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Ageing – Why Do We Get Old? · Talking Science

0:00
If you accidentally, say, slice your finger while
0:02
you're chopping vegetables, your skin eventually
0:05
heals. Right, yeah. It just fixes itself. Exactly.
0:08
Or, you know, if you have the misfortune of breaking
0:11
a bone, you give it a few weeks in a cast and
0:13
it knits right back together. It's pretty amazing
0:16
when you think about it. It really is. Your cells
0:17
are just constantly, quietly replacing themselves
0:20
behind the scenes, so you don't even need any
0:22
sort of science background to appreciate this.
0:24
No, not at all. Your body is, well, for all intents
0:27
and purposes, it's this... Astonishing self -repairing
0:31
machine. Which brings up the big question, right?
0:33
So why doesn't it just keep doing that forever?
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Yeah, that is the million -dollar question. Like,
0:38
why does the repair system over the decades just
0:40
slowly start to lose the battle? Put simply,
0:43
why do we age? Well, I mean, it's the kind of
0:47
question that is so baked into the human experience
0:50
that it almost feels silly to ask. Right. Because,
0:53
well, of course we get old. Exactly. Everything
0:55
gets old. When you pause and actually look closely
1:00
at the biology, the actual mechanism of aging
1:03
isn't obvious at all. And that is exactly our
1:06
mission for this deep dive. I'm very excited
1:09
for this one. Me too. So we are unpacking excerpts
1:12
from this incredible article, and it's simply
1:14
titled, Aging is so familiar that it almost feels
1:17
silly. Such a great title. It really is. And
1:20
we're going to explore one of the like liveliest,
1:23
most intensely debated questions in modern biology
1:26
right now. There is so much going on in this
1:28
field. So much. OK, let's unpack this because
1:31
getting older isn't this untouchable, mystical
1:35
mystery anymore, is it? No, no, it's not. It's
1:38
a biological story. And science is finally learning
1:41
how to read the pages. Exactly. And to truly
1:44
understand why our self -repairing bodies eventually
1:47
lose the battle, we first have to, like, discard
1:50
a very common misconception. Oh, right. The clock
1:53
thing. Yeah, the clock thing. A lot of people
1:55
imagine that somewhere deep inside our brains,
1:58
maybe our bodies, there's this master clock.
2:01
Like a literal timer. Right. A single, relentless
2:04
timer that's just ticking down to a preset expiration
2:06
date. Or they think there is one specific super
2:11
crucial part of the body that just eventually
2:13
breaks and brings the whole entire system down.
2:16
Right. It's this idea that we just run out of
2:18
sand in an hourglass. But the source material
2:21
makes it pretty clear that aging is definitely
2:23
not. one single thing going wrong. Not at all.
2:26
There is no master clock. Aging is what we call
2:29
the whole picture. My whole picture. Yeah, it's
2:31
the accumulated result of many different kinds
2:34
of physical wear and molecular damage that just
2:37
builds up in the body over time. So it's a bunch
2:39
of little things. Exactly. And scientists have
2:42
actually organized this messy reality into a
2:46
set of underlying processes. They call them the
2:49
hallmarks of aging. The hallmarks of aging. Okay,
2:51
so to find the first major one, we need to zoom
2:54
all the way in, right? Like right down to the
2:56
cellular level. Yes, I do, yeah. Down to the
2:58
absolute basics. So let's define a couple of
3:01
fundamental terms for you here as we get into
3:03
this. When we talk about DNA, think of it as
3:06
the, well, the ultimate instruction manual for
3:08
your body. That's a perfect way to put it. It's
3:11
the molecular code that basically contains all
3:13
the blueprints for making you function. Right,
3:15
and that vast instruction manual, it doesn't
3:17
just... Float around loosely inside your cells.
3:20
That would be a mess. A total mess, yeah. It
3:23
is neatly packaged and tightly wound up into
3:26
these structures called chromosomes. Okay, so
3:28
you have your DNA neatly bundled into these chromosomes.
