Related Content
"Truth and morning become light with time." -- Ethiopian Proverb
The more sure you are of science or politics the more things change. Just when the facts were about as solid as you thought they could be here comes a different premise.
Scientists in Denmark turned biology on it's head with what was the accepted wisdom about mitochondria. What you thought you knew about mitochondria was probably wrong if you thought your mitochondria only comes from your mother. It appears there is an exception.
In every cell in your body you have mitochondria, lots of them and the assumption has been you get it from your mother. They are small turbo-charged power generators which appears to be evolved from bacteria (according to a theory by Lynn Margolis a few years ago) which is an organelle which lives outside the nucleus and generates ATP, the fuel necessary for life.
These little organelles are as small as bacteria which are one hundred thousand times smaller than your cells. They make ATP which fuels everything in your body. They are so small that you could take a billion of them and easily fit them on a grain of sand.
As often happens with science, theories are constantly being tested and new research improve on those theories. Danish scientists, Marianne Schwartz, a geneticist at Copenhagen University Hospital, et al, have published their research in the New England Journal of Medicine, which document an exception to the assumption that mitochondria is exclusively from mothers. They discovered muscle cells containing paternal mitochondria.
The muscle cells had mitochondria with a "paternal" genetic defect. Other cells; in blood, skin and hair did not have the defect and the genetic pattern indicated they were "maternal" mitochondria.
Since both sperm and egg made the embryo and the egg contains about 100,000 maternal mitochondria the sperm contains about 100 copies of _paternal_ mitochondria. Apparently enough paternal mitochondria survived to get into those cells which differentiated into muscle cells.
"Evolutionary biologists have assumed that each person's mitochondrial DNA is a copy of their mother's, their grandmother's and so on, back to the dawn of the species...Dr. R. Sanders Williams, dean of Duke University's medical school, said the discovery could "generate new debate about the validity of the Eve hypothesis." (Daniel Q. Haney, Sunday Gazette-Mail - Aug 25, 2002)
I don't think this is going to have much influence on "Mitochondria Eve" since (1) this appears to be an exception, and (2) paternal mitochondria is unlikely to get into other differentiated cells. In the research paternal mitochondria were only found in muscle cells.
Mitochondrial Eve, the MOTHER of all mothers is assumed to have lived in Africa about 170,000 years ago and that won't change. She was also known as "African Eve." Mitochondria are the genes, which are different than genes in a cell's nucleus, which are compared by forensic scientists or techs to determine true identity of corpses, like the real identity of the last Russian tsar, Nicholas II - which was verified by comparing those genes.
Humans are more than 99.9% of us identical. We're the same except for that small percentage of our DNA which is our unique diversity, which makes each of us different from all the rest. Inherited differences are a recombination of our parent's DNA, found in each cell nucleus. DNA is our recipe for proteins that in all of us determine our biochemical differences and sameness. We are all to some degree related. And, we all have a common ancestor all the way back to our common ancestor which is LUCA ("Last Uniform Common Ancestor"), which is the genesis of our species.
It is our differences, our diversity which makes all of us, of the same species, who we really are as individuals.
It is that less than one percent that makes us interesting or boring (to someone). It is that diversity which also determines our shape and size and that genetic difference which makes me better looking than you.
Mutations caused by damage which have environmental causation or free radical damage to genes by oxygen leakage from the process of power generation by mitochondria and the mechanism for transcribing DNA though several steps to make amino acids which then make protein may or may not improve upon fitness; although I'd rather say, "successfulness" for reproduction and that, among many other things, assist evolutionary modification of you and I; the hosts for that world of cells which live in us. Along with our cells which are only about 10% of the cells which live in us are the cells belonging to commensal (beneficial and symbiotic) bacteria and parasites too, amounting to almost 90% of what is not us lives in there too.
In each of our cells there are mitochondrion organelles which like bacterial have membranes and inside those membranes are more curly membranes and each contains it's own genes and from 5 o about 10 copies of those genes and in each cell there are as many as hundreds of mitochondria, each with it's many copies so within each cell are thousands of copies of genes, all of which different from the genes in the DNA in the cell's nucleus.
Mitochondria is a respiration device. It makes the energy, called ATP for organs and tissue cells but it isn't spark proof. Remember, oxygen is combustible and during the process of making energy; that is, respiration, there is free radical leakage which is causes damage to cells and leads to sensescence - just another way of saying "aging."
Cells are damaged by free radicals. The body's antioxidants as-if by some magic formula, fixes the damage but when it can't fix them, cells dispose of themselves. Genes are damaged by oxidative stress among other things, like pollution and radiation. These genes are attacked from 10,000 to 100,000 times a day. That is about once every second.
