The Story of Human Hair

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This is Origin Stories, the Leaky
Foundation podcast. I’m Meredith Johnson.

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Today on the show we’re talking about
one of the things that makes humans

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different from other animals, our hair.

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From why we have it on the top of our
heads instead of all over our bodies to

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how we evolved so many variations
in color, texture, and curliness.

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Our guest is Dr. Tina Lasisi.

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She’s an assistant professor
at the University of Michigan
where she leads a lab

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researching the evolution and genetic
basis of human variation with a focus

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on pigmentation and hair.

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She’s also the host of a PBS
show called Why Am I Like this?

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And she’s the recipient of
the 2024 Science Communication
Award from the Leakey

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Foundation and the American Association
of Biological Anthropologists.

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I always frame it as we talk about
humans being the naked ape, but actually,

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there are plenty of mammals that are
naked. You have mole rats, elephants,

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depending on how you look at them,

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and definitely a bunch of
mammals that are in the sea,

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but we’re actually the only weirdos
that have no fur on our bodies,

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but decided to keep the
fur on our heads mostly.

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And that’s what I emphasize is
especially weird about humans and has not

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been studied enough for my liking.

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When we have something like this that’s
so, so different from other animals,

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what does that tell you as
an evolutionary scientist?

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So evolution is creative but also lazy.

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So if you find a good
solution for a problem,

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you tend to apply it again and again.

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That’s how we have things like
convergent evolution of wings.

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But if you see something
that has been evolved once,

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like scalp hair on a naked body,
that really tells you, okay,

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something must have happened
here. Some combination of traits,

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characteristics for that species and
the situation it was in must have been

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special enough that a new
solution had to arise.

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What was our situation
and how do you know?

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That’s a great question. We don’t know,

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but we do a lot of scientifically informed

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theorizing. Some would call it
guessing, but it’s a lot more intense.

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I would say it’s a lot more
careful work than guessing.

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So basically we put together
evidence from a lot of different

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avenues.

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One of the things that we can do
is look at the fossil evidence and

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understand what species were
closest to us and what their

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evolutionary history was.

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And what you start seeing is
basically the sequence of traits

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that appears in our lineage.

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We have this upright
posture, we have bipedalism,

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we have these large brains,

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and you see that there’s this
bipedalism that emerges about

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2 million years when you
start seeing Homo erectus.

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Now what you see in Homo erectus
is this modern day build.

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They have the same
proportions bodily as we do,

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but the brain size doesn’t seem to be

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quite where it is today in modern humans.

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And so there’s this really interesting
outstanding question in human evolution

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of, well, why did it take so long?

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Was there something that was preventing
brains from getting to their modern

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day size? And that’s kind
of where the hair comes in.

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And hair and skin are very difficult to
think about in terms of human evolution

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because they don’t leave this
really nice fossil evidence.

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So what we have to do then is
infer what makes sense in part

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using genetics.

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And what we know from the
skin pigmentation side is that

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there is evidence that the last common
ancestors of all humans had darker

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skin.

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And what I would love to do is see
if we could do a similar thing for

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hair,

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but we’re not quite there yet because
we don’t know what genes are involved in

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hair morphology very well.

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But what we can do is put together
testable evolutionary hypotheses.

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So you have a hypothesis about
why we have hair on the top of our

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heads and not so much on our bodies.

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Can you tell us about that and
about the research you did and how

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robots are involved.

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How robots are involved? Yes.
We will not forget the robots.

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So basically what me and my

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PhD advisor,

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Nina Jablonski were wondering is how hair

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might have a parallel
story to skin pigmentation.

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So Nina did the leading
work on the evolution

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of skin color in relation to
vitamin D and UV radiation.

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So we know that where there’s
a lot of UV radiation,

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you benefit from having more pigmentation
because it protects the Foley in your

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bloodstream. So the
question is what about hair?

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Could that help with anything?

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And we were testing out
this hypothesis that tightly

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coiled hair in particular could
reduce the amount of heat you gain

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specifically from solar radiation.

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And so I’m going to back up here a little
bit because I did talk about humans

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being very special in terms of
having scalp hair on naked bodies.

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But what’s even more exciting,

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it’s the presence of tightly curled hair.
And that is not something that you see

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in any other mammal.

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And this is something I always say
on podcast shows wherever I’m at,

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as far as I know,

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I have not seen any mammal naturally
occurring that has tightly coiled

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hair. Anything as close to the
tightest coils that you see in humans.

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If someone finds a mammal that
does fit that description,

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please send me pictures.
I’m always open to it.

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But that adds to this layer of, well,

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if we were the first ones to
have to evolve scalp hair,

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why were we also the first ones to
have to evolve this tightly coiled hair

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texture?

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And what we know from research
on mammalian coats is that hair

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offers a lot of protection.

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So a lot of the discourse that we have
in human evolution on hair hairlessness

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is of course you want to be naked, right?
If it’s hot, you want to be naked.

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However, there are hairy
mammals in very hot places.

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And if it’s so beneficial,

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why would you have mammals
in the desert that have hair?

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And that’s because hair
can offer protection,

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especially when it comes to reducing
heat gain from solar radiation.

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And I specify that because you
have ambient temperature and

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solar radiation, it
works in a different way.

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If you’re ever outside on a very,
very sunny day, what do you do?

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You seek shade.

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And it’s significantly cooler when you
are in a place where the sun’s rays

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are not hitting you directly.

