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Old 31st December 2018, 10:03 AM   #65
Giordano
Penultimate Amazing
 
Join Date: Apr 2011
Posts: 17,646
Originally Posted by GodMark2 View Post
Nope, cells simply divide: there is no 'replacement'. 'New ones' are just halves of old ones. The old ones were, themselves, just parts of older ones, all the way back...
At first I was also struck by your statement, thinking no he got it wrong, the amazing fact is that our DNA code represents a continuous line for the 3 billion years since the origin of DNA-based life on the planet. That is amazing enough and I've thought about it more than once: my DNA has been duplicated, mutated, rearranged, and altered dramatically in that time but what I have was copied from the DNA of my parents which was copied from the DNA of their parents which was copied....from the DNA of a shared ancestor with the chimps.. which was copied from a shared ancestor with all vertebrates... which was copied from the the DNA in original "first" organism.

But then I thought more about your post and I think you are right. All that copying of DNA took place in cells. So each of our cells originated from cells (including sperm and oocytes in sexual species) which originated from cells... all the way back. Many or most of the actual molecules in those cells may have been diluted out to zero during that time but the lineage of cell to cell to cell was absolutely continuous!

Just one twist: some of those cells may have been metabolically inactive spores. But biologically they were cells nonetheless.

Thanks! Neat idea! Everything now alive, including ourselves, are the unbroken children of children of children... from the very first life. We are the products of unbroken successful reproduction and selection at each step in that long trip.

So don't drive drunk this NYE: it took 3 billion years to create who you are and it would be very disappointing to the primordial ooze that first invented DNA if their invention, and their cells, were to come to an end in you for such a stupid reason as being killed in a car crash.
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