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And at the very ticks of those chromosomes, sitting
3:34
right on the ends, is this protective cap, right?
3:37
Yes. And that protective cap is called a telomere.
3:40
A telomere. And the telomere is just, it's crucial.
3:43
It's honestly one of the most striking revelations
3:45
in the whole study of aging. How so? Well, to
3:49
understand why it matters, we have to look at
3:52
the physical mechanics of how cells actually
3:54
replicate. Because they have to replicate, right.
3:56
Right. Every time a cell divides to make a copy
3:59
of itself, which, you know, it has to do to keep
4:01
your skin healing and your bones knitting, it
4:04
has to physically copy. All of its DNA. All of
4:07
those instructions. Exactly. But there's a biological
4:09
catch. The actual molecular machinery that travels
4:12
down the DNA strand to copy it, it simply cannot
4:15
reach the very end. Because the physical copying
4:17
machine needs actual space to sit on the strand,
4:20
right? Yes, exactly. Meaning it leaves this tiny,
4:23
tiny margin completely uncopied. Precisely. So
4:27
because the machinery can't reach the end, a
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tiny microscopic segment of that protective telomere
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cap is permanently lost with each and every cell
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division. Wow. And the text uses such a perfect
4:40
everyday analogy for this, which I love. For
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shoelaces, right. Yes. Think of the telomere
4:45
like the little plastic tip on the end of a shoelace.
4:47
Such a good visual. It really is. It's the thing
4:50
that stops the lace from fraying and just unraveling
4:52
into a total mess. But every time your cell divides,
4:55
that little plastic tip gets worn down shorter
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and shorter. And what's fascinating here is that
5:00
this built -in limit is one of the primary ways
5:03
our bodies essentially count out our biological
5:06
timeline. Like an internal counter. Exactly.
5:13
physical boundary to how many times our cells
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can actually divide and renew themselves. So
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eventually the repair machinery literally just
5:21
runs out of protective runway. It does. The tip
5:24
is gone. So, OK, if this cellular plastic tip
5:27
is physically gone, the vital DNA code is exposed.
5:31
What happens then? Like, what does a cell do
5:34
when it senses its own instruction manual is
5:37
physically unprotected? Does it just, you know,
5:39
politely self -destruct and clear out of the
5:42
system? You would hope biology would be that
5:44
tidy. That would be convenient. But no. When
5:47
a cell's columnars run down to nothing, or if
5:50
it suffers severe damage, it doesn't always die.
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Okay. Instead, it flips this sort of emergency
5:54
switch and enters a very strange state of forced
5:58
retirement. The scientific term for this is cellular
6:01
senescence. Cellular senescence. OK, but I remember
6:04
the researchers have a much more descriptive,
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honestly, much spookier nickname for them in
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the text. Oh, they do. They call them zombie
6:11
cells. It is an incredibly accurate nickname,
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honestly. Why zombies? Because they refuse to
6:15
die. But they are properly alive and working
6:18
either. So they're just in limbo. Basically,
6:20
they stop dividing. They abandon their designated
6:23
cellular jobs. But they absolutely refuse to
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clear off the stage. They just sit there taking
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up physical space. Okay, wait, wait, wait. If
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these zombie cells are basically broken, useless
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entities, why wouldn't the body just get rid
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of them immediately? That's a great question.
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I mean, we have entire immune systems designed
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to hunt down biological garbage. Why do we even
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have a built -in mechanism for this weird undead
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state? It just seems like a massive design flaw.
6:51
Well, the text provides a really crucial piece
6:54
of nuance here. In small numbers, senescence
6:57
is actually an incredibly brilliant necessary
6:59
defense mechanism against cancer. Really? How
7:03
does refusing to die stop cancer? So think about
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what cancer actually is, right? It's uncontrolled
7:08
cellular division. Okay. If a cell has suffered
7:11
severe DNA damage or, you know, its telomeres
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are dangerously frayed. you do not want that
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compromised cell to keep dividing and multiplying.