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So what we wanted to do is see
if we could find any evidence

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for that function. And
in order to do that,

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we bought a bunch of human hair wigs
and put them on a bunch of robots

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in climate controlled chambers and
turned them on and saw what happened.

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That’s a really creative solution. So
what were you testing and what happened?

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Yeah, so there are these robots

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that are very much shaped like
the terminator that are used

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across many fields to measure the

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insulation value of various fabrics.

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And so there are people who use them.

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So we reasoned, well,

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you can put a wig on it and
basically treat it the same as you

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would treat a piece of fabric.

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And so the way a thermal mannequin
works is it has a surface

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that is set to a particular temperature,

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and in order to keep that set temperature,

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it needs to pump in energy, electricity.

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If the external environment is warmer,

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then it doesn’t need to
pump in as much electricity.

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If the external environment is colder,

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then it needs to pump in more electricity.

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And so that difference in terms of how
much energy is required to keep that

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stable temperature,

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that’s what tells us about
how much insulation a given

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fabric or wig gives it.
And so we had four experimental hair

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conditions, a straight wig,
a moderately curled wig,

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and then a tightly curled wig.

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And then of course we had to have
the baseline calibration of no hair.

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So we also ran all the
experiments without hair,

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and we looked at how heat transfer
was affected without solar

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radiation, and then we simulated
solar radiation with floodlights.

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And what we noticed was an

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incredible undeniable
effect of not only the

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presence and absence of hair,

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but the curlier hair
was the more heat gain

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was reduced from that
solar radiation. Wow.

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It actually got to the point where
when we were running these experiments,

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we were randomizing the sequence
in which we were doing them.

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And so it started out with the tightly
curled wig ran the experiments,

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and when I ran them with the straight wig,

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the mannequin was overheating.

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And so we had to figure out how to change
the settings because that’s how much

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of a protective effect tightly coiled
hair gave that we needed to adjust

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the experimental settings so that it
worked across all of the conditions.

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That’s.

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Amazing. So if curly hair,

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tightly coiled hair protects
from solar radiation, so well,

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why doesn’t every human have curly hair?

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How did we end up with
so many different kinds?

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That’s one of the big things
that makes evolution so

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complicated.

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If there is a trait that is good, then
why doesn’t everyone have that trait?

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And the reason is that
this trait may not always

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be under selection. So let’s
take skin color for example.

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When you look at skin
color around the world,

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mostly yes,

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it does adhere to this pattern
of where there is more uv

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radiation skin is darker, and where
there’s less uv radiation skin is lighter.

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But especially once you
go into the Americas,

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you see that that doesn’t
hold as well anymore.

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And our understanding of this
is that there hasn’t been as

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much time for that trait
to be under selection.

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And so how much does having this trait
or not having this trait affect your

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ability to produce surviving offspring?

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Now when it comes to hair,

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the pattern doesn’t seem to
hold at all, does it? Right?

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There are many places that have a lot
of solar radiation where people have

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straight maybe wavy hair.
If you look across South Asia for

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example, and my thinking around
this is that this may have been an

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important point of selection
early on in human evolution.

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So going back to homo rectus 1.8 to

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1.5 million years ago after we’re
fully bipedal, fully naked in the sun,

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but brains are not quite
the size that they were yet,

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maybe tightly curled hair
represented a solution to

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release that constraint.

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So brains are very heat sensitive
and they also generate heat.

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The bigger your brain is, the more
dire your situation is going to be.

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So it’s very plausible that it may
have been the case that humans evolved

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this tightly coiled tear,

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which was able to minimize how
much heat they were gaining,

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minimize how much water they were losing,

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and now it was viable to have a
large brain. But the thing is,

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once you have this large brain,
you come up with solutions.

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And in much of the same way
as many people who turn red on

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the beach do not have to
suffer if they have sunscreen,

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there may have been other shade
seeking behavior or other behavioral

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adaptations.

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Okay. Is there a difference between
hair and fur? Is it the same thing?

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Hair and fur are exactly the same thing.

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Humans to make ourselves special
by using different words for us.

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And also it’s a pet peeve of
mine because people talk about it

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with dogs as well. My dog, I have a
poodle, is right next to me right now.

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So a lot of people will talk about, oh,
well this breed of dog doesn’t have fur,

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they have hair. And a lot of
times when I ask people, well,

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what do you mean by that? They’re
talking about how the hair is finer,

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but you have thick hair, you can have
thick hair fibers, thin hair fibers,

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the hair follicle is this
incredible, honestly,

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a super mini organ because
unlike many of our other

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tissues or other organs that
develop once and then you’re set

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and hopefully you don’t have to
lose them for the rest of your life.

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Hair follicles go through a growth phase,

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a resting phase,

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and then they completely
miniaturize and regenerate a

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whole new hair follicle. So that
entire cycle is the regeneration of an

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entire mini organ,

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and there is a supply of stem cells there
that helps with that regeneration of

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the hair follicle each time.
And going through that process,

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you have asynchrony
between our hair fibers.

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So our hair fibers grow for
anywhere between a couple of weeks.

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If you’re talking about our eyebrows
or our eyelashes to a couple of months

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00:14:06,430 –> 00:14:11,170
maybe, depending on what kind of body
hair you have to two to seven years,

227
00:14:11,170 –> 00:14:13,870
if you’re talking about scalp hair,
I’ve even heard like 10 years.

228
00:14:14,050 –> 00:14:17,110
So you have hair that is
growing for that long,

229
00:14:17,740 –> 00:14:21,730
but it’s not all synchronized. If it
was then however many years or weeks,

230
00:14:21,970 –> 00:14:25,540
all of it would fall out. But
you can have synchronization.

