Our forefathers were very wise and practical when they blessed youngsters with the soothing words “Sau saal jiyo beti”, “Vandellu bhathuku babu” or some such thing. Perhaps, they presciently knew the ‘limits’ of human life with all their blessings. A new study just published online in Nature suggests that the maximum lifespan of human beings is 115 or so. The peak of human lifespan has already been reached.

Therefore, instead of wasting resources trying to extend life, research should concentrate on extending health span and the duration of old age spent in good health. Scientists at the New York-based Albert Einstein College of Medicine suggest that it may not be possible to extend the human life span beyond the ages already attained by the oldest people on record. It was on August 4, 1997, that Jeanne Calment passed away in a nursing home in France. She died at age 122, setting a record for human longevity.

“Demographers as well as biologists have contended there is no reason to think that the ongoing increase in maximum lifespan will end soon,” said senior author Jan Vijg, professor and chair of genetics, at Einstein. “But our data strongly suggests that it has already been attained and that this happened in the 1990s.” Dr Vijg and his colleagues analysed data from the Human Mortality Database, which compiles mortality and population data from more than 40 countries.

Since 1900, those countries generally show a decline in late-life mortality. Based on maximum-reported-age-at-death data, the Einstein researchers put the average maximum human life span at 115 years. They calculated 125 years as the absolute limit of human lifespan. Since the 19th century, average life expectancy has risen almost continuously, thanks to improvements in public health, diet, technology, the environment and other areas.

Babies born in the US today can expect to live nearly until age 79, compared with an average life expectancy of only 47 for Americans born in 1900. Since the 1970s, the maximum duration of life (the age to which the oldest people live) has also risen. But, according to the Einstein researchers, this upward arc for maximal lifespan has a ceiling—and we've already touched it. “Further progress against infectious and chronic diseases may continue boosting average life expectancy, but not maximum lifespan,” said Dr Vijg.

“While it's conceivable that therapeutic breakthroughs might extend human longevity beyond the limits we've calculated, such advances would need to overwhelm the many genetic variants that appear to collectively determine the human lifespan.” The researchers focused on people verified as living to age 110 or older between 1968 and 2006 in the four countries (the U.S., France, Japan and the U.K.), with the largest number of long-lived individuals.

Age at death for these super-centenarians increased rapidly between the 1970s and early 1990s, but reached a plateau around 1995. Demographic evidence has revealed an ongoing reduction in old-age mortality and a rise of the maximum age at death, which may gradually extend human longevity. Together with observations that lifespan in various animal species is flexible and can be increased by genetic or pharmaceutical intervention, these results have led to suggestions that longevity may not be subject to strict, species-specific genetic constraints.

“We show that improve ments in survival with age tend to decline after age 100, and that the age at death of the world's oldest person has not increased since the 1990s. Our results strongly suggest that the maximum lifespan of humans is fixed and subject to natural constraints,” the scientists wrote. Biologists have always strongly suspected that maximum lifespan is genetically determined and specific to the species.

On this, Vijg says: “A mouse in the wild doesn't live more than seven, eight months or so. But if you take those mice and keep them in captivity and optimal conditions, they die when they are two years old or so. But they die. And that is because of the aging process.” Dr. Thomas Perls of Boston Medical Center and the Boston University School of Medicine, who is studying ‘super-agers’ i.e. people who live to be 110 or older, says:"We now have 150 people over 110.

They are very, very rare." He calculates that one in 5 million people lives to be 110 or older. “That is what the Seventh Day Adventist health study has shown us,” he points out. “If you take advantage of this average set of genes that we have — you don't smoke, you don't drink, you get regular exercise, you have a vegetarian diet, you're not overweight and maybe you do things to manage stress well, then you do what Seventh Day Adventists have, which is you have an average life expectancy of 89 if you are a woman, and 86 if you are a man… But to become super-old, it looks like you need a unique set of genes.”

He has identified more than 100 genes involved in healthy aging. David Sinclair, a pathologist at the Harvard Medical School, who also studies aging, is not among those who believe that there's a set limit to lifespan. He has been working for decades on various compounds that can reverse the aging process in cells. Sinclair argues there are no set limits, and doesn't believe that looking at past patterns can predict the future. “There are many species that live longer than us,” he says. “A bowhead whale lives to more than 200.” Still, man cannot have a whale of a time after 115- period.