Who's afraid of human enhancement?

We're not going to transcend the core elements of human nature ("Who's Afraid of Radical Human Enhancement?," January), but we'll adapt as we perceive it to be in our self-interest, and we'll change for the better when the talented among us teach the rest of us how to think more clearly about those interests. Knowledge and technology have advanced and brought us to a more comfortable way of life, but we're still pretty much a mirror image of our distant ancestors. Separate us from our technology, and don't we still react pretty much the same as those who came long, long before us?

Mark Selko

Beverly Hills, CA

As someone who has recently entered middle age (i.e., turned 40), I am enthralled by the possibility that I could live to see a radical extension of my life span. But such an extension will transform society in at least one important way that, surprisingly, was not addressed by any of the authors or questioners featured in "Who's Afraid of Radical Human Enhancement?"

Ron Bailey describes a world where 150-year-old great-great-great-grandparents are around to play touch football with the family and show no signs of kicking off soon. But if people really are able to live for hundreds of years (or longer), it could well be that they will put off having children until they are 100, or not have them at all, because having children could become prohibitively expensive.

Furthermore, if nobody ever dies, then where do you put all the new people? Does every spot on earth become a 100-story high-rise? Do we build colonies in space ? Do we all transcend our physical bodies and become bits of code in a virtual universe?

I'm not saying that the problem isn't soluble. But there at least exists the possibility that the ability to halt or even reverse aging could arrive well ahead of the technological advances required to deal with five, six, seven, or eight generations all cohabiting on the same planet, unless our reproductive rate slows to a crawl.

Phil Spoor 

Waterford, NY

Ronald Bailey replies: University of Illinois-Chicago demographer Jay Olshansky estimates that if everybody on the planet were made immortal tomorrow and fertility trends continue their projected decline, world population in 2100 would be around 12 to 13 billion. Interestingly, it is precisely those countries where life expectancy is longest that already have the lowest fertility rates.

As for resource use, agronomist Paul Waggoner calculates that simply deploying modern farming technologies worldwide could feed 10 billion people using just half the farmland currently being plowed. Other resource-sparing technologies, such as nanotechnology, will also likely keep humanity from reaching any limits to economic growth for quite a while.

In any case, immortality is not going to be available tomorrow, so humanity has a long time to figure out what do about it. Almost all human progress results from dealing with new problems as they arise. The implications of radically lengthened lifespans will be no different.