Immortality in the Palm of your Hand
Look at the palm of your hand. Look veeery closely. Do you see that spot next to the line which arcs around your thumb? Just below the epidermis, at that spot, is a tiny little blood vessel, and on the wall of that blood vessel is a cell that we will name 'Wilbur'. Why would we name a cell? Well, Wilbur is a truly remarkable creature. Wilbur has the distinction of having been alive for thousands of years!
'Preposterous!' you say. 'Inconceivable!' But let reason guide you from alarmism to wonderment. Where did Wilbur come from? From his parents, you might answer... but that's not really how Wilbur came to be. Wilbur and his 'sister' used to be one cell, not long ago. Then that cell split and became Wilbur (and another cell, who shall remain nameless). But if one cell splits and becomes two cells, did that cell cease to exist? Did that cell die? Did the 'daughter' cell 'begin' its existence at the time of the split? At what exact moment? The 'parent' cell's DNA splits first, is that when Wilbur comes into existence? Doesn't seem right... but there are all kinds of different phases to this division process, do we wait until the very last moment before those molecules drift apart and say that Wilbur never existed until the final molecule of a cell wall divided 'him' from his 'sister'?
When did Wilbur's life begin? The unsettling answer is that 'it always was'. Always? The little engine of life within Wilbur's core never 'started' running, it just executed a process of devision which resulted in two 'Wilburs'. Wilbur is his own parent! Every cell (it would appear) is just a part that broke off of 'another' cell, except there is no 'another' cell, because each cell is the parent (or a part of it anyway). The cell has 'always' been alive! That cell, at least in hindsight, is immortal!
Why hindsight? Well, because sadly, Wilbur will one day die, as only a few cells in your body are not programmed to die. But if you trace Wilbur's lineage back through history you will journey all the way back to creation (or to whatever you would like to call that first magical moment that non-creationists figure the first cell 'appeared'). Either way it's an insane amount of time for a little biological engine to run uninterrupted.
Think of it, since the dawn of life (regardless of how you define it) Wilbur's little life engine has been humming along. It has to have, or else he would have died and he wouldn't be there, sitting along the edge of a blood vessel in the palm of your hand! By even the most conservative measures, Wilbur has been alive for thousands of years.
It's not immortality that's hard to understand, it's death! Biological systems obviously have the capability to endure practically eternally. So why don't they? Oh you'll throw all kinds of reasons my way, but all I have to do is look at Wilbur. This or that could happen, but Wilbur has weathered the storms for centuries. Time or circumstance may cause the deaths of some cells, but there's nothing to say that (as a biological rule) life must end.
Take care of Wilbur... after all, you have immortality sitting right there, in the palm of your hand.