Kind: captions
Language: en
I am a sun sneezer which is also known
as having the photic sneeze reflex or
the autosomal dominant compelling Helio
Opthalmic Outburst syndrome which
basically means if I go from a dark area
into somewhere that's brightly lit you
know like looking at the sun I will
sneeze wait for
it
there you go I'm a sun
sneezer but why does this
happen people have known about this
effect for at least a few thousand years
Aristotle was probably a sun sneezer
because in his book of problems he asked
why does the sun provoke sneezing and
his answer was it was the heat from the
sun which causes sweating inside your
nose and so you sneeze to get rid of the
moisture but a couple Millennia later
Sir Francis Bacon demonstrated that this
could not be the case because when he
closed his eyes and turned towards the
sun well he did not experience that
photic sneeze reflect so his explanation
was that it was the eyes watering and
then when some of that moisture got down
into the nose that caused the tickle
which makes you sneeze but even this
theory has its problems because eye
watering is a much slower process than
the photic sneeze reflects so it can't
be the cause before I started
researching Sun sneezing I thought that
having the photic sneeze reflex must
convey some sort of evolutionary
Advantage onto the people who have it if
you think about it sneezing is a way of
transmitting disease in your snot there
can be the living bacteria that cause
tuberculosis and strep throat or viruses
that cause measles mums rebella and
influenza so if you're living in a moist
dark dark cave and you sneeze where your
snot lands on the floor or the walls of
the cave and those pathogens can stay
alive for hours or even days increasing
the likelihood of spreading that disease
to other people who live with you in
your cave whereas if you only sneeze
when you emerge from the darkness of the
cave and into bright sunlight well then
that mucus will quickly dry out or
because it's exposed to the harmful UV
rays of the sun it will kill all of
those pathogens greatly decrease ing the
risk of spread of
disease by the 1960s some studies were
revealing the hereditary nature of the
ftic sneeze reflex there was a father
who would sneeze two times when he
entered bright sunlight and when they
tested his baby daughter who was just
four weeks old moving her from a dark
room into full sunlight also caused her
to sneeze exactly two times and by the
1980s it was clear that this trait was
autosomal dominant meaning that you only
needed to inherit one copy of the gene
from just one of your parents in order
to exhibit the trait but when studies of
the population have been done only about
18 to 35% of people actually have the
photic sneeze reflex so I don't really
think this gives a great evolutionary
Advantage otherwise everyone would have
it you know it could just be one of
those random mutations that happens over
time and sustains itself because it's
neither good nor bad evolutionarily
speaking so it affects roughly one in
four people can you spot the person with
the ftic sneeze
reflex nowadays it's actually been found
that the gene responsible for the photic
sneeze reflex is on the second
chromosome and it's a single letter of
DNA that's been changed on my second
chromosome I have a c where nons Sun
sneezers have a t and the reason that we
know this is that back in 2010 there was
a study of about 10,000 people where
they went online and they reported
whether they were sun sneezers or not
and then their DNA was analyzed and the
groups were compared and what they found
was the thing the sun sneezers had in
common was this one particular letter
change in their
DNA that I think is pretty
amazing now it's unclear exactly how
this change affects your physiology and
makes you more susceptible to Sun
sneezes but the best theory at the
moment is that it involves the
trigeminal nerve which is the largest
cranial nerve it involves all of the
feeling that you have in your face and
as the name implies it actually has
three branches one of which receives
stimuli from your eye and another which
receives stimuli from your nose so the
thought is that this really active
stimulation of the optic nerve may cross
over into the maxillary Branch causing
that little tickle which gets you to
sneeze photic sneezes are generally
pretty harmless unless you're doing
something like flying a fighter jet or
performing some sort of delicate surgery
but this methodology can allow us to
learn a lot about different heritable
traits and diseases just by studying
lots of people and their
genotypes this episode of veritasium was
supported by 23 and me which is actually
the company that figured out that Gene
polymorphism uh responsible for the
photic sneeze reflex the name of the
company 23 and me comes from the fact
that humans actually have 23 pairs of
chromosomes and the purpose of the
company is to give people insight into
their own DNA so what you do is spit
into a vial which is actually much
harder than it sounds uh and send it off
to them and of course in your saliva are
some of the cells from your mouth they
analyze the DNA from those cells and
then they send you a report where you
can find out tons of stuff about your
genes like where do your genes come from
that is what's your ancestry and do you
have the photic sneeze reflex do we
share the same uh change of DNA on our
second chromosome you can also learn
about your health and other physical
traits and how much Neanderthal you are
so if you want to learn more about your
genotype then you should go to
23andme.com
veritasium so I want to thank 23 andme
for supporting me and I want to thank
you for
watching