7:19
Right, because if it did, the errors would just
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multiply with it. Exactly, and it would rapidly
7:23
form a tumor. So by forcing that damaged cell
7:26
into senescence, turning it into a zombie, the
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body essentially slams on the emergency brakes.
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Oh, wow. It permanently locks the cell out of
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the replication cycle, stopping it in its tracks
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before it can turn cancerous. So a zombie cell
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is basically trading a short term fatal threat
7:44
cancer for a long term chronic one. Yes. Because
7:48
keeping it locked down is only a good thing initially.
7:51
That is the ultimate tradeoff. Yeah. Yeah. Because
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as we get older, our immune cleanup crews become
7:55
a lot less efficient and these zombie cells start
7:58
to pile up. And they aren't just sitting there
8:00
quietly taking up space either. No, they are
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not. The source points out that these senescent
8:06
cells actively leak out a steady stream of inflammatory
8:09
chemical signals. Like they're constantly broadcasting
8:12
this chemical distress alarm that just irritates
8:15
everything in their neighborhood. Exactly. They
8:17
leak these things called inflammatory cytokines.
8:20
And that persistent chemical alarm irritates
8:23
and literally damages the perfectly healthy functioning
8:26
cells around them. So a growing population of
8:29
these, like... sulking, leaking zombie cells
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is gradually poisoning the surrounding tissue.
8:35
Exactly. So they're actively making it harder
8:38
for the healthy cells around them to do their
8:40
actual jobs. Yes, which just compounds the problem.
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And of course, the zombie cells aren't the only
8:45
thing going wrong as we age. No, sadly not. The
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text outlines a few other system -wide slowdowns.
8:50
We have... Small, unfixable errors accumulating
8:54
directly in the DNA itself, happening way faster
8:57
than our repair enzymes can catch them. Right.
9:00
And we also have the decline of the mitochondria.
9:02
Oh, the powerhouse of the cell. Do you remember
9:04
middle school biology? Right. Yes. These are
9:06
the microscopic structures inside your cells
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that act as power plants. They take the food
9:11
you eat and the oxygen you breathe, and they
9:13
convert it into chemical energy that the cell
9:15
uses to function. But the text notes that this
9:18
energy conversion process isn't, like, perfectly
9:20
clean. It is not. The chemical reactions actually
9:24
leak tiny, highly reactive byproducts. Which
9:28
they compare to sparks, right? Yeah. Think of
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them like stray sparks flying out of a furnace.
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Over the decades, these sparks bounce around
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and actually damage the power plant itself. So
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the mitochondria become less efficient over time.
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They do. They sputter. So the cells literally
9:43
just have less energy to conduct their daily
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maintenance. Man. So it is an energy crisis combined
9:48
with cellular pollution. A bad combination. Definitely.
9:51
Plus, we have the issue of proteins. And, you
9:55
know, we are not talking about protein as a dietary
9:57
macro here, like in a shape. Right. No. In biology,
10:01
proteins are the physical microscopic tools that
10:04
do the actual labor in your body. They're the
10:06
enzymes, the structural supports, the chemical
10:08
messengers. Exactly. And to function properly.
10:11
A protein starts as this long string and folds
10:14
itself into a highly specific three -dimensional
10:17
origami shape. Origami, I like that. Yeah, think
10:20
of it like a key that has to be shaped perfectly
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to fit into a specific cellular lock. But as
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the years pass and the cellular environment gets
10:27
more, you know, chaotic, some of these proteins
10:30
start to fold incorrectly. They do. They lose
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their precise 3D shape. And because they no longer
10:35
fit into their locks, they start to stick to
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each other. They kind of clump together like
10:39
tangled yarn. Yes. And the text specifically
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notes that these misfolded protein clumps are
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the primary suspects in neurodegenerative diseases
10:49
like Alzheimer's. So when you take all of this
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together, the shortened telomeres, the leaking
10:54
zombie cells, the sputtering mitochondrial power
10:58
plants, the clumping proteins, it creates a very
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specific physiological environment in the body.
