Related ContentOkinawans have the longest life expectancy and those living over 100 years are claimed to be about 34 per 1,000,000. HOWEVER, surveys done in various geographical locations and investigations have demonstrated that all records of longevity are extremely unreliable. It seems that life expectancies from old age; senescence, have never varied that much. People die of old age now at the about the same age as they always did. People died earlier at earlier times because of the brutishness and harshness of life, not because of natural aging. Most early deaths are caused by disease and accidents, but aging, an occurance after reproduction has stayed pretty stable.
The leading causes of death continue to be cancer and heart disease. You can include strokes in with that data which is also age related. However, when you make an effort to reduce these diseases by eating less, taking vitamins, exercising, eating in moderation - or even starving yourself on a calorie restricted diet you only gain a few years. Cancer and heart disease kill about HALF of all people in industrialized societies. HOWEVER, if all cancer was eliminated people would gain ONLY about two years overall. If heart disease was eliminated you would get another 4 to 6 years and that is it. Therefore, we have so far already achieved the optimum level of longevity from NATURAL aging.
There are several theories why people age. One of the most popular now is cellular damage from oxidative stress. Anther-words free radicals. The other theory which may be important is the length of telemeres; little tails at the end of chromosomes and each time they replace themselves which happens 80 to 90 times in a lifetime the telemeres get shorter until there is barely any left. It is more complicated than that and this is the short answer.
But the theory I like is free radical leakage; that seems to make the most sense - although I'm certain it is a combination of this and perhaps telemeres, etc.
There is free radical leakage from the manufacture of ATP, which is the energy which fuels all of your cells and organs and that work is done in your mitochondria. It is a multi-stage process which takes place only in mitochondria.
Eukaryotes have nucleated cells and lots of mitochondria. We, along with the rest of animals and plants are eukaryotes. Bacteria; our ancestors, I might add, did not have a nucleus and did not die. They just kept on dividing. And at some time after about 4.5 billion years, LIFE took a new direction and a merging took place and there was mitochondria. The theory is it only happened once because every eukaryote on the planet is related to each other - and to our bacterial cousins. You and that cockroach are also long lost cousins. Think about that next time you swat a fly or step on a roach or kill a snake.
And every eukaryote contains mitochrondria, usually from their mother - or in some cases they had mitochondria and lost it. That has happened. And on rare instances the father's mitochondria made its way into tissue cells but that is a real rarity. And mitochondria is about the size of bacteria, which is very much smaller than regular cells. Mitochondria DNA evolved with nucleated DNA and both depend on each other - which is why mitochondria is an organelle and not a symbiont.
For a cell to have mitochondria is pretty much sine qua non that the cell is a eukaryote and a eukaryote must have a nucleus. Eukaryotes are generally much bigger than proeukaryotes (bacteria) but some are as small - or smaller, i.e., the pico-eukaryotes.
What is interesting to me is the amount of collaboration which takes place between eukaryotes and prokaryotes and with mitochondria which as an organelle (similar to other organs in the body), it has the job of manufacturing the fuel or energy for the host it inhabits. All this cooperation to keep everything working.
Aging is a tough topic. There is a lot of research on how to extend life. There are groups of transhumanists who are interested in extending life, and think they can but this also involves augmentation which can make humans more like borgs than human beings. It's nevertheless fascinating and you can look it up on the Internet if you are interested in knowing more about transhumanism.
Also a paradox is why if there was so much collaboration between proeukaryotes and eukaryotes, why not more evolutionary forms and divergence in cells and other microorganisms - from this really great collaboration? Well, for one thing we are always discovering new forms of microorganisms and the numbers are astonishing. The more we look in SMALL places for SMALL things and in EXTREME places the more we find, i.e., the pico-eukaryotes. And a wide spectrum exists which we have yet to explore or discover. We may only be scratching the surface. While we explore our outer space, we have a huge inner space - inside our planet - deep in the oceans and even in us which remains unexplored or only partially explored or not at all.
Of course it is astonishing in itself that a merger occurred between mitochondria and resulted in multicellular, more complex organisms, and gave rise to animals like us. And practically everyone seems to be agreed that the acquisition of mitochondria, which was really the GREAT LEAP in multi complexity only happened once and thus WE ARE ALL RELATED and this great event was something of a miracle - as much as I dislike using that word. Why only once? Why us?
The pico-eukaryote live in extreme environments with micro-plankton in acidic rivers or high iron rivers (i.e., the "River of Fire" in southern Spain. and at the bottom of the Antarctic and other environments, like black smokers, i.e. thermo-vents, once thought to be the sole domain of only archaia extremophiles. The pico-eukaryote is a sub-species of the larger eukaryotes. Scientists have discovered perhaps 20-30 different sub-species of pico-eukaryotes, all of which are only about a micron in diameter, small as, or smaller than bacteria.
Mitochondria holds the key to our evolution and maybe also the key to why we only live so long and bacteria doesn't die NATURALLY, it just clones (it dies by accident, or antibiotics kills it, etc.) AND though we technically die, thermodynamically and there is equilibrium, we dissipate as energy back to the environment.