The cells which are not repairable commit suicide; they call that "apoptosis," which is dying for the sake of the whole body or a better way of saying it may be to refer to the body as the host. It was in the 90s that researchers discovered that apoptosis is not governed by genes from DNA in the cell nucleus. Apoptosis is a process which is governed by the mitochondria.
Some cells just decide to go somewhere else and continue to grow and they become cancers. Failure of the damaged cell to commit suicide (apoptosis) is a root cause of cancer.
"Without programmed cell death, the bonds that bind cells in complex multicellular organisms might never have evolved. And because programmed cell death depends on mitochondria, it may be that multicellular organisms could not exist without mitochondria." (Nick Lane, Power, Sex, Suicide, Mitochrondria and the Meaning of Life - Oxford U Pr - 2005)
All eukaryote multicellular plants and animals have mitochondria.
Free radical leakage leading to oxidative stress is also believed to be a root cause of what makes us age, to-wit: "senescence." Damage builds up over a lifetime and this steady damage causes degenerative diseases and affects a body's mortality, reducing our longevity.
Many inherited conditions are also linked to free radical damage. They increase with age. They are not selected against unless they affect "fitness" for reproduction (in populations). In populations, degenerative diseases from mutations which are a also a result of free radical damage generally manifest after reproduction and are not affected by natural selection.
"Mitochondrial diseases typically affect metabolically active tissues such as the muscle and brain, producing seizures, some movement disorders, blindness, deafness, and muscular degeneration." (Nick Lane)
Nature is not kind and we are all in a desperate race against time and oxidative stress.
Like our cells, a lifetime of accumulated
oxidative stress takes it's toll
and you and I will wear ourselves out and die.
Free Radical leakage is the cause of oxidative stress. It is just oxygen so why should it be so dangerous? Because oxygen is dangerous. Before there was multicellular life on the planet there was no oxygen. Oxygen accumulated in the atmosphere as a bacterial waste product. It is the reason things burn. Remove the oxygen from a fire and it goes out. Provide too much oxygen and everything burns; it becomes combustible. It is sold as a treatment for beauty; it is the "elixir of life" and there are "oxygen bars" and health clinics where it is hailed as a miracle therapy. There are some charlatans who promote it as a cure for cancer. But in fact oxygen keeps us breathing and alive now but eventually will kill us.
We are also sold the idea of taking antioxidants to protect us from the scourge of free radicals but what the body doesn't make it is unlikely will come from eating it. But what is the harm, you say, from eating too much fruits and vegetables and taking supplements? Often too much of anything, no matter how good you think it is, can be a bad thing - but I won't get into that here or now.
While oxygen is toxic and just the right amount of it, which we need to breath, is the amount of it in our atmosphere (21%). Not all life depends on it, not in those quantities anyway and some, not at all. Extreme life cannot assimilate it at all but if you and I stopped breathing it, we would be dead, whatever that means, in just a few minutes. I hesitate to define what is death because what is thermodynamically in equilibrium is considered dead but if it is a virus it is only technically dead until it gets inside the nucleus of your cells. And dead people may stop breathing but still return to disequilibrium and one of the laws of physics, specifically the "first law of thermodynamics" says you can neither destroy nor create energy or matter - so if what is dead is still capable of life in another form, even partially, is it really dead?
There are those who believe there is no science supporting the idea that our bodies must degrade. I believe there is. Nobody has ever extended life beyond about 120 years nor do I think it will ever be possible unless the body stops oxidizing, which can't happen as long as oxygen is extracted by mitochondria and utilized for the manufacture of ATP (Adenosine Triphosphate molecule), the unit of energy necessary for keeping the human machine running.
Therefore, death is as natural as life. It is a product as life and reproduction and after that the body stops being YOU but genes live on where they are inherited and chunks of it invade other hosts when infected by viruses and there is gene drift. And that part of gene transfer makes our genes at least capable of being immortal. But the host for those genes is not immortal. It becomes something else but it will not be you. Our bodies are programmed (to use a computer term) to age; to become decrepit and then to die in the human technical sense. No matter how much your watch your diet and how much you run or you jog, you will meet up with decrepitude, timed sensensence and you will die.
That fact is eminently clear to biologists. When salmon swim upstream and spawn, they die. After a marigold blooms it goes to seed and as those seeds are spread about by wind and birds, the particular marigold dies. If you go on a caloric restricted diet and do all those other healthy things like eat your spinach and exercise you may save yourself a few more years, but that is all - and the years you gain may be equal to the time you spent working out. Some might not consider that much of a trade-off. You won't gain 20 or 50 years. You may gain a year or two and that may be stretching it.
