The New World of Weather Forecasting & Interesting Ways the Human Body Adapts

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today on something you should know what people think when they see a typo in one of your emails then the new world of weather forecasting and why it's so important to you this is so much more than just do i need an umbrella going out the door today it's about being aware of the dangers and how to react to them and becoming weather literate trying to increase your weather literacy also some excellent advice if you're keeping a secret and how humans adapt to their environment.

Height, weight, skin color, immunity are all adaptations and there's more.

Here's a really fun one.

Your spleen.

So people probably don't think about their spleens too much.

So it turns out that people who live in either in high altitude or this population that lives at sea, we see larger spleen size.

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Something you should know.

Fascinating intel, the world's top experts, and practical advice you can use in your life today.

Something you should know.

With Mike Carruthers.

So how much harm can the occasional typo do?

It's no big deal, right?

Well, you might be surprised.

Hi, and welcome to something you should know.

Like everyone else, you occasionally make typos in your emails.

It just happens.

But does a typo in an email have any effect on the reader?

When a researcher at Harvard Business School had test subjects read an angry email from a fictional sender, The reader saw that person as angrier when the note had typos.

When he did the same thing with a joyful email, the typos made the sender come across as more joyful.

In other words, typos act as an emotional amplifier.

Since written communication is words only, there are no facial or verbal clues to give the reader any insight into the writer.

So essentially, the reader takes whatever clues they can get, and typos seem to give the clue that whatever emotion you're trying to convey is stronger.

The bad news is that those same typos also convey to the reader that you are less intelligent and that your response is being driven by emotion and not by careful thought.

But that may be okay in some situations.

If a typo in a sincere email makes you seem more sincere, it may be worth the price of not appearing as intelligent.

And that is something you should know.

What is one topic that affects every one of us every single day, and yet we have no ability to control it or do anything about it?

It's the weather.

And in recent years, we've seen some very extreme weather.

I know this all too well.

We've had winds here whip up two fires in California.

One of those fires literally burned right to my doorstep, and the other fire burned right to the doorstep of my business partner's home.

And we know several people who have lost their homes and everything else.

But it's not just extreme weather, even with everyday weather.

To some extent, it controls your life.

What you wear, where you go or don't go, what you do.

We are at the mercy of the weather.

And so knowing in advance about the weather can be very helpful.

In fact, accurate weather forecasts can save lives, which is why Thomas Weber is here to discuss the science of weather forecasting and what you need to know about it.

Thomas Weber is the former executive editor of Time Magazine and has taught journalism and publishing at Columbia, New York University, and Princeton.

He's the author of a book called Cloud Warriors: Deadly Storms, Climate Chaos, and the Pioneers Creating a Revolution in Weather Forecasting.

Hi, Tom.

Welcome to Something You Should Know.

Mike, it's great to be here.

Thanks.

So I've always thought weather forecasting is like the quintessential victim of negativity bias in the sense that weather forecasting today, I imagine, is mostly right,

but that's not what people remember.

They don't remember when it's right.

They remember when it's wrong.

And so it gets this bad reputation.

Yeah, forecasts are much better than people think.

And, you know, unfortunately, it's sort of a cultural joke, the forecast being always wrong.

I spoke to some undergraduate meteorology students at Penn State just to talk about their career plans.

And every one of them mentioned how many jokes they hear from their friends about they're going into a field where everybody's always wrong.

But forecasts really are much better than people generally appreciate.

Today, a five-day general forecast is as accurate as a one-day forecast from 1980.

So, I mean, mean, you know, think about that.

We basically can look five times further into the future than we could in 1980.

I'll tell you one other fact about forecast accuracy.

If you look at something specific like hurricane forecasts, when the National Hurricane Center predicts the track of a storm 72 hours out, the average error these days is less than 100 miles.

They've doubled their accuracy on that in the last 20 years.

And so these are just, you know, they're amazing accomplishments.

And those accomplishments are the result of what, technology,

better computers, better models, what?

All of the above, really.

And what's exciting is we're really entering a new age of even better forecasts.

If you think about modern forecasting, really the first wave came in the 19th century with the advent of the telegraph,

which basically let people in the West send word ahead, you know, here's the weather that's on the way because weather in the US moves predominantly west to east.

So that was something.

But the second wave in the 1950s and 60s with the space age, that is really where we started to get truly accurate weather forecasts.

And that's because we had radar, satellites, and computers that could run models on them.

