why cant human live forever

[K-Kool]

It will be interesting to see how the rise in obesity affects the average life span in the next 30-50 years.

[Strager]

The reason we get old and age, is because genes that are beneficial to us when were young aren't really needed as we get older, since supposedly the population has less of a chance of reaching advanced age.

 

Besides medicine, its evolution thats increasing age expectancy because people are having (and are able to have) children at an older age.

 

The average age of people having children has been increasing for a long time.

This 'naturally' increases life expectancy through evolution.

 

I disagree. The only way this would cause evolution is if people who CAN'T have children at older ages were dying off. The evolution taking place there is the ability for people to have children longer and longer - My personal feelings on the subject is that it is a direct result the development of hidden estrus (Concealed ovulation) in our females. As we have no obvious signs that women are in heat, people developed social skills to make that determination. We evolved in our ability to communicate, and even the way our brains are shaped because the ones who weren't able to communicate as well were having less children. People born with the traits allowing these skills were able to successfully mate and pass on those traits to subsequent generations. The evolution taking place IS the ability for women to have children at an older age- as generations of people began to use their social skills for mating behaviors, the age in which women are sexually active has been increasing. As such, over time the ones who developed traits that allowed them to have children later in life, were increasingly passing on those genes. Than again, there is also always the factor that since people are living longer, women are simply more likely to have children at a later age (probability factor) and the fact that the mass media has only been around for a short amount of time, so accurate counts couldn't be taken previously.

 

Going a bit off-subject for a sec, another contributing factor will soon be the recent introduction of "male enhancement" drugs, and artificial fertilization. As men are sexually active much later into their lifespans, genetic traits for impenitence will be passed on more often, and may even become the norm in several generations. The same can be said for women who can't get pregnant without help. How this will effect the age women have children is unclear, but it's likely to have a significant impact. If the current trends continue, we may one day "evolve" to the point where we are dependent on medications and science to reproduce at all.

 

and back on point....

 

I do see where your coming from however. We could artificially force evolution on the species the way you are talking about. For example if we took sperm from any male who lived over 100 years, and used that for all artificial pregnancies, those children would have a 50-50 chance (actually less as there are numerous other factors, as well as a lot of other stuff...not to mention factors like if the gene is dominant or recessive....) of getting the DNA that allowed his sire to live so long. Over time those genes would become more prevalent in the gene pool, and eventually over a significant amount of time everyone would live into their 100s. Artificially are working to find ways of getting those genes into the population faster (gene manipulation) so future generations will have those traits.

 

Finally I'd like to point out that all this is just of course my opinion. While I have done significant independent research, I'm not a biologist (I never even graduated college) by any stretch of the imagination. Basically I wouldn't quote this post as valid research - I could be wrong about something.....

[pioneer]

The ability for cells to regenerate or make new cells can't be the heart of the problem when it comes to aging (assuming a clean environment). The neurons of the brain, once they form in a small child (2-4 years), never replicate again. We have the same neurons our whole life. These cells can last 100 years, which shows that the DNA has cell repair mode. Not exactly perpetual but very long duration.

 

All the cells in the human body, use the exact same DNA. The neurons use the same DNA as the heart, lungs, digestive system, etc. What that means is the DNA has the capacity to make cells last longer. So if the DNA is able to duplicate say 50 times, to use a number, before it loses it little terminal tail, if we could make each cycle last ten years, then we get the body to 500 years. For some reason the rest of the body makes new cells, instead of maintaining the old ones. Maybe we need to make use of the genes the neurons use, designed for constant repair instead of throw away.

 

It is possible the DNA is designed by nature with evolution in mind. The best way to speed evolutionary change is to limit the life expectancy so the new is able to take root easier. Aging may be a natural way for population control, so there is constant renewal of fresh genetics and personalities for evolution. But it does need renewal mode for neurons.

Edited May 27, 2008 by pioneer

[bascule]

I'll defer to Dr. Aubrey de Gray, who proposes 7 principal causes of aging:

 

1. Cancer-causing nuclear mutations

2. Mitochondrial mutations

3. Accumulation of intracellular waste

4. Accumulation of extracellular waste

5. Cell loss

6. Cell senescence

7. Extracellular crosslinks

[jimmydasaint]

In answer to the OP, I thinkI know what you are getting at. However, I think you are asking the question: 'Why do humans die?' despite having near perfect DNA and RNA polymerases and 'fail-safe' mechanisms. People will answer you with how, but not why - that is a mystery...