Competition considered as the main thing in life is too grim, too tenacious, too much a matter of taut muscles and intent will, to make a possible basis of life for more than one or two generations at most. After that length of time it must produce nervous fatigue, various phenomena of escape, a pursuit of pleasures as tense and as difficult as work (since relaxing has become impossible), and in the end a disappearance of the stock through sterility.

想起高中的课文《旅鼠之谜》，生存环境资源的竞争过于激烈，旅鼠们会选择集体自杀。类比人类自己，如果因为竞争过于激烈，一直得不到情绪和生理上的放松，选择不再生育是必然的选择。