SoCaliGirl Posted May 14, 2016 Posted May 14, 2016 I have heard Stef state this in a few different podcasts/videos and thought it sounded hard to believe. It appears to be a bit more complicated than that; fascinating read @ the forum link below: http://www.scienceforums.net/topic/56869-every-atom-in-you-is-replaced-after-7-years/ http://askanaturalist.com/do-we-replace-our-cells-every-7-or-10-years/
McBeer Posted May 17, 2016 Posted May 17, 2016 There is a radiolab podcast explaining the science of how it is calculated. Skin- 14 days Gut lining- 5 days Intestine Muscles- 15.9 years Fat Cells - 10 years Hippocampus - 20-30 years Brain Cortex - As old as you are. http://www.radiolab.org/story/carbon/
Mrdthree Posted May 17, 2016 Posted May 17, 2016 Add on to brain discussion: a cell is 99.9% water, nucleotides, protein, lipid and carbo. DNA: C-14 replacement here would be done solely by DNA repair mechanisms. Protein: There is a high level of turnover for proteins in a cell, driven by the ubiquitin and other systems (http://www.ncbi.nlm.nih.gov/books/NBK22397/) Lipids: in secretory cells like neurons there is substantial lipid turnover. (membrane repair and vesicle recycling); https://www.quora.com/What-is-the-turnover-rate-of-the-lipids-in-the-cell-membranes-of-the-brain Carbs: are mainly metabolic in animals so replaced but the structural ones probably cycle with proteins. water.... well osmosis. So the scary thing is that the self may well be DNA linked. I think we can build a new variant of the Penrose theory now: consciousness is quantum entanglement of microtubules with DNA.
Will Torbald Posted May 17, 2016 Posted May 17, 2016 I think we can build a new variant of the Penrose theory now: consciousness is quantum entanglement of microtubules with DNA. No, I don't think we can build that. What you just said is absolute gibberish. On the topic of having atoms and cells replaced, yeah it's complicated, but it's the same philosophical thought experiment of the boat that has all its parts replaced at the end of the journey. So what if your atoms are replaced? What matters is how they are arranged.
Mrdthree Posted May 18, 2016 Posted May 18, 2016 No, I don't think we can build that. What you just said is absolute gibberish. On the topic of having atoms and cells replaced, yeah it's complicated, but it's the same philosophical thought experiment of the boat that has all its parts replaced at the end of the journey. So what if your atoms are replaced? What matters is how they are arranged. I like the ship analogy. But more interesting here is what McBeer said-- that the ship is not entirely rebuilt during the journey (* facts below). Specifically, cortical neurons do not replace their DNA. There are not many other cells in the body that can say this.. only perhaps egg cells in females (** facts below, other examples welcome). So one can ask why a part of the ship is never replaced in total during our journey. It could be coincidental or it could be crucial to understanding the self. I do not know. Whatever role it plays, it would be amusing to think that it ties into Penrose's theory of microtubule vibrations. They do after all have in common that I do not understand them (*** facts below) Were arguments to get scientific, my position would be that the role genetics plays in maintaining neural structure is not well enough understood to confidently say how much sensory information is encoded using epigenetic memory storage on DNA (methylation or histone modification). It seems likely that at most it could be low pass filtered versions (or other filters) of what is going on at the synaptic level. Which is a little less than the case of repair the ship but dont replace the helmsman. (* it is well known that mature nerve cells suspend mitosis. The new fact brought to the table is that base pair replacement in DNA is negligible in neurons outside of cell division. It exists as neurons have mechanisms of DNA repair but as per McBeer's citation their net effect is negligible) (** Female egg cells are suspended in meiosis (egg generation) prior to birth but all the DNA replication that will be done has been done and only the 'dealing of the cards of fate' remains-- the last 2 divisions of meiosis-- the segregation of parental contributions (chromosomes) to make a unique egg) (*** Nope dont understand it. Insert(laugh). But I keep annual tabs on the Penrose's idea because I have sympathies for the hypothesis that consciousness is a field or substance. Penrose's last update here: https://www.ncbi.nlm.nih.gov/pubmed/22925839)
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