Sexual selection as well as lethal is affected by war in manifold ways. Considering the armed force, there is an inter-group selection, when the enemy's women are assaulted by the soldiers. While this has been an important factor in the past, it is somewhat less common now, with better army discipline and higher social ideals.
Within the group, mating at the outset of a war is greatly increased by many hurried marriages. There is also alleged to be sometimes an increase of illegitimacy in the neighborhood of training camps. In each of these instances, these matings do not represent as much maturity of judgment as there would have been in times of peace, and hence give a less desirable sexual selection.
In the belligerent nation at home, the number of marriageable males is of course far less than at ordinary times. It becomes important, then, to compare the quality of the non-combatants and those combatants who survive and return home, since their absence during the war period of course decreases their reproduction as compared with the non-combatants. The marked excess of women over men, both during the war and after, necessarily intensifies the selection of women and proportionately reduces that of men, since relatively fewer men will remain unmated. This excess of women is found in all classes. Among superiors there are, in addition, some women who never marry because the war has so reduced the number of suitors thought eligible.
The five years' war of Paraguay with Brazil, Uruguay and Argentina (1864-1869) is perhaps the most glaring case on record[158] in recent years of the destruction of the male population of a country. Whole regiments were made up of boys of 16 or less. At the beginning of the war the population of Paraguay had been given as 1,337,437. It fell to 221,709 (28,746 men, 106,254 women, 86,079 children); it is even now probably not more than half of the estimate made at the beginning of the war. "Here in a small area has occurred a drastic case of racial ravage without parallel since the time of the Thirty Years' War." Macedonia, however, furnishes a fairly close parallel—D. S. Jordan found whole villages there in 1913 in which not a single man remained: only women and children. Conditions were not so very much better in parts of the South at the close of the Civil War, particularly in Virginia and North Carolina, where probably 40% of the young men of reproductive age died without issue. And in a few of the Northern states, such as Vermont, Connecticut and Massachusetts, the loss was proportionately almost as great. These were probably as good men as any country has produced, and their loss, with that of their potential offspring, undoubtedly is causing more far-reaching effects in the subsequent history of the United States than has ever been realized.
In the past and still among many savage peoples, inter-group selection has been affected by the stealing of women from the vanquished. The effect of this has been very different, depending on whether these women would otherwise have been killed or spared, and also depending on the relative quality of their nation to that of their conquerors.
To sum up, there are so many features of natural selection, each of which must be separately weighed and the whole then balanced, that it is a matter of extensive inquiry to determine whether a certain war has a preponderance of eugenic or dysgenic results.
When the quality of the combatants is so high, compared with the rest of the world, as during the Great War, no conceivable eugenic gains from the war can offset the losses. It is probably well within the facts to assume that the period of this war represents a decline in inherent human quality, greater than in any similar length of time in the previous history of the world.
Unfortunately, it does not appear that war is becoming much less common if we consider number of combatants rather than number of wars as times goes on,[159] and it steadily tends to be more destructive. War, then, offers one of the greatest problems which the eugenist must face, for a few months of war may undo all that eugenic reforms can gain in a generation.
The total abolition of war would, of course, be the ideal, but there is no possibility of this in the near future. The fighting instinct, it must be remembered, is one of the most primitive and powerful that the human mechanism contains. It was evolved in great intensity, to give man supremacy over his environment—for the great "struggle for existence" is with the environment, not with members of one's own species. Man long ago conquered the environment so successfully that he has never since had to exert himself in physical combat in this direction; but the fighting instinct remained and could not be baulked without causing uneasiness. Spurred on by a complex set of psychological and economic stimuli, man took to fighting his own kind, to a degree that no other species shows.
Now contrary to what the militarist philosophers affirm, this particular sort of "struggle for existence" is not a necessity to the further progressive evolution of the race. On the contrary it more frequently reverses evolution and makes the race go backward, rather than forward.