Kind: captions
Language: en
[Applause]
why are the most venomous species found
in the warmest places on Earth I mean
take Australia for example depending on
who you ask it has all or nearly all of
the 10 most venomous snakes in the world
plus the funnel web spider the blue-
ringed octopus box jellyfish paralysis
tick and stone fish all found in
Australia are the most lethal of their
kind and even this cute platypus has an
ankle spur which in the male secretes a
Venom that can kill a dog in humans it
would merely cause excruciating pain
this question why do the most venomous
species live in the warmest places is
one that I've wondered about for most of
my life perhaps it's because I was born
here in the small town of tralan
Australia this is the first house where
I ever lived as my mom recalls in the
backyard there was a shed where we found
red backs and I used to play in the shed
I don't think once we found the red
backs that we let you in there yeah
that's very comforting thanks Mom now if
you don't know what a red back is it's a
very poisonous spider hold up I got to
tell past Derek something you see it's
important that we say venomous and not
poisonous because poisonous means it'll
be harmful if you eat it whereas
venomous means it'll try to eat you and
that will be harmful continue so
thankfully they never bit me otherwise I
wouldn't be standing here today now
before we go any further it's probably
worth asking is it true do more venomous
species really live in hot places well
apparently I'm not the only one who
thinks so because I found this Reddit
thread on the topic though it really
didn't explain why that was the case but
what about the data well here is a map
of the global average temperatures
compare that with this map that I've
colored in according to the number of
venomous species in each country the
country with the most venomous species
is Mexico with 80 different organisms
with the power to kill you that's
followed closely by Brazil and then
Australia
well this seems to all match up very
well with the global average
temperatures so why is it so my first
hypothesis was that there's something
about the heat which enables the
formation of these Venom molecules so I
ran that idea past Professor poov a
periodic videos no I don't think so all
right because the reason is that if you
go up a 10° Centra change in temperature
roundabout room temperature will be will
only double the rate of most chemical
reactions and I don't think anything
evolutionary is likely
to um evolve to such a big difference
based on just a factor of two in the
rate so maybe it's worth asking what are
these Venom molecules exactly well in
most species where the Venom is
delivered by fangs it is evolved from
saliva in the funnel web spider for
example the lethal effect seems quite
accidental what you've got to understand
about the Venom it's there it's a
secondary thing that it actually kills
the actual reason that spiders have got
Venom is to digest their prey except
they happen to do most of it before they
actually eat it injecting the Venom and
the Venom will start to liquefy whatever
they've caught and once it's turned to
liquid all spiders live on soup the
funnel web evolved without any humans or
other primates around and yet ironic its
venom is most potent for exactly this
group biggest evolutionary joke ever the
only group of animals with
backbones that's actually allergic to
their venom are the primates we don't
have primates in
Australia all right so it's lemur
monkeys
apes and us most species deliver not
just one type of Venom molecule but a
whole cocktail of different proteins
that r in length from short chain to
very longchain molecules and these
molecules can serve a range of functions
some are neurotoxins which can disable
your nervous system others are
hemotoxins which actually attack your
blood cells and can dissolve tissues but
since we're talking about cocktails what
would happen if you drank some Venom you
could uh take a vial of Taipan Venom and
and happily have it with your scotch and
it wouldn't be a problem as long as you
didn't have any um irritation on the
mucosal lining or stomach ulcer or
things like this it's got to get into
the bloodstream to be a problem okay so
since drinking the Venom is not going to
kill you what should you do if you get
bitten by say an inland taian that's the
world's most venomous land snake what
you do don't panic stay calm I think
that would be easier said than done the
Venom travels through the lymphatic
system so it doesn't usually travel
through the veins or the blood vessels
so that's just quite close under the
skin and if it reaches your nervous
system it'll shut down the signaling
pathways that keep your heart beating
and your lungs breathing and so what
actually kills you is suffocation so
what you need to do is stay very still
and bandage up the limb that's been
bitten from the tip all the way back to
your torso now the bandage needs to be
really tight to trap the Venom within
the lymphatic system but not so tight as
to cut off the blood flow to the limb
now once you've got it bandaged up you
need to find some antivenom what is
antivenom well it's made by in in a
large organism like a horse with a
dilute solution of the Venom the horse
then produces antibodies for that Venom
which you can Harvest and inject into
yourself in case you get bitten making
antivenom is tough work it would take 70
milkings of a funnel web spider to get
enough Venom to make a single dose of
antivenom and what's worse antivenom can
only be used on an individual a limited
number of times because over those uses
your body will build up antibodies to
the antivenom making the antivenom
ineffective so you might wonder well why
