A well known study, published more than 60 years ago (Paul C. Aebersold, Radioisotopes — New keys to knowledge, p. 219
https://www.archive.org/stream/annualreportofbo1953smit/annualreportofbo1953smit_djvu.txt) concluded:

"Tracer studies show that the atomic turnover in our bodies is quite rapid and quite complete. For example, in a week or two half of the sodium atoms that are now in our bodies will be replaced by other sodium atoms. The case is similar for hydrogen and phosphorus. Even half of the carbon atoms will be replaced in a month or two. And so the story goes for nearly all the elements. Indeed, it has been shown that in a year approximately 98 percent of the atoms in us now will be replaced by other atoms that we take in our air, food, and drink." (p. 232).

Even if we accept this conclusion, it isn't clear for how long the last 2%, comprehending heavier elements, can subsist on the human body and if at least a small part can stay in our body until we die.

The Internet is full of stories on the issue, saying that all of our atoms are changed on a time frame of 5 to 9/10 years. But none of those articles quote any other scientific study. I couldn't find any study asserting a 100% change or its time frame. But since this isn't my professional field, I didn't exhaust the sources.

The same can be said about books that claim a 100% change between 5 and 10 years [for example, Richard Dawkins, The God Delusion (London, 2006), Chapter 10, p. 371, just quotes Steve Grand, Creation: Life and How to Make It, that tries to explain his conclusion on more or less common sense:  https://stevegrand.wordpress.com/2009/01/12/where-do-those-damn-atoms-go/].

But if we accept the conclusion that in only one year 98% of our atoms are changed, perhaps the percentage goes over 99% after some years more. And that has consequences about our identity.

Saying that our atoms change doesn't mean that also our cells change entirely. Cells can repair themselves and discard molecules and atoms without dying.

The best candidates to survive across our life are the neurons, even if we have other cells that survive more than 15 years (some cells of the muscles, especially the ones from the heart, and even of the gut).

However, the classic theory stating that the body didn't create any new neurons since birth it's no longer the state of the art.

It seems now accepted that many neurons die daily, but that also neurons are created and the brain can even regenerate within certain limits from an injury. There exists now ample evidence about the creation of neurons on the hippocampus.

If the number of neurons didn't increase since birth, we couldn't explain the increase on the dimensions of the brain as children grow up.

But it's still controversial if also new neurons of the cortex are created. The evidence is pointing on a negative sense.

See, for example, Kirsty Spalding et al., Dynamics of Hippocampal Neurogenesis in Adult Humans, Cell, Volume 153, Issue 6, 6 June 2013, Pages 1219–1227 (available at
https://www.sciencedirect.com/science/article/pii/S0092867413005333); D. Gentleman, Growth and repair after injury of the central nervous system: yesterday, today and tomorrow (Injury 1994, DOI 10.1016/0020-1383(94)90030-2: available at http://thirdworld.nl/growth-and-repair-after-injury-of-the-central-nervous-system-yesterday-today-and-tomorrow ; Tim Requarth, How Brains Bounce Back from Physical Damage, After a traumatic injury, neurons that govern memory can regenerate (2011): http://www.scientificamerican.com/article/how-brains-bounce-back/ ; Fernández-Hernández, Rhiner C.-New neurons for injured brains? The emergence of new genetic model organisms to study brain regeneration, Neurosci Biobehav Rev. 2015 Sep; 56:62-72. doi: 10.1016/j.neubiorev.2015.06.021. https://www.ncbi.nlm.nih.gov/pubmed/26118647 (just abstract); https://www.newscientist.com/article/dn23665-nuclear-bomb-tests-reveal-brain-regeneration-in-humans/.

Therefore, it seems that almost all the atoms on our body change, but there are at least some cells, the neurons of the cortex, that aren't replaced during our life.

Anyway, even if only 98 or 99% of our atoms were replaced, this is enough to force us to ask what is our identity's basis as individuals?

Our current body is mainly just a clone of the one we had 15 or 30 years ago. Even if the neurons of the cortex are the same, it seems that almost all of their atoms were replaced. So also they are just clones of itself.

The I that writes this, on the atomic level, has little to do with the I that register this account on Bitcointalk about 3 years ago.

If we don't seem to have a specific material support, the idea that we are our body ends up in open crisis.

Let's forget about any "soul" for the reasons stated here https://bitcointalk.org/index.php?topic=1424793.0

We can't also support an identity on our memories. An individual with amnesia doesn't cease to be that individual.

Moreover, memories usually can't be trusted: just watch again an old movie or read a second time an old book; rarely will it be exactly as you remember; sometimes, the differences are staggering.

If many of our neurons indeed are replaced (that seems to be clear on the hippocampus, but it is decisive mainly on the formation of new memories), our memories might be memories of memories. Copies of previous memories.

We can't also say that our identity is directly linked to our conscience. We don't cease to be a specific individual because we are in a coma or on a sleep without dreams (I'm not going to enter the discussion about deciding if we are aware when we are dreaming).

So, what are we? Obviously, we are a specific DNA (no one has exactly my DNA), since not even identical twins have an exact copy of their DNA, there are very slight differences (for instance, fingerprints are different).

It's the DNA's importance for our own individuality that makes cloning a so controversial issue.

As specific individuals we are mostly determined by our neurons and these are determined by our DNA. But we are not only our DNA.

We are more than our neurons. Many of our characteristics are mostly determined by the synapses neurons create between themselves.

As far as is known, these synapses are determined also by our DNA, but as well as by our environment: the quality of our education, our habits, our personal experiences, etc.

Children raised by animals aren't able to even use their hands (https://theweek.com/articles/471164/6-cases-children-being-raised-by-animals). Probably, a neural exam would show very low synapses on many decisive zones of their brain.

