Biology Media Appearances

Jorge Cham (00:00):

Hey, welcome to Science Stuff, a production of iHeartRadio. I’m Jorge Cham and today we’re asking why can’t we regrow limbs? If you lose an arm or a leg, we know that that arm or leg is not going to grow back, but we know there are animals in nature that can do that. If you cut off a starfish arm or a salamander’s leg, it’ll regrow a new one.

 

(00:24):

There’s even a fish that can regrow its heart if you cut off a piece of it. So how do they do it and why can’t we do it? We’re going to talk to several regeneration and animal experts and we’re gonna find out if it’s possible to activate that ability in people.

 

(00:44):

So get ready to go out on a limb with us as we explore the regeneration of body parts. I promise it won’t cost you an arm and a leg. Enjoy.

 

(01:00)

Hey everyone. To answer this question, I started by looking up a list of animals that can regrow their body parts.

 

(01:07):

Not all animals can do it, but a few, if you cut off a part of their body they’ll just regrow it back. On this list are starfish, flatworms, salamanders like the axolotl and some fishes like the zebrafish and the Mexican tetrafish. We’re going to talk to experts in each of these animals, and while we talk to them, we’re going to learn three things.

 

(01:30):

Number one, how these animals regrow their limbs, like what’s their secret? Number two why humans can’t regrow our limbs, or can we? And three, why do some animals evolve this ability and others don’t? It seems like a pretty handy skill to have. All right.

 

(01:53):

The first expert I talked to was Doctor Andrew Wolff. Doctor Wolff is a researcher at the University of Maryland, Baltimore County who studies regeneration in starfish and flatworms. The first thing I wanted to know is can these animals really regrow anything? Well, let’s start with the starfish and then we’ll do the flatworms.

 

Andrew Wolff (02:12):

So starfish are what are called echinoderms, so that’s a phylum of animals. So it’s things like sea urchins, sea cucumbers, things called sea lilies or crinoids, where they also have sort of called feather stars that can move, and also brittle stars, so they’re somewhat closely related to vertebrates.

 

Jorge Cham (02:32):

What do we know about tissue regeneration in sea stars and sea urchins?

 

Andrew Wolff (02:37):

So my work was understanding regeneration in their larvae. So they’re very small, probably like a millimeter or so, very clear. They started to swim around the ocean for about two months or so until they metamorphous into the adult. So you can cut them in half, but those halves will regenerate.

 

Jorge Cham (02:55):

Okay, so you’re saying, if you cut it, the bottom half will grow a top and the top will grow a bottom and you’ll get two identical animals?

 

Andrew Wolff (03:00)

Yes.

 

Jorge Cham (03:01)

Huh. And what about the flatworm?

 

Andrew Wolff (03:06):

That’s what I’m interested in now. So it not only does it regrow what’s lost, it sort of reshapes everything else such that it’s not out of proportion. So let’s say you cut a worm into three pieces like a top, a middle, and a bottom. They’ll all regrow what was lost, but the actual ending size of that worm is going to be smaller than the original whole worm.

 

(03:29):

Because if the tail regrows to be really small, the brain is going to be too big for the new body size. So now it needs to reshape everything to be in proportion to the new size that it is.

 

Jorge Cham (03:39):

So these animals will pretty much regenerate anything. If you cut them in half or in three pieces, each piece will regrow what’s missing, and then you’ll end up with almost identical copies of the original. Next, I talked to Doctor Nadia Fröbisch, who is an expert in salamanders.

 

Nadia Fröbisch (04:00):

My name is Nadia Fröbisch. I work at the Natural History Museum in Berlin and at Humboldt University. I’m a professor for evolutionary biology. Actually, everything that’s alive can regenerate tissue to a certain degree, which is very convenient because otherwise I think we would all grow up with a lot of open scrapes and scratches as we go through childhood.

 

Jorge Cham (04:23):

That makes sense, Yeah.

 

Nadia Fröbisch (04:24):

So of course we can all do wound healing to a certain degree, but some animals are even better at it than we are. Among vertebrates, so the animals that have a backbone, it’s only salamanders that are the masters of regeneration. I think a lot of people are familiar with lizards regenerating tails and sort of throwing them off as a decoy for predators.

 

(04:46):

But lizards, in contrast to salamanders, only get sort of like a fake tail back. It’s more like a rotch of cartilage that’s in there. And salamanders, if they lose their tail, they get a brand new tail with vertebral column and you know, spinal cord and musculature, so just like it was before.

 

(05:06):

And they cannot only do that with their tails. They can also regenerate their limbs. They can regenerate the lenses of their eyes, a huge portion of their hearts, liver, so they’re really really excellent at regeneration.

 

Jorge Cham (05:23):

Pretty much any part of the body has been tested?

 

Nadia Fröbisch (05:27):

Oh yes, this has been tested. Not any part, but a lot of the parts of the body. So they cannot lose their entire heart, for instance, and then regenerate it. There still has to be like a critical amount left in order for regeneration to proceed.

 

Jorge Cham (05:41):

So the muscles, toenails, everything.

 

Nadia Fröbisch (05:44):

Indeed. And sometimes it’s really amazing because when the salamanders bite each other they can have quite gruesome injuries. So where like, for instance, the upper arm bone is sticking out and all the soft tissue is gone. Looking at it, you would think, oh my god, this is never going to grow back, but it does, and it’s really quite amazing.

 

Jorge Cham (06:06):

And the last expert I talked to was Esra Sengul, a graduate researcher at Oxford University who studies Mexican cavefish.

 

Esra Sengul (06:17):

I am Esra, and I use animal models, particularly Mexican cavefish and zebrafish.

 

Jorge Cham (06:25):

Okay, what do we know about tissue regeneration from zebrafish and cavefish?

 

Esra Sengul (06:30):

To start with zebrafish. Together with zebrafish, there are certain kinds of cavefish have regeneration capacity, and they have a remarkable precision while doing that. They repair their fins, they replace it with a new functional one. They also regenerate their heart, spinal cord, retinas, and kidneys.

 

(06:53):

We use them to study heart repair in particular because unlike humans, where heart damage leads to scarring in us, whereas in zebrafish the heart cells replace that lost tissue.

 

Jorge Cham (07:08):

So all these animals basically have a superpower. If you’re thinking of Deadpool or Wolverine from the Marvel movies, these animals can do what they do and they’re real. Chop off a leg and a new one grows back. Cut some of them in half, and both halves regrow into whole new organisms. I had a lot of questions.

 

(07:32):

First of all, how do you even regrow a limb? And second of all, why can’t we and other animals like cats and dogs and birds do this? To start, I asked our experts to give me a play by play of what actually happens when these animals are missing a body part.

