Some children born today can expect to live very long lives. The average age in the United States today is 78, with more than 800,000 people living to 100.  University of Texas biogerontologist Steve Austad expects longevity to increase.

He says the reason goes beyond good genes and low calorie diets. "The other part of the picture is that we can now alter dozens of genes and make rodents live longer and some of those advances will be applicable to humans. We just don't know which ones yet."

Austad says much remains to be learned about the process of aging. Some of the laboratory rats whose lives were extended suffered from side effects such as greater susceptibility to infections, reduced fitness and fertility. "What we are able to do now is to slow the aging process," Austad says. "No one is really looking to keep unhealthy people alive for another 50 years. What we are really trying to do is to extend health. And one of the side effects of making 60- and 70- and 80-year-olds live longer is that some people are going to live much, much longer, maybe as much as 150 years or more."

He says this could bring about tremendous demographic and economic changes.

Austad and colleagues discussed these issues at the annual meeting of the American Association for the Advancement of Science in San Francisco.