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[–] 0x5f3759df 0 points 4 points (+4|-0) ago  (edited ago)

With the caveat that atoms being "the same" or "different" does not mean exactly what you think it means, it's almost certain that everyone has atoms in their body from every other person that has ever lived. Also, from every single Tyrannosaurus etc. But, that doesn't necessarily mean that all your current atoms were previously in use by another creature, since on the one hand, some atoms might have passed through thousands of bodies, and on the other hand there are a lot of atoms in a body (about 1027 to 1028).

You can see some nice statistics here on how many organisms have ever lived. They get, among other results, a total of 1020 mamals to have ever lived. Obviously, this is an extremely rough estimate, so it might be a few zeros more or less, but this would mean there are 10,000,000 times as many atoms in a human body than the total numbers of all mammals, ever.

Here's another, similar bit of fun: according to NOAA, there are about 3.5267*1020 gallons of water in the ocean. But one gallon of water contains about 1.265*1026 molecules. So, if you pour a gallon of water in the ocean, stir the ocean until it is uniformly redistributed, and fill your gallon again from the ocean, you'll have about 1,000,000 of your original molecules back.

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[–] Dereliction [S] ago 

Enjoyable answer, though I'm still left wondering how much of us is made up of stuff that was, at one time or another, part of another critter on this planet? Or is most of our atomic make up "freshly" used, essentially untouched by other life on this planet during its billions of years spinning around the sun?

I realize that inspecting a newborn, which has been laying about in the soup of its mother for nine months, will undoubtedly result in a different answer than that of a 100 year old who has been eating and doing who knows what during its existence. But by how much?

More importantly, and to iterate my original question, how much of me (or you) is T-Rex atoms? Are we 10% T-Rex in terms of the atoms we've shared? 1%? 0.00001%?

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[–] 0x5f3759df 0 points 1 point (+1|-0) ago 

Well, on that link I gave you can also see there were an estimated 1050 bacteria in the history of ever. Since the majority of organisms are, and have always been bacteria, this could just as easily be taken as the total number of critters ever (and certainly it is a lower bound). Compare this to the only 1027 atoms in a body, there have been 1022 more creatures than atoms in a creature. Given these numbers, I would guess the majority of the atoms in a body would have been part of many others before.

However, I doubt it will be all of your atoms. The total amount of atoms in the earth, even only counting the major components of organic materials, is far larges still than the number in the entire biomass. So, despite the huge number of atoms in those 1050 organisms, there are even more that have not been used yet. Question is, though, how likely it is that an atom from the center of the earth gets to the surface to be absorbed into the biomass. I have no idea about the answer to this; I guess volcanoes probably bring up some not yet used material. There is also a constant stream of matter coming of from the sun, called the solar wind, which deposits new atoms on the earth. Since they come down from the atmosphere, they are more easily absorbed in a body than the ones from deep inside the earth. Chances are, at least a few of those will end up being first used in your body.

So, in summary, probably most atoms have been used before, but most likely not a hundred percent.

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[–] escapefromredditbay 0 points 1 point (+1|-0) ago 

another person? basically absolutely, given the proliferation of matter and the bodies rebuilding efforts. a trex? same odds prolly