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  • Are you your body?

  • Well, kind of, right?

  • But, is there a line where this stops being true?

  • How much of yourself can you remove before you stop being you,

  • and does the question even make sense?

  • Your physical existence is cells, trillions of them,

  • at least ten times more than there are stars in the Milky Way.

  • A cell is a living being, a machine made of up to 50 thousand different proteins.

  • It has no consciousness, no will, no purpose; it just is,

  • but it is still an individual.

  • Together, your cells form huge structures for jobs like preparing food,

  • gathering resources, transporting stuff around,

  • scanning the environment, and so on.

  • If you extract cells from your body and put them in the right environment,

  • they will continue to stay alive for a while,

  • so your cells can exist without you, but you can't exist without them.

  • If we take all the cells away, there is no "you" anymore.

  • Is there a line where a pile of your cells stops being you?

  • For example, if you donate an organ, billions of your cells will continue

  • to live on inside someone else.

  • Does this mean that a part of you became a part of another person,

  • or is this other body keeping a part of you alive?

  • Or, let us imagine an experiment:

  • you and a random person from the street exchange cells.

  • One at a time, your body gets one of their cells;

  • their body gets one of your cells.

  • At which point would they become you?

  • Would they ever, or is this just a very slow and gross way to teleport you?

  • Let's make this more complicated!

  • The image of ourselves as a static thing is untenable.

  • Almost all of your cells have to die during your lifetime.

  • Two hundred and fifty million have died since the beginning of this video, alone,

  • between one and three million per second.

  • In a seven-year period, most of your cells are replaced at least once.

  • Every time your cells' setup changes, you are slightly different than before,

  • so a part of you is dying constantly.

  • If you are lucky enough to become old,

  • you would have cycled through roughly a million billion cells,

  • so what you consider yourself is really just a snapshot,

  • but sometimes, cells are broken and don't want to die

  • questioning the very nature of the unity of our bodies.

  • We call them cancer. They cancel the biological social contract

  • and become basically immortal.

  • Cancer is not an outside invader;

  • it's a part of you that puts its own survival over yours,

  • but you could also argue that a cancer cell becomes another entity inside us;

  • another being that just wants to thrive and survive.

  • Can we blame it for that?

  • A chilling cell story is that of Henrietta Lacks,

  • a young cancer patient who died in 1951.

  • Usually, cells only survived for a few days in the lab,

  • making research very hard.

  • Henrietta's cancer cells were immortal.

  • Over the decades, they were multiplied over and over again

  • and used for countless research projects saving countless lives.

  • Henrietta's cells are still alive and overall have been grown to

  • at least 20 tons of biomass,

  • so there are living parts around the world from someone who has been

  • considered dead for decades.

  • How much of Henrietta is in these cells?

  • What makes one of your cells "you," anyway?

  • Maybe the information contained in it, your DNA?

  • Until recently, it was believed that all the cells in your body

  • had basically the same genetic code,

  • but it turns out this is wrong.

  • Your genome is mobile, changing over time

  • through mutations and environmental influences.

  • This is especially the case in your brain.

  • According to recent discoveries, a single neuron in an adult brain has more than

  • one thousand mutations in its genetic code that are not present

  • in the cells surrounding it, but how much "you" is your DNA, really?

  • About eight percent of the human genome is made up of viruses that once

  • infected our ancestors and merged with us.

  • Mitochondria, power plants of the cell, once were bacteria that merged

  • with the ancestors of your cells. They still have their own DNA.

  • An average cell has hundreds of them, hundreds of little things that are

  • not really human, but they still kind of are.

  • It is confusing. Let's backtrack a bit.

  • We know that you're made up of trillions of little things

  • made from more little things that are constantly changing.

  • Together, all those little things are not static, but dynamic.

  • Their composition and condition is changing constantly,

  • so we might just be a self-sustaining pattern without clear borders

  • that gained self-awareness at some point and now has the ability

  • to think about itself through time and space,

  • but really only exists in this exact very moment.

  • Where did this pattern start:

  • with your conception, when the first human arose,

  • when life first began conquering our small planet,

  • or when the elements that make up your body were forged in a star?

  • Our human brains evolved to deal with absolutes.

  • The fuzzy borders that make up reality are hard to grasp.

  • Maybe ideas like beginning and end, life and death, you and me,

  • are really not absolutes, but ideas belonging to a fluent pattern;

  • a pattern that is lost in this strange and beautiful universe.

  • (Shifting to the voice of CGP Grey) The problem of who we are isn't just

  • a question of ourselves, but it's also a question of our minds.

  • Just as our cells can be divided and separated from us, so can our very brains

  • be divided and separated from us while still in the skull.

  • Click here to go to my channel and watch the next part.

  • Okay, so now, go watch CGP Grey's video.

  • If you're not yet subscribed to his channel,

  • you should really change that now.

  • Subtitles by the Amara.org community

Are you your body?

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