first arrived in the Americas,

he had no way of knowing that he had

set off a complex chain of events

that would lead to everything

from humanity's largest demographic disaster,

to the founding of a new nation nearly 300 years later,

to you watching a video about the history

of that nation right at this very moment.

It's strange, right?

Columbus's voyages to the New World

and those of the navigators and settlers who came after him,

changed the worlds to an extent

rarely seen in human history.

Let's briefly review the effects

of these transatlantic voyages on Europe,

Africa, and the Americas between 1492 and 1607,

the period between first contact

and the establishment of the first permanent

English settlement in the Americas at Jamestown.

So you might call this the pre-British era

of colonization in the Americas.

So what changes did these voyages cause?

Well, there were demographic changes,

and by demographic I mean shifts

in the structure of populations.

The indigenous populations of the Americas

faced a catastrophic decline in numbers

as a result of diseases carried by Europeans.

On the flip side, the populations of Africa and Europe

grew with the introduction of nutritious foods

found in the Americas like potatoes and corn.

Contact also led to the creation of new cultural groups,

as indigenous people, Europeans, and Africans

mixed in the New World and had children together.

The transatlantic voyages also led to economic changes,

including shifts in the systems of money and labor.

Spain extracted gold and silver from the New World by force,

compelling indigenous people and then later

enslaved Africans to labor in mines.

These riches flooded into Europe

and caused a huge increase in prices,

which may have led to the development

of banking and capitalism there.

And European demand for laborers in New World mines

and plantations led to the expansion of the slave trade,

resulting in the forced migration

of millions of African people to the Americas.

Columbus's discovery also fostered

political changes in Europe and the New World,

as other European countries wanted

to claim colonies of their own.

And the power structure among indigenous nations

changed, too, with the addition of European allies

and the destruction of large portions of the population,

leading to the downfall of powerful empires like the Aztecs.

The cultures of indigenous people changed,

as Europeans introduced new material goods

and animals into their environment.

For example, the Spanish brought horses to North America,

changing the society of plains people,

who could now hunt and follow herds of bison on horseback.

And new religious practices also emerged in the Americas,

as indigenous peoples combined their own beliefs

with those of Catholicism.

By examining the effects of transatlantic voyages,

what we're really doing is practicing

the skill of causation.

This is probably the most important

skill in the historian's toolbox.

Understanding and arguing about

what caused an event to happen,

or what consequences an event had on society later on.

Now this seems pretty straightforward.

For example, a cause and effect statement might be,

I slept through my alarm this morning, so I missed the bus.

Cause: oversleeping.

Effect: missed bus.

Notice that the effect has to happen after the cause.

Missing the bus didn't cause me to oversleep.

So until we invent the time machine,

effects must happen later than causes.

But there can be a few pitfalls to watch out for

when we try to determine causes and effects.

First, not everything has just one cause and one effect.

For example, maybe I slept through my alarm

because I stayed up too late last night watching TV.

That's another cause for missing the bus.

And there could be more than one effect

of sleeping through the alarm,

not just missing the bus,

but also missing my test in first period.

Which was the most important cause of missing the bus,

oversleeping or watching too much TV?

And which was the more important effect

of sleeping through my alarm,

missing the bus or missing the test?

These kinds of questions are what historians argue about.

Which was the most important cause of Atlantic exploration,

competition between European countries,

or the desire to convert new people to Catholicism?

Another potential pitfall is one you might have seen

in a science class or in statistics,

which is correlation does not imply causation.

In other words, two events aren't necessarily related

just because they happened close together in time or space.

For example, although epidemic diseases led to the deaths

of indigenous people in the New World

at the same time that the discovery of new foodstuffs

increased the population of Europe and Africa,

the introduction of diseases didn't cause

those populations to increase.

Those were just two things that happened simultaneously.

One way you can check whether one event

was caused by an earlier one,

is to ask whether event B would have happened

whether or not event A happened.

The populations of Europe and Africa

would likely have increased with the addition

of those new foods even if there

hadn't been any epidemic diseases at all.

The last thing that we wanna take into account

while we're thinking about causation,

is the difference between short

and long-term effects of an event.

Missing my first period test might

be a short-term effect of oversleeping,

but failing the class because I missed tests

would be a long-term effect.

And maybe because I failed that test

I ended up focusing on a different subject in school,

and heading into a different career.

That would be a really long-term effect.

Think about the effects of transatlantic voyages

that we've discussed,

and see if you can categorize them

into short-term effects and long-term effects.

You might find that some things fit into both categories

as processes that started immediately

but then went on for a long time,

like the epidemic diseases that immediately

affected indigenous people,

but then continued to reshape the demographic composition

of the Americas for hundreds of years.

So let's recap what we've learned about causation.

First, historians argue about causation

as they try to pin down the reason an event happened.

Second, causes must happen before effects.

Third, a single event might have more than one cause

or more than one effect,

and some causes and effects may be

more important than others.

Fourth, events that happened near to each other

in time or space, aren't necessarily related

by a cause and effect relationship.

Coincidences happen.

And lastly, causes may have both short

and long-term effects, immediate results,

and downstream impacts that go

far beyond the time in question.