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- [Narrator] We are the paradoxical ape. Bipedal. Naked. Large brain. Long the
master of fire, tools, and language, but still trying to understand ourselves.
Aware that death is inevitable, yet filled with optimism. We grow up slowly. We hand
down knowledge. We empathize and deceive. We shape the future from our shared
understanding of the past. CARTA brings together experts from diverse disciplines
to exchange insights on who we are and how we got here. An exploration made possible
by the generosity of humans like you.
- [Pascal] I hope that this afternoon's excellent presentations have convinced you
that the skin is very much worthwhile as a target of anthropogony, the study of human
origins. Skin is also very powerful. In some places more than others. We are not
comfortable with nakedness depending on where we grew up or when we grew up.
So we like to cover skin and we learn today that this creates a new ecosystem
for some interesting animals. And we've also learned that we have changed our
colors many times in different directions. And our hair, shape and color. It is fair
to say that skin is our largest organ. We have an ideal model, the wet suit, in
southern California. Two millimeters, about the thickness of your skin, and the
surface of one of these banners, about two square meters. It is a self-healing
barrier. It provides protection. It provides defense, thermal regulation and
energy in form of the brain battery and in form of your first food. Naturally, for
two and a half years until average weening age, before agriculture. We synthesize
vitamins there. It's a very important sensory organ. It's an ecosystem in more
ways than one. And it has strong signaling value. It even signals our internal state
of mind when we blush or flush, either saying a lie or being embarrassed. More so
if you are melanically challenged as us people coming from northern places where
we lost melanin. So I think we have many, many things to discover in the future
study of skin, and I urge you to stay here for the question answer session. But I'd
like to, for those who might leave before the answer session, I'd like to thank all
of you in the audience. To those who made the symposium possible. The symposium
chairs, my co-chair Nina Jablonski, our featured speakers, our individual
supporters and, of course, all of you for attending. So I look forward to question
session and I think my co-chair Nina Jablonski
will address the first set of questions.
- [Nina] We have, not surprisingly, some wonderful questions that have come
forward. A question first for Doctor Gallo. Since the sterile wound has more
inflammation, should we be scrubbing people with betadine et cetera
pre-operatively or not?
- [Dr. Gallo] Well that's an excellent question and it brings to distinction
between pathogens and commensal organisms. First of all, scrubbing with betadine does
not sterilize the skin. There's still a tremendous number of microbes that
persist, but betadine does minimize the number of pathogens,
so absolutely we should scrub.
- [Nina] That was clear enough.
Two good questions for Doctor Sawka. The first, does the scalp and hair
play a big role in heat loss?
- [Dr. Sawka] It does in cold environments. You have a tremendous amount
of heat loss through the head because that's the exposed area and you don't get
the constriction. But in a warm environment you don't have any exceptional
amount of heat loss through the head. It's predominantly your skin of your torso and
these areas are overlying the active muscle.
- [Nina] Hold on, there's another question. A second question. Many cultures
believe that eating hot chilies in hot weather causes a cooling effect from
sweating. Is this valid?
- [Dr. Sawka] Not that I'm aware of but...
- [Nina] Not surprising, we have a group of people absolutely obsessed with the
microbiome, and so we have a large number of questions, and some of these might be
shared between Richard and Rob so you guys can sort of divvy them up. Do chemical
additions to western biomes negatively impact our health? You've covered a
comparison, but I'm wondering about the implications of research like this.
So I think the effect of chemical additives.
- [Dr. Knight] So we saw that data for the first time last night. We haven't had time
to fully look into the health implications. So that's certainly the
direction we would like to take the research though.
- [Nina] With respect to the fecal microbiome, your studies show that it
matures at about two and a half years. This coincides with the weening time of
the Hadza. Is there a mismatch between early weening in the west and the gut
microbe maturation at two and a half years?
- [Dr. Knight] That's a very interesting question. We've looked across culturally
the specific effect of weening and what we see is the maturation effect overall,
although it's affected by weening, children who were weened at different ages
still follow the overall pattern of maturation. So probably it's not going to
be an issue to ween earlier. Again, none of this data existed three years ago, so
the kinds of perspective or ... studies you'd want to see have not yet
been done. One thing I'll note briefly is that because the technology to do this has
dropped in cost so rapidly, a huge number of studies are possible now that weren't
possible a few years ago. So it's a tremendous opportunity for students
getting into this field.
- [Nina] What is known about the skin microbiome of
populations with great longevity?
- [Dr. Knight] Nothing.
That's another great example of one of those projects that you could do now but
you couldn't have done a few years ago.
- [Nina] Does eating probiotic food, is that useful for the microbiome after
taking antibiotics? Can we regain our microbiome?
- [Dr. Knight] Yes. A number of different probiotics have been clinically validated
for post antibiotic diarrhea, so in general any of those probiotics or eating
live yogurt, has been shown to be beneficial
in several different clinical studies.
- [Nina] Does chlorine in swimming pools act like antibiotics on the microbiome?
- [Dr. Knight] Great question. No data.
- [Nina] There we go Richard.