 

(07:54):

According to them, it’s a step by step process, and it’s pretty similar whether you’re a starfish or a flatworm or a salamander. Step one is basically: stop the bleeding.

 

Nadia Fröbisch (08:06):

So the very first thing that’s happening and that has to happen in order for regeneration to proceed is the wound healing. So the wound has to close over just like you know, we would have a wound.

 

Andrew Wolff (08:18):

If you think: you’re in the water, you don’t want a bunch of stuff coming in and bacteria and all that stuff. So you have to heal the wound. There’s different mechanisms that they do. Think like a purse string it sort of seals it, or you just have cells that spread that just close it up. Obviously, if you don’t heal, then you’re gonna fall apart. So there’s a structural component, but that’s the first thing.

 

Jorge Cham (08:38):

Okay that makes sense. You first have to close off the gaping wound that happens when you get an arm or a leg cut off. But that also happens when we get cut. Our bodies also close the wounds. So why do we stop there and those animals don’t.

 

Andrew Wolff (08:59):

And it’s really interesting is that the wound itself can signal to the rest of the body that regeneration needs to happen. Big major thing that needs to happen for regeneration to proceed. So it’s like a general response to a wound. But then from there it either says now I need to regrow or not.

 

Jorge Cham (09:18):

It says different signals.

 

Andrew Wolff (09:19):

There’s some sort of mechanism that they can detect that tissue was lost versus I just sort of made a cut. Something from the wound itself is able to recognize: now I need to regrow a head.

 

Jorge Cham (09:33):

So this is a key part of the process. Somehow these animals as bodies are able to tell it’s missing a limb or a body part. There’s some kind of signaling that happens that says, hey, this isn’t just a flesh wound. We’re missing an arm or a leg, and that calls in the cavalry.

 

(09:58):

So once this signal goes out you said it mobilizes things. What does that mean?

 

Andrew Wolff (10:01):

So for regeneration, you need cells to make stuff, right? Anything that you need that was lost needs to regrow, so you need to have cells for that. They have some sort of stem cells that mobilize, they divide, then move to whatever they need to be, and they become the tissues that they need to become.

 

Nadia Fröbisch (10:22):

In salamanders, you have a few stem cells that are still in the system, but you also have cells that are sort of losing their identity that are sort of re-entering the cell cycle to become something new everywhere in the body, and then are recruited to that side.

 

Jorge Cham (10:40):

They actually move.

 

Nadia Fröbisch (10:41):

Yeah, cells move a lot all the time actually.

 

Jorge Cham (10:42)

Really? Okay. The next step is for the body to recruit a bunch of cells where you want the missing body part to grow. But these aren’t just any cells. They have to be stem cells. If you haven’t heard what these are: Stem cells are cells that can become any other kind of cell. If you think about it, the cells in your skin are very different than your eye cells, or your muscle cells, or your brain cells.

 

(11:12):

That’s because these are all cells that have become specialized: parts of their DNA have been switched on or off so that they grow a certain way. That’s good because you wouldn’t want your skin cells to suddenly turn into an eyeball cell, or you wouldn’t want your brain cells to suddenly become muscle cells.

 

(11:32):

Stem cells are cells that still have all their options open, and these are the cells that get

called up to regrow a missing body part. Now, what’s interesting is that some animals just have stem cells floating around their bodies, and some animals are also able to roll back their specialized cells to become stem cells.

 

(11:55):

This part is going to be important later, but for now, just imagine a whole bunch of stem cells congregating at the wound site where the animal lost a body part.

 

Andrew Wolff (12:08):

And they form these sort of massive cells at the wound site.

 

Jorge Cham (12:10):

Oh okay.

 

Andrew Wolff (12:11):

Blastema, it’s a term for sort of they haven’t fully met their fate yet. They sort of accumulate at the wound site.

 

Nadia Fröbisch (12:21):

Which is sort of like a nose if you want, or like a cone on the end of the limb, which is the growth zone where all the cells are proliferating.

 

Jorge Cham (12:32):

Okay, so where you cut off a limb, or a piece of heart, or a fin, a blob of stem cells forms, and from that blob grows the new part. We’re gonna talk about how that blob knows what shape to grow into, which is super fascinating, and we’ll talk about why us humans can’t do any of this. But first let’s take a quick break. You’re listening to Science Stuff.

 

Jorge Cham (13:09):

Okay, all right, so now we’ve got this mass of cells who are there to regrow whatever’s missing. How do they know what to regrow?

 

Andrew Wolff (13:16):

It’s a great question, a very complicated question that we don’t quite one hundred percent know the answer to. It depends on sort of what the tissue is. There’s some sort of way that the animal is able to detect ‘this is what’s missing’, and I think it’s related to the idea of positional information.

 

Jorge Cham (13:35):

Okay, we talked about how when you cut off a limb or a body part, these animals with this superpower start by closing the wound and then amassing a lump of stem cells where the body part used to be. The next question is how do these cells know what to grow into? I mean, you wouldn’t want a tail or a brain to grow where your arm used to be.

 

(13:58):

And the answer is that every cell in your body gets signals about its positional information. That is, somehow cells seem to know where they are or where they should be in the body. And this is something that scientists don’t fully understand yet, but it involves basically every cell talking to every other cell through special chemicals and molecules.

 

(14:23):

And in this case, scientists have noticed an interesting pattern about how this works.

 

Nadia Fröbisch (14:30):

The way it works is that the tip of what has been lost is sort of specified first genetically, and then you have sort of a dissonance between that very tip and whatever the stump area is, and that dissonance or that disconnect between those two genetic identities leads to that growth and to the exact replacement of everything that’s in the middle.

 

Jorge Cham (14:53):

In between. Wow, how does the tip know to turn into the tip?

 

Nadia Fröbisch (14:59):

It’s a genetic marker sort of there are genes expressed there that are saying you are the tip now and like giving it that identity.

 

Jorge Cham (15:07):

Oh I see. It’s like the stem cells that are at the tip, they’re like, okay, I don’t see anyone else around us. We must be the tip.

 

Nadia (15:12)

Exactly.

 

Jorge Cham (15:13)

That’s fascinating. But then how do the cells in the middle know how to fill in the middle?

 

Nadia Fröbisch (15:18):

Well, we haven’t actually sort of researched all the details of that entire process. It’s really it’s sort of an interplay between cells dividing and genetic markers giving those cells positional identity, like saying this is where you are now you are a wrist bone, or you will be part of the wrist area, or you will be part of the musculature that is in the lower arm, kind of like that. It’s an incredibly complex process actually, so it’s quite amazing that it works so well.

