In March 2005, Technology Review published "Do You Want to Live Forever?," an article by renowned physician and writer Sherwin Nuland that took a deeply skeptical view of the claims by Aubrey de Grey, a theoretical biologist at the University of Cambridge who believes that human aging can be "fixed." Our story elicited much lively debate among readers, including Dr. de Grey, his followers, and his critics.

Yesterday, TechnologyReview.com published an open letter by Richard Miller, MD and professor of pathology at the University of Michigan, responding to de Grey's theories (in a decidedly humorous vein). This is de Grey's response to Miller's letter. -- Editors.

Dear Rich,

How delightful to hear from you. I am so heartened that you have chosen to dissociate yourself publicly from the anti-SENS sentiment recently expressed by some of our colleagues in EMBO reports [the November 2005 issue of this molecular biology journal published a letter critical of de Grey's theories, signed by 30 or so scientists, as well as a reply by de Grey. -- Editors.]. I hope you will succeed in extracting from them an apology for including your name in the list of authors (and so outrageously parodying your inestimable writing style). Perhaps, since your name was midway down a long author list, they thought no one would notice.

What an interesting problem you raise. I confess I had not considered the hardship endured by pigs as a result of their flightlessness, but you articulate it most effectively. I think I can indeed help.

Before addressing the marketing aspect, I feel it is worth examining this problem for alternative solutions that may be even more straightforward than those you list -- and which may be applicable to those unfortunate pigs who are already alive, and so for whom your strategies 1, 2, and 5 are inapplicable. It would surely be best to alleviate as much porcine suffering as possible, so these alternatives would be a definite improvement. Further, since those who might fund your project are also already alive, this might facilitate the marketing of your idea, too.

In considering this question I have adopted the age-old strategy of looking to evolution for clues. Evolution has of course created flying creatures from flightless ones several times. However, most of these processes are thought to have been slow, progressing through long periods of aeronautical semi-competence that far exceed that of contemporary pigs. Moreover, almost all flying species share with birds most of the seven differences from pigs that you list.

However, after much research I have identified a remarkable exception to this pattern.

Amazing though it may seem, the species homo sapiens progressed, about a century ago, from a state of absolute flightlessness (unless we count floating, which you clearly do not) to one of considerable competence at flying -- and they did so over a period of only a few years. I am therefore inclined to look to the methods that our species has adopted, as a starting-point for freeing our porcine friends from their current misery.