1. Charles Darwin, The Origin of Species by Means of Natural Selection or the Preservation of Favored Races in the Struggle for Life (New York: The Modern Library, n.d.) (originally published in 1859) Chapter XV, “Recapitulation and Conclusion,” p. 371.

2. From George Seldes, The Great Thoughts (New York: Ballantine, 1985), p. 302.

3. E.g., Natalie Angier, “Pit Viper’s Life: Bizarre, Gallant and Venomous,” New York Times, October 15, 1991, pp. C1, C10.

4. Snakes certainly fight over territory as well—rat snakes, for example, over knotholes in trees where birds nest. The loser looks for another tree.

5. David Duvall, Stevan J. Arnold, and Gordon W. Schuett, “Pit Viper Mating Systems: Ecological Potential, Sexual Selection, and Microevolution,” in Biology of Pitvipers, J. A. Campbell and E. D. Brodie, Jr., editors (Tyler, TX: Selva, 1992).

6. B. J. Le Boeuf, “Male-male Competition and Reproductive Success in Elephant Seals,” American Zoologist 14 (1974), pp. 163–176.

7. C. R. Cox and B. J. Le Boeuf, “Female Incitation of Male Competition: A Mechanism in Sexual Selection,” American Naturalist 111 (1977), pp. 317–335.

8. E.g., Peter Maxim, “Dominance: A Useful Dimension of Social Communication,” Behavioral and Brain Sciences 4 (3) (September 1981), pp. 444, 445.

9. Charles Darwin, The Descent of Man and Selection in Relation to Sex (New York: The Modern Library, n.d.) (originally published in 1871) Part II, “Sexual Selection,” Chapter XVIII, “Secondary Sexual Characters of Mammals—continued,” p. 863.

10. Paul F. Brain and David Benton, “Conditions of Housing, Hormones, and Aggressive Behavior,” in Bruce B. Svare, editor, Hormones and Aggressive Behavior (New York and London: Plenum Press, 1983), p. 359.

11. Ibid., Table II, “Characteristics of Dominant and Subordinate Mice from Small Groups,” p. 358.

12. Dominance in a one-on-one encounter and dominance rank within a hierarchy are not necessarily the same and cannot always be predicted from one another. See Irwin S. Bernstein, “Dominance: The Baby and the Bathwater,” and subsequent commentary, Behavioral and Brain Sciences 4 (3) (September 1981), pp. 419–457. Some animals distinguish only between those lower and those higher in rank. Others—baboons, for example—behave differently to those of very distant rank than to those nearly co-equal in rank (Robert M. Seyfarth, “Do Monkeys Rank Each Other?” ibid., pp. 447–448).

13. W. C. Allee, The Social Life of Animals (Boston: Beacon Press paperback, 1958), especially p. 135 (originally published in 1938 by Abelard-Schuman Ltd.; this revised edition published in hardback in 1951 under the title Cooperation Among Animals With Human Implications).

14. V. C. Wynne-Edwards, Evolution Through Group Selection (Oxford: Blackwell, 1986), pp. 8–9.

15. Neil Greenberg and David Crews, “Physiological Ethology of Aggression in Amphibians and Reptiles,” in Svare, op. cit., pp. 483 (varanids), 481 (crocodiles), 474 (Dendrobates [dendratobids]), and 483 (skinks).

16. B. Hazlett, “Size Relations and Aggressive Behaviour in the Hermit Crab, Clibanarius Vitatus,” Zeitschrift fur Tierpsychologie 25 (1968), pp. 608–614.

17. Patricia S. Brown, Rodger D. Humm, and Robert B. Fischer, “The Influence of a Male’s Dominance Status on Female Choice in Syrian Hamsters,” Hormones and Behavior 22 (1988), pp. 143–149.

18. One of many other examples: Bart Kempenaers, Geert Verheyen, Marleen van den Broeck, Terry Burke, Christine van Broeck-hoven, and Andre Dhondt, “Extra-pair Paternity Results from Female Preference for High-Quality Males in the Blue Tit,” ?ature 357 (1992), pp. 494–496.

19. Mary Jane West-Eberhard, “Sexual Selection and Social Behavior,” in Michael H. Robinson and Lionel Tiger, editors, Man and Beast Revisited (Washington and London: Smithsonian Institution Press, 1991), p. 165.

20. In 1857, Elizabeth Cady Stanton wrote: “[H]ow perfectly [woman’s dress] describes her condition. Her tight waist and long, trailing skirts deprive her of all freedom of breath and motion. No wonder man prescribes her sphere. She needs his aid at every turn. He must help her up stairs and down, in the carriage and out, on the horse, up the hill, over the ditch and fence, and thus teach her the poetry of dependence.” (J. C. Lauer and R. H. Lauer, “The Language of Dress: A Sociohistorical Study of the Meaning of Clothing in America,” Canadian Review of American Studies 10 [1979], pp. 305–323.) Stunning change has occurred since 1857, although the poetry of dependence is still widely recited in the women’s fashion industry.

21. Owen R. Floody, “Hormones and Aggression in Female Mammals,” in Svare, op. cit., pp. 51, 52.