So, where were we?
Right ... Our group of disease survivors moved out
and started a new settlement.
They cleared more land. They planted more seeds,
and after a while, they figured out how to tame
a handful of wild animals. 
This was a very exciting development 
for germs.
For the first time in history, humans started living
in close contact with other animals.
Twenty-four seven.
Milking them.
Taking care of them.
Living with them.
And eating them.
All that touching and sharing gave animal germs
plenty of chances to get inside of us.
Like measles.
Researchers think that up until about 5,000 years ago,
it didn’t exist.
But its older cousin rinderpest, a cattle disease, did. 
Now that humans were spending so much quality time with cows,
little rinderpest germs started jumping over into us.
And a few of them had a lucky mutation that allowed rinderpest
to evolve from a cattle disease into measles - a deadly human virus. 
As if that wasn’t bad enough, something else was happening around this time
that supercharged the amount of damage this new measles virus could do.
There were now a lot more humans around, living much closer together. 
And when the world’s first cities hit the half-million mark,
that meant measles and other germs could spread from one person to another,
and never run out of new people to infect, 
even though they were killing us off at a record pace.
Scientists think measles, along with other nasty diseases like mumps,
diptheria, scarlet fever and whooping cough
all evolved to live permanently in humans around this time.
But our ancestors had no idea what the problem was.
Or how to fix it.
One common solution - Run away!
But this usually ended up just spreading the new diseases
to new people and places.
And the better the roads got, the faster the germs could travel.
When people figured out how to sail around the world,
the new germs came with them.
The results weren’t pretty. 
In the centuries after Columbus’ voyage across the Atlantic,
some estimates say 
90 percent of the entire naitve population of The Americas died,
mostly from diseases the Europeans brought with them.
Not to be outdone, the newly-named ‘Americans’ 
likely sent syphillis back the other way
to wreak havoc on the sex lives of Europeans.
So this Golden Age of Discovery was also a Golden Age for Germs.  
They ruled the high seas and everything in between
They never had it so good! 
Until ...
This happened.