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00:14:25,540 –> 00:14:27,910
And that’s some stuff that we
see across different mammals,

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00:14:27,910 –> 00:14:30,130
especially when you’re
thinking about seasonal coats.

233
00:14:30,430 –> 00:14:34,990
That’s the synchronization of different
types of hair follicles falling,

234
00:14:34,990 –> 00:14:39,370
shedding at different times and
regenerating at other times. Which again,

235
00:14:39,370 –> 00:14:41,170
I think hair is awesome. It’s super cool.

236
00:14:41,800 –> 00:14:42,880
Yeah, it’s so interesting.

237
00:14:42,880 –> 00:14:47,590
I guess I never I mean I
think about eyebrows like you

238
00:14:47,590 –> 00:14:49,870
do, but I never considered that.

239
00:14:49,930 –> 00:14:54,230
What if they grew like our
head hair and just kept going.

240
00:14:54,260 –> 00:14:57,290
And they do. Once you become an emeritus
professor, I just want to specify.

241
00:14:57,890 –> 00:15:01,790
And our hair changes over our
lifetimes. It changes color.

242
00:15:02,300 –> 00:15:04,040
Some people lose their hair.

243
00:15:06,120 –> 00:15:10,970
And going through puberty and
going through chemotherapy,

244
00:15:10,970 –> 00:15:13,400
for example, can change its texture.

245
00:15:13,400 –> 00:15:16,550
So that’s something that I get questions
about all the time, and honestly,

246
00:15:16,550 –> 00:15:21,260
it’s the next thing I think I’m
going to focus on because that to me

247
00:15:21,260 –> 00:15:22,610
is very exciting.

248
00:15:23,180 –> 00:15:28,040
And you mentioned that we’re the only
animals that have this kind of tight,

249
00:15:28,070 –> 00:15:32,780
curly hair pattern. But then a
lot of people will say, well,

250
00:15:32,780 –> 00:15:36,020
what about poodles what
you have right next to you?

251
00:15:36,470 –> 00:15:40,580
And then when Ray and I were doing our
research, we found all these cute, cute,

252
00:15:40,580 –> 00:15:45,530
cute pictures of tiny baby gorillas
in the midst with their curly hair.

253
00:15:46,590 –> 00:15:51,200
They’re so cute. They’re
so cute. I love them.

254
00:15:51,380 –> 00:15:51,590
So.

255
00:15:51,590 –> 00:15:56,120
Much. Yes, absolutely.
But let’s dig into that.

256
00:15:56,120 –> 00:15:58,640
So funnily enough, see,

257
00:15:58,640 –> 00:16:01,700
this is how I know I’m in an anthro
crowd because y’all will bring up the

258
00:16:01,710 –> 00:16:05,450
gorillas before the sheep,
which is usually what people
do. People will be like,

259
00:16:05,450 –> 00:16:06,283
oh, what about sheep?

260
00:16:06,890 –> 00:16:11,870
So sheep have wool,
right? Wool is also hair,

261
00:16:11,930 –> 00:16:13,520
wooler hair, it’s all the same thing.

262
00:16:14,030 –> 00:16:18,980
And one of the misnomers of tightly
coiled human hair is woolly,

263
00:16:18,980 –> 00:16:20,510
right? Like, oh, you have woolly hair.

264
00:16:20,840 –> 00:16:25,520
And that connection between
wool and tightly coiled

265
00:16:25,520 –> 00:16:29,090
hair, that has definitely
some racist roots,

266
00:16:29,300 –> 00:16:31,400
but even that aside,

267
00:16:31,400 –> 00:16:36,260
it confuses people and it makes sense
why nobody looked at this until I did.

268
00:16:36,260 –> 00:16:40,190
And my advisor thought to look at
it because they were thinking, well,

269
00:16:40,190 –> 00:16:43,940
wool keeps you hot. So if you have
tightly coiled hair that’s like wool,

270
00:16:43,940 –> 00:16:44,780
it must be hot.

271
00:16:45,020 –> 00:16:50,000
But those are two very different
structures. So wool has a bilateral

272
00:16:50,000 –> 00:16:50,570
wave,

273
00:16:50,570 –> 00:16:55,460
and we actually know the process
that is occurring in order to

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00:16:55,460 –> 00:17:00,140
create that bilateral wave because
wool is an industry and it has

275
00:17:00,150 –> 00:17:02,180
money and you need to understand it.

276
00:17:02,240 –> 00:17:07,160
So we have spent so many years
looking at what the process is

277
00:17:07,160 –> 00:17:07,280
there,

278
00:17:07,280 –> 00:17:11,480
and we actually understand it really well
when people try to look for that same

279
00:17:11,480 –> 00:17:13,940
process in humans, they did
not find those in humans.

280
00:17:15,320 –> 00:17:19,970
If you pay attention to human hair,
you’ll note that curls are hele.

281
00:17:20,000 –> 00:17:24,380
They’re not waves. Human
hair coils, it curls.

282
00:17:24,770 –> 00:17:27,950
Now, poodles, that’s easy.