However the body is not subject to the same restraints as the second law of thermodynamics which is why bearings rust, the blades on knives get dull but life takes its energy from the sun and environment which is why you can add a couple of months and dump entropy back to the environment. Your DNA is the recipe and you can repair yourself but we aren't starfish and we can't grow new arms or an entire new body.
AS robust as we are at regeneration, making more cells to replace those which committed suicide, a starfish also regenerates more than we do but it also dies and so do we.
[E]volution has devised for all of us a system of maintenance and repair that is remarkably efficient. It's a genuine curiosity that evolution, after creating such intricate and comprehensive systems of repair, refuses to deploy them in a way that would maintain the body in a state of peak performance. This is the classical problem of aging, the problem that has baffled and confused generations of evolutionary theorists. (Joshua Mitteldorf, The Humanist - January 1, 2002)
Not all of our cells divide and create new cells. Our brain cells don't replace themselves but they do keep on dying.
(August Weismann in the 1890s) ..."Weismann was the first to speculate that the evolutionary reason for aging and death has something to do with the good' of the species. He called it "making room" in the environment. When their lease was up, the old would have the good grace to pack their bags and vacate the premises, leaving space for the young. The constant turnover of the population would help to maintain its diversity, and make the species more adaptable to changing circumstances." (Humanist)
I recall reading somewhere that we may exist for the good, not of us, but the bacteria that gave us life in the first place and they keep us around to help keep the planet in sync and when this collective bacterial brain no longer needs us they will get rid of us too, like the other 99% of all species which walked or brachiated or swam or flew here before us. That may be farfetched, or it may not be? It is just one hypothesis.
Weismann's point is that the only thing necessary for life is to reproduce and when reproduction is done there is no need to exist. That is why the salmon die. That is why after reproduction we age and break down. After reproduction we become superfluous. Nature doesn't give a damn about keeping us alive. Only our money and the doctors can do that for us and no amount of money will keep us alive forever. There is no real positive advantage or contribution for post-reproductives to make to the population. Only populations evolve and after reproduction there is nothing worth evolving unless there is a benefit to those which do reproduce.
The only way post-reproductive humans could be enough of a benefit for natural selection is if they were a benefit to reproduction.
Here is an excellent explanation why aging cannot be part of the natural selection process:
"In the 1960s, evolutionary theorist George Williams argued that benefits to the group are too weak a force to be invoked as an evolutionary explanation. Evolution is in the business of testing random mutations that first arise in a single individual. The first test for any new trait is whether it can progress from the individual to achieve prevalence in a group; only traits that passed this test can ever be tested in competition group against group. Hence individual selection will trump group selection every time, Williams said. Aging and the imposition of a finite lifespan may well have the potential to help maintain population diversity, but this benefit accrues only to the group. Aging harms the individual who ages and puts that individual at a selective disadvantage; hence aging can never be selected as an adaptation." (The Humanist)
Astrobiology is a relatively new science, the synthesis of biology, astronomy and paleontology - the objective of which is to gather information about our biological and cosmological past, including our universe and from that extrapolate what the future holds for us. Not to become too nonplussed, we won't be here. Nothing will be here.
Although I do think it is coming sooner, rather than later - given the damage we are causing to our own little space in the cosmos with space junk, pollution and the result which is global warming and what this will do for our short-lived species. I say short because we haven't been around all that terribly long.
Geologist Peter Ward and astronomer Donald Brownlee have proposed several scenarios for the end. They say the Earth's bio-diversity was at it's peak or apogee just about 250 million years ago so we're on the downside now.
They speculate the Earth will return to a period when it resembled the first 4000 million years, the Hadean eon, which name doesn't derive from Hades for no reason. It is going to be really hot, a whole lot less diverse and animals will disappear as will the oceans. Well you can guess the rest. It will be grim. I don't know about you, but I'm not going to worry about it.
Nothing lasts forever; including us. Did you think it did? If there is any consolation to any of this, there won't be anymore suffering. There won't be anymore handicapped who get fucked by the system and there won't be anymore inequities. Pain will be gone.
The good thing is you don't really die.
Your molecules will go back to the
earth, to the bacteria you inherited them from.
###
All quoting per the Fair Use Doctrine
for educational and
discussion purposes pursuant to
Title 17 U.S.C. Section 107,
Copyright Law.