if i were to ask you what you think the
average human body temperature is
you'd probably respond with 37 degrees
celsius
or 98.6 degrees fahrenheit it's a handy
number to know if you're trying to game
the thermometer to get out of school but
new studies have uncovered that the real
average human body temperature
is actually lower than that and
it's dropping so where does this classic
number of 37 degrees celsius even come
from
anyway well in 1851 a german doctor
named
carl vunderlich conducted a years long
study
he went room to room in his hospital
with a thermometer
taking the temperatures of some 25 000
different patients to try and pin
down the average human body temperature
and
he did 17 years later when he published
a paper with that well-known metric
of 37 degrees he also gave us the first
quantitative measurement for determining
if someone has a fever
38 degrees and above that's a fever baby
and then
for the next 140 years we just accepted
this number as correct
despite the fact that dr wunderlich
collected this data
using a comically large foot long
wooden thermometer that had to be held
in a patient's armpit for
20 minutes because believe it or not
portable thermometers small enough to
fit under your tongue
weren't invented until 1866 so it wasn't
until the 1990s that another doctor
decided to revisit this question
using more modern equipment and he found
that
yeah the average human body temperature
is actually
around 36.8 degrees celsius
and it varies throughout the day
throughout someone's
hormonal cycle throughout someone's
lifetime so
determining whether or not someone
actually has a fever
depends on a lot of different factors
which is pretty important to account for
in a clinical setting and then a
2020 study out of stanford university
took
hundreds of thousands of measurements
and found that the average body
temperature was around
36.4 degrees celsius and this made them
ask what if this drop in average
temperature isn't
entirely due to the difference in
thermometer accuracy
but is instead because average human
body temperature
is actually falling to answer this
question
they embarked on a fascinating research
journey that took a historical view
of human temperature data in the u.s
they used
huge existing data sets ones measuring
from
1860 to 1940 1971 to 1975
and 2007 to 2017 to get a sense of how
human body temperature
may have changed over the past 150 odd
years
and each of these groups after adjusting
for age
height weight and other variables show a
clear decrease in average temperature
over time
there's also a drop between groups as we
move from past to present
even with groups where comparable
thermometers were used so
it's clearly not just an equipment issue
so
what is going on the researchers
hypothesized that this decrease in
average body temperature over time
could be due to a decrease in resting
metabolic rate
essentially that's how hard your body is
working when
at rest and they also take it one step
further
saying this reduction in resting
metabolic rate could be due to lowered
overall
inflammation see modern populations
typically have
lower chronic infection better dental
hygiene and just
generally improved living and hygiene
standards
this could be why people in wealthier
countries like the us
are experiencing this drop in body
temperature over time
but there's other data that throws that
hypothesis
off because another recent study tracked
the average body temperature of over 5
000 members of the
chimane a community in the remote
bolivian rainforest that doesn't have
as much access to that modern health
care that the stanford study proposed as
the potential cause of the temperature
drop
and even still the average chumani body
temperature in 2002
was around 37 degrees celsius while the
2020 average
was 36.5 so now
we have a clearly documented decrease in
body temperature
in populations that are in very
different parts of the world and
we still don't know exactly why it could
still be due to that improvement in
healthcare and sanitation that we
mentioned already
it could be due to greater temperature
control of our surroundings through
things like electric fans and air
conditioning
it could be because people are less
active than we were
200 years ago and get this some
scientists have even suggested
that using more antibiotics has reduced
our body's microbial diversity so much
that it's had an impact on our overall
temperature
like because we no longer have the heat
from all those microbes we are now
colder people which is totally wild
so there's still lots to explore here
and whatever the reason the fact remains
no matter how dorky you may feel like
you are
humans are getting cooler over time and
speaking of human body temperature
one place you'd really want to keep cool
is the australian outback
be sure to check out lightspeed our new
docu series on an incredible solar car
race
across the continent new episodes will
be released every monday through january
4th and make sure you subscribe to
seeker so you don't miss one
thanks for watching and i'll see you
next time