And we've made steady progress since then.

Now we're hitting kind of a third wave,

artificial intelligence.

There's something called the Internet of Things, which just means data from all sorts of sources that are plugged into the Internet, like your smartphone, which knows the atmospheric pressure, or your car,

which knows whether it's raining or not because your car turns the windshield wiper on and off.

So that's a lot of new data to plug into the computer models that are already good.

And then one more thing in this third wave,

we're getting knowledge from studying people and understanding how people use forecasts so that we can not just give them great information, but we can try to give it to them in a format that they can put to better use.

Well, the assumption is, I think, that, you know, people use weather forecasts the way I use weather forecasts.

Like, am I going to need an umbrella today?

Do I need a coat or not?

It's that kind of thing.

That's how I tend to use it, except for when there's, you know, a major emergency.

But other than that, it's kind of easy day to day.

Yeah, honestly, that's part of what got me interested in this story in the first place.

I was just thinking about how I use forecasts myself.

And I'll wake up and I'll ask my smart speaker to to tell me what the weather is going to be today.

And I realized like I take it for granted and I think most people take it for granted as well.

And forecasting is so much more than that.

So I wanted to learn how they get made, but also how good they are and how to put them to work.

And a lot of what I wound up focusing on is the use of forecasts for dangerous weather.

It's pretty important.

Last year, the United States saw 27 distinct weather disasters where the costs from damage were more than $1 billion

in each of those incidents.

And there were at least 568 deaths attributed to those events alone.

And weather fatalities are often undercounted, especially for things like heat waves.

The year before, there were 28 of those billion-dollar disasters.

So, a big big takeaway from me when I would talk to people in the weather world

was that this is so much more than just, do I need an umbrella going out the door today?

It's about

being aware of the dangers and how to react to them and becoming what I've been calling weather literate, you know, trying to increase your weather literacy to be able to understand what these forecasts mean.

So let me ask you a question about meteorologists

before we go further into the...

Sure.

What do they do?

And what I mean by that is it seems like weather forecasting is a formula.

There are models and computers that run the formula.

So what do the people do and what makes a great meteorologist versus a not-so-great meteorologist?

What's the human element here?

So I think what you're you're talking about are what I would consider an operational forecaster, not somebody in research, but somebody who's actually putting out the forecast that you might

read or hear.

I had an opportunity to embed myself in the forecast office in State College, Pennsylvania.

What I learned when I watched people at work was the people in these office are really your local expert on weather, right?

You know, the computer does the best it can, which is pretty amazing these days.

But there are quirks of geography that people come to know when they become an expert in their area.

So in every office, the people are very familiar with the local quirks of the weather.

And when they see what comes out of the computer, they're able to look at that and say, okay, yeah, no, that tracks.

Or, you know what?

I think the computer is getting fooled a little bit here.

So that's one one way in which those forecasters are really important.

Okay.

Well, I get that.

But what I guess what I'm wondering is, like when these guys get together, and I'm sure there are plenty of women meteorologists as well, but when they get together, do they sit around and go at the convention and go, you know, Bob, he is a meteorologist's meteorologist.

He is the best guy in the business.

And if that's true, if they do that, what is it that makes him the best guy in the business?

I don't get that.

I think that varies a little bit depending on the weather.

You don't get to be a meteorologist in a National Weather Service office unless you've already demonstrated

that you're pretty good.

But within each office, there's a role called the warning forecast coordinator.

And so those are the people who are really on the hot seat when it's tornado weather.

And they're sitting there making the decisions about issuing tornado warnings that have all sorts of implications for people.

The warning coordinator meteorologist, you know, that's one of the key people in that office.

It would be fun to be able to say, and the best meteorologist in America or the five best are these people,

but it's such a diffuse operation.

There's local weather, there's hurricane weather, there's tornado weather, and there are people who specialize in each of these areas.

Okay, I understand.

It's more complicated than I guess I thought.

I'm talking with Thomas Weber.

He's author of the book Cloud Warriors, Deadly Storms, Climate Chaos, and the Pioneers Creating a Revolution in Weather Forecasting.

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So Tom, When a weather forecast goes wrong, and here's my favorite story of this.

When I was a little kid, I remember this so well, I grew up in Connecticut and in Connecticut we had a lot of snow days.

And one night the weather forecast was there are provisional heavy snow warnings in effect.

And I thought, great, no school tomorrow.

