Human beings have an instinct for survival. Early in our history, human life was short, as we confronted constant threats from nature and predatory animals. Later, once we had secured a certain level of safety, we began fighting disease. In the past century and a half, particularly, we have greatly extended human life.

Recently, however, an analysis published in Nature argues that we may have reached the natural limit to our human lifespan. The authors of the study say their data indicates it is unlikely anyone will outlive Jeanne Calment, a Frenchwoman who died in 1997, at 122 years old. Even if we continue to find cures for all the diseases that afflict humanity, and the degenerative conditions of old age, we may already be living as long as humanly possible.

Study authors Xiao Dong, Brandon Milholland, and Jan Vijg believe the essential issue is exactly how flexible the maximum human lifespan may be. We know the lifespan of some organisms is quite flexible, but for some species, biological factors provide a fixed limit.

They write that the data they have analyzed “strong suggest that human lifestyle has a natural limit,” but they cannot know for sure whether it is possible to extend that limit. To explore the question, the researchers analyzed demographic date from 41 countries around the world.

Human life expectancy shot up drastically in the past century because we eliminated many of the diseases that took the lives of children. Antibiotics, vaccinations and other measures to lower infant and maternal mortality made it possible for many more people to reach old age.

In recent decades, there have been strides in reducing mortality among older people. Those strides seemed to plateau around 1980, according to the researchers.

The research team analyzed the mortality rates of supercentenarians (people 110 years of age or older) in the United States, the United Kingdom, Japan and France. Of course, there are a limited number of supercentarians living in the world, so the data on their death rates is inconclusive. However, the lifespan among this group appears to have plateaued around 1995, just two years before the death of Ms. Calment.

Since the late 1990s, even the healthiest people who appear to have genes for longevity have not live longer. The authors believe the chance of anyone living past 125 in any particular year are below 1 in 10,000.

The question now is, can we break this barrier? Tech billionaires, medical researchers and philosophers are caught up in trying to defeat age. Is it possible?

The researchers who conducted the Nature analysis believe the limits on human lifespan are lifely the result of the way our bodies develop through life, rather than any particular disease. Our bodies have a natural endpoint beyond which our cells are unable to continue to sustain life. Curing the diseases that afflict us, they argue, will not change that reality.