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It really does. The whole body basically begins
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to drift into a state of persistent, low -level,
11:10
simmering inflammation. And researchers have
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coined a very fitting term for this, haven't
11:14
they? They have. They call it inflammaging. Inflammaging.
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It perfectly captures that background static
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of damage. that our body is constantly trying
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and just slowly failing to fight off it's a great
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word for it but you know it's not all doom and
11:27
gloom in the text scientists are actually actively
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hunting for ways to combat this all right absolutely
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specifically they're targeting those zombie cells
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with a new class of drugs called senolytics yes
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senolytics are honestly one of the most exciting
11:43
frontiers in aging research right now how do
11:45
they work well the goal of the senolytic drug
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is to act almost like a highly targeted strike
11:51
force. Oh, cool. Yeah, it goes into the tissue,
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hunts down the specific chemical flags of zombie
11:56
cells, and selectively clears them out, leaving
11:59
the healthy cells completely alone. And the source
12:02
mentions that in animal testing, clearing out
12:05
these zombie cells has actually restored youthful
12:08
function to older mice. It has. It's incredible
12:11
to see. But we have to be clear for everyone
12:13
listening. It is still early days, mostly confined
12:16
to laboratory animals. Right, right. We aren't
12:19
quite there for humans yet. But if we connect
12:21
this to the bigger picture, the key takeaway
12:23
here is that none of these single factors is
12:26
the sole cause of aging. It's everything all
12:28
at once. Exactly. It's the slow, steady accumulation
12:31
of all of them, all interacting with each other,
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that we actually experience as growing old. Which
12:37
forces us to look at a massive, glaring biological
12:40
puzzle. Something that the text says has genuinely
12:44
bothered biologists for a very, very long time.
12:47
Oh yeah. The evolution question. Exactly. Because
12:50
evolution and natural selection are notoriously
12:53
ruthless, right? Mother Nature is totally obsessed
12:56
with survival and efficiency. Completely. If
12:58
a trait helps an organism survive, it gets passed
13:00
on. If a trait causes a body to slowly fall apart,
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you would think it would be ruthlessly weeded
13:06
out over millions of years. You really would
13:08
think so. So why hasn't natural selection built
13:11
us to just repair ourselves perfectly? Well,
13:13
the leading answer provided in our source material,
13:16
it relies on... looking at the world from evolution's
13:19
incredibly cold accounting point of view. Cold
13:22
accounting, okay. Yeah, because evolution really
13:24
only cares about one thing, getting you to survive
13:27
long enough to reproduce and successfully raise
13:29
the next generation to independence. Meaning,
13:32
once you have passed on your genes and ensured
13:34
your offspring can survive, you are basically
13:37
off the evolutionary payroll. Pretty much. From
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a purely genetic standpoint, yes. Evolution has
13:44
a massive blind spot when it comes to old age.
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Wow. Your biological fitness matters far, far
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less once your reproductive years are behind
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you. I guess we've put this in historical context
13:55
too. Like, think about our ancestors living in
13:58
the wild. tens of thousands of years ago. Right.
14:01
Totally different environment. They were overwhelmingly
14:03
being killed by predators, freezing to death
14:05
in the cold or dying of sudden infections or
14:08
starvation long before they ever had the chance
14:11
to experience things like gray hair, cataracts
14:14
or arthritis. Exactly. Because the environment
14:16
was so incredibly hostile, there was simply zero
14:19
evolutionary pressure to build a human body designed
14:22
to last a century. It just wasn't needed. Right.
14:25
It would be an inefficient waste of biological
14:27
resources. Evolution completely optimized us
14:30
for a strong, vigorous youth because that was
14:33
the absolute requirement to survive and reproduce.
14:36
Okay, here's where it gets really interesting
14:37
because I want to try an analogy to make sense
14:39
of what the text says about our genes here. Oh,
14:42
let's hear it. Imagine you're buying a brand
14:44
new car from a, let's say, somewhat cynical manufacturer.