I'm not going to do my homework.

So I didn't do my homework and I woke up the next morning.

There was not a flake of snow anywhere.

And I went to my father and I said, what are provisional heavy snow warnings?

And he said, well, providing it snows,

probably snow a lot.

But it didn't snow at all.

Well, why didn't it snow at all?

When it goes wrong, what, if there is an answer to this, what typically goes wrong?

And do they go back and go, oh yeah, we missed that?

Or is it more fluky than that?

And it just,

we missed it.

Sometimes it's a matter of a few miles.

And I can tell you my own experience with this and something I've talked with meteorologists about.

So I live in New York City.

And I would say, you know, at least once a year, you hear, oh my gosh, there is a potentially big snow event on the way.

New York City needs to be prepared.

And then no snow.

It rains for a couple of hours.

What that reflects where I live and probably, you know, parts, some of the parts of Connecticut that you're talking about, the line between where it is cold enough for that precipitation to turn into snow versus fall is rain, if that shifts by five miles, it means New York City either gets big snowfall or New York City is completely untouched by snow, but gets some rain.

So some of it is really

just how localized some of the effects of the weather can be.

Yeah, but sometimes it's just wrong.

It's like, you know, it's supposed to rain and it was sunny.

I mean, it was just sometimes it's wrong.

And I'm trying to get a sense of, was that a mistake?

Or it's just that we can't be accurate all the time.

And sometimes things happen that we just cannot predict.

Okay, I'm going to throw a word out at you that you're probably going to kill me for introducing here, but there's deterministic forecasting and there's probabilistic forecasting and this is really inside baseball but it illustrates a big

point for the public trying to understand when forecasts are right or wrong uh the public or if you look on your smartphone app you know you see a little icon right and it says sunny or you know, has a little cloud or whatever.

And so you think like, okay, the forecast for today is sunny.

Then it turns turns out to rain, or you, you know, might be the opposite.

That's a deterministic forecast because it's just saying it's this or the other, right?

It's saying it's going to be sunny, it's not going to be sunny.

What actually comes out of the computers and gets

interpreted by the meteorologists is a probability.

Right.

So, and you know, sometimes you see this in your phone app or when the forecaster is talking on TV and they'll say a 40% chance of rain.

So, you know, maybe you think like, well, 40%.

I'm not going to worry about it that much.

But then you walk outside and, you know, you wind up without your umbrella and you wind up getting slammed.

Humans are notoriously

not great.

at handling probabilistic information.

Small probabilities seem like things that just definitely won't come true.

But

if there's a 30% chance of something happening,

it's a one in three roll of the dice for that coming true.

Meteorologists are actually working on how to try to better communicate the probability information around forecasts, but it's it's hard.

I mean, it's we our natural instinct is to want certainty, is to want to know yes or no.

It's going to snow.

It's not going to snow.

Well, you mentioned this earlier, and it's something I've thought about a lot.

And that is it's one thing to be able to predict the weather very accurately.

And in the cases of extreme weather,

a major snowstorm, hurricane, tornado, that kind of thing.

It's one thing to accurately predict what's going to happen, the damage it's going to do,

but it doesn't tell the people who live there what they should do.

Should they stay?

Should they go?

That's kind of the missing link in the chain is, okay, here's the horrible thing that's going to happen.

And here's what you specifically need to do.

And then how accurate are those directions?

I can tell you that when we had the big fires here,

there were people, we were all told to get out and many of us did.

But there were people who stayed and fought the fire because the fire department wasn't here.

And they stayed, fought the fire, and I have no doubt saved our home and other homes on this street that would have burned had they not stayed, even though they were in violation of the police directive to get out.

Mike, you know, what's becoming even more complicated is

we all may face any type of weather at almost any time

as the atmosphere seems to get, you know, more active and the climate seems to evolve.

You know, Last year there was a wildfire in Brooklyn.

People living in New York City, they haven't really ever had to think too much about wildfire weather,

but

this actually happened.

A more serious example, I might say, the big heat wave in 2021.

that struck the Pacific Northwest.

And that was an event that went on for days.

The forecasters a week out for the Northwest were warning that there would be record high temperatures six, seven days from

those early forecasts.

But hundreds of people died across Washington state and into Canada and British Columbia and Oregon.

And part of that just reflects that the Pacific Northwest, you know,

people there are used to dealing with rainy weather, right?