Therefore, another being that has a copy of our genes won't clearly be us. He won't have the same synapses, since many are created by specific experience.

But even those synapses are simple a form of organization of our neurons.

This means that we are mainly a specific pattern of organization of any atoms and molecules.

Let's accept this conclusion and think about the so-called theoretically possible upload (usually, people write download, but, of course, we are the sender, so it's an upload) of our brain to a machine.

Of course, this is still impossible to do. But just follow me on the theoretical consequences of this on our identity.

If we uploaded a copy of our neurons with all of their synapses to a machine we would be uploading all of our memories, personality and mental capacities to the machine, since all of this is formed and conserved on our neurons and their connections.

Would the machine become us?

The answer is a clear no. The machine would be just a digital super-clone of us; we would be the original. He would be only a copy. We would still be an autonomous individual from our artificial super-clone.

But imagine that all our cells are replaced by artificial cells, including our neurons and their synapses. One by one, our cells would be replaced with some kind of artificial cells.

Imagine that the process was a slow one. We would be aware, as our neurons were slowly replaced. Perhaps during some days, perhaps during a few hours.

We would end up doing what our body does more or less in one year (or more) at the atomic level, but with a change of the nature of our cell's physical elements. We would cease to be beings mainly of oxygen, carbon, hydrogen, nitrogen, calcium and phosphorus, to be made of some other elements.

During the time of the transformation, our natural body would be slowly killed, more or less as our own body slowly dies with the dead and replacement of most of its cells with new cells.

But in the place of the old body we would have a new one, with an exact copy of our DNA.

On the end of this transformation, would the new body be us or a clone?

Since we are already natural clones of our previous bodies, it seems it would be us as well as we are us now, compared with the body we had several years ago.

Would you do this transformation on your free will, to be healthier? Probably, no.

But we would do it for sure to avoid certain death.

Is this our future?

The truth is we are all part of the same organism. Our, bodies, our minds, possibly even our souls (citation needed). The way we perceive the world gives us the illusion of individuality, but in reality we all share a common body and mind. There is increasing evidence to the effect of a collective conscious, meaning that our thoughts may not even be uniquely our own, but rather a cobbling of everyone's ideas.

Now for the mind blowing part. The human brain is psychologically designed as a scalar transceiver! Energy can be transmitted and relieved via our brain, outside of our bodies. The two hemispheres of our brains are designed to create an interference pattern which can either send or receive information via electrical waves. We are effectively electrical instruments swimming in a sea of resonant energy. No one is really truly independent.

At this point I am sure some of you expect me to start talking about reptilians or ESP or something, so I am going to stop trying to simplify this very complicated subject and suggest that if you find this concept interesting, you should research scalar resonance and scalar waves, and compare how those devices function in relation to the physiological design of the human brain.

Ies disagree. Both of Ies would think myselves to be the original, and both would be correct, except in the narrow sense that Ies would not made of the original material, but as the thread title points out, nobody is.

Stop equivocating. At first you used the word "clone" to mean "a copy of our neurons with all of their connections" with "all of our memories, personality and mental capacities", and in this sense, the clone would indeed be another me, regardless of all other factors, as identity is an aspect of consciousness, which is a property of the mind, which is a process of the brain. Same brain = same person. But here you're using "clone" in the traditional sense of a being with identical DNA, like a twin. Obviously these clones do not have, and have never had, the same brain, and cannot in any way be considered to be the same person, and it is absurd to suggest I said otherwise.

Huh? 50% of their fortune is less than what they started with, when there was just one of them in the world. By having to share one person's property between the two of them, both the clone and the original have been robbed by scientist, who is now faced with two people who hate him instead of one person who didn't. Not the best idea ever.

We are just a tool for little bacteria to spread and thrive off,nothing more to us than that. The interesting aspects that make us human like personality are the interesting cog that I stumble on when thinking about what we are. If everything is done before we actually think it than its not me thinking it.

I see zero reason we could not replicate us into a machine.

We are simply a store of memories and we react to those memories for our own advantage.

We are the ship of Theseus, the key mistake people make is to reduce the system to its elements, yet this doesn't work for any system. A great example is DNA, not long ago people were starting to sequence genomes and thought that this would give them all the required information about species, as it turned out it's not. Epigenesis, the way genes interact with inviroment is reciprocal, it activates and deactivate genes and adds more to the system, of course the invorment for a system of a cell is different than that of a cardiovascular system etc. Knowledge that reduces things to their component is just the starting point, its much more important to know how the system behaves and interacts with its outside. Your consciousness is replaced every day, you wake up feeling the same, although your gamma neural oscillations took a break from existence, no problem as long as the conditions to recreate it are there.

Alright, I accept you were writing only about a super-clone (with the same neurons and synapses), not a usual one, with only the same DNA.

But that changes nothing. The super-clone would never have a right to your property. He didn't made anything to earn it. He only would have the memories of doing it.

He would only by a copy, not the original. Actually, realizing he was just a "super-clone" would be a trauma that would provoke changes on his personality, making him different.

Loving or hating the mad scientist is irrelevant to the issue. But the "super-clone" would own his life to him.

Anyway, if this technology became available, probably there would be criminals willing to kidnap rich people and create an "adult super-clone" out of their DNA and a "scan" of their brain. Then, kill the original person and make the clone assuming his place, in order to blackmail him, thanks to small secret changes on the DNA allowing to see he wasn't the original.

This could make a good science fiction novel or movie... probably, someone has already wrote it.

That does not make me a descendant of monkeys!

It already is a movie. "The 6th Day" starring Arnold Schwarzenegger.

http://www.imdb.com/title/tt0216216/

A sieve.