14:49
They give you a warranty, but it explicitly only
14:52
covers the first 50 ,000 miles. Why? Because
14:55
their data shows that historically, in the wild
14:58
environment of the roads, most of their cars
15:00
get totaled in accidents by 50 ,000 miles anyway.
15:03
Ah, I see. So why spend the money? building an
15:07
engine designed to last 200 ,000 miles. Exactly.
15:10
The manufacturer might even intentionally use
15:13
cheap, hypercombustible parts that make the car
15:16
run incredibly fast and strong for those first
15:18
50 ,000 miles, completely ignoring the fact that
15:21
those exact same parts will cause the engine
15:23
to aggressively burn out and seize up at 70 ,000
15:26
miles. Because in their cold accounting, the
15:28
car was probably going to crash anyway. Yes.
15:30
That is a brilliant way to understand how evolution
15:32
actually treats our genes. It happily keeps genetic
15:36
traits that provide an early benefit because
15:38
that early benefit is what gets you to survive
15:40
and pass on your DNA. Like the zombie cell mechanism.
15:44
Precisely. The mechanism that creates zombie
15:46
cells is the cheat part in the car engine. Oh,
15:49
that makes so much sense. Right. It works flawlessly
15:52
to slam the brakes on cancer when you're 20,
15:54
ensuring you survive to reproduce. The fact that
15:57
those same zombie cells pile up and cause devastating
16:00
and flammaging when you are 75, evolution simply
16:03
does not care. The manufacturer's warranty expired
16:06
at 50. Exactly. As the text puts it, we grow
16:09
old, in a sense, because our ancestors rarely
16:12
lived long enough for growing old to matter.
16:15
Man, it totally reframes the entire concept.
16:18
Aging isn't a failure of our biology. It's just
16:20
that our biology never had a reason to plan for
16:23
our 80th birthday. That's exactly it. So what
16:25
does this all mean? If evolution has essentially
16:27
left us to fend for ourselves in our later years,
16:30
where does that leave... You, the listener, today,
16:34
where does it leave the whole dream of living
16:36
longer? Well, to answer that, the source draws
16:39
a very sharp, very important line between two
16:41
concepts that frequently get tangled up in the
16:43
media. We have to definitively separate lifespan
16:46
from healthspan. Okay, lifespan versus healthspan.
16:50
Let's break that down. Lifespan is just a raw
16:52
number, right? Right. It is simply the total
16:55
chronological number of years you are breathing
16:57
on the planet. But healthspan is the metric that
16:59
actually dictates your quality of life. Yes.
17:02
Healthspan is how many of those years you spend
17:05
physically healthy, vigorous. cognitively sharp,
17:09
and independent. And the text makes a huge point
17:12
to emphasize that rigorous researchers in the
17:15
field of aging care far, far more about extending
17:18
healthspan than simply dragging out lifespan.
17:21
Because the goal of aging research is not to
17:24
add 20 years of frailty and medical dependence
17:26
to the very end of your life. The goal is to
17:29
compress the period of decline, to be, you know,
17:32
85 years old and still able to hike a trail,
17:35
travel the world and easily get down on the floor
17:37
to play with your grandkids. Exactly. That's
17:39
the dream. But how do we actually get there?
17:41
Because right now, I mean, there is a massive
17:43
multibillion dollar industry. actively trying
17:47
to sell us the fountain of youth in a bottle.
