Is there a limit to Human Lifespans?

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Discussion Overview

The discussion centers around the question of whether there is a limit to human lifespans, exploring historical averages, maximum recorded ages, and potential future advancements in longevity. It encompasses theoretical, biological, and technological perspectives, as well as references to specific studies and examples from nature.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note the historical increase in average life expectancy, highlighting figures from 2,000 years ago compared to modern averages.
  • Bruce J. Klein discusses the theoretical maximum human lifespan, suggesting that while 120 years is often cited, there is evidence indicating that the maximum age at death has been rising.
  • John Wilmoth's research is mentioned, which argues that the maximum lifespan is not a fixed biological constant and has been increasing over time.
  • Some participants reference the longevity of specific individuals and populations, such as Jeanne Calment and centenarians in Japan, to illustrate variations in lifespan.
  • There are mentions of advancements in medical science, including genetic manipulation, stem cells, and nanotechnology, as potential avenues for extending human life.
  • Other participants introduce external sources discussing telomeres and theoretical limits to lifespan, suggesting that there may be biological constraints that have not yet been fully understood.
  • Some express skepticism about the long-term implications of current trends, indicating uncertainty about whether a ceiling on lifespan exists and where it might be.

Areas of Agreement / Disagreement

Participants express a range of views, with some supporting the idea that human lifespans are increasing and may continue to do so, while others introduce the possibility of inherent biological limits. There is no consensus on whether a definitive limit exists or what that limit might be.

Contextual Notes

The discussion includes references to various studies and theories but does not resolve the complexities surrounding the biological, environmental, and technological factors influencing human lifespan. Assumptions about future advancements and their impact on longevity remain speculative.

Who May Find This Useful

This discussion may be of interest to those studying gerontology, biology, and medical advancements, as well as individuals curious about the implications of longevity research.

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2,000 years ago the average life expectancy for humans was 19 years old. I mean, can you image having to kick the bucket before you’re even old enough to drink?

2,000 years later, with a little hand washing and a booster shot, you’ve got a pretty good chance of living to the ripe old age of 63. This average is for the whole world population. If you’re lucky enough to live in a developed country, which I’d guess you probably are since you’re reading this, your lifespan jumps considerably.

Take Japan for instance, which has the longest average expectancy at 79.9, according to government figures. If you live in the US, however, expect to live to an average of 77.3.

Separate the figures by gender, and men live to 72, while women live to 79, a whopping difference of seven years according to the 2001 CIA World Factbook.

Can we really expect to live this long or longer? The key question here is not what is the average human lifespan, but what is the maximum human lifespan.

In nature, there are quite a few examples of extreme lifespan. At 40,000-years the King's Holly shrub is the oldest living organism in the world. Located in a remote southwest corner of Tasmania, it is older than the last ice age.

Also, look to bacteria, which are in essence immortal as they do not change their structure over time. Plus, there is the famous HeLa cells case. Henereta Lacks, died Oct. 4, 1951, cervical cancer, yet her cancer cells still live on. Research centers worldwide use her immortal cells for medical research. The cells of her cancer, known as HeLa cells were the first human cells discovered to grow and thrive outside of the human body. And they are still growing to this day, as they were instrumental in the cure for polio and may one day solve the problem of cancer itself.

For the past few decades, scientist in polite circles have generally agreed upon the idea that humans couldn’t live much past 120. This theoretical lifespan limit has been tossed around so often, that it's hard to believe otherwise. Yet, is there any truth to this number? Well, it’s probably safe to say that few people, if anyone, have lived longer than 130 years, or at least the case has not been documented well enough to be granted passage into the honored halls of Guinness World Records.

Jeanne Calment, the oldest person to ever to live, was a Frenchwoman who died in 1997 at 122 years. She rode a bicycle until the age of 100 and once met Vincent Van Gogh in her father's painting shop. Her longevity is linked to her genes, as her father lived to the age of 94 and her mother to the age of 86.

According to Guinness, Japan is home to the world's oldest woman, Kamoto Hongo, who turned 115 this year; the oldest man, 113-year-old Yukichi Chuganji; and the community with the highest proportion of centenarians – 33 people per 100,000 in Okinawa.

According to a longevity study conducted by John Wilmoth, a UC Berkeley associate, the "oldest age at death for humans has been rising for more than a century and shows no signs of leveling off."

Wilmoth and fellow colleges in the US and Sweden, researched the national death records in Sweden and found an increase in the average maximum lifespan each year since 1861. This finding calls into question the 120 lifespan limit.

"We have shown that the maximum life span is changing. It is not a biological constant. Whether or not this can go on indefinitely is difficult to say. There is no hint yet that the upward trend is slowing down," said Wilmoth.

Wilmoth’s statements about maximum lifespan run counter to common wisdom that there’s a natural limit. “Those numbers are out of thin air... there is no scientific basis on which to estimate a fixed upper limit. Whether 115 or 120 years, it is a legend created by scientists who are quoting each other."

The rising trend in lifespan is credited to improved “medical practice concerning heart disease, stroke, smoking cessation, and the development of new drugs.”

"One of the assumptions is that life expectancy will rise a bit and then reach a ceiling it cannot go through” says Mr Oeppen, senior research associate at the Cambridge Group for the History of Population and Social Structure. "But people have been assuming that since the 1920s and it hasn't proved to be the case.”

"If we were close to the ceiling we might expect the survival of Japanese women now to be improving at a slower rate. But the improvement in Japan is among the fastest in the world." Oeppen said, "I think there is a ceiling, but we don't know where it is. We haven't got there yet."

Look for advancements in anti-aging research to come hot and heavy as the baby boom generation gets ready for their “golden years”. While scientists are far from having a cure for aging, there’s a concerted effort on the part of numerous scientist on many fronts. The potential cure for aging will likely come from one or more of the following:

1. Genetic Manipulation
With the human code now mapped, the race is on to find the anti-aging genes.

2. Stem Cells
While still a hot button issue, the potential here is enormous. Imagine growing a new heart from your own stem cell. Take a stem cell from your skin and harvest replacement organs without the dreaded problem of immune rejection from your body.

3. MEMS and Nanotech
With nanotech growing up, doctors are willing to look to Microelectromechanical System, MEMS and Nanotechnology for smaller and less evasive devices to monitor and repair aging cells and organs.

Does all this add up to extremely long life? No one knows for sure, but who’s ready to bet against it?

- Bruce J. Klein
 
Biology news on Phys.org
atyy said:
Oh, there are also scenarios like http://arxiv.org/abs/hep-th/0106109 (bottom of p16) which would limit human life span.

Lol, I doubt this kind of problem will manifest for a long time. But true nevertheless.
 

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