Third, man's body and man's mind profoundly affect each other in all of their actions and reactions and have affected each other through all the centuries of their simultaneous evolution. EVOLUTION OF BLONDES AND BRUNETTES Men's bodies differ from one another in many ways. A little scientific investigation soon proves to us that these differences are the result of differences in heredity and environment. Men's minds differ from one another in countless ways. Scientific investigation also proves that these mental differences, or differences in character, are also the result of differences in heredity and environment. For example, people whose ancestors, through countless ages, lived in the bright sunlight and tropical luxuriance of the warmer climes, have dark eyes, dark hair, and dark skin because nature found it necessary to supply an abundance of pigmentation in order to protect the delicate tissues of the body from injury by the actinic rays of the sun. The same soft luxuriance of their environment has made these people slow, easy-going, hateful of change, introspective, philosophical and religious. On the other hand, people whose ancestors dwelt for centuries in the cold, dark, cloudy and foggy climate of Northwestern Europe have less need for pigmentation and are, therefore, flaxen-haired, blue-eyed and white-skinned. The hardships and rigors of this Northern climate made these people aggressive, active, restless, fond of variety, and, because of their fierce struggle for existence, exceedingly practical, matter-of-fact, and material. WHY NOSES DIFFER IN SIZE AND SHAPE Another example illustrates this truth clearly: The type of human nose evolved in warm, humid climates is low and flat, with large, short passageways directly to the lungs. People living in such a climate have little need for great energy and activity, since there is food in abundance all around them. On the other hand, the type of nose evolved in a cold, dry climate is high in the bridge, with thin nostrils, so that the air may be both warmed and moistened before reaching the lungs. People living in such a climate have great need for activity, both in order to secure the means of subsistence and in order to keep themselves warm. Thus we find that the low, flat nose is everywhere the nose of indolence and passivity, while the large nose, high in the bridge, is everywhere an indication of energy and aggressiveness. WHY SOME HEADS ARE HARD, OTHERS SOFT In brief, then, darkness of color is not the cause of deliberation and conservatism, but both darkness of color and conservatism are results of the same causes, namely, a heredity and environment which produce these characteristics. Blonde coloring is not a cause of restless activity, but both the color and the activity are the result of evolution in a cold, dark, rigorous climate.