283
00:17:28,670 –> 00:17:33,350
There’s a lot of weird dogs, domesticated
animals, not to make them not count,

284
00:17:33,350 –> 00:17:36,230
but we can make a lot
happen. So I would argue,

285
00:17:36,230 –> 00:17:38,330
and this is me even looking at my dog,

286
00:17:39,860 –> 00:17:42,740
even if I see some things
that are approaching a coil,

287
00:17:42,740 –> 00:17:46,070
even though I would say a lot of
what I see is this bilateral waving,

288
00:17:46,610 –> 00:17:50,460
it’s not the same
structure human hair curl,

289
00:17:50,730 –> 00:17:55,470
and this is not me being pedantic, but
after having done the experimentation,

290
00:17:55,470 –> 00:18:00,210
there actually is a really
significant functional difference.

291
00:18:00,390 –> 00:18:04,920
If you have a bunch of especially
very thin hairs that are

292
00:18:05,370 –> 00:18:08,430
lining up very closely together,

293
00:18:08,580 –> 00:18:13,260
you have a lot of density, a lot of
hair fibers packed closely together.

294
00:18:13,710 –> 00:18:17,820
That’s not good if you want
to be losing heat versus human

295
00:18:18,180 –> 00:18:23,070
coils are this chaotic
lattice of coils where

296
00:18:23,070 –> 00:18:27,420
you have a lot of airspace, a
lot of empty space in between.

297
00:18:27,420 –> 00:18:31,800
And that’s what allows us to have this
incredible absence of a trade-off,

298
00:18:31,800 –> 00:18:36,000
which there usually is with hair of we
can reduce how much heat is coming down

299
00:18:36,000 –> 00:18:38,880
from the radiation, but we can also
maximize how much heat we’re losing.

300
00:18:39,090 –> 00:18:42,690
That’s not the case with wool for sure,

301
00:18:42,690 –> 00:18:47,670
because that stacks up perfectly
with dogs like Winston,

302
00:18:47,730 –> 00:18:51,210
my poodle. That’s not the case
either. You have all of this density,

303
00:18:51,210 –> 00:18:55,500
there’s no airspace in the
hair. And with gorillas, well,

304
00:18:55,500 –> 00:18:59,250
I’m going to need a gorilla hair sample.
But from the pictures that I saw,

305
00:18:59,550 –> 00:19:04,470
it doesn’t appear to be as
tightly coiled as human hair.

306
00:19:04,470 –> 00:19:05,670
And I would add to that,

307
00:19:05,670 –> 00:19:10,260
that I’m starting to think
that there is a lower

308
00:19:10,260 –> 00:19:14,370
density of hair when I
look at human hair curls.

309
00:19:14,560 –> 00:19:17,250
It’s not as closely packed together,

310
00:19:17,370 –> 00:19:19,890
but that’s still something
that we’re having to explore.

311
00:19:20,520 –> 00:19:25,350
And a lot of your work has sort of
defined what our curls are, right?

312
00:19:25,350 –> 00:19:28,530
You’ve come up with ways to
talk about more precisely.

313
00:19:28,710 –> 00:19:30,540
Can you tell us a little bit about that?

314
00:19:31,230 –> 00:19:36,060
Yes. So any trait that you want to study,

315
00:19:36,070 –> 00:19:39,030
you have to operationalize,

316
00:19:39,330 –> 00:19:43,590
and that means you are defining
it in a very specific way.

317
00:19:44,070 –> 00:19:46,980
I try to be very careful
when I talk about it,

318
00:19:46,980 –> 00:19:49,920
but it’s especially evident in
the way that I measured hair.

319
00:19:49,920 –> 00:19:54,360
I spent a lot of time literally over a
decade of my life trying to figure out

320
00:19:54,370 –> 00:19:59,160
how best to measure hair
curl because there is a

321
00:19:59,160 –> 00:20:02,910
lot that is captured within
the concept of hair texture.

322
00:20:03,180 –> 00:20:04,650
And when we’re talking about hair shape,

323
00:20:04,890 –> 00:20:07,260
we’re talking about a lot of
things combined together. This.

324
00:20:07,270 –> 00:20:09,570
Must be such an exciting area of study.

325
00:20:09,720 –> 00:20:12,750
There’s still so many
questions to answer. Yes.

326
00:20:12,750 –> 00:20:16,440
I’m very still after all
these years. I’m very excited,

327
00:20:16,800 –> 00:20:17,700
otherwise I would not be here.

328
00:20:19,860 –> 00:20:24,720
So we have some more questions
and I was wondering if I could

329
00:20:24,810 –> 00:20:29,550
ask Ray to come on because he has a
haircare hairstyle related question.

330
00:20:30,390 –> 00:20:31,410
Hi, Meredith. Hi Tina.

331
00:20:31,860 –> 00:20:33,000
Hi Ray. Hi Ray.

332
00:20:33,420 –> 00:20:36,870
So when we were getting ready for this,

333
00:20:36,900 –> 00:20:39,840
we both heard you say a bunch of
different times in different places.

334
00:20:40,710 –> 00:20:45,630
So much of research is me
search. And as you can see,

335
00:20:45,840 –> 00:20:47,070
I have curly,

336
00:20:48,310 –> 00:20:52,600
and I usually don’t let
it get this long because

337
00:20:53,590 –> 00:20:57,160
I’ve always been under the impression
that also because my hair is black,

338
00:20:58,000 –> 00:20:59,800
it gets really hot in the summer.

339
00:21:00,580 –> 00:21:05,320
It just holds all of this
heat on my head because it’s

340
00:21:05,320 –> 00:21:09,130
absorbing all the sun rays
and then I am sweating.

341
00:21:09,970 –> 00:21:14,560
And so I was kind of blown
away by the finding that

342
00:21:15,730 –> 00:21:20,500
maybe I might be better off
with some curly hair in the

343
00:21:20,500 –> 00:21:25,210
summer versus just slathering my

344
00:21:26,440 –> 00:21:29,650
bald head and a lot of
sunscreen every day.

