Mitch640 wrote:In fact, when I first heard about them in school, it crossed my mind, that the very first amoeba that ever developed, is still alive. They multiply by dividing and before long, there are so many of them that even a large natural disaster could not kill them all. So, by definition, one part of that very first amoeba is still crawling around.
It's an attractive thought, but the world doesn't work that way.
The average amount of ancestral material in each amoeba drops by half each generation, being replaced by newly assembled atoms. Once the population gets large enough to become stable, the total amount of ancestral material in all amoebae combined also drops by half each generation, the remaining part being lost to individuals that die.
This gives us a classic decay model, with a "half life" of one generation.
Using that decay model, and estimating the number of atoms in one amoeba as perhaps 10^17, we find that the expected time to lose even the last atom is remarkably short: less than 60 generations! After that, the odds having one left drop by a factor of a million roughly every 20 generations. I'll let you work the rest of the odds yourself, but be sure that you have space for lots of zeros!
Of course atoms do get recycled, so one could alternatively think about the odds that even one atom of that original amoeba now occupies some place in some current amoeba, albeit in a far different role. That number turns out to be substantially larger and does not diminish much over time. But it's still something like one in a trillion.
So alas, it is almost certain that no physical part of that first amoeba is left crawling around. Only the pattern remains. But isn't it cool that that happens?
--Rik
