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Life Span Determinants

Posted May 26, 2011

DNA Structure

Changes in DNA Assure Survival

Biologic reproduction assures the continuation of life. Reproduction also assures adaptive change due to environmental conditions so that a life form can survive. The continuation of life depends upon being able to change with varying conditions. The extinct life forms that litter Earth’s history were not able to make the necessary changes (or at least not in time) that would have stayed their kind from extinction.

Lifespan periods today may be reflective of an Earth that has a continually changing environment. Nothing is ever as static as it seems. We have found evidence of ancient oceans on the highest mountains and old tropical forest in the frozen tundra. Through all of the environmental changes, life has remained tenacious because the DNA that describes a life form has the ability to change with conditions. The ability of life to make changes and adapt to differing environmental situations has been a staple of Darwin's theory since its inception. But it is important to note that the changes come through the reproductive system. Once reproduced, the properties of that individual remain with that life form throughout its life. If you have big feet, you will have big feet throughout your life. But that doesn't mean that you automatically pass this trait on to your offspring.

DNA changes to a given environmental change usually do not happen in one life cycle of an organism. It may take several life cycles to rebuild a viable population that can exist under the new and different circumstances. Since the changes come about via the reproductive process, a long lifespan works against being able to adapt to the faster environmental fluctuations. Necessary changes may not have time to save the life form. Taking several life cycles to reestablish a modified version of a life form works well because the changing environment may be temporary in nature and full adaptation not actually required.

Rapid environmental changes can be too fast for an organism to adapt and in the process, dooming the affected organism. Some of the forces that can change the environment too quickly are cosmic collisions, volcanism, and changes in the Sun's output.

Examining geologic evidence of the past demonstrates how dynamic things were in Earth’s earlier time-periods. During the Precambrian/Cambrian period, there was a virtual explosion of life forms developed. But the Earth was in a state of rapid change and in order for life to stay viable, rapid changes to DNA was necessary. In order to produce the changes fast enough, shorter life spans would have been necessary. The passing years have calmed the Earth's dynamism and mellowed out its wildly varying environmental changes. These longer periods of stability have reduced the need for rapid organism change due to environmental concerns. Translocation and predatory practices probably drive the slight changes in life forms we observe today.

Overall, the increase in stability means less demand for DNA changes and consequently, longer life spans become possible.

This article is not including the DNA accidents from radiation and other factors that generally produce dead-end abnormalities. Further, I believe that most changes, no matter how small, were made in response to an external event. (even the accidental changes)

What determines when DNA needs to change? And where do the changes come from? For instance, the evolution process works through the reproductive system. Think about that for a moment. During the era of the Black Death where so many people died, enough were immune to the disease to withstand it and eventually pass on that resistance to their offspring. How did that happen? Where did the resistance come from?

The same thing happens on the micro-scale. We use antibiotics against pathogens, but there are always survivors that eventually render the antibiotic useless. Somewhere, somehow, there were pathogenic survivors. The survivors then allowed natural selection, via reproduction, to establish resistance to the antibiotic. This has everything to do with lifespan. Consider the logic. If an organism lived longer, and reproduced less frequently, it would not allow the few survivors enough time to establish viable colonies.

We refer to natural selection as a winnowing term representing the successful change of an organism. But the term ‘natural selection’ is also suggestive of being the arbiter of several solutions spawned from chaos to a specific problem. This idea lends itself to the notion of a randomness that I reject. Logic interferes with the chaotic randomness idea and completely ignores any suggestion that DNA makes purposeful changes to meet new situations.

Additionally, it is the sheer number of DNA changes possible that rule out any chaotic randomness. Using the at random type of scenario, it could take eons of random DNA changes to solve a problem. An organism may not have time on its side and perish waiting on a specific DNA combination.

I would suggest that in every organism, whether simple or complex, there is a mechanism for adjusting to whatever environmental changes that comes its way. Is this ability the workings of intelligence within the organism or just blind luck? If it is luck, then life has been very lucky to survive from its beginning so long ago. Yes, DNA and its attending retinues that maintain it are a marvel.

Natural selection is a forwarding of a process that is started with DNA changes. You have to hand it to the DNA structure; it realizes that a change would be beneficial so it starts the process of modification. The conditions that start the DNA to modify may be climate, predation, or competition with other organisms. The life structure seems self-programmed to succeed against a variety of obstacles. You can be sure that something in the inner workings of this life structure determines that a change is necessary. That is why I believe that DNA, because of its ability to self-program, is a creation of intelligence. DNA doesn't care what life form it describes as long as that life form is successful. The dead-end life form fails because the time it had to adapt was either too short or conditions changed again leaving no time for further changes. Adaption time can be cut short because of severe climate changes, predation, or cosmic events. I'm sure there are other reasons but the idea is only to demonstrate some of the possible causes for extinction of different life forms. But given ample time to adapt, the DNA will see to it that needed changes will emerge that will enhance the survival of the organism.

To bring the conversation full circle and link human lifespan with their abilities to adapt, we note that the entities with the shortest lifespan can make systemic changes faster than the longer-lived entities. Other than calamitous events, the rhythm of Earth’s climate in comparison to the length of human lifespan is slow. Ice age to ice age can take thousands of years. The oceans of the world form a buffer against chaotic temperature swings with their ability to absorb and release heat. Logic dictates that our lifespan connects to the rhythms of the earth and the story of human evolution is also tied to those same rhythms. Human lifespan is probably at the limit that would allow time enough to adapt to future enviromental changes.

The opinions expressed here about DNA are mine. This is not a scientific document.

Robert welcomes your comment to this or any other of my commentaries.

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A Physics Major at the University of Texas
Retired from the offshore drilling industry where he worked as an Electrical Supervisor, Licensed Chief Engineer, and Electrical Designer.

Robert Writes for 2 Online Magazines and three private web sites.
Interests include computers, Cosmology, Evolution, and Environmental Research.

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