“Well, at one time, we thought that all creatures required seven sexes as a minimum. After your explorers arrived, however, we investigated and found that this was not true even of the animals here on our planet. My ancestor, nzred fanobrel, had many profitable talks with the biologists of the expedition who provided him with theoretical knowledge to explain that which we had only known in practice. For example, the biologists decided that we had evolved into a seven-sexed form in order to stimulate variation.”

“Variation? You mean so your children would be different?”

“Exactly. You see, there is only one thing that all the ravening life-forms of Venus would rather eat than each other; and that one thing is a Plookh. From the other continent, from all the islands and seas of Venus they come at different times for their Plookh feed. When a Plookh is discovered, a normally herbivorous animal will battle a mighty carnivore to the death and disregard the carcass of its defeated opponent—to enjoy the Plookh.”

Our civilizer considered me with a good deal of interest. “Why—what have you got that no one else has got?”

“We don’t know—exactly. It may be that our bodies possess a flavor that is uniformly exciting to all Venusian palates; it may be, as one of the biologists suggested to nzred fanobrel, that our tissue contains an element—a vitamin—essential to the diet of all the life-forms of our planet. But we are small and helpless creatures who must reproduce in quantity if we are to survive. And a large part of that quantity must differ from the parent who himself has survived into the reproductive stage. Thus, with seven parents who have lived long enough to reproduce, the offspring inherits the maximum qualities of survival as well as enough variation from any given parent to insure a constantly and rapidly improving race of Plookh.”

An affirmative grunt. “That would be it. In the one-sex stage—asexual is what the bio professors call it—it’s almost impossible to have varied offspring. In the bisexual stage, you get a good deal of variation. And with seven sexes, the sky must be the limit. But don’t you ever get a Plookh who isn’t good to eat, or who can maybe fight his way out of a jam?”