 

Jorge Cham (15:49):

In other words, scientists don’t quite know how the cells in animals that regrow body parts know what’s missing or where they are or what shape they’re supposed to make. They just do, like all of that is in our DNA to recognize, ‘Oh, I’m between the tip, I’m about three quarters of the way between the tip and the shoulder. I must be, you know, for our bicep cell.’

 

Nadia Fröbisch (16:18):

Yes, it’s all in the genetic markers.

 

Jorge Cham (16:23):

Like I said, it’s a superpower. But as our experts point out, it’s basically what happens when you grow in the first place. When you go from a fertilized egg to a fetus and eventually to a grown person, somehow your cells know how to grow every part of you. Animals that regrow their body parts basically just reactivate that growing ability we all have in our DNA.

 

(16:45):

Okay, the next big question is why don’t all animals have this ability? How’s a starfish, a flatworm, or a salamander different than us or dogs or cats or monkeys? Why can’t every animal regrow limbs? What do you think it is that flatworms and starfish have that humans don’t have?

 

Andrew Wolff (17:12):

Yeah, the million dollar question. People are always like, if you find something in the lab, can I just grind up the worms and inject it into my arm?

 

Jorge Cham (17:22):

You could be a starfish man.

 

Andrew Wolff (17:24):

Yeah, I mean, hey, that wouldn’t be too bad, I guess. So one other thing that I haven’t mentioned so far is scarring. It stops regeneration in a lot of contexts. So if you cut off your hand, God forbid, you have obviously a wound response, and it’s going to heal and it’s going to scar. When a lot of these other things regenerate. The starfish, the worms, even things like a salamander, an axolotl, they don’t scar.

 

(17:50):

It’s a major sort of block of regeneration, and also that inflammation prevents a lot of these other steps that could be happening. There’s little to no inflammation in a lot of these animals that can regenerate. So it’s a relationship between scarring, inflammation and ability to regrow.

 

Jorge Cham (18:07):

Ah, here’s the first piece of the puzzle. Animals with the ability to regrow body parts don’t scar and they don’t get inflammation when they get cut. Making a scar is basically like patching a hole in your wall with a giant pile of bricks. Scar tissue is thick and tough and dense, and it basically gets in the way of regrowing a new body part.

 

Andrew Wolff (18:32):

But these simpler animals, they just seal it up and that seems to be enough.

 

Jorge Cham (18:37):

They don’t make a scar, basically.

 

Andrew Wolff (18:38):

They do not.

 

Jorge Cham (19:39):

So that’s one factor. The other factor you said was inflammation. So when we get cut, it becomes inflamed, and how does that make things hard to regenerate?

 

Andrew Wolff (18:48):

So it prevents any of the later steps from happening. It just prevents the ability of the tissue to regrow.

 

Jorge Cham (18:57):

It’s not a happy state for cells to regenerate.

 

Andrew Wolff (18:59)

No, that is not.

 

Jorge Cham (19:01)

What Doctor Wolff is saying is that when we get an arm or a leg cut off, our body basically overreacts. It rushes to patch up the wound, building thick scars that block any regrowth, and it deploys the immune system, which makes everything so inflamed that it prevents all the steps needed to regrow the body part.

 

(19:25):

Cells don’t revert back to stem cells, they don’t divide well, so they don’t form that blob of generic cells that can then become the missing part. So now the question is why do we do that?

 

(19:39):

Why do our bodies react that way, especially because at some point in our evolutionary history it seems we did something different. Okay, now the question is why can’t humans regrow our limbs? Or can we? Is that possible?

 

Nadia Fröbisch (19:55):

Well, that’s a question that always comes to all people who work on regeneration. We always get that question, and that’s not an easy question to answer because it’s probably a combination of very complex factors that played a role in this.

 

Jorge Cham (20:12):

Ah.

 

Nadia Fröbisch (20:13):

But we know from the fossil record that a lot of the ancient amphibians could regenerate too, and lungfish are the closest living relatives of us four limbed vertebrates can also regenerate very similar to salamanders. So it is likely that regeneration as we see it in salamanders now is actually not something that is special to modern salamanders that evolved.

 

(20:34):

But salamanders probably are the only living vertebrates today that can still regenerate. Back in evolutionary history, that was probably a widespread feature that then got lost in the course of evolution.

 

Jorge Cham (20:49):

Oh so interesting. It’s not like they developed the special ability, they’re the only ones who kept it.

 

Nadia Fröbisch (20:53):

Exactly.

 

Jorge Cham (20:55):

Oh my goodness. What Doctor Fröbisch is saying is that at some point basically all animals were able to regrow their body parts. Salamanders, starfish, flatworms. They don’t have a superpower.

 

(21:09):

It used to be a standard feature of all animals. But evolution at some point said, eh, you know what, let’s not do that. It’s not a skill some species evolved, it’s a skill some of us lost. Okay. The obvious next two questions are why did evolution choose not to regrow limbs in species like ours?

 

(21:31):

And if it’s something we had but lost, could we bring it back? We’ll answer both those questions after the break. We’ll be right back.

 

(21:51):

And we’re back. All right, we just learned a shocking piece of information, which is that scientists believe it’s likely that basically all animals, or at least amniotes, which are all for legged animals, used to be able to regrow missing body parts, but at some point in our evolution this ability was selected as not being the best for our survival.

 

(22:12):

Which is strange because you think that being able to regrow limbs would be a good thing. I mean, if you lose a leg you can’t really run away from a predator that’s trying to eat you. So I asked our experts, why would we lose this ability?

 

Nadia Fröbisch (22:31):

It seems like something so useful to have, right, that capacity to regenerate? But it also comes at a cost. So during the course of evolution, it probably was a matter of a trade off, and it’s probably for that reason that regeneration was selected against during evolution at some point in amniote evolution.

 

(22:54):

And it could have happened once, it probably had happened multiple times.

 

Jorge Cham (22:58):

Oh well, what’s the trade off?

 

Nadia Fröbisch (23:00):

Salamanders have giant cells. So they have huge cells because they do have a lot of DNA that they accumulate. They just can afford to have all that DNA. But all that DNA has to be transcribed, right? It has to be done for a second copy, and that causes a lot of energy and resources.

 

Jorge Cham (23:22):

Okay, the first reason we might have lost our ability to regrow body parts is that there’s a cost to having that ability. First of all, it requires extra DNA. The program to regrow a limb takes extra instructions and extra genes that can come at a cost, especially if you want to move faster and have a faster metabolism.

 

(23:45):

I wonder if what you’re saying is that at some point in our lineage, the evolution pressure was to like, hey, let’s make things more efficient. We don’t need all this DNA, and maybe one of the cuts was our ability to regenerate.

