Listener Mail: Fields of Ancient Void

Once more, it's time for a weekly dose of Stuff to Blow Your Mind and Weirdhouse Cinema listener mail...

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Episode Transcript

Speaker 1 (00:02):
Welcome to Stuff to Blow Your Mind production of iHeartRadio. Hello,
and welcome to Stuff to Blow Your Mind the listener mail.
My name is Joe McCormick. My regular co host Robert
Lamb is out today, so I'm trekking on my own
once again, with none but Carney the mailbot at my side.
But Rob is going to be back with me soon.

(00:25):
We're going to have a vault episode for you tomorrow.
That's going to be Tuesday, and then there should be
an all new short form on Wednesday and a new
core episode with Rob and me back together on Thursday
of this week. All right, I guess we should jump
right into the messages. This first message is from Vic.

(00:50):
She says, Hi, Robert and Joe. I love your podcast.
I was hooked after I listened to the multi part
episode on mirrors, but my favorite of all time is
the history of the odometer, absolutely blew my mind. For
my question or possible show suggestion, do you know any
theories on why humans evolved away from having thick fur

(01:11):
or hair like that of our closest living relatives in
the Great Ape family. I heard somewhere recently that humans
actually have the same amount of hair on average as
a chimpanzee. But human body hair is so fine and
or short for the most part that it doesn't appear
to be fur. I don't know if this is true.
I had a good laugh wondering if our early ancestors

(01:33):
started wearing coverings while they still had thick coats, and
my brain started playing Planet of the Apes. Maybe there
are advantages to our naked mole rat status in the
great ape family, maybe something about fleas lice and other
fur loving pests. Sorry for the long email, would love
to know what you think. Thank you for all the
great shows, Vic. Thank you for the message. Vic. Now,

(01:56):
initially I did not know the answer to your question
about hair follical density and hair thickness in humans versus chimpanzees.
But interesting thing in trying to answer your other question,
I came across an answer to that one too, So
more on that in a bit. But the main question here,
how did humans come to be relatively hairless compared to

(02:20):
our nearest relatives in the animal kingdom. This is a
really interesting question and one we've looked at on the
show before, so I just did a little reviewing to
refresh myself on it. So we don't know for sure.
With a lot of these evolutionary questions, we can come
up with good guesses at the answer, but sometimes it's
hard to know for certain what the actual reasoning or

(02:41):
pressure driving and adaptation in the distant past was. But
I think there are some pretty good guesses about what
drove the human adaptation for comparative nakedness. One thing to
note starting off is that although we are relatively hairless
overall compared to most st other mammals, there's a fair
amount of variation in the amount of body hair present

(03:04):
on humans, like in between different human individuals, and I
think it's interesting that there are pretty consistent patterns of
hairiness versus hairlessness on different regions of the body that
are common to almost all people. So, for example, we
don't grow hair on the palms of our hands or
the soles of our feet for the most part. Though
if you look, these skin surface patterns are somewhat shared

(03:28):
by our closest relatives, even the very hairy ones. So chimpanzees, gorillas,
and other great apes also don't have fur on their palms,
and this is probably all for the same reason. In
all of us. It's so that we can have improved
grip and dexterity. Imagine trying to grip a tree branch,
to climb a tree, or swing from a tree branch,

(03:50):
or to manipulate objects in your hands. If those hands
were covered in fur, things would really kind of slide
around in there, it seems. However, when it comes to
the general loss of over the covering the whole body,
one of the major explanations is that it has to
do with thermoregulation, the ability to manage the body's internal temperature.

(04:14):
Fur helps insulate the body against the cold. It's very
useful for that, and many mammals use it to that end,
but as an insulation method it's inflexible. A mammal with
thick fur can't quickly take its fur off when it
gets hot, so it has to be careful to avoid, say,
overexerting itself out in the sun. And the thermoregulation hypothesis

(04:38):
says well, human ancestors, by losing most of their body
hair massively increased their ability to cool the body, especially
during exercise in hot climates, maybe under the direct sun.
And I think one thing that makes the thermoregulation hypothesis
strong is that the loss of body hair is the

(05:00):
only observed genetic change that would serve this purpose. In fact,
you can see other signs that there was intense pressure
on human ancestors to develop genetic adaptations for cooling the body.
And a big example here is sweat glands. So if
I asked you to think what distinguishes us from our
closest relatives like chimpanzees, what are some body differences you

(05:22):
can think of? You might think of things like bipedal locomotion.
We tend to walk upright on two legs, the relative
lack of body fur as in your question here. Of course,
other behavioral and intellectual things like the capacity for language
and so forth. But another major difference is that humans
have way more sweat glands, also known as ekrone glands.

