It is always easier to get your new ideas accepted in mainstream society if there is some other person, or some other idea, out there that makes your idea seem less radical, even tame, by comparison.

King's message of racial equality might have remained a bit too much for even relatively liberal whites to accept if it couldn't be contrasted with the Black Muslims' much more confrontational and separatist beliefs. Playboy's Girl Next Door seems innocuous, if not positively benign, compared to - we hear - Hustler's grotesque subjugation of women.

And, happily, the effort to reintroduce native wolves to Utah and other areas of the American West will seem much more like the normal process that it is now that some serious scientists have proposed importing African lions, cheetahs, even elephants, to the American Great Plains.

The animals this group of scientists thought about moving - the result of a brainstorming session at media mogul Ted Turner's New Mexico Ladder Ranch - are about as close as modern beasts get to the creatures that populated the American landscape some 13,000 years ago. That's about the time humans are thought to have brought forth on this continent the weapons that hunted various species to extinction.

Instead of Pleistocene mammoths and saber-toothed tigers, you'd have elephants and lions fulfilling their ecological duties. For elephants, it would be chewing up woody plants and churning up the prairie to reinvigorate the natural grasslands. For lions, it would be restoring the natural balance to the deer and elk populations that are exploding, and risking the spread of brain-wasting diseases, due to the deficit of wolves and mountain lions to keep their populations intact.

But it's all too neat, and ignores disasters that have occurred when people thought they were smart enough to move plants and animals from one region to another. We don't know, and can't predict, every interaction a new species would have with predators, prey, parasites and plants.

But, having rejected this idea, we might more easily return to the understanding that American wolves and mountain lions ought to be doing the job nature has called them to for the past 13 millennia, and not be importing homeless aliens to do it for them.