That's kind of their default uh bad weather a heat wave of that magnitude uh you know if you live in arizona you're i mean it's not pleasant but you understand what the effect of heat like that can be if you live in the pacific northwest you may not have an air conditioner you may not even realize what health symptoms might occur if you're being affected by the heat.

And that's one of the reasons that event was so dangerous and resulted in so many fatalities.

This was new to the people who lived there.

And so a big point for me in increasing your weather literacy is kind of being ready for anything and not just what you think of as your local weather.

Well, I think it's very hard to know what you will do until you're actually faced with, you know, the evacuation order.

You've got to get out.

The hurricane is coming or the fire is coming.

And people really don't want to leave their homes to wash away or burn.

Well, it's true.

I talked to

I was talking to some law enforcement officers who have been involved in hurricane evacuations.

The first responders, they're hearing this official information that's being passed on to them from forecasters.

through the state hierarchy.

And, you know, they're hearing it's pretty serious.

And they told me, you know, they'll resort to things like saying to somebody, okay, then here's, here's a sharpie.

I want you to write your telephone number and your name and your social security number on your arm right now.

Because, you know what?

I can't, I don't know if we'd be able to rescue you if it gets as bad as they're saying.

There was a forecaster in New Jersey at the weather service when Sandy was headed to New Jersey.

And he was worried that just the regular language of warnings wasn't enough.

And so he put out this thing that said a personal plea.

And it basically said, this is going to be worse than anything you've ever seen.

I would rather you take the steps that I'm suggesting.

And then if it turns out to not be so bad, call me up and yell at me.

I will be fine with that because at least you will be there to call me and yell at me.

I'm willing to take that heat.

I do not want to think about what happens to you if you don't heed the warnings.

And so listening to a forecast really means accepting that there's some uncertainty.

It might not turn out to be as bad as the forecast is saying.

But do you really want to take that chance?

Well, that's a question everybody's going to have to ask and answer for themselves.

But I certainly like hearing how the weather forecasting business has improved and how not only are they trying to improve how they predict the weather, but also what that information means to the public.

I've been talking with Thomas Weber.

He is the former executive editor of Time magazine and author of the book Cloud Warriors, Deadly Storms, Climate Chaos, and the Pioneers Creating a Revolution in Weather Forecasting.

And there's a link to that book in the show notes.

Tom, thank you for being here.

Thanks, Mike.

It's good to talk about it.

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So here's something I bet you haven't thought much about, but human beings biologically adapt in ways that are fascinating based on where they are or where they're from.

Through evolution, populations adapt to fit the environment, from the color and shade of your skin to the size of your spleen to how tall you are.

These adaptations can sometimes be very subtle and even invisible, but interesting and worth understanding nonetheless.

And here to help us understand it is Herman Poncer.

He is a professor of evolutionary anthropology and global health at Duke University.

He's conducted research all over the world, and that research has been covered in the New York Times, the BBC, the Washington Post, the Atlantic, and Scientific American.

He's author of a book called Adaptable, How Your Unique Body Really Works and Why Our Biology Unites Us.

Hi, Herman.

Welcome to Something You Should Know.

Thanks for having me.

So explain a little deeper here what you mean by how we adapt and why this is important.

Every part of our body is this interplay of evolutionary adaptation and the way things are shaped and the way things work,

but also our adaptability in terms of how our unique genetics, our DNA, interacts with the environments that we grow up in and we live in to kind of make us unique.

So there's, you know, you can find books out there on human physiology and that kind of thing, and that'll tell you how some sort of average human's bodies work.

But of course, each of us is unique.

We're all different.

So what I want to talk about and

open people's eyes to just how adaptable we are and how that adaptability makes each of us unique.

And so to get a better understanding of that, give me an example of how the body, the human body, adapts to its environment.

Here's a fun one.

Something as simple as height, for example.

So, you know, of course, we all know how tall we are, and we all think we understand sort of why that is.

You know, your genetics obviously plays a good big part.

But there's sort of layers of adaptability there.

So, first of all, we're all sort of human-sized and not giraffe-sized or mouse-sized because of the

evolution of our species put us in the human range of where we are.

And so, you know, people are taller and shorter around the world, but there's a human size.

And so that's the sort of old evolutionary adaptation.

But then within that, as we grow up, you know, the amount of nutrition you get is going to affect how well your body is able to build your skeleton and build your body.

And so your genetics plays a role too.