345
00:21:30,430 –> 00:21:34,060
And so I guess maybe this
is a dear Tina question,

346
00:21:34,070 –> 00:21:39,040
but would I be better off in the
summer with my curly hair versus

347
00:21:39,050 –> 00:21:39,883
no hair?

348
00:21:40,150 –> 00:21:43,900
Well, first of all, thank you so much
for offering to extend our research.

349
00:21:43,900 –> 00:21:47,140
I’m really excited about this partnership.
We’re going to do good work together.

350
00:21:47,890 –> 00:21:51,280
Yes, trust me on this.

351
00:21:51,340 –> 00:21:54,820
Even if you leave your hair to what it
is now, if you want to grow it out more,

352
00:21:54,820 –> 00:21:55,690
that also works.

353
00:21:58,210 –> 00:22:03,160
Stand in the sun and see how you feel

354
00:22:03,280 –> 00:22:07,750
and look at the difference if
you can even just touching it

355
00:22:08,800 –> 00:22:12,820
in temperature between your scalp
and then the top of your hair.

356
00:22:13,060 –> 00:22:17,770
And here’s another fun anecdote.
10 years ago or something,

357
00:22:18,010 –> 00:22:22,720
I was outside somewhere with a
friend who had very straight light

358
00:22:22,720 –> 00:22:27,430
hair that laid very flat on
his head and he touched the

359
00:22:27,440 –> 00:22:29,560
top of my hair. Consensually

360
00:22:31,180 –> 00:22:33,570
always ask if you want to touch someone
else’s hair. And he was like, ow.

361
00:22:34,060 –> 00:22:37,150
He burned his hand. He was like,
oh, it’s so hot. Are you not hot?

362
00:22:37,420 –> 00:22:40,690
And I didn’t feel anything
but the top of my hair,

363
00:22:41,260 –> 00:22:46,030
not the head top of my hair was really
hot. And yes, it does absorb that heat,

364
00:22:46,210 –> 00:22:47,140
but again,

365
00:22:47,140 –> 00:22:52,000
this is one of the peculiarities
of how radiative heat works.

366
00:22:53,590 –> 00:22:55,450
And we have seen this in mammals.

367
00:22:55,450 –> 00:22:58,480
There are really interesting
studies from the eighties,

368
00:22:58,510 –> 00:23:02,470
I want to say from the seventies
through the nineties of various

369
00:23:03,610 –> 00:23:08,200
mammals, they were looking at their
coats and looking at the effect of color.

370
00:23:08,590 –> 00:23:10,060
Everyone has this idea of, well,

371
00:23:10,070 –> 00:23:14,800
you must be better off
having lighter hair and less

372
00:23:14,800 –> 00:23:17,590
hair if you’re somewhere where
there’s a lot of solar radiation,

373
00:23:18,010 –> 00:23:22,360
it should reflect the light. But
it turns out that in practice,

374
00:23:22,360 –> 00:23:26,860
it’s not how it works because
this idea of dark objects,

375
00:23:26,870 –> 00:23:31,210
heat up light objects reflect
light is so misapplied.

376
00:23:31,240 –> 00:23:34,510
And we even see this all the way
from people thinking that, well,

377
00:23:34,510 –> 00:23:35,620
people with dark skin,

378
00:23:35,860 –> 00:23:39,970
they must be in so much trouble in
the sun because black objects heat up,

379
00:23:39,980 –> 00:23:40,930
right?
Meanwhile,

380
00:23:41,140 –> 00:23:44,650
black people are fine and some
people are turning into lobsters.

381
00:23:45,260 –> 00:23:50,090
So what happens is that you don’t
have these flat surfaces like what we

382
00:23:50,090 –> 00:23:53,420
usually think about when we’re measuring
this reflectance and absorbance of

383
00:23:53,420 –> 00:23:55,730
heat. Now, when it comes
to hair specifically,

384
00:23:56,540 –> 00:24:00,470
especially if you have these fibers that
are pointing in all these directions,

385
00:24:00,830 –> 00:24:05,660
the straight radiation of the sun
bounces off. It gets absorbed,

386
00:24:05,900 –> 00:24:08,120
but your hair is not living tissue.

387
00:24:08,660 –> 00:24:12,890
So if it gets absorbed by the top of
your hair and it bounces off some of it,

388
00:24:12,920 –> 00:24:14,900
that’s great. Meanwhile,

389
00:24:15,230 –> 00:24:20,060
if you have straight hair that is flat

390
00:24:20,070 –> 00:24:20,990
against your scalp,

391
00:24:21,980 –> 00:24:26,630
there is no distance between the top
of your hair and the top of your scalp.

392
00:24:26,630 –> 00:24:30,560
And that’s something that we see in that
mammalian literature that they say that

393
00:24:30,570 –> 00:24:34,100
once you have over two
inches of fur, hair, coat,

394
00:24:34,110 –> 00:24:37,880
color doesn’t matter anymore. Coat color
doesn’t make a difference in how much

395
00:24:37,890 –> 00:24:42,530
you heat up or don’t because it’s that
distance from the skin that matters the

396
00:24:42,530 –> 00:24:47,480
most. And if you have light hair on top
of that, yes, you have this reflection,

397
00:24:47,480 –> 00:24:49,730
but it’s not necessarily
going to bounce off,

398
00:24:50,060 –> 00:24:53,300
it’s going to bounce around your
hair and probably hit your scalp.

