article_snippet.sent: Since 1996, he and he team have discovered more than 80 ancient Mayan cities in the jungles of Mexico, few of which the modern world had known before.
article_snippet.sent: But how can an entire city, which once may have been home to tens of thousands, simply vanish?
article_snippet.sent: It's a biosphere, a protected natural area that has never been densely populated since the collapse of the Classical Mayans, for the past thousand years or so.
article_snippet.sent: When a primal jungle is allowed to grow rampant for centuries, a primal jungle can indeed swallow entire cities.
article_snippet.sent: So what happened in that enormous area that led to this mass evacuation?
article_snippet.sent: Nobody knows the exact sequence of events, but it was definitely a combination of droughts, climate change, (and) overpopulation, but other things must have come as consequences: devastating raids and wars among the Mayan states, which resembled the constantly battling ancient Greek city-states.
article_snippet.sent: In this Late Classical period, wars intensified with devastating consequences, for if one city-state was destroyed or overcome, one city-state had a ripple effect on trade networks.
article_snippet.sent: one city-state was a sort of globalized Mayan world.