Thank you to KiwiCo for supporting PBS Digital Studios.
In this world nothing can be said to be certain, except death and taxes.
Taxes may not be a law of the universe, but death is, whether you’re a star, a car,
or a human.
That’s because the Second Law of Thermodynamics ensures that we inevitably break down over
time.
Life is a struggle against entropy.
That’s what makes living things different from cars and burning balls of gas.
That our bodies actively fight against entropy - at least for a while.
Sooner or later, the Second Law gets us all.
Can we shift the balance of power to beat entropy, and live longer?
Or is life a battle that we’re all doomed to lose in the end??
[MUSIC]
Death is a law of nature, but dying of old age isn’t - in fact, dying of old age is
illegal in the U.S. and many other countries, at least as an official cause of death.
If an accident or trauma doesn’t kill us, we actually die of “age-associated diseases.”
These are diseases that get more common as we age, things like cancer, Alzheimer’s,
heart attack, and stroke.
But why do we become more vulnerable to these diseases when we’re old?
That’s where our friend entropy comes in.
The longer we live, the more we accumulate disorder: mutated genes, warped molecules,
and cells and tissues that no longer do their job properly.
Even breathing has risks.
When we take in oxygen to break down food and power the body, we let loose super reactive
molecules called free radicals that build up in the body and attack our tissues and
organs.
Another ticking bomb our bodies harbor are transposable elements.
These are wildcard regions in our DNA that can basically jump out of their correct location
and insert themselves in different parts of chromosomes, which can potentially scramble
our genes.
Transposable Elements make up nearly half of our genome, but luckily, our cells are
usually able to keep them under control.
But as we get older, we lose control over our transposable elements and they start to
run wild, causing all kinds of problems from cancer to degenerative diseases.
All of this starts happening in your body long before you realize you’re on the slow
decline toward death.
As entropy runs its course, it’s just a question of which cells or tissues or organs
will fail first, and which age-associated disease will get us.
Leonard Hayflick, one of the founding fathers in the field of biogerontology, basically
the biology of aging, puts it this way: “Good health is merely the slowest possible rate
at which one can die from an age-associated disease.”
which is giving me some serious anxiety right now.
In the US average life expectancy is 79 years, and globally Japan tops the list at 84.
So what if we could eliminate all those age-associated diseases that kill people today?
Scientists think the average human life expectancy would be a whopping 89 years.
Why not longer?
Even without age-associated diseases, our cells have a sort of “maximum expiration
date.”
In other words we have biological programming that determines our maximum lifespan.
It’s written in our DNA, or more specifically, in our chromosomes.
Each of our non-reproductive cells contains 46 chromosomes, and at the end of each chromosome
is a cap called a telomere.
These are protective regions that don’t really code for anything.
We need them because every time our cells divide, and a chromosome gets copied, a bit
at the end of each telomere gets lost in the process.
Eventually, the telomeres get too short, the chromosomes can’t be copied anymore, and
that means no more cell division.
When our cells can no longer divide, to grow and heal and stay youthful, this is the beginning
of the end for our cells and eventually for us.
The length of your telomeres is like your life line - that line across your palm that
fortune tellers use to predict the length of your life.
Except it actually works.
Leonard Hayflick found that normal human cells will only divide 40 to 60 times before they
enter senescence, that state where cells no longer grow.
It’s mainly due to shortened telomeres.
So why didn’t nature give us longer telomeres?
It’s all down to evolution and Natural selection.
Once an organism passes on their genes and ensures their offspring survive, they’ve
basically done all that natural selection requires of them.
That’s why human telomeres don’t get longer as we get older.
We’re products of evolution, and evolution didn’t optimize us to work well after the
age that we can have kids.
And eventually entropy overpowers our ability to repair ourselves.
I know this is super depressing, but don’t blame me.
Blame evolution.
Take it up with Darwin or something!
So evolution isn’t going to help us win the fight against entropy.
But there are other animals out there that have evolved resistance to aging.
Maybe they can teach us to stack the odds in our favor.
Like this one: the naked mole rat.
They can survive up to 32 years, making them the longest-living rodents.
It’s thought the naked mole rat achieves this record by occasionally slowing down its
metabolism and reducing those nasty free radicals in its body - in other words, slowing down
entropy.
Some people are copying naked mole rats and restricting the amount they eat in the hope
of lowering their own free radicals.
It’s called caloric restriction, basically eating fewer calories than recommended for
one’s age.
Research has shown that caloric restriction can prolong life in many laboratory species,
but this has huge risks in humans, and really the jury is still out on how effective it
is.
I mean, according to science, humans are not actually naked mole rats.
But if we can’t beat entropy, maybe we can strengthen ourselves, by looking to lobsters
for inspiration.
Unlike us, lobsters never stop growing, because their cells never stop dividing.
The oldest lobster ever caught weighed 20 kg – the weight of a medium-sized dog.
It’s likely that lobsters only ever die because they get eaten, or they just get so
big they can’t safely regrow their shell.
Lobsters have telomeres like we do that get shorter after every cell division, but they
also have an enzyme called telomerase that constantly rebuilds the telomeres, ensuring
the lobsters’ cells can go on dividing forever.
So let’s pump ourselves full of telomerase!
Right?
In fact, adult humans already have some cell that produce lots of telomerase – like special
cells lining our intestines.
But, you know what else makes a lot of telomerase?
Cancer cells.
All this telomerase means cancer cells are immortal, but the people who possess them,
sadly, are not.
So this solution to aging, might just mean another way to die.
So what about, those disruptive jumping elements in our genes?
Can we control those?
The freshwater hydra can.
Hydras don’t seem to age, and scientists think they may even be immortal.
They seem to be able to keep their transposable elements and jumping DNA in check, and not
scramble their genome.
Who knows?
Maybe with more research, one of Earth’s simplest animals could teach us a trick or
two for extending our own life.
Humans have won some battles against entropy, thanks to things like better diets, modern
medicine, and public health, but no one has ever won the war.
Our body may have a built-in maximum expiration date thanks to evolution.
But if we can learn more about how, exactly, entropy chips away at our bodies as we get
older, maybe we can learn to build ourselves back up faster than we break down.
But if we do conquer aging, we’ll also have to figure out how to feed those billions of
newly immortal people.
Will this be an advancement that everyone has access to, or just a privileged few?
And what will we do for fun in a world where most of our lives are no longer spent working.
Would we run out of YouTube videos?
Nah.
If we answer these questions, as we get older we’ll be living *better* too.
Or… just maybe, by chasing this dream, as the great architect Michael once put it, we’re
just setting ourselves up to “do the most human thing of all: attempt something futile
with a ton of unearned confidence and fail spectacularly!”
Stay curious!
Big thank you to KiwiCo for supporting PBS Digital Studios and It’s Okay To Be Smart.
Some people say that the first person to live to be 150 years old has already been born.
I don’t know if that’s true, but if you’re out there, can you keep people me from getting
older too?
Problems like beating aging are going to take some creative science and engineering solutions.
And KiwiCo’s mission is to make tools to inspire and educate for the next generation
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KiwiCo delivers monthly projects designed to make learning about science, art, math
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They have six different crates for kids from 0 to 16 and beyond.
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Whether you are a kid, or you know a curious kid who might enjoy this, you can go to
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