The reason of this is that heredity follows the law of "recession to mediocrity." This is, that all groups of living things vary around an average or mean as regards each of their characters; and those near the average are always numerous, while as we approach the extremes in either direction the numbers become less and less. Families follow the same law. If you take a family for three or four generations, including perhaps some hundreds of persons, some will be short, some tall; but the majority will be near the mean, and the tallest of all will be less likely to have taller descendants than themselves than those nearer the average. But the children of the tallest, though generally shorter than their parents, will still tend to be above the average height.
When a character is so useful to its possessor in the struggle for existence as to be of what is termed "survival value," then those that vary most above the average will be preserved or selected generation after generation as long as the increase is useful.
It is because the higher intellectual or moral powers are so rarely of life-preserving value, and are not unfrequently the reverse, that they are not cumulative, though they are hereditary.
With this explanation we will now proceed to examine somewhat closely our moral position as a nation; what is the nature of our social environment; how it came to be what it is, and what lessons we may learn from it.
CHAPTER VIII
ENVIRONMENT DURING THE NINETEENTH CENTURY
During the eighteenth century our material civilisation, which had long been almost stationary, began to advance with the growth of the physical sciences, but at first with extreme slowness. The earliest steps were made by the application of machinery to some of the domestic arts. Some refinements were made in the manners and customs of our daily life; but there were few, if any, indications of permanent or widespread change, either for better or worse, in our intellectual or moral nature.
The nineteenth century, however, saw the initiation of a great change in the economic environment due to the rapid invention of labour-saving machinery; which, with the equally rapid application of steam power, led to an increase of wealth production such as had never been known on the earth before. During the same period new modes of locomotion were brought into daily use, the facilities for inter-communication were increased a hundred-fold, scientific discoveries opened up to us new and unthought-of mysteries of the universe, and the whole earth was ransacked for its treasures, both vegetable and mineral, to an extent that surpassed all that had been accomplished since the dawn of civilisation.