Immortal Genes

Do you want to be immortal?

Well, yes, now that you ask the question.  Living a very long time, if not forever, has been the dream of humans for at least as long as we have been recording dreams.  (Although, to tell you the truth, if I were to be suddenly struck immortal, I’d argue for living on as a younger version.)

Immortality is not just a crazy dream.  Amoebas are, in some sense anyway, immortal.  Since they reproduce themselves by simply dividing in two, the first amoeba who ever lived is still alive.  Or maybe one should say that when an amoeba splits into two, it is impossible to say which one was the original.  At any rate, except for some accident like getting damaged or eaten, an amoeba just goes on forever.

One could make the same argument for any single-celled organism and quite a few of the more primitive multi-celled ones.  But somewhere along the line sexual reproduction was invented, which, along with some rather enjoyable benefits, made it pretty easy to distinguish between a parent and child.

Unfortunately, along the way we “higher organisms” also developed that other useful invention, death.  No longer could we expect, barring a misadventure, to simply go on and on.  As our DNA strands got longer and longer and our organs more complex and interdependent, systemic failure became programmed into our futures.

One could argue that, far from being a drawback, this is all part of the Plan.  That evolution depends on old ones being replaced by new ones who are not exact copies.  If the basic model were that each creature simply produced perfect clones of itself, evolution would be impossible.  Three billion years after life first appeared on this planet, all that would be alive today would be a soup of identical single-celled organisms happily devouring each other.

To put it another way, evolution stands on two legs: imperfect copying of DNA and new generations replacing the old.  Immortality, either by perfect copying of DNA for new generations or the absence of death for the old, would mean that new species could never evolve.  Specifically, it means that we wouldn’t be here.

Would it surprise you, then, to learn that a portion of you is immortal?  That part of each of us is immune to the whole system of evolution?  And that we share this immortal something-or-other with all living creatures?

Genes are sections of DNA that are used to encode the proteins of life. (To be fussy, a gene is a string of nucleotides that encode the RNA that serves as the template to create the protein.)  We have something like 20-25,000 genes in our DNA.  Genetic mutations occur within all DNA.  Should the mutation occur in the DNA that is used for reproduction, that mutation will be passed along to the offspring.  Some will be fatal, some benign, and a few beneficial.  Should those last few prove beneficial enough to improve the chances of an organism living and procreating, that mutation may be “selected” and Voila!  Evolution.

Evolutionary biologists can use these mutations, the useful and the benign, to trace our family trees.  If you imagine a branch in some genealogy from which two species derive, then the DNA of each species would share all of the mutations of the parent up to the time of the split.  From that point on, each branch would begin to acquire its own set of mutations.  Hence we can map the history of each branch by tracing the mutations.

While DNA may seem a bit cavalier about allowing so many changes, it’s not quite so easy.  DNA actually has some mechanisms (grammar checkers and redundant segments) to guard against “errors” in those genes that are important to survival.  Mutations still occur there, but at nothing like the rate that are allowed in the vast regions known as “junk” DNA.  Still, mutations in DNA are just part of the system.

That is, for almost all of our DNA.

At the lowest level there are a couple of hundred genes that are just too important to be allowed to mutate.  They encode the proteins that are required to decode DNA itself.  Without them, no DNA-based life can function.  And so for those special genes, no mutations are permitted.  They are so fundamental that all living things, humans, animals, archaea that live in Yellowstone’s hot springs, fungi, you name it, have those same genes.  And since they show no trace of mutations, they must have been part of the very dawn of life, 3 billion years ago.

In every practical sense of the term, they are immortal.

To look at another side, we humans have managed to find our own two roads to “immortality.”  We can do something so great (good or bad) that future generations remember it or we can simply pass our genes to our children and live on (steadily attenuated) in our descendants.  Either buys us a few generations of “immortality.”

But 3 billion years!  My God!

Kind of makes you realize what pikers we are, doesn’t it?

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