20 The Eugenics Review Just as cultivation of one crop-plant here provided the basis for the later development of another, so the social environment appropriate to one stage of human culture gives opportunities for the expression of human traits which may be destined to become dominant at a later stage. The eliciting effect of environment is in both cases essential. The United States furnishes a classical human example. Pre-selection was at work on the pioneers. The human cargo of the [italics]Mayflower[end italics] was certainly not a random sample of the English population. Religious zeal, independence of character, perhaps a tendency to fanaticism, together with courage, must have been above the average among the leaders, and probably the whole band. The early settlers in Virginia and Carolina were pre-selected on other lines, though some of the characters involved were the same. After the first settlements were made, further immigrants until near the end of the nineteenth century were pre-selected for restlessness, initiative, adventurousness, and the qualities making up the pioneer spirit. The easily contented, the unadventurous and the timid, were pre-selected to remain behind. So, too, on the average, must have been those with artistic, philosophic, literary, or mathematical gifts. Even if the mean differences between those who went and those who stayed were not large, they must have been significant. Once the immigrants were established in the country, selection continued. This post-selection, so long as there was an open physical frontier to the west, and an open economic frontier in the more settled regions, must on the whole have encouraged and discouraged the same qualities favoured by pre-selection; in addition, assertiveness and ambition were encouraged in the acute phase of "rugged individualism," while artistic and literary endowment still were at a discount. Of course the direct moulding effect of the social environment must have acted in the same sense as its selective effect; so that here again genetic differences would be masked. Yet on deductive grounds we can be certain that the selective effect would be at work, and would produce genetic differences: the only question is the extent of those differences. Whenever there are mass-movements of population, we are sure to find similar selective effects. The difference between the Southern Irish in America and in Ireland strikes every observer: we can hardly doubt that it is due in part (though doubtless not entirely) to a sifting of more from less adventurous types. And the same holds true of the obvious differences between rural and urban population in a country like our own. Whatever may be the effect of country life and labour on a man's temperament, we can be sure that those who stayed behind were not as a group genetically identical with those who ventured away into the new life of the towns. One of the profoundest selective influences ever brought to bear on the human population of the globe must have been that exerted by the invention and spread of agriculture, as has been well stressed by Ellsworth Huntington.* A settled agricultural civilization demands qualities in its members very different from those demanded by a nomadic or a hunting existence. Agriculture demands constant application; the pastoral life is freer, and hunting demands rather occasional outbursts of maximum energy. Agriculture demands foresight and the sacrificing of present comfort to future benefit; in the more primitive modes of life, activity springs more immediately from events. Agriculture demands steady routine in one spot; the nomad and the hunter can profitably indulge the spirit of restlessness. Inevitably, it would seem, where early agricultural civilizations were growing up, there must have been a considerable drift of the more restless types out of them into the nomad and hunting cultures on their borders; and quite possibly there occurred also a converse movement inwards of more calculating and less restless types. Further, once the agricultural civilizations were well established, a dominant class [hairline rule right side column-width] [footnote]*Huntington, 1928, Chapter XIV. [end]