this episode of scishow is sponsored by
brilliant go to brilliant.org
scishow to learn more
[Music]
there are a lot of anecdotal cases of
animals getting stoned or tipsy like the
ones we talked about in our list show of
high animals but as we noted for the
dolphins getting high on puffer fish or
the elephants
having a night cap of marula fruit
pretty much
every case we've examined closely has
found that there isn't any evidence that
these animals consume mind-altering
substances
because they feel good to them which
ultimately
makes it appear that the fondness for
psychoactive drugs
is pretty human and it raises questions
about
why what is it about humans that makes
us so attracted to these substances
totally up front here we don't have a
solid answer to that question if that's
what you're looking for
you could go watch videos where they say
things without knowing them for sure the
internet's full of them you might think
we do
you might have heard that these drugs
hijack our mental reward systems
so obviously we seek them out because
our brains have this inherent weakness
for them but some scientists have
pointed out that the whole idea doesn't
hold up as well as you might think
and by digging deeper into how our
closest relatives and our laboratory
proxies interact with mind-altering
substances
we can get a better understanding of
what might really be setting us apart
the simple answer to why humans like
drugs
appears to be quite obvious they feel
good
in neurological terms that means that
they activate the parts of our brain
that signal rewarding experiences
and this seems pretty clear when you
look at drug use in lab animals
mice and rats are used to model many
human illnesses so it makes sense that
they've been used to study why humans
seek out drugs too
and we know that they become addicted to
almost anything
nicotine alcohol cocaine you name it
left to their own devices
rodents will often self-administer drugs
until they become
very intoxicated or even overdosed this
has allowed scientists
to study the genetic basis and brain
chemistry of drug seeking behaviors
as well as test ways of treating
addictions and such research
tends to support the idea that drugs are
just really good
at hijacking mammalian brains but these
studies don't actually
confirm that non-human animals would do
drugs under normal circumstances or
that they are something the animals
enjoy you see the whole setup is pretty
artificial in many cases researchers use
what are called
self-administration models where the
animals end up
at least somewhat controlling how much
of the drug they get but to convince
lab animals to take the drugs in the
first place researchers do all kinds of
strange things like
starve them that's all well and good if
you want to get a rat hooked on
something so you could see what happens
to their body or brain when they are but
they aren't
seeking that drug because they like it
they're motivated by a real biological
need like
hunger or the animals maybe put in a
situation where they're so
bored that doing anything seems better
than nothing and that might be why all
you have to do to disrupt their drug
seeking behavior
is to make their environment more
ecologically realistic
lab animals often reduce their drug use
or even lose their addictions when you
make their lives more interesting
like if you give them friends to hang
out with or place toys or running wheels
in their cages
if these animals were truly seeking the
drugs for the feeling of being
high or the drug's effects were
powerfully rewarding on a neurological
level
it shouldn't be so easy for them to just
say no
of course as we often say here on
scishow mice and rats
aren't people neither are apes and
monkeys but they are at least
primates and therefore a lot more
closely related to us so they might give
us more insight into why
humans seek out highs and there are
cases of primates that
choose to intoxicate themselves like on
the island of saint kitts in the
caribbean
their vervet monkeys are infamous for
stealing tourists cocktails
almost right out of their hands this has
become a bit of a joke but the monkeys
actually
inspired a series of scientific studies
beginning in the late 1980s one found
that 17 percent of caribbean monkeys
brought into the lab preferred a mix of
alcohol and sugar water
over a drink of just sugar water and it
seemed like the drunk monkeys were
behaving pretty much like drunk people
falling off of perches getting cozy with
other monkeys or
just sitting alone with a bottle in the
corner but we can't really tell from
early experiments like this
what's motivating the monkeys to drink
while they eagerly consumed booze it
seems unlikely that they were seeking
out alcohol for its intoxicating effects
some scientists think that instead they
may have fallen into an evolutionary
trap
that's where a trait that was useful for
the survival of a species
is now harmful instead see the taste and
smell of alcohol
may be similar to ripe fruit which is
more likely to contain a lot of sugar
and therefore calories
and when there's a lot of competition
from other fruit eaters and relatively
little fruit
those monkeys want to make sure they get
as many calories as they can per bite
to ensure that they get the nutrients
they need so the monkeys may have
thought the presence of
alcohol indicated a high quality food in
fact when the saint kitts monkeys were
first brought to the island around 300
years ago
they were often seen feasting on sugar
cane particularly the fermenting kind
that contained alcohol seeking out that
tasty sweet treat
might have later led to going for drinks
that smelled or tasted similar
like a tourist's fruity cocktail but the
cocktails aren't great for the monkeys
nutritionally speaking
also that is true of the tourists but
getting drunk puts the monkeys in risk
of
harm in all sorts of ways so an evolved
attraction to booze that was meant to
help them survive
may have turned on them when stronger
doses of alcohol became available
then they simply weren't able to learn
that booze is harmful but it's also
important to note that only 17
of those monkeys preferred the alcoholic
beverage so
even if an evolutionary trap explains
their preference
it's not a trap that all of them are
falling into there are other primates
that consume
alcohol which we can consider like the
group of chimpanzees and guinea
that regularly steals fermenting raffia
palm sap but the chimps in question
don't really help us figure out if
primates are prone to this kind of
evolutionary trap because
they live in an area where people have
all but destroyed their habitat and
natural food sources
if humans weren't destroying these
animals homes and providing concentrated
alcohol
the animals might not go for the
