What's in store for humanity? It is becoming clear that we will use our growing technological powers to transform not only the world around us but ourselves, too. Many forms of human enhancement are already routine--sports medicine, psychotropic mood drugs, wakefulness and alertness enhancers, cosmetic surgery, drugs for sexual performance. Much more will become possible in coming decades.

Joel Garreau's Radical Evolution joins several recent titles that attempt to make sense of the radical future possibilities for our species. The potential prospects include superintelligent machines, nonaging bodies, direct connections between human brains or between brain and computer, fully realistic virtual reality, and the reanimation of patients in cryonic suspension. As enablers of such miracles, Garreau mentions especially "GRIN technologies"--genetics, robotics, information technology and nanotechnology.

The focus of Garreau's book, however, is not on the nuts and bolts of the technology itself but rather on what it will all mean for us humans. His reporting skills well honed by his work as a journalist and editor at the Washington Post, Garreau is constantly on the lookout for the human story behind the ideas. Biographical sketches of the people he has interviewed for the book get approximately equal airtime with their opinions about human extinction and transcendence. The bulk of one interviewee's beard, the size of another's collection of musical instruments, the length of a third's pants: as Garreau knows all too well, these are the indispensable rivets to hold the attention of the current version of Homo sapiens while we try to ponder whether we will have indefinite life spans or whether the world will end before our children have a chance to grow up.

Garreau organizes his material around several scenarios. Unfortunately, these are not very carefully delineated. It is not clear whether all of them are meant to represent separate possibilities.

In the Curve Scenario, information technology continues to improve exponentially, and this progress bleeds over into adjacent fields such as genetics, robotics and nanotechnology. In the Singularity Scenario, "the Curve of exponentially increasing technological change is unstoppable" and leads, "before 2030, to the creation of greater-than-human intelligence," which proceeds to improve itself "at such a rate as to exceed comprehension." There is a Heaven Scenario, which serves as a rubric for a future in which "almost unimaginably good things ... including the conquering of disease and poverty, but also an increase in beauty, wisdom, love, truth and peace" are happening pretty much on their own accord, without deliberate steering. Garreau associates this view with the distinguished inventor Ray Kurzweil. We are told that one of the early "warning signs" that we are entering the Heaven Scenario is that the phrase "The Singularity" enters common usage.

There is also a Hell Scenario. The chief talking head assigned to this scenario is Bill Joy, who was a co-founder of Sun Microsystems. In April 2000 Joy published a bombshell article in Wired entitled "Why the Future Doesn't Need Us," which described how the author had come to the realization that advances in genetics, nanotechnology and robotics will eventually pose grave threats to human survival. The article argued for the relinquishment of some lines of research in these fields. Since then, we learn, Joy has got divorced, quit Sun, and put the book he was preparing on hold. "Overall his affect was markedly flat," Garreau writes.

One of the early warning signs that we are entering Hell is that "almost unimaginably bad things are happening, destroying large chunks of the human race or the biosphere, at an accelerating pace." Aside from Bill Joy, the chapter on the Hell Scenario features appearances by Francis Fukuyama, Martin Rees, Bill McKibben, Leon Kass and Frankenstein. The common denominator of these fellows is that they have confronted the potential for catastrophic technological downsides. But their worries are not all of the same kind. For example, while Joy focuses on direct threats to human survival (such as bioterrorism), Kass, who is chairman of President Bush's Council on Bioethics, is more concerned about subtle ways in which our quest for technological mastery could undermine the foundations of human dignity. These very different sorts of concerns could have been kept more clearly distinct.

Garreau's last scenario, Prevail, extols the human knack for muddling through--"the ability of ordinary people facing overwhelming odds to rise to the occasion because it is the right thing." The defining characteristic of the Prevail Scenario is that human beings are picking and choosing their futures in an effective manner. The main representative selected for this scenario is Jaron Lanier (the guy with the large collection of musical instruments). Lanier dreams of creating more ways for people to share their thoughts and experiences, and he is fond of pointing out that faster computer hardware does not necessarily lead to equivalent improvements in the usefulness of the software that runs on the computers.

In the final chapter, Garreau asks: "Will we forever keep mum about our obviously intense desire to break the bonds of mortality? Or should we lift the taboo and start dealing with it?" His implied answer is yes. He then asks, "Shall we be bashful about these lines we are crossing because we do not have a way to make them meaningful?" At this point, Garreau has a constructive proposal: let's create some new rituals. Perhaps, he suggests, we should have "a liturgy of life everlasting as a person receives her first cellular age-reversal workup." Why not indeed?

In the meantime, there is still some work left to do in the laboratories. If we develop the cure for aging in a timely fashion, while steering clear of the disasters that Joy and others have foretold, we may one day get to enjoy indefinite life spans with much improved physical and mental capacities--and some cracking new ceremonies, too.