© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm

12.2  The Bisexual Universe

The apparent general restriction of ETs to only two sexes is no cause for alarm. An incredible number of variations can be played on the single theme of bisexuality.

For example, bisexuality -- contrary to popular belief -- does not demand the existence of distinct male and female forms. A case in point is the black mold Rhizopus nigricans, which displays an unusual type of sexual behavior known as "heterothallism."

This species of fungus is bisexual, inasmuch as two organisms are required for fertilization and reproduction. However, the two sexes are indistinguishable! There are no constant differences between members of opposite mating groups other than their reciprocal behavior when crossed. Thus, it is impossible to designate one form of the black mold as male and the other as female. The complementary groups are labeled merely "+" and "-" for convenience during experiments.

One can imagine a race of intelligent extraterrestrials, apparently unisexual to our undiscerning eyes but which actually practices heterothallic sex. Such creatures would most certainly lack secondary sexual characteristics, those hormone-induced physical landmarks such as beards and breasts to which we humans are accustomed. They might even lack distinctive primary sexual characteristics such as internal or external gonads.

Last updated on 6 December 2008