4
$\begingroup$

The evolutionary biologist and Oxford professor Richard Dawkins makes on his TED talk the rather interesting suggestion that we human beings, are in nature more similar to a wave than an object. In the sense that we are a persistent structure travelling trough a constant flow of atoms that only transiently form part of our body. Citing Steve Grand and his book Creation: Life and How to Make It, he argues that the body of a grown up man doesn't preserve any of the atoms that formed his body by the time of his earliest childhood's memories. Is that fact widely accepted by the scientific community?

I know that this question is a duplicate of Are all body atoms really recycled several times during a life? (or this one), however I want to put the emphasis on the atom constituents of cells, as the accepted answer there doesn't fully answer that question. Following those answers and the references within, a consensus seems to exist that most of the body is in constant renovation, with the exception of the cells in the cerebral cortex and the inner lens of the eye, whose cells persist trough life. But to what extent cellular metabolism replaces individual constituent molecules and atoms throughout those cell's life? Is that true also for DNA? What about mitochondrial DNA?

Are the processes that repair DNA damage operating only in damaged areas? Or do they constantly "repair" also healthy areas leading to the constant replacement of the atoms that constitute the DNA?

Others argue that tooth enamel does not regenerate or get replaced, been that what allows carbon dating to be accurate to the year of birth plus or minus a few months. However, as my question begins with a philosophical issue, I'm mostly interested in the atom constituents of the cerebral cortex. I am in particular aiming to figure out if we are more precisely described as a brain travelling through time or just a wave in a sea of atoms.

Improve this question
$\endgroup$
2
  • $\begingroup$ What defines childhood? Anytime before puberty? $\endgroup$
    – Sudachi
    Commented Feb 28, 2018 at 23:48
  • $\begingroup$ @Sudachi Considering the context of the example I've pointed, it would be any age you can preserve memories of in adulthood. So I would guess from 3-4 years of age onward. $\endgroup$
    – Camilo Rada
    Commented Feb 28, 2018 at 23:50

2 Answers 2

Reset to default
6
+50
$\begingroup$

Is there a point in our life when ALL the atoms from our childhood's body gets replaced?

No. There is no point where ALL atoms have been replaced.

This has been shown by tracing distinct carbon isotopes in DNA [which reflect upon atmospheric 14C at the year of their generation (which reflect the extent of human atom bomb testing)]; Bergmann et al. 2009, Science: Evidence for Cardiomyocyte Renewal in Humans.

for your other questions:

Is that fact widely accepted by the scientific community?

The phrasing of Richard Dawkins, which you also list, uses "more similar" (rather than the absolute ALL). These words provide quite an accurate approximation to express that most building blocks of cells undergo a constant renewal. The choice of words of Grand seems a bit unlucky, if read out of context.

Are the processes that repair DNA damage operating only in damaged areas?

As a first approximation: yes. For instance the image below shows the localized detection of H2A.X histones upon damage at the DNA (red: H2A.X staining -> much stronger in treated cells which have high level of damage; blue: DNA staining)

enter image description here

Or do they constantly "repair" also healthy areas leading to the constant replacement of the atoms

As one approximation this would be true, e.g.: proteostasis (a process whose failure contributes to aging).

that constitute the DNA?

Note that DNA molecules are vastly outnumbered by other molecules in a cell.

DNA is quite static (see above publication), although individual parts could possibly be repaired (see above image on H2A.X);

Also there might be a selective retainment of more "healthy" DNA strands with less mutations (the immortal strand hypothesis).

Improve this answer
$\endgroup$
0
$\begingroup$

Just adding my two cents about this particular point:

Others argue that tooth enamel does not regenerate or get replaced. If that is true what makes carbon dating to the year of birth +/- months possible?

Because the principle of carbon dating is not counting atoms being replaced, but measuring the same atom decaying into a different isotope of its element, which is physically totally different. Wikipedia has more info about radioactive decay.

Improve this answer
$\endgroup$
3
  • $\begingroup$ That's not what I said. The meaning of that sentence was changed by who edited it. Look at the original text on the edition history. I've corrected it. But thanks anyway for the clarification. $\endgroup$
    – Camilo Rada
    Commented Mar 1, 2018 at 22:21
  • $\begingroup$ Note that in the study cited in my above answer, carbon dating primarily does not measure decay of radioactivity, but inclusion of a (radioactive) isotope that happed do be created by unusual conditions (such as atom bomb tests), and its "decay / inclusion" in DNA molecules which are known to replicate in a semi-conservative way (that essentially depends upon biology and differs from pure physics / chemistry). $\endgroup$
    – tsttst
    Commented Mar 1, 2018 at 23:20
  • $\begingroup$ @CamiloRada sorry about that, I indeed did not read the original question before it was edited. I will remember to do that from now on (I started using SE only recently). $\endgroup$
    – Guillaume
    Commented Mar 2, 2018 at 21:40

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .