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Humanity is hitting the upper limit of life expectancy, according to a new study. Advances in medical technology and genetic research—not to mention larger numbers of people making it to age 100—are not not translating into marked jumps in lifespan overall, according to researchers who found shrinking longevity increases in countries with the longest-living populations.

"We have to recognize there's a limit" and perhaps reassess assumptions about when people should retire and how much money they'll need to live out their lives, said S. Jay Olshansky, a University of Illinois-Chicago researcher who was lead author of the study published Monday by the journal Nature Aging.

Mark Hayward, a University of Texas researcher not involved in the study, called it "a valuable addition to the mortality literature."

"We are reaching a plateau" in life expectancy, he agreed. It's always possible some breakthrough could push survival to greater heights, "but we don't have that now," Hayward said.

What is life expectancy?

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