calorie-laden liquid
in fact in lab studies most chimps
prefer non-alcoholic fruits
over fermented ones which isn't what you
would expect if drinking was something
universally enjoyable to them or they
had evolved to associate
alcohol with better food sources now
it's possible
humans have fallen into an evolutionary
trap of some kind when it comes to
psychoactive drugs but the prevailing
hypothesis
isn't that they were once a signal of
something good and have since become bad
for us
it's that they trick our brains into
making us think they are
awesome for us even though they aren't
and never have been
the basic idea is that the neurological
pathways we use to evaluate things that
are good for us
developed in the absence of psychoactive
substances
you see our brain's reward system is
supposed to identify things we need to
survive
like food and when it activates it can
either block
or overwhelm feelings that tell us
something is bad like pain
it's possible drugs just so happen to
trigger this system
even though they aren't something we
need to survive and if evolutionarily
speaking
they're a new thing then we wouldn't
have had time to evolve countermeasures
so that we don't get fool but that idea
does not
hold up as well as you might think it's
not clear when this magical time was
when these substances weren't around for
example
the entire lineage of humans the
hominins evolved enzymes to detoxify
alcohol some
10 million years ago it would be pretty
weird for that trait to have just
evolved if we weren't regularly being
exposed to booze and the main group of
enzymes that we use to neutralize plant
toxins date back
even further cytochrome p450 hema
proteins have been detoxifying the
compounds found in plants like tobacco
and coca for us
and our other animal kin for about 400
million years
really it doesn't make much sense that
these chemicals would
accidentally affect our brains so
positively anyway plants produce things
like nicotine morphine and cocaine
to be toxic and stop us and other plant
eaters from consuming them so scientists
have pointed out
that it doesn't really make any sense
for toxins meant to fend off creatures
like us
to accidentally encourage significant
consumption instead and on our end if
these
compounds did accidentally set off our
reward systems researchers say
it's implausible that our bodies
wouldn't have eventually developed ways
of recognizing them as the toxins they
rightfully are
scientists refer to this evolutionary
mismatch as the paradox of drug reward
one intriguing explanation for this
paradox
is that the triggering of reward systems
isn't accidental at all
we've actually evolved to find them
rewarding because they have medicinal
value
see popular drugs like caffeine or
nicotine do what the plant evolved them
to do
they harm animals and there are cases
where we want to harm
animals that are inside of us
specifically parasites
and we see evidence for this idea in
human studies for example a study of the
akka indigenous people of the congo
basin
found that men who smoked more tobacco
had a lower parasite burden and they
were less likely to be reinfected with a
parasite one year later
many other psychoactive drugs also have
anti-parasitic effects
if eating these plants helped us survive
in the past by getting rid of nasties
inside us
our brains could have evolved to reward
us for
eating them or our affinity for
mind-altering substances could
somehow stem from our minds basically
some researchers suggest that there are
complex
social or psychological benefits to
psychoactive substances
and that those are what drive our
attraction to them so it's not that the
drugs hijack our brains
it's that our brains exploit the drugs
to maximize their benefits
and downplay their costs alcohol lowers
your inhibitions for example that's why
people call it liquid courage and if
say you became more talkative at a party
the first time you drank alcohol then
even if you felt physically terrible the
reward you got from the social behavior
might have made the overall experience a
positive one there could also be
psychological benefits to drugs like
cocaine might give you a temporary
cognitive boost if the reasons we find
drugs so rewarding are social or
psychological then it wouldn't be so
surprising if they were
unique to humans after all our
socialness and our cognitive abilities
are somewhat extreme when compared to
our fellow animals and we might be
uniquely capable of learning how to use
psychoactive substances to our advantage
and not to our detriment
but that is a hard hypothesis to test in
part because it's really hard to study
the motivations of animals
that can't tell you what they're feeling
or thinking the bulk of research on
animals and drugs is to understand the
mechanisms of addiction which makes
sense because
it's a big public health problem and to
be clear none of these hypotheses about
why we started using psychoactive
substances
really speak to that side of drugs the
neurological basis of addiction like
that the overuse of substances which
trigger the reward system
can lead to a chemical dependence on
them holds whether that reward is an
accident of evolution or not which is
why models like rats and mice are still
useful
because if you want to study the biology
of addiction it doesn't really matter
how the animals get hooked
just that they are but if you want to
know if there are other animals that
truly enjoy being high
rodents can't tell you that much even
studying non-human primates has
ultimately left us with more questions
than
answers in the end we don't really know
why our species
is so enamored with mind-altering things
but the more we look into it and the
more we learn about our complex
relationship with psychoactive
substances
the closer we get to some real answers
it's going to take a lot of research and
problem solving to get to the bottom of
this
and if that sounds like your cup of tea
then you might want to check out
brilliance daily challenges every day
brilliant releases new challenge
questions that cover fields from
computer science to statistics
recently for example they had one about
how to win at 20 questions
which is my kind of challenge you can
access the daily challenges for
free but if you sign up to become a
premium member you'll get access to the
whole
archive so whether you're chilling on
the bus home or you just want to brush
up on your skills
you'll have plenty of content also if
you really like a challenge and you want
to learn more about that subject there's
always a related course that explores
the same concept in greater detail you
can learn more at brilliant.org
scishow and if you're one of the first
200 people to sign up there you'll get
20
off an annual premium subscription