Short Wave - How to Talk About Hair Like a Scientist

Episode Date: February 14, 2022

Humans have scalp hair. But why is human scalp hair so varied? Biological anthropologist Tina Lasisi wanted to find out. And while completing her PhD at Penn State University, she developed a better system for describing hair — rooted in actual science. (Encore)To hear more from Tina, check out these webinars: Why Care About Hair (https://bit.ly/3liJZ96) and How Hair Reveals the Futility of Race Categories (https://s.si.edu/3Dik6g8). And to dive deep into Tina's research, we recommend her paper, The constraints of racialization: How classification and valuation hinder scientific research on human variation (https://bit.ly/3DfDrOS). See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

Hey, shortwivers, we want to wish you a happy Black History Month. And this month, as we do all year, we are celebrating and amplifying Black voices in STEM. Scientists, engineers, folks in medicine and math. And this week, we're bringing you new guests with expertise and insights to share and returning to some of our favorite conversations. Tina Lassisi is one of the few biological anthropologists in the world who studies the evolution of hair. And we wanted to give you the chance to meet this history-making hair scientist again. Enjoy. You're listening to Shortwave from NPR. Tina Lassisi has some news for you. That stuff growing on your head is technically fur.

Humans like to pretend that they're special. And, you know, in some ways we are, okay. But having a whole different word. for our fur, that's just vanity. That's right. Our hair is technically fur on our heads. Just carotanized fiber growing from scalp follicles. But for your vanity and for mine, we're going to call it scalp hair. And Tina is one of the few biological anthropologists in the world who studies it. I'm a postdoctoral researcher at Penn State University who works on human evolution and specifically the evolution of human scalp hair.

Tina first got curious about the evolution of human scalp hair. pair in college. She was in her first biological anthropology class, and her teacher pulled out this world map showing the distribution of UV radiation, so where UV rays hit the most closest to the equator. And right next to it, the teacher had a map of the distribution of skin pigmentation. And it absolutely mirrored that map of UV radiation almost perfectly. And that just blew my mind, I had never thought about the fact that skin pigmentation varies in this gradient way. But seeing this map really made me think about how natural selection can affect things in ways that are a lot more structured. And it immediately made me wonder, okay, so now that I know

why I'm brown, why is my hair curly? And that's what set me on this path where, you know, eight years later, I'm still asking questions about the evolution of hair. Tina has come a lot closer to answering these questions, using some really cool science. Wigs, mannequins, microscopes, taking this thing we kind of generalize, hair, and finding some serious scientific nuance. Well, I mean, you know how they say that, you know, research is me search. Hold on. People love to learn. Wait, what's me search?

Oh, well, people are really interested in looking into things that teach them more about themselves. So having that information presented in front of me, I was, you know, satisfied with knowing like, you know, okay, this is why I'm brown, but why is my hair curly? That was really the thought process there. Today on the show, hair. Why we have it, why it's all different, and why we should be talking about it like a scientist. Biological anthropologist Tina Lassisi takes us into her world and shows us a better way to describe our own hair. This is Shortwave, the Daily Science Podcast, from NPR. So, Tina, to start, there's lots of different theories for why humans evolved scalp hair.

What's your favorite one? Well, the one that I think makes the most sense to me and that I'm most interested in pursuing is one about thermoregulation that says that we evolved scalp hair to protect us from gaining a lot of heat from solar radiation. And how would that help us evolve and keep us safe? So actually, a lot of mammals keep their fur because it protects them from the sun. And what's interesting about humans is that we know that in order to stay cool, we traded all these hair follicles in to sweat glands. So we could sweat, evaporate, and stay cool. So the question is then, why would we have kept it on our heads? And on top of that, you have this really fragile brain that you're trying to protect. So what I tried to look at is, well, does hair actually provide you with any protection?

And I did a bunch of experiments on that. And the Cliff Notes version is, yes, it's absolutely important. Do not go out there with your bald head into the sun or you will cook. And if you have straight hair, you are not much, much better off. Well, you're significantly better off than being bald. All those people get sunburned on their scalp or nodding their head like, yeah, that's true. to where I have. Exactly.

Right? So the interesting thing about straight hair is that it provides this barrier. You have less radiation that's hitting your scalp, but because straight hair lies flat on the scalp and all these hairs are tightly packed, it doesn't allow you to lose as much heat. And what's really incredible about tightly curled human hair is that it's this perfect combination, this unique structure that minimizes the amount of heat. that comes down to your scalp, and it maximizes the amount of heat that you can lose.

So it's the best of both worlds. Okay. We humans, we love to categorize things. We've been doing it since we were, you know, a species. What are some of the ways that we have developed shorthand for discussing hair variation? So the way we usually talk about hair morphology, hair shape, or hair texture, like these things all basically cover the same thing, is we talk about it in these categorical terms of straight, wavy, curly, and then sometimes you have people throwing in frizzy or kinky as a distinct

category. So that's one way of typing it. Another way that is still honestly very common is by using racial categories. But the issue there is that if you are stereotyping what that hair looks like, you're not able to appreciate the variation in that. And you have the really huge and inconvenient fact that a lot of people have admixt ancestries. African Americans, for example, often also have some European component to their ancestry. And that is something that racial classification does not take into consideration at all. And if you can't see variation, then you can't see what genetic variation is associated with that trait variation. It really captures this feedback loop we have between science and society when it comes to race,

right? Like how these terms become racialized. And it's a reminder that we have all this variation within the human species and it's so much variation that any kind of categorization misses representing all that. Yep, exactly. Like even the individual hairs on our head are different. And you couldn't like determine. a person's race from that alone. Yeah, absolutely. We have a lot of variation within our own scalps. So one

example that I like to give as a black woman is, well, think about baby hairs. We always talk about our edges and laying our edges. And a lot of times, the morphology of those hairs is very different from the hair that's just, you know, two inches further into your scalp. And the texture that you have on the crown of your head or the back of your head might also be completely different. Yeah. I really wish you had been there when I was in college. I was in the library and this guy came up to me and he was like, what are you? You know, the classic. And I said, I said, okay, my dad's Chinese and my mom's white. And he was like, oh, I can tell because of the texture of your hair. You have white girl hair instead of Chinese girl hair. So I know that your dad is the

