Harmony and Conflict in the Living World - Alexander F. Skutch [23]
This strenuous sexual rivalry is induced largely by hormones that the reproductive organs release into the bloodstream at the period of their greatest development and activity. It has long been known that geldings and oxen graze pacifically together while stallions and bulls brook no rivals. Castrated pigeons and other birds remain tranquilly with their male companions at seasons when they would normally fight. Conversely, by injections of appropriate hormones, quails can be made pugnacious in the winter months when otherwise they would be foraging in amicable flocks. Here, too, the basic and primary state of the animal is pacific and sociable. Sexual jealousy, with all the exclusiveness and sometimes fierce belligerency that accompany it, results from the modification
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of this prevailing condition by a chemical poured into the bloodstream and acting upon the nervous system, thereby inducing distinctive attitudes and modes of behavior. There are reasons for believing that this whole arrangement was brought about by natural selection, because of the advantages that accrue to a species in a world of conflict when the strongest males win more mates and leave more progeny than the weaker ones, or when the breeding individuals are scattered rather than crowded together.
In many species, the male reproductive apparatus is a Nessus' shirt that diffuses a subtle poison through the unfortunate animal, destroying his amiable tranquillity and bringing on a sort of madness. The hormones it releases have much the same effect as a blow in the face of a peaceful man, who doubles up his fits to strike back almost before he is aware of what he is doing. The effects of anger, as of fear, are intensified by a hormone that quickens circulation, deepens breathing, and tenses muscles. But no special hormone is needed to make animals placid and sociable. This is their primary state, which may be masked by the goading of hunger or the disquieting secretions of the sexual glands but can hardly be permanently altered without destroying their health or sanity. Yet even in this upsetting matter of sexual jealously, life's integrative force has asserted itself, turning rivals into associates and making of competition a mode of cooperation, as in the courtship assemblies of male birds mentioned in chapter 4.
How Strife Entered the Living World
Our survey of some of the pertinent facts of animal behavior suggests that friendly or integrative attitudes are more fundamental or central, closer to the basic, unmodified character of animal life, than are hostile or disruptive attitudes. When we reflect upon the origin of organisms, we see that it could hardly be otherwise. Life arose as a late phase in a long course of harmonization, which is, above all, the process of building up coherent patterns. Life could not flourish on this planet until cosmic and terrestrial developments had prepared a fairly stable, orderly environment for it. First, diffuse
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nebular material condensed into definite, widely separated bodies, moving rhythmically in dynamic equilibrium with distant neighbors. Then on the cooling surface of Earth the mixed vapors separated out, forming the atmosphere and the oceans, with emergent areas of land. The peculiar properties of air and water and the regular diurnal rotation of the sphere stabilized the temperature within limits compatible with