(05:45):
We have something like ten times the density of ekron
glands found in animals like chimpanzees and macaques. So we
are not only the ape that can walk, the ape
that can talk, We are by far the sweatiest of
all apes. And so I was looking for some research
on the genetic basis of this difference in the sweat glands,

(06:06):
and I found the following study. It was won by
Daniel aldea at all called repeated mutation of a developmental
enhancer contributed to human thermoregulatory evolution. This was published in
Proceedings the National Academy of Sciences in twenty twenty one,
and it was by a team of researchers I think

(06:26):
primarily from the University of Pennsylvania School of Medicine, and
they write in their summary quote, the effectiveness of human
thermoregulatory sweating is underlain by the evolution of a dramatically
increased density of water secreting ekrone sweat glands in human
skin relative to that of other primates. Here we show

(06:48):
that the accumulation of human specific mutations in a developmental
enhancer collectively promoted the production of ekrone glands in humans
by upregulating the expression of the engrailed one also known
as the e in one transcription factor in the skin.
So here is apparently the genetic basis of the difference.

(07:10):
I was reading some comments by the authors in a
press release associated with this study, and one thing they
highlighted is that while a lot of other human genetic
traits that show differences from our nearest relatives are thought
to come from a complex interaction of different heritable factors.
The human beings ability to outsweat its relatives seems largely

(07:31):
traceable to mutations in one single regulatory region called the
he CE eighteen. Now also related to the study here, Vic,
We're going to come back to something you asked in
your email, the part where you wrote, quote, I heard
something recently that humans actually have the same amount of
hair on average as a chimpanzee. But human body hair

(07:53):
is so fine and or short for the most part
that it doesn't appear to be fur. Well, I was
reading about the paper I just mentioned in an exerpt
from a book called The Joy of Sweat, The Strange
Science of Perspiration by Sarah Everts. This exerpt was published
by Science Friday, and Everts here cites one of the
authors of the twenty twenty one study, who is the

(08:15):
upin Geneticistiana Kambarov, and she confirms that quote we look naked,
but we are not actually naked. We have the same
density of hair follicles as apes have fur follicles end
of quote. But most of those hairs are miniatureized. They're
shrunken down to the point that they are nearly invisible.

(08:36):
So yes, it appears vic what you heard was true.
It's not that we have fewer hair follicles. It's just
that most of that hair doesn't really it doesn't really
become you know, it doesn't achieve hair's full potential, so
we don't have fur coats. Instead, we got little bumps
and sweat glands and things. So it looks like human

(08:57):
ancestors underwent multiple changes would have helped keep our bodies
cooler than would be possible if those bodies were more
like the bodies of chimpanzees. And those changes are the
reduction and body fur and the higher density of sweat
glands for evaporative cooling. Now, another thing that's worth noting
is that these adaptations stack. The loss of body hair

(09:20):
appears to make sweating more useful as a cooling technique,
because if you think about it, it's like harder to
achieve much evaporative cooling if you are covered in a
mat of fur. And it also seems that these two
changes could even have a common cause. Coming back to
that exerpt from the book by Sarah Everts, she's writing

(09:41):
about research by Camperov and colleagues. Quote. Camberov and her
colleagues are finding evidence that the biological signals nudging these
precursor cells toward an ekrone sweat gland density also inhibit
the formation of hair. So given all this evidence, it
seems very plausible to me that there was a pressure

(10:02):
on our ancestors causing them to survive and reproduce better
if they could cool their bodies more efficiently. Now, what
would that pressure be. It could be that they changed habitats,
maybe say from living in fully shaded forests with like
a thick canopy cover to living in more direct sunlight,
either in an open savannah or in a woodland that

(10:25):
was less dense with thinner canopy and more direct sun.
Or it could be a change in survival niches, behavioral
survival niches, So imagine a change to relying on more strenuous,
prolonged exercise to survive, maybe through endurance running during hunting
or something else. Or there could be reasons that we're
not even thinking of that would have caused this need

(10:47):
to cool the body. So the thermoregulation explanation seems pretty
strong to me, maybe the probably the strongest explanation I've
come across, But there are plenty of other possible reasons
for ancestral fur laws, and they could have been complementary
to one another. I'm not going to cover all of
the hypotheses out there, but one other idea we've talked