Chinese one. And I was like, you can't tell that at all. I wish you had been beside me. But seriously, I mean, we do use racial categories every day to talk about hair. And this can have serious consequences on people's lives. You've written about this. So some of the worst and genuinely most dangerous ways that have had horrible consequences have related to forensics. Because if you are trying to compare, compare a sample that you found with a database of individuals. And one of the categories you're

trying to figure out is what their race is, that is really dangerous because if you get it wrong, that could have consequences for that person's life. And this has happened before. Like, the FBI in, I think, 2008 or 2009 had to exonerate a huge number of people because they were convicted based off of bad, you know, quote unquote hair science. And in one case, I remember that the hair sample that was used to convict this one person was actually a dog hair. That is really devastating, Tina. Like how hair science has harmed people and how problematic it is that we use our words to describe hair when words kind of fail. So I want to know with your PhD, what are you proposing as a new and better system for typing hair? So what I'm proposing is that

we measure it. Measure it. Like with a ruler? Well, so that's the thing. There weren't really easy methods for measuring it. So I had to develop them. There's two aspects of hair morphology that I try to measure. One of them is the curvature, so that variation from straight to tightly curled. And the other aspect is the cross-sectional shape. So for the cross-section, it tells you how thick is the hair or, you know, what shape is it? Is it really round or is it really flat? And for the curvature, what it does is it fits these imaginary circles to the fiber that tell you how tight the curl is. And this is the cool thing about measuring hair curvature. It's that once you have a circle that fits that curve, the bigger the circle is, the straighter the hair is. The smaller the circle is,

the curlier the hair is, and curvature is basically the inverse of the radius of that circle. So I know that's a lot of math. Well, it's a fancy way of saying my kind of straightish hair wouldn't fill a circle that's super small. Exactly. It would take a huge circle. And the cool thing about really straight hair is, like, if you think about it, what is the radius of a circle that fits a straight line? It's infinity. Oh, oh, that's cool. Okay, so you're developing your system using science, and there's this other system we got to talk about that's popular and controversial from the world of beauty.

We're talking about the Walker system named after hairstylist Andre Walker. It's quick. It uses a few letters and numbers. Here's YouTuber Kim Foster, who runs the channel for Harriet. Today, I'm here with Queen and Jay. We are going to talk about black women in our relationship to hair. Sometimes I get concerns because I feel like the threes, you know, that three category, still gets elevated above the kinkier, coilyer textures.

And I worry that we are just replacing one harmful beauty standard with another harmful beauty standard. So, yeah, the Walker system has been heavily critiqued for reinforcing texturism in how we talk about hair. And thinking about these videos, I had to ask Tina what she thought about these conversations on YouTube. As a biological anthropologist, do you feel some type of way about beauty YouTube for introducing this way of describing hair? So this has been a point of discretion among black women in the natural hair community for a long time. And the issue tends to be that certain textures are seen as more valuable or prettier than others. And so you have these kinds of discussions. So I think that the main issue with this typing system and any typing

system is, how do you know if someone is a particular hair type? There aren't any universal cutoffs. But what I feel I can do as a scientist then, and I hope to do in the near future, is, okay, if we want to divide it into these categories for shorthand, what is the curvature, of someone who is a type 4C as opposed to someone who's a 4B or a 4A and so on and so forth. Yeah, yeah, I hear what you're getting at. So like going back to your system, if we were to add this layer you're proposing, the science of curvature and cross-section and just be more specific in our language, how could that change the world?

Like, what excites you about how we could talk about hair differently? Well, I really hope that it gives people a sense of pride, and especially black people, a sense of pride, because they've had this hair type demonized. We've had our hair be dehumanized as woolly and treated as undesirable as something that needs to be straightened. And being able to say that it served an incredibly important function evolutionarily can be a sense of pride. that's what I see happened with skin pigmentation. To look online and to see people talking about melanin, the word melanin itself, that they know that, and that they know that it protects your skin from the sun, is beautiful.

And if I could contribute in some way to hair in a similar way and see if one day people are saying, like, hey, you can say what you want about my hair, but our ancestors evolved this tightly curled hair to protect us. And if it wasn't for this crown on my head, we wouldn't have the big brains that we do. So there. Thank you so much for bringing this like really brilliant insight, but also just like, you're not only stating a problem, you're coming up with new scientific methodologies. Unbelievable.

That's exactly the kind of thing that like you hope for science, you know. You hope it's like changing the way we talk about the world on each other. So really appreciate your work. Thank you. To check out more of Tina's research and her talks on hair, check out our episode notes. Today's episode was edited by Sarah Saracen, produced by Rebecca Ramirez, and fact-checked by Tyler Jones, who also pitched the episode and did amazing research. Special thanks to Ramey Barnwell and to Natasha Branch, the audio engineer for this episode. I'm Emily Kwong. Thanks for listening to Shortwave, the Daily Science podcast from NPR.