The longevity business is booming. People are flocking to longevity meetings and taking compounds they hope will extend their lives. Investors are backing scientists researching techniques to reprogram cells to a younger state. Longevity influencers argue that if they can live long enough, scientific breakthroughs will keep them going indefinitely. “We are going to start to understand how to rejuvenate and revitalize ourselves. This is what science does,” said Dr. Peter Diamandis, a 63-year-old entrepreneur who runs longevity trips for investors.

But S. Jay Olshansky, who studies the upper bounds of human longevity at the University of Illinois Chicago, believes people shouldn’t expect to live to 100. He contends most will reach between 65-90. Olshansky said, “It’s basic biology. As people grow older, their cells and tissues accumulate damage. Breakdowns of one kind or another happen more frequently and get increasingly difficult to repair.”

Nobel laureate Venki Ramakrishnan explained the many reasons in his book, Why We Die. He doesn’t believe current interventions will dramatically extend lifespan. Techniques to reverse aging would have to help every system in the body, including the brain, over a long period.