(11:08):
about on the show before is the role of ectoparasites.
And here I'm going to consult a paper called a
naked ape would have fewer parasites. This was published in
two thousand and three by Mark Pagel and Walter Bodner
in Proceedings of the Royal Society of London Series B
Biological Sciences. From their abstract, they write, quote, Unusually among

(11:32):
the mammals, humans lack an outer layer of protective fur
or hair. We propose the hypothesis that humans evolved hairlessness
to reduce parasite loads, especially ectoparasites that may carry disease.
We suggest that hairlessness is maintained by these naturally selected
benefits and bisexual selection operating on both sexes. Hairlessness is

(11:55):
made possible in humans owing to their unique abilities to
regulate their environment via fire, shelter, and clothing. So, to
summarize elements of this hypothesis, you know we can get ticks,
we can get lice, and these parasites infest body hair,
they become harder to remove if that hair is thick,

(12:16):
and they're not just annoying like they spread disease. So
they do actually have an impact on survival and fitness
in a natural setting. Once humans could control fire and
could surround themselves with external insulation, now that might be
what you would think of his clothing, like maybe animal
skins or grass or other auxiliary materials from the environment,

(12:38):
or it could be thinking of shelters. All of these
changes make it less important to have biological equipment for
keeping warm, meaning the fur that other mammals have for
warmth is just less necessary for survival if you've got fire, clothes, shelter.
It's also possible that if hairlessness enhances survival benefits by

(13:00):
reducing parasite loads, it could also help enhance reproductive fitness
through sexual selection by providing an honest signal to potential
mates of the lack of external parasites. Sort of, you know,
look and see how attractive I am, And in this case,
attractive means relatively free of lice and ticks. And there's

(13:21):
another interesting point of comparison the authors make. They say,
you know, what are some other mammals that are relatively hairless, well,
one would be naked mole rats. These are animals that
live in large colonies underground where you would expect a
lot of parasite transmission, but their hairlessness offers resistance against ectoparasites.

(13:43):
And they can of course cope with the lack of
fur for warmth because they huddle together and they share
body heat and they stay away from cold air in
their subterranean layers. So what a naked mole rat has
in a warmth from underground rat piles? We have in
technology through fire and clothing, and I guess in evaluating

(14:05):
this hypothesis, I would have questions about, Like my big
questions would be like, how do the timelines compare. What
is the evidence of when our ancestors started undergoing mutations
to lose their fur, and how would that match up
against to our best guests at the timeline when we
started controlling fire or wearing clothes or had other forms

(14:28):
of external insulation. But anyway, very interesting question. Thank you, vic.
All Right, this next message is about our episodes on
heart burial, heart removal and heart burial. It's from Kenneth

(14:49):
in Glasgow. Kenneth says Hi, Rob and Joe, thanks for
the fascinating episodes discussing all the ins and outs of
heart removal. You finally helped me make sense of the
post mortem journey of the Heart of the Bruce. Robert
the Bruce was the Scottish king responsible for the defeat
of the English army at Bannockburn, effectively ending plantagenet claims

(15:12):
to the Scottish throne. When it came time for him
to consider his own death, he requested that his heart
be taken on a tour of the Holy Land. His
entrails were buried where he died in Cardross, and his
body went to dunferm Lean Alley. A night by the
name of Sir James Douglas took the heart in the
form of a metal urn on a necklace with him.

(15:38):
I assume this means on one of the Crusades, but
I'm not sure. But then Kenneth continues, but on the
way he was called to help fight the Moors in Spain.
At some point during the Battle of Taba, Douglas is
said to have hurled the heart into the midst of
the enemy with the cry, lead on, braveheart, I'll follow

(15:58):
the entheses. No prizes for guessing where the movie got
its title. Douglas, killed in battle, was then transported back
to Scotland with the heart and buried near Melrose Abbey.
The heart itself was exhumed and reburied within the abbey
in nineteen ninety six. I had no idea heart burial

(16:18):
had been such a widespread tradition, so the story of
Robert the Bruce's heart had always seemed very strange. Thank
you for giving it context. Kenneth from Glasgow. Thank you, Kenneth.
Very interesting all right. This next message is in response
to our episodes on tea. This is from Eric. Eric says, hey,

(16:42):
Rob and Joe. I enjoyed your episodes about tea and
its accessories. One thing that could have been mentioned is
the Utah teapot, which is an object commonly rendered when
testing computer graphics. I remember seeing teapots everywhere in my
early computer science courses, and it's pretty common to see
a teapot hid or not so hidden in various video

(17:03):
games or rendering engines like CAD software that's computer aided
design or something CAD software. You can look up what
it stands for. It's sort of an in joke for
computer nerds. I always thought that a teapot was an
odd choice since everyone knows that software is ultimately fueled
by coffee. But it makes sense since the teapot is

(17:24):
a really unique and non uniform object, so it's more
complicated than a simple sphere or polyhedron. But it's also
smooth and shiny, which is a lot easier to render
than something with rough or fuzzy textures. Thanks for the
great episodes, Eric, Okay. One last message this comes from Kurt.