 

Nadia Fröbisch (23:58):

Yes, that’s it. So it’s not just that we lost DNA. It’s also that we have to go through cell cycles at a certain speed in order to keep our very high metabolism that allows us to run really fast, to sustain a constant body temperature, and do really powerful energy consuming things like run and fly and do these kind of things.

 

(24:20):

If you have a very high metabolism, you have to go through these processes of making new cells quicker than when you’re an organism with a very slow metabolism. We’re constantly building new cells all the time, regenerate your skin, your hair is growing, you’re making new blood cells all the time.

 

(24:45):

Salamanders, they can regenerate because they don’t have to sustain such a high metabolism. We cannot regenerate, but we can run fast and keep our body temperature or fly and these kind of things.

 

Jorge Cham (24:57):

What Doctor Fröbisch is saying is that any extra ability needs extra DNA. And that can come at a cost if you want to be more active, because being more active means you’re cycling through cells more. And each time you make new cells, you have to copy all that DNA, which takes a lot of energy.

 

(25:19):

And the other cost is that it’s just a lot to grow a new arm and a leg. I mean, you have to make a whole new limb from nothing.

 

Andrew Wolff (25:27):

Can you imagine having a stump for how long to regrow all of this complex tissue? It would take a lot of energy and it’d take a lot of time. If the best thing to do is just to close it and seal it and make sure the structure there with that scar is sound, then maybe that’s for the best. Maybe more advantageous energetically and also just structurally to do that.

 

Jorge Cham (25:50):

Oh interesting. Maybe we don’t need that extra arm.

 

Andrew Wolff (25:52)

Maybe.

 

Jorge Cham (25:53)

Huh, I guess you don’t. Technically, you don’t need an extra arm to have more babies.

 

Andrew Wolff (25:59):

Yes, that is also true.

 

Jorge Cham (26:02):

So that’s the reason we can’t regrow limbs. We, meaning four legged animals, used to be able to, but evolution at some point decided it’s not worth it. Losing an arm or a leg is a huge deal if it happens to one of us, but as a species, maybe it’s okay.

 

(26:24):

Maybe it’s better to just cut our losses, patch things up quickly with scar tissue, clean it up, and move on if it means everyone collectively being more efficient and having a faster metabolism. Now you’re probably thinking, if the ability to regrow body parts was in the DNA of our animal ancestors, could we revive it somehow so that we can all regrow limbs again.

 

(26:47):

I’ll get to that in a minute, but first I wanted to tell you about something kind of cool about the Mexican tetrafish that sort of proves the whole hypothesis about why we can’t regrow limbs. Here’s how Esra describes these fish.

 

Esra Sengul (27:04):

It is such a unique and perfectly suited model organism to study because it has two different subtypes. So the surface dwelling version has this silver colored functional eyes and they live in streams. They look very much like what we know as fish. But the cave dwelling version is tail pink.

 

(27:25):

It is almost translucent. They don’t have functional eyes.

 

Jorge Cham (27:30):

Okay, the Mexican tetrafish is fascinating because it’s at a point where it’s about to possibly evolve into two different species. There are currently two kinds of Mexican tetrafish. The ones that live normally in the rivers above ground. Those are called the surface dwelling kind, and there are the ones that live inside of caves.

 

(27:52):

And the ones that live in the rivers on the surface can regenerate their hearts, but the ones that live in caves can’t, even though they’re still technically the same species. So some of them can and some of them cannot. You said, it’s related to where they live. What do you mean it’s related to where they live?

 

Esra Sengul (28:10):

During evolution, the cave dwelling version lost its ability to regenerate their hearts, and it is because they entered the caves, they got trapped there and they had to continue living in complete darkness with not enough food and no external food sources.

 

(28:33):

They had to minimize their metabolism, and they had to find a way to compromise from the things that they don’t really need to survive, and heart regeneration happened to be one of them.

 

Jorge Cham (28:44):

So basically we’re seeing the whole theory of why we can’t regrow limbs play out right in front of us. Some of the tetrafish have migrated to live deep inside caves and because there is little food, low oxygen, and not as many predators, we can see evolution in real time basically say, eh, we don’t really need to regenerate hearts.

 

(29:07):

It’s better to throw out that skill and save energy. Wow, that’s so interesting that they would lose that ability. Do they know how they lost it?

 

Esra Sengul (29:19):

There are some genes that are responsible, but there are so many we only started exploring these.

 

Jorge Cham (29:27):

And this is where we get to the edge of current science, because if we can figure out how exactly we lost our ability to regrow limbs, like if we figure out which genes got turned off or lost, then maybe we can get that ability back. I asked our experts if they thought this was possible.

 

(29:48):

All right, last question, Doctor Wolff. If you could enable humans to regenerate limbs, parts of our organs, how would you do it?

 

Andrew Wolff (29:54):

Ooh, okay, Well, technically, I will say we do have some regenerative capacity, so parts of your liver can regenerate. There’s also a lot of research and information about the tips of your fingers, so kids could regrow the tips through your fingers.

 

Jorge Cham (30:12):

I’ve had that happen to me, yeah.

 

Andrew Wolff (30:14):

Yeah, so we do have some ability, but over time you just begin to lose that ability. So we’re not quite the worst. I believe birds are famously not that regenerative. But if I had to make a human regenerate, I think there’s several things that need to happen.

 

(30:36):

One is, scarring needs to be minimized, Inflammation needs to be minimized. We need to mobilize those cells enough.

 

Jorge Cham (30:42):

What you said that it’s probably the same kind of signaling that happens when we’re first growing the arm, originally.

 

Andrew Wolff (30:49):

Yes, that would be the idea. So how is it that digits were made in an embryo, take some of that information and see if those sorts of things can be turned on again because we have them now.

 

Nadia Fröbisch (31:00):

There might be a shared genetic program in all four limbed vertebrates that is still present to a certain degree.

 

Jorge Cham (31:08):

Meaning it might still be hidden somewhere in our DNA, but somehow it’s not activated? How would that work, like through gene editing, go into human DNA and like, oh wait, here’s something that needs to be tweaked, and this here and there and there, and oh, now we have the ability to regenerate limbs?

 

Nadia Fröbisch (31:23):

So it will require a lot of different scientists coming together, which will be like the biomedical people, the molecular biologists, people working specifically with axolotls and other organisms as model organisms to really understand all the details of the processes.

 

(31:38)

So I think in the end, all these lines of evidence will come together to know what the process is triggered by and how to maybe implement it in humans at some point in time.

 

Jorge Cham (31:53):

All right, So the answer to the question why can we regrow limbs seems to be: Who says we can’t? That ability might be hidden inside of us and all we have to do is regrow it. Thanks for joining us. Be sure to subscribe. See you next time.