If you have tall parents, you're going to have tall, you're more likely to be tall.

So you have this sort of interplay there.

And then what's interesting then is if we look across the world, and as an anthropologist, I get to work with communities all over the world.

When we find local populations, sometimes there are local,

you know, very kind of regionally specific selection pressures that favor a very tall, thin, or a shorter, stockier build.

So for example, working in northern Kenya, We work with a population called the Dosnich, and they live with their herds.

They're sort of goats and cattle and camels.

And they tend to grow just tall and thin.

And that's an adaptation in that local environment to be able to

thermoregulate, to stay cool in really hot environments.

And there's a funny story there.

We

started working there.

We were talking to one of the local charities that was trying to do food supplementation in that community.

And the guy we talked to said, oh, it's terrible.

All the kids here, about 60% of the kids are malnourished.

And there's just nothing we can do about it.

We're doing these food supplementations and we can't seem to change the way they grow.

And we were able to actually get a hold of growth chart data from the local health clinic of this population.

And when we had data from sort of thousands of kids, we were able to see that actually these kids weren't malnourished.

They're just growing.

That local population is sort of adapted to live in a very hot environment.

And they're adapted to have a tall, thin bodybuild.

And so, you know, what that looks like on a growth chart is that you're not getting enough nutrition because you look too skinny for how tall you are.

But actually, that's an example of local adaptation to that particular environment.

So we look across the body, all of our different organs, systems, and

everything about us has a story like that to tell and helps understand what we're about.

So in that case, if you took someone from here and put them there,

and they were not tall and thin, would they relatively quickly become tall and thin because of the environment, the lifestyle, the diet?

Or is the tall and thinness that that would take generations for that to happen?

Yeah, so in that case, that kind of local adaptation,

that would take generations.

That's right.

So

populations, we tend to kind of get it a little bit wrong, I think, when we think about why populations differ from one another.

We tend to think of these big kind of racial categories.

Well, race is actually not a biologically coherent category.

What you see when you look around the world is actually sort of, most folks are all the same.

Most of the gene variants that we'd find in one population, we'll find in another.

But every now and then, there are, in different systems, in different populations, there are conditions that will favor

particular genetic variants.

We call them alleles.

And those variants, because they're adapted, because they improve survival and reproduction, they'll be favored in that environment, they become more common.

And what happens over time is those alleles, those gene variants that in this case tend to make people grow up taller and thinner, will be more common.

So when we do a survey of that local population, we'll see mostly people with those gene variants.

Now, if you or I were to move there, if we don't carry those gene variants, of course, we're not going to grow up like that.

And our kids won't grow up like that if they don't have those gene variants.

That sort of change in what gene variants become really common takes generations and generations.

Of mixing with that population and then becoming more like them.

Well, so yes, there would be gene flow, there'd be intermarriage, but it wouldn't take just that because those tall, thin alleles are also present here in our American population.

They're just less frequent, right?

So of course we can all think about people who grow up a bit tall and thin.

That just happens to be the way that their bodies grow versus people who might grow up a bit shorter and stockier.

Well, so those tall, thin variants are in every population, but they just become really common there so that everybody has them as opposed to here in the United States, for example, where it's much less common.

Aaron Powell, Jr.: Well, what about the common experience now of it seems that people in the West are much more overweight than they used to be?

Well, that's a great question.

So that gets us to the sort of evolutionary history of our diet and why it is that we tend to overeat.

People in the Western industrialized countries tend to overeat.

What is it about that?

And that's another story of sort of how our digestive systems evolved and then how they adapt to our different food environments.

So,

of course, humans are adapted to a human diet.

What does that mean?

Well, you know, it's actually quite variable what humans are able to thrive on.

People are, you know, a whole mix of different things.

But that's, you know, we can see that in our digestive system, the human digestive system is built to thrive on any mix of kind of animal and plant foods.

Okay, well, so why is it then that we are tending to have this overweight issue, this obesity issue, in the U.S., in Europe, and other industrialized countries.

Is it the diet?

Well, it probably isn't any one thing about the diet because humans can eat a range of things and be healthy.

We see that over and over again in other sort of traditional populations.

But what we can find is that, ah, okay, the foods that we have sort of engineered and filled our supermarkets with here in the U.S., for example, are foods that light up our brain's reward system.

and kind of push us to overeat.

And the way that we learned that is through, of course, experiments here, studies here in the U.S., kind of controlled lab studies where we can watch people's brains light up when they eat particular foods.

