ALL ANIMALS HAVE TO DEAL WITH SEX

by Whit Gibbons

September 22, 2003

Gender equality is a contentious issue within human societies. In the United States, our laws declare that both sexes merit equal representation in government and equal opportunity in personal and professional pursuits. Supreme Court rulings and the Nineteenth Amendment to the U.S. Constitution have been necessary to establish the point, although some people seem oblivious of it even today. Of course, such rulings do not imply that the sexes are indistinguishable, for men and women are inherently different. The message is only that equality of the sexes is proper in regard to voting privileges, employment opportunities, and other cultural aspects of life.

Looking at gender distribution patterns in other species probably won't provide any insights for humans, but we never know when someone might draw a helpful analogy that makes for a better person. At the very least, looking at what other animals have to deal with, some similar and some different from the human condition, gives a fresh perspective to our own situation.

In some parts of the animal kingdom the gender issue could easily become confounded, at least by human standards, because the diversity of sexual differentiation among species is immense. The array of patterns is fascinating. For some species, determining how to balance male-female rights would be baffling, especially in regard to voting rights.

A common difference between the sexes in many species, including humans, is body size. In some species, adult males characteristically are larger and stronger than females. Such is true for rattlesnakes, turkeys, and white-tailed deer. All have evolved social systems in which males engage in physical combat or display with other males of the species. Contests are typically fought for possession of resources, including access to females. The biological premise among such species is that males that inherit genes favoring large body size and greater physical strength have a higher probability of reproductive success. The chances they will pass their genes on to succeeding generations are therefore increased. Although the sexes differ in body size, by U.S. standards each individual, male and female, in such species should get one vote.

In even more species, however, females get noticeably larger than males. Female size dominance occurs in turtles, spiders, and birds of prey. Numerous hypotheses have been proposed to explain why females have evolved to be larger than males. One relatively consistent observation is that males in these species do not engage in combat with each other. Another reliable attribute of species having female size dominance is that larger females lay more eggs or produce more offspring than smaller ones.

Would "one critter, one vote" still apply? Maybe. But a trait that could lead to dissension is an associated population feature in some of these species: the sex ratio is nowhere near equal. For example, in adult diamondback terrapins the number of males may be nearly double that of females. Should females get twice as many votes as males because they are so outnumbered? Or would the male-dominated society let females vote at all?

In some animal species differential size and number of the sexes would pose no problem because each individual possesses both male and female reproductive organs. For example, when two earthworms mate, each provides sperm to fertilize eggs in the other. Each earthworm would naturally get two votes in an election. That might be handy when trying to decide whether to vote for Candidate A or Candidate B. Just vote for both. But imagine how confusing the issue of sexual harassment or gay rights would be among earthworms.

In some fishes, the same individual may function as one sex when young and become the other sex at an older age. This would definitely muddle surveys that attempted to determine how gender is related to salary levels or management opportunities. Equally bizarre, from a human perspective, are several species of whiptail lizards in the Southwest among which no males have ever been discovered and presumably do not exist. The females lay unfertilized eggs that hatch into little female lizards that are genetic copies of themselves. The Nineteenth Amendment giving women the right to vote would be unnecessary for whiptail lizards. Either everyone votes or no one does. With regard to the gender issue, this might be the most harmonious society imaginable.

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