399
00:24:53,570 –> 00:24:58,430
So having it absorb in the
melanin that is kept in your dead

400
00:24:58,430 –> 00:25:02,660
hair shaft that is there to protect you
is much better than it coming down to

401
00:25:02,660 –> 00:25:05,750
your living scalp. So I expect a
full report by the end of the summer.

402
00:25:05,750 –> 00:25:06,583
Thank you.

403
00:25:06,710 –> 00:25:07,050
Okay.

404
00:25:07,050 –> 00:25:12,050
I feel really emboldened
to keep my hair over the

405
00:25:12,060 –> 00:25:13,250
summer. Thank you so much, Tina.

406
00:25:13,790 –> 00:25:14,623
Thank you, Ray.

407
00:25:15,440 –> 00:25:16,310
Back to you Meredith.

408
00:25:16,700 –> 00:25:17,533
Okay.

409
00:25:18,020 –> 00:25:22,460
So how did you first get interested
in studying hair from an evolutionary

410
00:25:22,460 –> 00:25:23,180
perspective?

411
00:25:23,180 –> 00:25:27,440
So it all started with a lecture on

412
00:25:27,590 –> 00:25:32,300
human skin color variation and
how it relates to UV radiation.

413
00:25:32,300 –> 00:25:35,690
And just seeing those maps of the
distribution of skin color and the

414
00:25:35,690 –> 00:25:39,710
distribution of UV radiation was
such a eureka moment for me that

415
00:25:39,860 –> 00:25:43,970
I was just so impressed at such an elegant

416
00:25:44,330 –> 00:25:47,450
explanation. I had never thought
about evolution in that way.

417
00:25:48,710 –> 00:25:53,330
And going back to the whole
research is me search the way

418
00:25:53,330 –> 00:25:57,170
my 20 something year old brain
processed, it was like, cool,

419
00:25:57,180 –> 00:25:59,330
now I know why my skin is
brown. Why is my hair curly?

420
00:25:59,510 –> 00:26:02,870
And that didn’t have
a satisfactory answer.

421
00:26:02,870 –> 00:26:07,610
And so I was like a dog with
a bone clenched between my

422
00:26:07,620 –> 00:26:12,110
jaws, and I needed to get my answer.
And here I am over a decade later,

423
00:26:12,410 –> 00:26:13,520
still trying to get this answer.

424
00:26:14,900 –> 00:26:19,040
And that’s really cool that you were able
to join Nina’s lab and study with her,

425
00:26:19,460 –> 00:26:24,380
the person that did that elegant
research about skin color variation and

426
00:26:24,380 –> 00:26:25,640
vitamin D. That’s so cool.

427
00:26:25,970 –> 00:26:26,990
Yeah, it was incredible,

428
00:26:26,990 –> 00:26:30,230
and especially because I actually
wasn’t intending to be a biological

429
00:26:30,230 –> 00:26:31,063
anthropologist.

430
00:26:31,400 –> 00:26:35,420
I did my undergrad at the University
of Cambridge where they taught it as a

431
00:26:35,430 –> 00:26:40,280
three field cultural anthropology or
social anthropology as they call it over

432
00:26:40,280 –> 00:26:42,980
there, archeology and
biological anthropology.

433
00:26:42,990 –> 00:26:45,600
And I was so sure I wanted to do cultural.

434
00:26:45,990 –> 00:26:50,340
And it wasn’t until this lecture that
I had entertained the idea of doing

435
00:26:50,340 –> 00:26:54,840
biology. And if it wasn’t for my
undergraduate mentor at the time,

436
00:26:54,900 –> 00:26:57,450
I wouldn’t have gone down this path.

437
00:26:57,480 –> 00:27:02,340
It very much wasn’t a strategic
plan or the result of a lifelong

438
00:27:02,550 –> 00:27:06,480
at that point, interest in
something, but more, Hey,

439
00:27:06,480 –> 00:27:07,620
this is kind of cool.

440
00:27:07,680 –> 00:27:11,580
And getting the kind of encouragement
that I got of you can do this was

441
00:27:11,580 –> 00:27:13,920
instrumental to me feeling like I could.

442
00:27:13,920 –> 00:27:18,000
And so I really tried to pay this forward
now because I noticed that when I talk

443
00:27:18,000 –> 00:27:22,620
about my research, it’s really
intelligible to people. They’re like,

444
00:27:22,650 –> 00:27:25,860
oh yeah, no, that makes sense to me
that you would ask that question.

445
00:27:25,860 –> 00:27:28,680
I also have questions and I
want to tell people, I’m like,

446
00:27:29,010 –> 00:27:29,970
your questions are good.

447
00:27:30,060 –> 00:27:33,240
You have good questions in
case no one has told you this.

448
00:27:33,240 –> 00:27:34,680
Your questions are awesome.

449
00:27:35,070 –> 00:27:40,020
And I might be the first person to
entertain the idea that they are

450
00:27:40,020 –> 00:27:41,820
having really good questions, and.

451
00:27:41,820 –> 00:27:42,653
We love that.

452
00:27:43,770 –> 00:27:46,920
And it feels like such
a new area of study.

453
00:27:47,520 –> 00:27:51,720
So you have the opportunity to
do a lot of foundational work,

454
00:27:51,750 –> 00:27:53,220
and that’s pretty exciting.

455
00:27:53,610 –> 00:27:58,530
I mean, I can see how from the
outside, it might seem this way,

456
00:27:58,980 –> 00:28:01,920
to be honest, being in it, I don’t know.

