I find genetics remarkable, and look forward to the day when medicines will be custom-designed for an individual's genetic makeup. My SWAG is: if a person lives another 25 years, he'll live another 50. If he lives another 50, he'll live another 100. And if he lives another 100, the sky's the limit.

That's barring accidents and suicides, of course, and raises some interesting questions about work and retirement, among other things, but I find it all very positive.