But another source of information on that is, well, we can test the idea, for example, that carbohydrates or sugars are the really root cause of obesity.

When we look around the globe, we can find lots of traditional societies that are eating lots of high-carb diets, and they don't have an obesity issue at all.

So again, humans can thrive on a range of foods.

We see that again and again around the world and through time.

But the foods that we've engineered for ourselves and fill our supermarkets with are some of them are really, you know,

you probably can imagine which ones they are, you know, the donuts and the chips and everything else that's sort of engineered to be hyper-delicious.

Yeah, but as we've talked about here before, not everybody succumbs to that.

Not everybody becomes overweight because of those engineered foods.

Why is that?

Ah, well, that comes down to your unique genetics.

Are you born with, you know, did you happen to get lucky and get gene variants from mom and dad that make your, build your brain and build your reward system sort of less responsive to these cues that push other people to sort of overeat?

If you did get those alleles, then lucky you.

You're less likely to be, you know, just to struggle with your weight in adulthood.

If you didn't get those alleles, then you're very likely to be kind of struggling with portion control and that kind of thing.

So that's why some people have a problem and other people don't.

It's possible, to your point, that, you know, given enough time, and this would have to be hundreds of generations, thousands of generations, that somehow those alleles that are less responsive to modern foods might become more common.

But I don't think we want to wait around for that.

I think we want to address the issue now in our environments.

So what's another good example of human adaptability that I probably have never thought about?

Well, your immune system is a great example, right?

So your immune system has parts of it that are built to be the infantry that'll take care of any pathogen that comes your way, bacteria and microbes, that kind of thing.

And, you know, the common cold, other viruses and bacteria that we see all the time.

You've got what's called an innate immune system that is just your first line of defense against all that stuff.

But then you have this very clever, adaptable immune system that is paying attention to what what you are

seeing today and what you're getting sick with today and building antibodies as a response to be smart to be able to respond to it tomorrow, right?

Or maybe not tomorrow, but the next time you get sick with

this pathogen.

And so that's a clear case of sort of adaptability through a lifetime.

If you are

sick with something as a child, you're less likely to get it again or be as sick if you get it later.

And I think this is not only an important example of that adaptability, if we understand our bodies and understand our biology, that's an important way in to address a lot of the big questions we have in society today.

I mean, there's not more of a hot-button topic out there than vaccination.

And

vaccination has actually been a kind of a hot-button issue

since it was first started hundreds of years ago.

But today we see it as a really big polarized issue and people talking about, well, it's not natural or whatever.

Actually, it's incredibly natural.

It's an evolved,

you know, your learned immune system, the learned immune response, your adaptable immune response, acquired immunity is what we call it, is actually an evolved, natural part of how your immune system works.

And vaccination just sort of takes advantage of that and introduces a pathogen so you can learn from that and adapt to that pathogen without getting really sick.

So talk about how skin color, the shade of our skin, is an adaptation, a human adaptation to our environment.

Why is it that some folks have darker skin than others?

Well, it turns out that there's a cell type in your skin called a melanocyte that makes this stuff called melanin.

Melanin is the pigment that makes you darker.

And we all, all of us, all of our skin has cells that makes melanin.

If you have darker skin, it's because you make more melanin.

If you have lighter skin, it's because you make less.

Well, why do people vary in how much melanin they make?

Well, because it's an adaptation to sunlight, basically.

When you have really intense sunlight, like at the equator, all that ultraviolet radiation can be really damaging to your DNA and damaging to this molecule called folate that you need to make DNA.

And your cells are constantly dividing.

You're constantly making DNA.

And so that's a real problem if you damage the DNA or damage the folate.

So you don't want to get too much UV.

However, you do want to get some because ultraviolet light is also important for making vitamin D.

So you're caught in this balance.

You want to get enough UV,

enough ultraviolet light to make vitamin D, but not too much that you damage your DNA.

Here's where melanin comes in.

Melanin is a natural sunblock.

So that pigment that makes your skin a bit darker is acting like a natural sunblock, and it absorbs ultraviolet light, will prevent you from having DNA damage, but it will also minimize how much vitamin D you can make.

Okay, well now we can see how

skin color then, how light or dark your skin is, is responding to the amount of ultraviolet light in your environment.

If you're from a population that's been there for generations in a tropical,

high ultraviolet light intensity environment, there's been selection there

to favor the gene variants that make cells that make more melanin.

