervous system, susceptibility to, or freedom from dis-ease, etc., are more matters of nutrition and environment than of inheritance. The idea that consumption, alcoholism, etc., are inherited, or that the education or training of parents along certain lines will result in children with faculties adapted to similar education, is not in accordance with scientific knowledge.