Page:Territory in Bird Life by Henry Eliot Howard (London, John Murray edition).djvu/221

Rh it is along these lines that the evolution of the voice has proceeded.

In all probability there was a time when vocal expression was limited to primitive social and family cries which would be called into play with special force during times of excitement, more particularly during the sexual season which is the period of maximum emotional excitement. But the excitement would express itself j in all the congenital modes of behaviour peculiar to the season, and thus the repetition of these cries would become associated with combat, with extravagant feats of flight, and with other forms of motor response. Now the more emotional individuals would be the more pugnacious, and all the more likely therefore to secure territory and so to procreate their kind; and, being of an excitable disposition, they would at the same time be the more vociferous. Hence variations of the hereditary tendency to vocal expression, even though in themselves they were not of survival value, would be fostered and preserved, so long as they were not harmful, in virtue of their association with pugnacity. But if, instead of being neutral, they helped to further the biological end of combat, the relationship between the voice and pugnacity would be of a mutually beneficial kind; and those individuals in which variation in both directions happened to coincide, would have a better chance of success in the attainment of reproduction.

A territorial system, closely corresponding