(17:48):
Kurt says, hey guys, longtime listener over the years. I
don't know why this just occurred to me today. I
was listening to the three part series on tea recently.
In the third part, Joe started to talk about the
drip tea spout problem and Russell's teapot analogy. This started
to take the conversation outside the realm of the subject,
with just a thread of the original topic. This isn't

(18:10):
a criticism at all. I like the tangents that bring
up the things that I probably wouldn't otherwise think about
in that moment. My question is what is your process
for creating episodes based on a topic. Do you have
discussions beforehand about areas you'd like to investigate, or do
you both investigate certain areas individually and just see where
it takes you without the other person knowing what topics

(18:32):
you'll bring up. If so, is it more of a
surprise where the conversations take you based on this, as
neither of you would have a full indication as to
where a conversation might go. I don't know if you've
outlined this before. You guys have a ton of episodes
and mail ins, so it might have been addressed previously. Anyway,
Thanks for what you guys are doing. Love being in

(18:53):
on the conversations no matter where they go. Kurt, Well, Kurt,
thank you for the message. Yeah, I guess our method
is somewhat free form, but I'll try to explain as
best I can. We don't approach every episode exactly the
same way, but most of the time it looks something
like this. You know, one of us gets an idea

(19:13):
and shares it with the other and we will talk
it over and figure out if it will actually make
for a good episode. So after we do that, after
we figure out that something is probably a solid episode
or has a series in it, we you know, work
from a shared notes document which contains some pre written
thoughts and information that we want to refer back to.

(19:36):
But it's not like a strict script. So what you
hear in an episode is a mix of some pre
written thoughts, some paraphrasing and summarizing of notes, some extemporaneous
thoughts and conversation. And ultimately this means that we know
some things, but not everything that's going to happen going
in and so are there are still often plenty of

(19:56):
surprises we have for ourselves and for each other during
a recording session, and sometimes we do agree beforehand on
which subtopics we'll focus on, but sometimes not often. I've
said this on the show before, but the you know,
the contents of the episode are kind of an emergent
result of the research process. It's not like we can

(20:17):
know before researching what all of the interesting things to
talk about will be. It's kind of through the process
of reading about something that we discover even what questions
there are to look into. So so, yeah, a lot
of times we just kind of end up going on
our own tangents and then we have something interesting to
come share with each other when we return. But other times, yeah,

(20:40):
we know about certain things we're going to look into,
and we we kind of divvy it up accordingly. So
to answer your question as directly as I can, it's
just it's a mixed bags. Our conversations on Mike are
partly predictable to each other and partly surprising to each other.
All right, I think that's going to do it for
the mail bag today. One more reminder. We're going to

(21:03):
be running a vault episode tomorrow, and then we'll be
back with new episodes for you on Wednesday, and going
forward after that, we should have a new Core episode
for you on Thursday of this week. If you're new here,
this is the Stuff to Blow your Mind podcast. Our
Core episodes publish every Tuesday and Thursday. Those are most
often about science, but we also hop across disciplines and

(21:26):
get into all sorts of things. On Mondays, we read
back listener mail in episodes like this one, though usually
both Robert and I are co hosting them. On Wednesdays,
we do a short form episode called The Artifact or
the Monster Fact. On Fridays. When the week is done,
it's time for Weird House Cinema. That's a series we

(21:47):
do where Rob and I just to feature and discuss
a weird movie. Weird is really the only criterion. Sometimes
we look at great movies, sometimes we look at bad movies.
Some are well known classics, are obscure that nobody's ever
heard about. Basically all of its fair game as long
as it's weird. And then, finally, on Saturday's we feature

(22:07):
an episode from The Fault So Big thanks to our
audio producer JJ Pauseway. If you would like to get
in touch with us with feedback on this episode or
any other, to share your thoughts, or to share something
that you think we'd be interested in, to suggest a
topic for the future, or just to say hello, you
can email us at contact at stuff to blow your

(22:30):
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