 

(32:15):

You’ve been listening to Science Stuff, a production of iHeartRadio. Written and produced by me, Jorge Cham and edited by Rose Seguda, executive producer Jerry Rowland, and audio engineer and mixer JC Pepper. And you can follow me on social media, just search for “PhD Comics” and the name of your favorite platform.

 

(32:36):

Be sure to subscribe to Science Stuff on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts, and please tell your friends. We’ll be back next Wednesday with another episode.

Jorge Cham (00:00):

Hey, welcome to Science Stuff, a production of iHeartRadio. I’m Jorge Cham, and today we’re diving into the science of beauty. What makes someone beautiful? What’s going on in our brains when we see a beautiful thing? And is it possible to be addicted to beauty? We’re going to talk to a couple of beauty experts, including an evolutionary biologist who has a brand new theory about what beauty is.

 

(00:22):

So get ready with me as we explore what makes something beautiful? I promise the answers are a real beauty. Enjoy. Hey everyone, Okay, here are some interesting facts about beauty.

 

(00:45):

Babies as young as two months old can tell the difference between someone who’s supposed to be attractive and someone who’s not. In a famous 1987 study, scientists showed a bunch of babies photos of women that were rated by adults to be attractive or not, and then they measured which photos the babies would stare at more.

 

(01:07):

They found that babies would look at the faces of women who were rated to be attractive more than the faces of women rated to be less attractive. Other studies on beauty have found that people who are considered beautiful are also more likely to be thought of as being smarter, more trustworthy, and confident.

 

(01:28):

They get hired more for jobs, and they are more likely to get paid more and get more promotions. Studies have even found that being beautiful or attractive will make you less likely to be found guilty if you’re ever accused of a crime. Clearly it helps to be beautiful. So the first thing I did was try to see how I could be more beautiful, and to do that I reached out to a plastic surgeon.

 

(01:50):

Well, thank you, Doctor Sadegi, for talking with us.

 

Payam Sadeghi (01:57):

Well, thank you very much for inviting me to your studio.

 

Jorge Cham (02:02):

I called up Doctor Payam Sadeghi. Doctor Sadeghi was a plastic surgeon in his home country of Iran and did his medical fellowship in plastic surgery at the Cleveland Clinic in Ohio. Currently, he’s the resident in pathology at Eastern Carolina University. I wanted to ask doctor Sadeghi what he would do to make me more beautiful, but apparently that’s not how it works.

 

Payam Sadeghi (02:30):

A doctor’s job and responsibility is first to listen to the patient to know what exactly the definition of beauty of that patient is and what it means to them. So that’s very important to first understand the beauty standards. A doctor should spend a great time dealing with the patient to be able to understand those standards.

 

Jorge Cham (02:56):

Okay, According to doctor Sadegi, a plastic surgeon’s job is to quote promote a patient’s beauty standards unquote, which means it all depends on what the patient considers to be beautiful. But that’s kind of the question I wanted to know.

 

(03:15):

Now, the reason I reached out to Doctor Sadeghi in particular is that he’s written several academic papers on plastic surgery procedures, and specifically, he and his colleagues at the Cleveland Clinic published a paper titled What is Beauty? So I asked him to tell us, how do you define beauty?

 

Payam Sadeghi (03:33):

That’s a great question and a simple question, but a very sophisticated answer. I want to answer your question with this. Beauty is a multi-dimensional concept that has intrigued philosophers, artists, scientists, and surgeons for centuries.

 

(03:55):

Cannot be fully defined, as Plato suggested, beauty is not just what appears pleasing. It often harbors a deeper meaning or essence, inviting us to contemplate beyond the surface. From both philosophical and neurobiological perspectives, beauty engages not only our senses, but also our emotions and memory, evoking a powerful, often mysterious response. So good luck with that, yeah.

 

Jorge Cham (04:28):

Thank you. We’re trying. Yeah, thanks a lot, Doctor Sadeghi. It’s a tricky concept, so I asked him if he could be more specific. For example, what makes a human face or body appear more beautiful?

 

Payam Sadeghi (04:44):

So from a surgical and scientific perspective, symmetry, proportion, and harmony are key elements of facial and bodily beauty. For the face, features such as balance, third and fifth symmetry, and the proportions like the golden ratio play important roles.

 

(05:04):

Similarly, for the body, characteristics like waist to hip ratios in women or muscular symmetry in men are often perceived as attractive.

 

Jorge Cham (05:14):

You mentioned proportions. Can you explain what that means?

 

Payam Sadeghi (05:17):

So the proportions of the elements in the face are like different in different people and in different cultures.

 

Jorge Cham (05:26):

Meaning some people might have larger eyes.

 

Payam Sadeghi (05:29):

Correct, like the distances between the eyes, the nose, the nose with the lips, the length of their lips, the proportion of the upper lip to the lower lip.

 

Jorge Cham (05:42):

Okay, here’s our first clue about what makes something beautiful, and this is the idea that it’s related to ratios or proportions, for example, the ratio between the waist and the hip in women, or the shoulders and the waist in men, or for faces, how symmetric you’re is, or what the relative distances are between your eyes and nose and ears and mouth and cheeks are.

 

(06:05):

But searching the scientific literature on this, it’s hard to find a study that conclusively proves there’s a perfect face or an ideal set of ratios that people find beautiful. Some studies find that symmetry is important, some don’t.

 

(06:25):

Scientists have tried to look for common features in the proportions of faces that are ranked by test subjects to be beautiful, and it seems there are none. It’s like, we can all tell if a face looks beautiful to us, but trying to say why that face is beautiful is hard.

 

(06:46):

In one 2008 study, researchers at Google and Tel-Aviv University had to use 98 variables about the face to get a computer program to predict how human judges would rate faces to be beautiful. In other words, when we’re looking at a face and judging whether we find it handsome, pretty or not, we might be juggling as many as 98 variables in our heads.

 

(07:09):

And there are several ideas that make this even more complicated. So there is sort of like a general idealized face and body for men and women. But I imagine that it can vary depending on the person and the culture, right?

 

Payam Sadeghi (07:27):

Correct. For example, in Asia, the curvedness in the forehead and also the ratio of forehead between like the hairline and the eyebrows is different.

 

Jorge Cham (07:39):

Oh, how is it different? So in Asia prefer… what?

 

Payam Sadeghi (07:42):

Not to be like totally flat, let’s say. And that is more correlated in Asian cultures, so we need to also consider that. For example, if you want to practice in Asian countries, you might get more requests from the patient who want to do these types of procedures rather than the others.

 

Jorge Cham (08:05):

Yes, as you can imagine, beauty standards vary with culture. What’s considered beautiful in one culture might be different to what’s considered beautiful in another culture. Beauty standards can also change over time within a culture.