457
00:28:03,600 –> 00:28:06,000
It doesn’t feel, that’s
not to say that it isn’t,

458
00:28:06,030 –> 00:28:09,450
but when something’s in front of you
and you’re doing it, you’re like, yeah,

459
00:28:09,630 –> 00:28:11,280
I know. I’m just doing it.

460
00:28:11,720 –> 00:28:16,440
And hopefully over the
years, over the decades,

461
00:28:16,440 –> 00:28:20,580
it’ll accumulate to something
that is very valuable. And I mean,

462
00:28:20,910 –> 00:28:25,260
really one of my biggest
inspirations is my former advisor,

463
00:28:25,260 –> 00:28:29,070
Nina Jablonski, because I
remember when I was younger,

464
00:28:29,070 –> 00:28:32,580
nobody knew what melanin was.
That’s not a word that people used.

465
00:28:32,580 –> 00:28:37,050
And now there’s literally melanin
merch you can get on Instagram.

466
00:28:37,950 –> 00:28:39,450
We’re living in a different world,

467
00:28:40,140 –> 00:28:44,940
and I think most of us couldn’t imagine
a world now where not only did we not

468
00:28:44,940 –> 00:28:45,990
know what melanin was,

469
00:28:45,990 –> 00:28:50,370
but maybe even believed that
dark skin had no benefit in

470
00:28:50,610 –> 00:28:52,530
solar radiation. Yeah.

471
00:28:52,650 –> 00:28:56,550
How do you think the
evolutionary perspective of this

472
00:28:57,090 –> 00:28:58,830
topic benefits people are?

473
00:28:58,920 –> 00:29:02,760
So I would say one of the things that’s
really interesting about having done the

474
00:29:02,770 –> 00:29:05,400
work that I’ve done is that, yes,

475
00:29:05,400 –> 00:29:09,030
within biological anthropology and
let’s say anthropology generally,

476
00:29:09,030 –> 00:29:12,540
but especially biological
anthropology, I am weird.

477
00:29:12,540 –> 00:29:15,090
I stand out because I work on hair.

478
00:29:15,540 –> 00:29:20,340
It’s a multi-billion dollar
industry. Dermatology is a thing.

479
00:29:20,520 –> 00:29:24,900
And so I could not possibly claim to be
the first person to have ever thought

480
00:29:24,900 –> 00:29:29,670
about it. But what you see is this
really interesting conundrum of,

481
00:29:29,970 –> 00:29:30,690
well,

482
00:29:30,690 –> 00:29:35,160
why do people who work
on hair look at it so

483
00:29:35,160 –> 00:29:40,020
differently? And that’s really
where just the benefit of

484
00:29:41,080 –> 00:29:44,980
coming up academically, intellectually,

485
00:29:45,070 –> 00:29:47,830
in an evolutionary
anthropology environment,

486
00:29:48,160 –> 00:29:50,140
it shapes the way you look at the world.

487
00:29:50,140 –> 00:29:52,000
It shapes the way that you ask questions.

488
00:29:52,450 –> 00:29:56,980
And no one would argue that there are
incredible benefits to thinking directly

489
00:29:56,980 –> 00:30:00,850
about how can you make certain haircare
products to make hair do certain kinds

490
00:30:00,850 –> 00:30:05,800
of things? How can you fix various
issues that people have with their

491
00:30:05,800 –> 00:30:07,480
hair and skin from a medical perspective?

492
00:30:07,540 –> 00:30:12,100
There’s a need for basic
scientific research to be funded,

493
00:30:12,110 –> 00:30:16,840
which absolutely includes
evolutionary biology,

494
00:30:16,840 –> 00:30:18,040
evolutionary anthropology work,

495
00:30:18,040 –> 00:30:22,990
because I’m looking at just this tiny

496
00:30:22,990 –> 00:30:27,100
piece of something and saying,
how does this thing work?

497
00:30:27,110 –> 00:30:29,500
How does this thing humans work?

498
00:30:29,710 –> 00:30:34,510
What are all of the fundamental
processes and structures

499
00:30:34,570 –> 00:30:35,860
that affect us?

500
00:30:35,860 –> 00:30:40,240
And that gives you power and that it
allows you to make sense of things,

501
00:30:40,240 –> 00:30:43,930
how they fit together, and in a lot
of ways allows you to predict, right?

502
00:30:43,930 –> 00:30:48,850
And that is really what we’re seeing with
the research that’s been done on skin

503
00:30:48,860 –> 00:30:49,330
color.

504
00:30:49,330 –> 00:30:53,920
Knowing that there would have been
some kind of selection in both

505
00:30:53,920 –> 00:30:57,040
directions allows us to then say, okay,

506
00:30:57,040 –> 00:30:59,980
well what would that thing have been?

507
00:31:00,130 –> 00:31:04,090
We know that it has to be something
that probably influences fitness,

508
00:31:04,150 –> 00:31:05,710
the birth of offspring, folate,

509
00:31:05,800 –> 00:31:09,610
folate is really important. And being
able to put all those things together,

510
00:31:09,760 –> 00:31:14,650
you now have this incredible
scaffolding for being able to

511
00:31:15,400 –> 00:31:18,460
personalize and even think about how
these things are affecting different

512
00:31:18,460 –> 00:31:19,120
people.