can't you just inject yourself with
dilute amounts of Venom and build up
your own antibodies to the Venom that
would work except for the fact that when
you get bitten you need to have a lot of
antibodies in your system and to keep
your antibodies at that high level you
would need to keep injecting yourself
with the Venom say every month and
that's probably not the best thing for
you but why is it that people in warm
climates need to worry about this and
not people in cold climates well I went
to The Experts to find out about this
trend you know broadly yeah there's
really not much of a pattern happening
really what about that Reddit thread and
the map I made now if you're saying is
there a a global pattern showing that
you get more venomous animals in hot
places I don't know if there is in
snakes which is the group that I'm most
familiar with in Australia the pattern
is the diametric reverse of that one if
you wander around Southern Australia
every snake you find on Mount Kiosco is
venomous if you wander around the
Tropics of Daran you're very unlikely to
see a venomous snake they're all pythons
and harmless calri snakes now this is
unexpected the most venomous snakes in
Australia live in the coldest places and
the reason for that is 20 million years
ago uh an itinerant sea snake coming
down from Asia as Australia drifted up
to Asia got to Australia it was venomous
to start with there were no snakes in
Australia at the time and so venomous
snakes radiate through Australia this
big family called the elapid the Cobra
family okay but on a global scale my
point remains there are more venomous
species in hot countries there's going
to be vastly more venomous snakes in a
warm climate area than in a cold climate
area the problem is that there's vastly
more snakes so as a proportion of the
snakes that are there the venomous guys
are probably going to be about the same
and maybe even less in the in the case
of a place like Australia than they
would be in a cold area so why are there
more venomous species in warm places
places well the truth is there aren't at
least not as a proportion of species the
majority of venomous species on Earth
are ectotherms those are organisms whose
body temperatures are regulated by their
surroundings now that means that they
can only really have short bursts of
energy so instead of chasing down prey
and running away from predators they
needed a different strategy to allow
them to survive and so many of them
evolved Venom there is a greater
diversity of ectotherms in warm climates
so it only stands to reason that there
will be a greater number of venomous
species but that's not to say that there
aren't venomous species in cold places
the only snakes that get into the Arctic
Circle are European vipers of enous
species but biodiversity alone isn't the
complete answer to this question it also
depends on evolutionary history if you
had come to Australia 20 million years
ago there would have been no snakes at
all the venomous ones got here first and
the non-venomous came after I think it's
a really lousy explanation but it's the
best one that we've
got why is that allow the explanation oh
well it's uh doesn't uh invoke any
lovely complicated piece of uh
ecological Theory or anything else it's
just relying on history but this is a
pattern that's very strong and doesn't
seem to be explicable any other way and
nowadays in Hawaii there are no venomous
snakes and the same goes for Jamaica
these are warm places that just haven't
evolved or have lost any venomous snakes
that they may have had so just been a
lucky accident that we've been fortunate
enough to be blessed with a few um
venomous
spiders I am also reminded that we're
living in a particular point in time
roughly 15,000 years after the last ice
age now that would have wiped a lot of
the ectotherms from the northern
latitudes of the northern hemisphere for
example in Ireland there are no snakes
because the place was wiped clean by an
ice sheet and snakes haven't managed to
get back to the island yet my point is
the distribution of species depends on
what what happened it may be an
unsatisfying explanation but I'd rather
know the truth than just believe in a
trend that's not actually
there beautiful iridescent blue so what
do you think is going to happen this
spot on the screen as I narrow the color
of the blue Moro is created by the
structure of its scales you see exactly
what
You' Nar and Nar the sides are getting
cut off by the makes complete sense the
light and if you sto there you would
never realize that
the as I started to go through this big
investigation I realized just how
complicated this is and how many
Mysteries are still out there for
example why are some species deadly
venomous and in others the Venom is is
pretty weak and I didn't end up with
anything um The Deadly guys turn out to
have ecologies that are very similar to
the guys with very weak Venom and it may
be an historical accident another
strange observation is that a lot of
snakes that that have evolved more
recently have actually lost the ability
to produce Venom the big success story
in snakes worldwide are the harmless
ones they've actually evolved from
venomous snakes Venom is an ancestral
characteristic in modern snakes the
successful snakes are the ones that left
it behind and they gave it up and
they're proliferated despite not having
Venom apparently the cost of making
Venom isn't much more than the cost of
making saliva so it seems curious that
they would lose what seems to be a
killer advant AG over other species if
you have thoughts about this or any
other Mysteries regarding the global
distribution of venomous species put
them in the comments below