 

Payam Sadeghi (08:21):

These standards of beauty have evolved dramatically across time and cultures. In ancient Greece, proportion and mathematical harmony were central. During the Renaissance, fuller figures were admired as symbols of fertility and wealth.

 

(08:45):

Today, especially in Western media, beauty often favors thinness, youth, and flawlessness, though this is now being increasingly challenged by more inclusive ideals that celebrate diverse body types, ages, and skin conditions. Importantly, each culture defines beauty in its own way.

 

(09:08):

This emphasizes that beauty is not only in the eye of the beholder, but also shaped by the society and time in which we live.

 

Jorge Cham (09:16):

Okay, how do we make sense of all of this? It seems that beauty is definitely a thing. Babies can recognize it, which means there’s something inherent in our DNA about it, and there’s also something universal about beauty. No matter what culture you’re in, people talk about beauty, and everyone in the world has opinions about whether something or someone is beautiful or not.

 

(09:36):

At the same time, it’s hard to describe exactly what it is that makes us think, ah that’s beautiful and what’s considered beautiful can be different depending on the person, their culture, and it can change over time.

 

(09:57):

So to date, there hasn’t really been a strong scientific theory about what beauty is until now. On our next segment, we’ll talk to an evolutionary biologist who thinks she has a theory of beauty that covers all of these aspects of beauty and how it has played a role in our evolution.

 

(10:18):

But first, I was curious about something Doctor Sadeghi brought up. You mentioned that the goal is to promote the patient’s quality of life. What does that mean?

 

Payam Sadeghi (10:28):

Right, so when you think of the beauty concept and when you have a beautiful image of yourself in your subconsciousness, you think in a positive way. When you think that you are the most beautiful person, not comparing to anyone, but just you are beautiful, this is a positive statement of your mind.

 

(10:49):

And this positivity, this mindset, positivity is very important in your daily job, in your daily activities because it gives a positive energy to your mind, so then you can better perform in your daily basics.

 

Jorge Cham (11:07):

I see, feeling beautiful is part of how we feel better about ourselves in general.

 

Payam Sadeghi (11:12):

That’s right, and also it can affect the others. It can be transmitted to coworkers, to friends, to anyone because it’s a positive energy, and that’s why I believe it can promote the quality of life.

 

Jorge Cham (11:28):

All right, we’ll dig into the biology of beauty and how it’s affected evolution after the break. Stay with us, we’ll be right back.

 

Jorge Cham (11:40):

Welcome back. All right. We talked about how beauty is hard to define and how there doesn’t seem to be a standard for what beauty is.

 

(11:51):

It can vary from person to person and from culture to culture. But does that mean that it’s impossible to study scientifically? Not necessarily. There’s a growing group of scientists who think they figured out the right way to define beauty and they think it works for humans and possibly other animals.

 

(12:13):

To fill us in I talked to one of those scientists, Doctor Tamra Mendelson.

 

Tamra Mendelson (12:21):

My name is Tamra Mendelson, and I am a professor of biological sciences at the University of Maryland, Baltimore County. I study evolutionary biology and specifically animal behavior.

 

Jorge Cham (12:31):

So to start us off, how do scientists define beauty?

 

Tamra Mendelson (12:35):

You know, it’s hard to pin down, so you might get a different definition from every scientist you ask.

 

Jorge Cham (12:40):

I guess that’s kind of the beauty of it.

 

Tamra Mendelson (12:42):

Sure, I would say only relatively recently have a critical mass of scientists really started to address the question. Philosophers have been asking for centuries, and scientists surely ask here and there. But I think recently, with the development of technology in artificial intelligence and in neuroscience, I think we’re better able to ask this question from a scientific perspective.

 

Jorge Cham (13:11):

What do you mean advances in AI and neuroscience, what has been happening there?

 

Tamra Mendelson (13:16):

Well, we can use neural networks to visualize activity in the brain and figure out where in the brain information is processed, how it’s processed.

 

Jorge Cham (13:27):

And so what have those scientists been finding in terms of beauty?

 

Tamra Mendelson (13:31):

Well, maybe it makes sense to start with our definition of beauty and then I can talk about how the technology relates to and enforces that definition. We just wrote a paper that just came out in Biological Reviews. This is with my colleagues Julien Renoult from the CNRS in France, Dave Shuker from the University of Saint Andrews in Scotland, and Gil Rosenthal from the University of Padova in Italy.

 

(13:53):

And we are all evolutionary biologists who study animal communication, and we define beauty then as the pleasure or hedonic impact of fluent information processing, independent of the function or consummatory reward of that stimulus.

 

Jorge Cham (14:14):

That’s a bit of a mouthful there, right. Okay. What doctor Mendelssohn is doing here is trying to come up with a definition of beauty that holds up and that is useful to scientists. If a definition is vague or can’t be tested, then you can’t really do science with it. Say it one more time, what’s the definition of beauty?

 

Tamra Mendelson (14:38):

The pleasure or hedonic impact of fluent information processing, independent of the function or consummatory reward of that stimulus.

 

Jorge Cham (14:48):

Okay, so I guess we’ll start with the first part. It’s a feeling. Beauty is a feeling.

 

Tamra Mendelson (14:53):

Yes, beauty is a feeling. Absolutely, it’s the pleasure or what psychologists or neuroscientists called hedonic impact.

 

Jorge Cham (15:00):

What does that mean?

 

Tamra Mendelson (15:01):

It feels good. So every animal has some kind of a reward system. Vertebrates especially, like us and other primates and fish, which is what I study, all have what’s called a mesolimbic reward system that generates positive feelings.

 

(15:17):

It seems clear from early studies of beauty and philosophy to now empirically, it’s been shown that beauty is pleasure and that at least all vertebrates, if not all animals, should have the capacity to experience that.

 

Jorge Cham (15:35):

To experience pleasure, or to experience the sense of beauty?

 

Tamra Mendelson (15:39):

Good question. So let’s start with pleasure. You have to have that. If other animals are going to experience beauty, they must also be able to experience pleasure. That’s like the first piece.

 

Jorge Cham (15:48):

So it seems like you’re saying that beauty is an experience felt by the person looking at something that’s quote beautiful unquote, meaning that it’s not an inherent property of something.

 

Tamra Mendelson (15:59):

Very much so, yes, it’s an interaction.

 

Jorge Cham (16:01):

It’s the reaction that person or animal has looking at this other organism.

 

Tamra Mendelson (16:07):

Yes, exactly, or listening to a beautiful piece of music for example.

 

Jorge Cham (16:11):

Oh right, right. All right, the first part of Doctor Mendelson’s definition of beauty is that it’s a feeling felt by the person looking at or listening to something. It’s not inherent in the thing being observed. In other words, beauty really is in the eye or ear of the beholder.