- [Dr. Knight] Maybe Rich has data.
- [Dr. Sawka] No.
- [Nina] That's it, thank you. A question for Sarah Miller. How different are the
human and chimpanzee mammary glands?
- [Sarah] So I don't think there's been a lot of comparative studies on that, but
they, in each case, there are two mammary glands which are pectoral. So the basic
structure is the same, but I'm not aware of any detailed investigations. But they
would be interesting.
- [Nina] A question for anyone, but I'll take a stab at it myself. When, during
evolution, did the sclera of human eyes become white rather than dark? We know
that this is something that is a physical distinction of humans compared to
non-human primates, including our closest relatives.
I would think that this occurred quite early in our evolution, and that it was an
important part of our long distance signaling and visual display adaptation.
It's hard to say exactly when this could've occurred, but certainly much of
human facial gestures and many aspects of human gestural vocabulary are visible from
a great distance, or at least from several meters. And I would think that there was
probably selection for white sclera for increased visibility and for understanding
the direction of gaze at the same time.
- [Pascal] Traditionally, high incidences of neural tube defects have been found in
northern latitudes such as the UK and northern China. How did this correlate to
UV damage folic acid?
- [Nina] High prevalence of neural tube defects in these populations is associated
with extreme low folate diets. And so there was probably minimal amounts of
ultraviolet radiation induced loss of folate in those populations. Rather there
has been historically, and fairly recently, tremendously low folate in the
diets. Folate comes from fresh green vegetables, citrus fruits and whole grains
and we know that in populations that are eating very highly refined grains with not
a lot of fresh fruit and veg, that there's a lot of folate deficiency.
- [Pascal] I have a question for Mark Stoneking. Does your study of body lice
not shed light on the evolution of sleeping blankets? Skins of animals, not
clothing. This seems more likely in light of the 40,000-year evidence of needles.
Fossil needles.
- [Mark] Yeah we don't know for sure exactly what the evolution of clothing
involved, but it seems reasonable to think that humans would have started out with
wearing skins of animals, which would have probably been similar to the hair. May
have facilitated the movement of lice into the hides or skins that humans were
wearing. And then you later have the production of real woven clothing and so
forth. I don't think humans were weaving that much 70,000 years ago, so...
- [Pascal] Another question for Sarah Miller. At what point in evolution did
humans develop only two mammary glands? We kind of touched upon this so I
would...what is the implication of supernumerary nipples?
- [Sarah] So I don't think it's known at what point humans developed two mammary
glands. But it's assumed that it happened perhaps in response to the decreased
number of babies that humans have compared with some other species. In terms of
supernumerary nipples, so I talked a little bit about how the mammary or milk
line is an important embryological precursor of mammary glands and this is
found in humans as well. And supernumerary nipples often develop along those lines.
They can, in fact, very small ones, can even develop during pregnancy. And this is
thought to be due to mammary tissue that has somehow got left behind during the
formation of the mammary glands. So some circumstantial evidence and some
of our own unpublished data suggests that during the formation of the embryonic
mammary gland, cells actually move along the mammary line and end up in the
positions where the mammary gland will form. So if those migrations fail or
happen abnormally this can leave behind a little bit of tissue that could develop a
supernumerary nipple, either during a re-genesis or even later in life in
response to hormones.
- [Pascal] Thank you. If you don't mind, I have a question. A follow up question. Do
we have any information on the age of the permanent breast in humans as opposed to
chimpanzees and bonobos, where breasts are not permanently enlarged?
- [Sarah] Yeah, I'm not aware of any evidence about that but that doesn't mean
there isn't any. They may... somebody may know.
- [Pascal] Thank you. And one last question for Ron Knight. And this is the
question whether breast fed babies or formula fed babies differ
in the gut microbiota.
- [Dr. Knight] Yes. There's been several studies showing that, and in general the
microbial diversity in the gut is higher with breast feeding. There's also some
suggestion in the literature that breast feeding may ameliorate the effects of
early life antibiotics or C section delivery.
- [Pascal] Thank you very much. I think that's it for questions.
- [Male Voice 1] I have a follow-up for Rob. Rob, you mentioned in the C section,
the effects on the microbiome. Does that have any kind of noticeable health effects
in later life?
- [Dr. Knight] So we're not sure whether the noticeable health effects of C section
in later life are mediated by the microbiome yet. So whenever C section
affects the microbiome, we know that C section affects the risk of several
diseases including atopic dermatitis, let's see...food allergies, pet allergies
I think are on that list, obesity, asthma. What we don't know for sure is whether the
mechanism by which C section affects those conditions is via the changes in the
microbiome, although we know mostly from animal model work with some evidence in
humans that all of those conditions have been linked to the microbiome. So the
links that exist are between C section and disease, C section and the microbiome and
microbiome and disease. But we don't know if the specific mechanism of action of the
C section is via those particular changes in the microbiome yet.
Does that make sense?
- [Pascal] Okay, so this concludes our first ever CARTA symposium on the human
skin. I look forward to a future one. Thank you all very much for being here
today, and thanks to all the speakers for the excellent presentations.
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