513
00:31:19,120 –> 00:31:24,100
Like if you have darker skin in
a place that does not have a lot

514
00:31:24,110 –> 00:31:26,680
of solar radiation, just
because you don’t have rickets,

515
00:31:26,920 –> 00:31:31,270
just because you’re not bow-legged doesn’t
mean that you may not have a vitamin

516
00:31:31,270 –> 00:31:36,160
D deficiency that might affect you so
significantly that 2 million years ago,

517
00:31:36,280 –> 00:31:41,230
it would’ve meant that your offspring
wouldn’t have survived at the same rates

518
00:31:41,230 –> 00:31:43,600
as people with lighter skin.

519
00:31:44,470 –> 00:31:49,150
And the same thing can be said
of what we’re learning now

520
00:31:49,150 –> 00:31:52,510
about folate and what it has to do with
pregnancy and how it travels through the

521
00:31:52,510 –> 00:31:56,830
bloodstream. Just all of this stuff
is incredibly useful and interesting,

522
00:31:56,830 –> 00:32:00,820
and a lot of the money

523
00:32:01,990 –> 00:32:05,530
and how it flows would
make you think that it’s

524
00:32:06,220 –> 00:32:10,630
superfluous research that’s
very just like useless.

525
00:32:10,630 –> 00:32:15,610
And it is so important to be able to
tell the difference between things that

526
00:32:15,610 –> 00:32:20,530
have direct application versus
things that are useful and

527
00:32:20,890 –> 00:32:21,820
they can be different.

528
00:32:22,750 –> 00:32:27,700
Yeah. I and I work for the
Leakey Foundation, so we
obviously know this. Some

529
00:32:29,440 –> 00:32:34,360
type of basic research is so
important for understanding who

530
00:32:34,360 –> 00:32:38,560
we are and why we are the way
we are and how it all happened.

531
00:32:38,570 –> 00:32:43,430
So do you have a closing thought
that you’d like to share to wrap

532
00:32:43,430 –> 00:32:45,350
up our interview then? So you can go.

533
00:32:46,730 –> 00:32:50,000
It’s like holding me hostage until I
say something interesting. Just kidding.

534
00:32:51,740 –> 00:32:56,300
So what I’ll say is I
just opened my lab at the

535
00:32:56,300 –> 00:32:59,750
University of Michigan. The actual
physical lab space is still being built,

536
00:32:59,810 –> 00:33:01,850
but it should be done by the summer.

537
00:33:02,240 –> 00:33:06,410
And I’ve taken on a couple of students
and we’re working on some really

538
00:33:06,410 –> 00:33:07,130
interesting stuff.

539
00:33:07,130 –> 00:33:10,910
And one of the things I wanted to talk
about especially is some of the work that

540
00:33:10,910 –> 00:33:13,430
I’m starting to do with
my student, Sarah Taylor.

541
00:33:13,940 –> 00:33:18,560
We are really interested in
sexualism and natal coats in

542
00:33:19,520 –> 00:33:21,650
non-human primates
across the primate order,

543
00:33:21,980 –> 00:33:26,720
because that’s another dimension
of hair morphology that we

544
00:33:26,730 –> 00:33:30,890
kind of touched on in the beginning of
how it changes over time and different

545
00:33:30,900 –> 00:33:32,210
parts of your body. Well,

546
00:33:32,210 –> 00:33:36,050
one aspect of that is this dimension
of variation that sex gives us, right?

547
00:33:36,050 –> 00:33:39,980
Sex is this dynamic thing that changes
over time. You go through puberty,

548
00:33:40,040 –> 00:33:44,540
and depending on what receptors
you have at different places,

549
00:33:44,550 –> 00:33:47,870
different parts of your body are going
to respond differently to hormones being

550
00:33:47,870 –> 00:33:48,260
there.

551
00:33:48,260 –> 00:33:52,760
And so what we’re trying to understand
now is how do sex hormones interact with

552
00:33:52,760 –> 00:33:56,570
hair follicles to create
differences in hair growth,

553
00:33:56,580 –> 00:33:59,510
but also differences in hair
color. So watch out for that.

554
00:33:59,630 –> 00:34:04,130
Well, thank you so much for joining us
today and sharing your work and all this

555
00:34:04,130 –> 00:34:05,780
interesting information about hair.

556
00:34:05,810 –> 00:34:06,740
Thank you for having me.

557
00:34:11,540 –> 00:34:15,290
You can learn more about Tina
Lai and her work on her website,

558
00:34:15,440 –> 00:34:19,850
tinalasisi.com. We have that
link and more in your show notes.

559
00:34:20,930 –> 00:34:23,510
Origin Stories is a project
of the Leaky Foundation,

560
00:34:23,780 –> 00:34:28,400
a nonprofit dedicated to funding human
origins research and sharing discoveries.

561
00:34:29,330 –> 00:34:34,160
You can support this show by going to
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562
00:34:34,160 –> 00:34:36,290
clicking the origin stories donate button.

563
00:34:37,220 –> 00:34:42,050
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564
00:34:42,050 –> 00:34:46,520
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565
00:34:47,720 –> 00:34:51,890
Support for Origin Stories comes from
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566
00:34:52,130 –> 00:34:56,390
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567
00:34:56,690 –> 00:34:59,480
and the Joan and Arnold
Travis Education Fund.

568
00:35:00,800 –> 00:35:04,610
This episode was produced by Ray
Pang. Our editor is Audrey Quinn.

569
00:35:06,230 –> 00:35:10,040
Theme music by Henry Nagel and
Additional music by Blue dot Sessions.

570
00:35:11,120 –> 00:35:11,870
Thanks for listening.