 

(16:32):

And it’s not just any feeling, it’s a feeling of pleasure. Now, she mentioned the reward system, and that is the circuit in your brain that gets turned on when you feel good. If you’ve heard of dopamine, dopamine is the brain chemical that gets released that makes this circuit work. It’s also the circuit that gets hijacked when you become addicted.

 

(16:55):

We’ll get to that later, but for now, just remember that beauty is a feeling. Okay, so it’s a feeling and you said it’s a feeling that’s related to information processing.

 

Tamra Mendelson (17:07):

Yes, great, so that’s like the next piece, right? And it’s specifically, the word we use in our definition is fluent information processing. I think most people can wrap their minds around the concept of fluency, like when you’re fluent in a language, it’s easy, right? You don’t even have to think about it. It’s easy to speak that language; you’re fluent. So psychologists use fluency as the basis of beauty.

 

(17:30):

So beauty is something that is easy, easy to process. So in neuroesthetics they model beauty as efficient information processing. It’s when something is processed at low cost.

 

Jorge Cham (17:45):

Oh, I guess this is bringing to mind the phrase that someone is easy on the eyes? Is that sort of what this relates to?

 

Tamra Mendelson (17:53):

Absolutely, one hundred percent, that’s exactly it, yes.

 

Jorge Cham (17:55):

Meaning if I look at something and somehow my brain doesn’t have to think much about it, somehow that’s beautiful.

 

Tamra Mendelson (18:03):

Yes, that is the core piece of beauty. And so we’re arguing that not necessarily all efficiently or fluently processed information is beautiful, but that all beautiful stimuli have this in common of being efficiently or fluently processed.

 

Jorge Cham (18:19):

Okay, this gets a little bit technical, but the main point is that, according to Doctor Mendelson , a key part of something being beautiful is that it gives us information, and that it gives us that information in a way that’s easy for our brain to process. For example, you might apply that to a face.

 

(18:40):

If a face has balanced proportions, maybe that’s easier for our brain to process that it’s a face, and because it’s easy, our brain goes, ooh, that was easy, and it gives us a little pang of pleasure. And that experience of pleasure, Doctor Mendelson and her colleagues argue, is what beauty is.

 

(19:00):

It makes me notice that you’re using the word efficiency, meaning that it’s not how much information is being given to my brain, it’s how easily my brain can process it.

 

Tamra Mendelson (19:09):

That’s right. Efficiently processed information isn’t necessarily simple. It can be complex. But if that complex information is processed efficiently at low cost, then that is pleasurable.

 

Jorge Cham (19:20):

Well, I guess what would be the opposite of that? Does that mean that’s something that’s not beautiful or ugly? Would you say something that’s not beautiful? Would you use the word ugly?

 

Tamra Mendelson (19:29):

I think that possibly this concept of ugly might have more cognitive connotations, so it may remind us of something gross. So ugly isn’t necessarily just inefficiently processed information. Inefficiently processed information is uncomfortable, for sure, that’s been shown. But whether it’s ugly, I think, is another question.

 

Jorge Cham (19:52):

It’s true some people find ugly things beautiful. Okay, we talked about how beauty is a feeling and how it’s about information being efficient. Now let’s talk about what’s in that information. And do you apply this definition of beauty that we have so far to just other organisms or does it apply to all things?

 

Tamra Mendelson (20:14):

All things.

 

Jorge Cham (20:16):

So then what sort of information am I getting when I look at a beautiful face?

 

Tamra Mendelson (20:20):

Well, you’re getting a lot of information, right, at all levels. But if we were to judge whether a particular face is beautiful or not, then by our definition, we would be asking if that face is more efficiently processed than other faces. So there are some really basic ways that information can be efficiently processed.

 

(20:42):

Like symmetry is efficiently processed because that’s basically you’re getting two for one, right? So that’s cheap. Prototypicality, when a stimulus is like the best representative of a category, that is efficiently processed.

 

Jorge Cham (20:55):

All right, this is kind of interesting. What Doctor Mendelson means here when she talks about prototypicality is basically the average face in a group of people. And this is something that was found in some of the studies I mentioned earlier. If you take a bunch of photos of people’s faces and you add all those faces together to get kind of the average face of that group, test subjects will generally think that face is more beautiful than any one of the other faces in the group, especially for women’s faces.

 

(21:18):

In other words, part of having a beautiful face is having features that don’t stand out very much. And Doctor Mendelson argues, that face is beautiful because it’s easy for our brains to process since the average is kind of what our brains are expecting.

 

(21:42):

So you’re saying that our brains are sort of tuned to recognize some certain things or like certain things, and so when something satisfies that tuning in a really easy and efficient way, then we think, oh, that’s beautiful.

 

Tamra Mendelson (21:56):

Yes, I mean, arguably there’s potentially more to it than that, but that’s a necessary but potentially insufficient component of beauty.

 

Jorge Cham (22:03):

I see. You said that there was another component, which was its independent… What is it independent of?

 

Tamra Mendelson (22:08):

It’s independent according to the definition of the function or consummatory reward provided by the stimulus. So this goes back to Kant and his idea of disinterestedness, that beauty, beauty is a self sufficient source of pleasure that we don’t necessarily want to own it. That beauty then is liking without wanting, and the only wanting maybe you feel towards something that’s beautiful is you just want to keep processing it.

 

(22:32):

You want to keep listening, or you want to keep looking, but you don’t want to have it. You don’t want to eat it, you don’t want to mate with it.

 

Jorge Cham (22:44):

Okay. The last part of this definition of beauty is that we should like beauty for beauty’s sake. In other words, part of the definition of beauty is that it’s addictive. We want it just for the pleasure of experiencing it.

 

(23:05):

Okay, when we come back, we’re going to talk about how beauty could have affected our evolution and whether it’s possible for an animal like a dog or cat or fish to experience beauty. Stay with us. You’re listening to Science Stuff.

 

Jorge Cham (23:10)

And we’re back. All right, cool, so we have a definition of beauty, and then how does that apply to evolution and our biology and why we are all here?

 

Tamra Mendelson (23:34):

Great, I love that question. So the way we came at this, my colleagues and I, is because we study animal behavior and we’re interested in how animals choose their mates. I study fish that are stunningly beautiful. Are they beautiful to other fish? Are our peacocks beautiful to pea hens? What is the experience that those animals have? What are they feeling?

 

Jorge Cham (23:57):

Meaning is it a coincidence that we find a peacock still beautiful and that it’s also something pea hens find attractive, is there a connection there that’s kind of what you’re asking.

 

Tamra Mendelson (24:06):

Yeah, and then key, if animals experience it as beautiful, how does that affect their decision to choose or not choose that other individual that has this ornament as a mate?

