How did humanity survive the first cataclysm?

Question

Starting from Assassin's Creed 2, Minerva, Jupiter and Juno tell Desmond and his team about the first cataclysm that caused their kind (the roman deities) to go extinct. However, humankind was also present over Earth on their time, and was also exposed to the coronary mass that burned the whole planet.

How did humans make it through an event in which the gods themselves fell?

I have only played Assassin's Creed up to Black Flag, so I apologize if this has been explained later on.

Answer 1

As Minerva says to Ezio in 1499:

The earth shook for days. The fires burned for weeks. And when the ash had settled, less than ten thousand of your kind still lived... and far fewer of ours. But we carried on, together. To rebuild. To renew.

There were far more humans than Isu ("Those Who Came Before"), and so more of them survived. As for how humans survived at all, Minerva also says this:

We built you in our own image, we built you to survive.

That's all we have to go on.