17:49
Oh, there absolutely is. And this is where we
17:52
have to deliver the unglamorous truth straight
17:54
from the source text. Bring it on. Despite all
17:56
the thrilling progress happening in laboratories,
17:59
like targeting zombie cells with senolytics in
18:02
mice, or even partially resetting the biological
18:05
age of isolated human cells in a petri dish,
18:08
there is currently no magic potion available
18:10
at the pharmacy. Right. There's no secret pill
18:13
that will magically fix your telomere. overnight
18:16
the field of anti -aging attracts an immense
18:19
amount of hype there are all these expensive
18:21
products dietary supplements and specialized
18:23
clinics making these sweeping promises that are
18:26
frankly miles ahead of the actual peer -reviewed
18:30
clinical evidence in humans so the text explicitly
18:33
warns us to maintain a healthy rigorous skepticism
18:36
about anyone who claims they can basically sell
18:40
you youth. Yes, heavily emphasized. So if the
18:42
magic pills are mostly hype for now, what are
18:45
the actual levers we can pull to improve our
18:47
odds? What actually works to protect our health
18:49
span? Well, the most powerful levers are incredibly
18:52
familiar. I feel like I know where this is going.
18:54
You probably do. They aren't glamorous, they
18:56
definitely don't come in a shiny package, and
18:58
they require actual daily effort. But they are
19:01
profoundly effective at influencing those underlying
19:06
hallmarks of aging. Okay, let's list them out.
19:08
First, not smoking. No sense. Staying physically
19:11
active, which actually physically stresses your
19:14
mitochondria in a good way, forcing them to repair
19:17
themselves. Like exercise for the power plants.
19:19
Exactly. Eating a highly nutritious diet. Maintaining
19:22
strong social connections and a sense of community.
19:24
And of course, getting proper restorative sleep.
19:27
So sleep, food, movement, and friends. They're
19:31
basically the original senolytics. For now, they
19:33
truly are. Nothing you can buy currently comes
19:36
close to the biological power of those basic
19:38
human habits. But even though the current practical
19:41
advice is still basically eat your vegetables
19:43
and get some sleep, the underlying paradigm of
19:46
how we view getting older has completely shifted.
19:49
It really has. And that is what I find so empowering
19:52
about this entire deep dive. Aging is no longer
19:55
seen as this untouchable, inevitable force of
19:57
nature that we just have to quietly accept. No,
20:00
it is increasingly understood as a highly specific
20:03
set of biological processes. It's written in
20:07
the shortening of the telomere shoelace caps.
20:09
It's written in the accumulation of those inflammatory
20:12
zombie cells. And it's written in the sputtering
20:14
mitochondria and the cold reproductive logic
20:16
of evolution. Exactly. And as the text beautifully
20:20
points out, anything you can understand as a
20:22
mechanical process, you can at least begin to
20:24
imagine influencing. We are finally learning
20:27
how to read the incredibly complicated story
20:29
of why a self -repairing body eventually loses
20:32
the fight. This raises an important question,
20:34
though, a deeply philosophical one to leave you
20:37
with. Ooh, okay. Let's assume the laboratory
20:39
science continues to advance. Let's say in the
20:41
coming decades, human trials for senolytics succeed,
20:45
and we actually figure out how to safely clear
20:47
zombie cells in humans or, you know, protect
20:50
our telomeres from shortening. Basically, if
20:52
we can successfully hack the hallmarks of aging.
20:55
Exactly. If science eventually allows our health
20:59
span to truly match our maximum lifespan, if
21:03
you knew for an absolute fact that you would
21:06
have a vigorous, highly energetic, fully capable
21:09
body at 90 years old, how differently would you
21:13
plan your 40s and 50s? Wow. That completely upends
21:17
the psychology of a human life, doesn't it? It
21:19
really does. You wouldn't be winding down your
21:21
career in your 50s. You'd just be hitting the
21:23
halfway point of your active life. You could
21:25
start an entirely new profession at 60 and still
21:27
have three decades of energy to dedicate to it.
21:29
The societal implications of that are just truly
21:32
profound, Chih -Wan. They really are. Well, we
21:34
have covered a lot of ground today, from the
21:36
microscopic unraveling of our DNA to the sweeping
21:39
ancient forces of human evolution. We want to
21:42
thank you so much for joining us and exploring
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the science of yourself. in this deep dive until
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next time keep questioning keep learning and
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remember to take care of that astonishing self
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-repairing machine you call a body