So the darker skin variants are going to be favored.

If you live in a north,

far north or far south away from the equator, where the sunlight's weaker, you're going to have less melanin favored because

you want to be able to absorb whatever sunlight's there.

So that's a great example of people's adaptability over time, evolutionarily, to their local environments.

Now,

can you or I, so I have light skin.

I'm from a northeastern European population.

Can I go to someplace that's got really intense ultraviolet light and be okay?

Sure, if I put on sunblock.

But if I don't, then I'm at a higher risk of skin cancer and other problems like that.

So yes, we're adaptable and sort of culturally adaptable, but there's also this interesting biological adaptation that's underlying all of that that I think also helps us make sense of the diversity around the world.

Well, but there are other differences too.

When people have, say, darker skin, they also tend to have darker hair.

When people have lighter skin, they may have lighter hair.

They may have blue eyes, where dark-skinned people have darker eyes.

Are all these things related or are these all separate adaptations?

So melanin is an important pigment for your eye color and your hair color too.

And so people who tend to have darker skin also tend to have darker hair.

So give me another human adaptation that

maybe is invisible, like you don't see it, but it's still important.

Yeah, here's a really fun one.

Your spleen.

So people probably don't think about their spleens too much.

It's this sort of slipper-shaped organ that's tucked under the left side of your rib cage, there below your diaphragm.

And it's a spongy organ, and it's full of, it sort of monitors blood cells that come through, and it's part of your immune system to monitor that.

But it's also this kind of reserve tank of red blood cells.

Now, red blood cells are the ones that carry oxygen around your body.

So it turns out that people who live in either in high altitude or this really,

really interesting case of a population that lives at sea.

They're basically a hunting and gathering group who lives their whole life on the ocean in boats and dives

over 100 feet sometimes into the water to get food.

If you are spending your life underwater,

diving for your food, or you're spending your life at the top of a mountain like in the Andes or in the Himalaya, you actually have the same problem, which is oxygen is scarce, right?

And so in those populations, we see larger spleens evolved and gene variants that actually favor a larger spleen size.

That's a great example of a local adaptation in something that you would never notice.

Of course, you can't tell by looking at somebody how big their spleen is.

But evolution is working behind the scenes in some cases to favor these features like that.

There are people who live on boats.

Isn't that great?

You know, when we think about human diversity,

often we kind of still have a very American mindset.

You know, we only kind of notice what we see around us.

And that's a really limited slice of what's out there.

You know, when you go around the world, you look at populations who live in all kinds of environments, all kinds of lifestyles, all kinds of contexts, you see the human body really pushed and pulled into

different adaptations.

This is a population that they're called the Sama.

And yes, they live their lives.

They're in the South Pacific, on islands in the South Pacific.

And of course, they'll come to land sometimes.

But they will spend weeks, months,

lots and lots of time at sea.

That's where they spend most of their lives is on boats.

And they fish, of course,

for their food.

And the men, especially, will free dive.

They just jump.

They don't have scuba or anything like that.

This is a traditional society.

They dive down there and they're

spearfishing and that kind of thing for their food.

So yeah, I mean, that's a great example of how the diversity in cultures that we see around us can also push our bodies in interesting ways.

Well, it's interesting to hear of these

very peculiar adaptations.

And yet, it's still within a fairly small window.

Humans are humans.

They can only adapt so much.

That's right.

So the human body, there are still limits on how warm the body can get, how cold you can get,

how many calories you need.

But we are adaptable.

And part of what we're adaptable about is we have this really rich cultural set of adaptations that we live with, clothing, shelter,

ways to prepare our foods, way to go get food that makes us sort of,

we're the only big mammal that can live just about anywhere in the globe.

I think we're probably the most widespread large mammal ever.

And it's because we're so adaptable in our bodies, but also in our behaviors.

Well, see, this is one of those topics that I would never even think to think about until you came along.

But it makes you think about how just how adaptable humans have been and have had to be in order to survive and thrive.

Herman Ponser has been my guest.

He is a professor of evolutionary anthropology and global health at Duke University.

And he is author of a book called Adaptable, How Your Unique Body Really Works and Why Our Biology Unites Us.

And there's a link to his book at Amazon in the show notes.

Herman, hey, thank you for coming on and talking about spleens and things.

I appreciate it.

Yeah, thanks, man.

I appreciate it too.

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