 

Jorge Cham (24:16):

Meaning is a peacock’s tail beautiful to a pea hen?

 

Tamra Mendelson (24:18):

Correct.

 

Jorge Cham (24:19):

Okay, the last question we’re asking here today is what is the role of beauty in nature? If animals and our ancestors could experience beauty, how did it shape evolution? And here Doctor Mendelson doesn’t have a lot of answers. Like I mentioned, this theory is still pretty new, which is exciting.

 

(24:41):

If you’ve never talked to a scientist while they’re still formulating their hypothesis, it’s interesting to hear how they think. You know, it seems like we as humans use beauty as a factor in our choice of who we want to mate with. Is that the same for animals as well?

 

Tamra Mendelson (25:00):

So here’s an analogy. You would need to buy a new car, so you go to the car sales place, or you want a candy bar. You have a hankering for something sweet, and you go to the grocery store and you look at all these candy bars. Which candy bar? To what extent does the wrapper influence your decision? You already want the candy bar, you already want to mate.

 

(25:23):

What role does the beauty play in that process?

 

Jorge Cham (25:24):

Yes, do we know?

 

Tamra Mendelson (25:27):

No, I don’t think we do.

 

Jorge Cham (25:28):

Okay, what are some of your hypotheses?

 

Tamra Mendelson (25:30):

So we argue that this beauty, this experience of beauty, encourages proximity. So the idea is that an animal already wants to mate, say it’s breeding season, they’re already looking for a mate. Then they see something beautiful that makes them feel good and they’re attracted to it for that reason, so they want to keep processing it.

 

(25:51):

So it just encourages proximity, and then once they’re physically proximate to that individual, then they mate. So it’s just kind of like it’s a marketplace, and you know, there’s a lot to choose from. You just don’t know which one. And there’s something that really catches your eye or catches your ear and makes you feel good, so that’s the one you go to.

 

Jorge Cham (26:08):

All right, Doctor Mendelson hypothesis is that beauty evolved as a kind of hack to give animals an edge during mate selection. Being beautiful or having features that turn on our potential mate’s information processing reward system has nothing to do with survival, but it does help you get attention.

 

(26:29):

So I feel like maybe you’re saying that beauty is something that has come up even though it’s not useful for survival. Like, maybe it’s just useful for choosing a mate.

 

Tamra Mendelson (26:43):

Yeah, for sure. Our brain’s tuning to our environment and wanting to process information efficiently. So then what’s happening is that mutations arise that exploit this bias and that make themselves attractive because they’re efficiently processed.

 

Jorge Cham (26:58):

Hmmm.

 

Tamra Mendelson (27:00):

It has nothing to do with whether they are more fit if you will, or have you know, quote unquote better genes.

 

Jorge Cham (27:07):

Meaning a peacock’s tail obviously has nothing to do with how it might get food in the wild. But because it tickles the pea hen’s soft spot for information processing, that’s why peacocks over time evolved these huge, colorful tails.

 

Tamra Mendelson (27:24):

Yes, and in fact, arguably it’s not good for them to have these big tails, right? It does actually affect their ability to find food in a bad way. I saw this great video of a tiger just totally nailing a male peacock who is displaying because they’re just so obvious, right? Tigers can just [obscured] right.

 

(27:47):

So, and Darwin famously said that a peacock’s tail, when I look at it, it makes me sick. Because he had developed his whole theory of natural selection and then he looks at this tail and he’s like, that’s ridiculous. That does nothing for its survival.

 

(28:07):

So then he publishes his book on sexual selection to explain that maybe sometimes traits can help you with reproduction, even at a cost to survival. And that’s where beauty might come in.

 

Jorge Cham (28:13):

I see, sometimes beauty might be a burden on your survival.

 

Tamra Mendelson (28:16):

Yes.

 

Jorge Cham (28:17):

But because we have a beauty response, it’s there because it gives you an advantage in mating. And you’re saying, we have this beauty response because our brains like information that’s easy to process.

 

Tamra Mendelson (28:31):

Got it, that’s it.

 

Jorge Cham (28:33):

Yeah, apparently Darwin was not a fan of peacocks. Okay, the last part of our conversation I want to play for you was when we talked about whether we can change what we find beautiful. If beauty is what our brains find easy to process, and if we find easier to process things that match what we expect.

 

(28:53):

Does that mean changing beauty standards is just about changing expectations?

 

Tamra Mendelson (28:59):

And then throw another puzzling piece on top: the mere exposure effect. So familiarity can make something more beautiful. When you have been exposed to something, it becomes more beautiful to a certain extent.

 

Jorge Cham (29:12):

But the more we were exposed to something, the more we grow to appreciate it.

 

Tamra Mendelson (29:16):

Yeah, the more we like it.

 

Jorge Cham (29:17):

Yeah.

 

Tamra Mendelson (29:18):

And these are mostly in psychology studies where they flash things for people and then they ask them what they like, and they’ve shown that the things that have been flashed, that they’ve been exposed to more are more liked.

 

Jorge Cham (29:30):

Oh, so we can influence what we find beautiful. I just had some interesting thoughts because you know, I also produce a television show, and so there’s always questions about representation and what we portray in the media. And then you’re seeing that a lot in advertisements today, different body types, different skin tones. People are trying to change the standards of beauty.

 

Tamra Mendelson (29:52):

A lot of beauty is genetic or something that you can’t really change. But I think a lot of beauty is what you can change, right, because it’s just all about efficiency and our brains are being tuned all the time.

 

Jorge Cham (30:02):

We’re receptive to having standards of beauty change.

 

Tamra Mendelson (30:06):

I think so just by mere exposure, you can start to influence people’s standards of beauty.

 

Jorge Cham (30:12):

All right, I think that answers our question: what makes something beautiful? It’s not skin deep. It’s all in the brain of the beholder. To close us off, I’m going to let Doctor Sadeghi have the last word.

 

Payam Sadeghi (30:28):

The majority of the anatomy of human beings is pretty much similar. We are all the same. We all have the major organs, we all have the liver, we all have the lungs. I believe that every person is beautiful. We just need to explore it and discover it. And that is the beauty of the beauty concept.

 

Jorge Cham (30:51):

Thanks for joining us. See you next time. You’ve been listening to Science Stuff, production of iHeartRadio. Written and produced by me, Jorge Cham, edited by Rose Seguda, executive producer Jerry Rowland, and audio engineer and mixer Kasey Pegram. And you can follow me on social media, just search for PhD Comics and the name of your favorite platform. Be sure to subscribe to Science Stuff on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts, and please, tell your friends. We’ll be back next Wednesday with another episode.