The cell is the smallest life and bacteria is life; the life that was here for billions of years before our nucleated cells, eukaryotes, evolved. That which is currently defined as life is [should be] a verb, NOT a noun.
Bacteria doesn't need to eat organic organisms to survive. They can consume the garbage in land fills. They can consume carbon dioxide and they can clean up after oil spills.
"Life is distinguished not by its chemical constituents but by the behavior of its chemicals. The question `What is Life?' is thus a linguistic trap. To answer according to the rules of grammar, we must supply a noun, a thing. But life on Earth is more like a verb. It repairs, maintains, recreates and outdoes itself." (L. Margulis and D. Sagan - What is Life? - 1995)
"The surge of activity which not only applies to cells and animals but to Earth's entire atmosphere, is intimately connected to two of science's most famous laws--the laws of thermodynamics. The first law says that throughout any transformation of the total energy of any system and its environment is neither lost nor gained. Energy--whether as light, movement, radiation, heat, radioactivity, chemical or other--is conserved." (ibid)
"But not all forms of energy are equal; not all have the same effect. Heat is a kind of energy to which other forms tend to convert, and heat tends to disorganize matter. The second law of thermodynamics says that physical systems tend to lose heat to their surroundings." (ibid)
"The second law was conceived during the Industrial Revolution, when the steam engine represented the state--of-art in engineering. French physicist Nicolas Carnot (1796-1832), aiming to improve the efficiency of the steam engine (whose governor mechanism was invented by James Watt), came to realize that heat was associate with the movement of minute particles. And from that, he envisioned the principle that is now known as the second law. In any moving or energy using system entropy increases."
"....(the first law of thermodynamics of conservation of energy holds), the amount of energy available to do work decreases. In computer science entropy is measured as the uncertainty in the information content of a message. The second law unequivocally claims that in changing systems entropy increases, implying that heat, noise, uncertainty, and other forms of energy not useful for work, increase. As local systems lose heat, the universe as a whole is gaining it. Although not so popular now, in the past physicists and chemists have made the prediction that the universe will whimper out in a `heat death' as a consequence of the tendency for entropy to increase. More recently, they have even invented the word `negentropy' for life, which in its tendency to increase information and certainty, seems to contradict the second law. It doesn't; the second law holds as long as one regards the system (LIFE) in its environment." (ibid)
Important to life is the ability to be self-sustaining and increasing itself. This is the basis of evolution. Natural selection is one aspect of evolution. And maintaining itself [autopoiesis] is a fundamental aspect of life.
"Islands of order in an ocean of chaos, organisms are far superior to human-built machines. Unlike James Watt's steam engine, for example, the body concentrates order. It continuously SELF-REPAIRS (emphasis mine). Every five days you get a new stomach lining. You get a new liver every two months. Your skin replaces itself every six weeks. Every year, ninety-eight percent of the atoms in your body are replaced. This nonstop chemical replacement, metabolism, is a sure sign of life. This `machine' demands continual input of chemical energy and materials (food)." (Margulis and Sagan)
And the fundamental component of life must be `autopoiesis' The reference is to the continuous producing of itself. The reference applies to all life. Life is purposeful. It reproduces. The molecules at the end of eukaryote life dissipates back to the external environment.
Life is metabolism. It is Redox Reactions. In the context of thermodynamics life is what makes our atomosphere orderly while disorder and heat is released into space. Life is a mechanism to self maintain. It is holarchic and some scientists believe it includes the biosphere itself.
Life is a simple code, just four acids, ergo adenine, thymine, guanine and cytosine, spelling out the recipes for life. That is the makeup of our genes. Whereas proteins are composed of twenty different amino acids, yet only FOUR amino acids can spell out exactly how any of us humans becomes a host for 90% bacteria and only 10% of our cells - which are us.
And creationists will tell you by the 2nd law of thermodynamics life should elude us by tending towards entropy. Scientists argue the point because we are ALL open systems and we replenish ourselves with energy from the environment and heat waste is radiated to the external environment.
When the body dies the constituent parts recycle back into the environment and our molecules start all over again as part of something else. We don't simply fade away and disappear. That might be comforting news for those of you who thought when we die we just non-exist. Not exactly. We cease to be what we formerly were but even dust is matter. Even the state of maximum entropy is not completely thermodynamic equilibrium. But especially in open systems. And, we are not machines. And even machines are made of matter.
But that is not the core reality of life as we know it, is it? The life that means anything to us is DNA significant and includes some kind of consciousness.
Some scientists are now re-interpreting entropy; that is, the second law, and our predilection for heat and energy as `purposefulness.'
Life is most definitely not a bowl of cherries, but neither is it without its rewards. The rewards may not be entirely ours though. It may belong to bacteria who came here to seed the planet (panspermia) and harvest our tissue. While we look beyond the earth for extra-terrestrials and exoplanets, we might not need to look beyond our own host bodies for life which is manipulating our behavior and how we conform to the laws of thermodynamics.
Hank Roth
For those of you with an interest in the way we might define life and wish to explore a non-theistic view of life, including the proposition that death does not exist, I recommend the following resources:
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Today is Friday May 18, 2012