Stupidity and sadness, cancer and bad golf scores. In the world according to transhumanism, these and other human frailties will eventually go the way of scurvy. Also on the horizon: immortality.

The possibilities are either tantalizing or terrifying, depending on your point of view. Transhumanists embrace a future in which everyone has the right to live a life beyond current biological limitations. Their detractors argue that all these radical enhancements will make us less human.

That depends on what you mean by "human," say transhumanists, whose very name suggests a species in flux.

As the World Transhumanist Association notes on its Web site, transhumanism is based on the premise that "the human species in its current form does not represent the end of our development but rather a comparatively early phase." Eventually, say transhumanists, we may indeed become "posthuman" — such an amalgamation of nanotechnology and neuropharmaceuticals, so changed by our interface with microchips and nanorobots, so much smarter, happier and healthier, that we hardly would be recognizable to early 21st century eyes.

It's science fiction based on science fact, a trajectory that begins with emerging technologies like cyberkinetic chips and gene therapy, says James Hughes, president of the World Transhumanist Association and author of "Citizen Cyborg." Actually, says Hughes, that trajectory began as soon as our Paleolithic ancestors started taking care of everyone who was toothless, a point at which we first transcended natural selection, he says. We have relied on technologies of one sort or another for millennia — from eye glasses to antibiotics — to continually make ourselves better than we naturally are.

But where do we draw the line? Or should we draw a line at all?

How smart should we be allowed to be? How tall? How happy? If we can make depressed people less depressed, should we make happy people more happy? If we can make our children healthier and smarter, if we can eliminate much of the suffering in the world through technology, do we have a moral responsibility to do so? Or do we have a moral responsibility to speak out against it?

These questions and hundreds of others will face humanity in the decades to come. There will likely come a time in the not-so-distant future when we will look back on simpler issues — steroid use by baseball players, for example — with a certain nostalgia for simpler times.