Every single monkey in South America is a descendant of African monkeys. We know that
because we’ve looked at their DNA. But – and this is going to sound pretty obvious – South
America and Africa are not close to each other – and even back in the day when those monkeys
first arrived in South America, those continents were still very far apart. So how did monkeys get
from Africa to South America? Strangely, most scientists think they took a raft.
Hi, I’m David, and this is MinuteEarth. When I say the monkeys took a raft, I don’t mean that they
actually built some sort of sea-faring vessel. I mean they rode on a collection of driftwood,
debris and vines, or on a piece of a boggy marsh that broke off the mainland and floated
away. But even still, the rafting hypothesis is, on its face, ridiculous. Think of all the
things that need to go right for a monkey rafting trip to actually happen. First,
a mat of vegetation – one that for some reason had a bunch of monkeys on it – would have had
to break off and float out to sea perhaps as a result of a once-in-a-millennium storm. Second,
that mat would have had to stay afloat for weeks on the waves without breaking apart. Third,
the monkeys would need to have enough food and water on that raft to survive the journey. Fourth,
the mat would have had to land in a place that monkeys could actually live. And fifth,
enough monkeys of the right age and sex would have to have survived in order to successfully
make new monkeys. The probability of any of these things actually happening are incredibly small,
and the probability of all of them happening are astronomically tiny.
But there just aren’t any other potential explanations that could work.
We know from studying plate tectonics that even 30 million years ago, when monkeys likely arrived,
there were no land bridges connecting the continents of Africa and South America,
so the monkeys did not simply walk into South America. We know from studying fossils that those
ancestral primates were not great swimmers, so they couldn’t have monkey-paddled over there. If
they didn’t walk and they didn’t swim, and they didn’t fly – because this isn’t the Wizard of
Oz – then the only remaining way for them to get there would be to float. And we've learned a few
things that make a successful ancient rafting trip slightly more likely than it first appears. First,
back then, the powerful east to west equatorial currents were even stronger than they are now. So
once a raft was adrift from Africa, it would head basically straight West – and perhaps arrive in
South America within just a few weeks, which means the monkeys wouldn’t need to be as lucky with
their route. Secondly, we know that back then – just like now – there were times of the year when
the Atlantic had very few waves, which means the monkeys wouldn’t need to be as lucky with their
raft’s survival. And third, we know that back then, it rained basically every day along tropical
latitudes, which means the monkeys wouldn’t need to be as lucky with their food and water supplies.
But perhaps most importantly, given enough attempts, extremely unlikely events can
happen. Let’s say that a storm strong enough to send a monkey-laden mat of vegetation into
the sea only happens once every two thousand years. Even still, over a few million years,
there would be thousands of chances for voyages to start, and only one of them
would actually need to succeed in order for old world monkeys to become, well, new world monkeys.
In fact, scientists are pretty sure that this kind of rafting also brought the ancestors of
lemurs 400 miles from mainland Africa to Madagascar. And brought reptiles and
rats about 600 miles from the South American coast to the Galapagos islands. And in 1995,
scientists actually documented the voyage of a natural raft;
this one brought 15 green iguanas more than 100 miles across the Caribbean to the island of
Anguilla for the first time. It turns out that the world is big enough and time is long enough that
things that we think are so improbable as to be impossible have actually happened many times ove
You can now send us Super Thanks! If you liked this video – or any of our
other science explainers – you can directly support us by clicking on the button below.
It’s like a tip jar – a one-time payment of a dollar or two that says “keep up the
good work” or “get your next cup of coffee on me”. A few bucks might not sound like much,
but every dollar helps us spend more of our time making videos about the amazing
science that fascinates us all and less of our time figuring out how the heck to
sell Battle Royale Mobile Minigames or Mega Massage Chairs or whatever. We just want to
nerd out and make videos for you, so give it a click and let us know what you think. Thanks!