Why We Age
Okinawans 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 younger 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. Strokes are usually 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. We have already achieved the 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. Antherwords aging as a consequence of free radical leakage. Another theory is the varying length of chromosomal 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 are barely any left. It is more complicated than that but this is the short answer. Aging is a combination of multiple causes - and among them are telemere shortening and free radical oxigen leakage.
Free radical leakage results from the manufacture of Adenosene Triphospates (ATP), which is the energy which fuels all of your cells and organs, a photon pump process in mitochondria. This is a multi-stage process which takes place only in mitochondria.
Eukaryotes have nucleated cells and lots of mitochondria. Animals and plants have nucleated cells. Our ancient ancestors, bacteria do not have a nucleus and they did not die. They just kept on dividing. And at some time after about 4.5 billion years, LIFE took a new direction, merging took place and mitochondria joined the family. The theory is it only happened once because every eukaryote on the planet is related to each other and they are also related to our bacterial cousins. All life on this planet is related. Think about that next time you swat a fly or step on a roach or kill a snake [that could be you].
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 rarity. And mitochondria is about the size of bacteria, which is very much smaller than regular cells. Mitochondria DNA evolved with a eukaryotic cell's 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 kill it) AND though we technically die thermodynamically; there is equilibrium, although we dissipate as energy back to the environment.
Hank Roth
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Today is Friday June 19, 2009
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