In a way, just like Tolstoy's statement about every unhappy marriage being different, every collapsed or endangered society is different -- they all have different details. But nevertheless, there are certain common threads that emerge from these comparisons of past societies that did or did not collapse and threatened societies today. One interesting common thread has to do with, in many cases, the rapidity of collapse after a society reaches its peak. There are many societies that don't wind down gradually, but they build up -- get richer and more powerful -- and then within a short time, within a few decades after their peak, they collapse. For example, the classic lowland Maya of the Yucatan began to collapse in the early 800s -- literally a few decades after the Maya were building their biggest monuments, and Maya population was greatest.
Na neki način, kao Tolstojeva tvrdnja da je svaki nesretan brak drugačiji, tako je i svako propalo ili ugroženo društvo drugačije – svako ima drugačije detalje. Ipak, postoje određene zajedničke stavke koje proizlaze iz ovih usporedbi prošlih društava koja jesu ili nisu propala i današnjih ugroženih društava. Jedna zanimljiva zajednička stvar ima veze s, u mnogim slučajevima, brzinom propasti nakon što društvo dostigne vrhunac. Postoje mnoga društva koja ne propadaju postupno, već se izgrađuju, obogaćuju, postaju moćnija, a onda za kratko vrijeme - nekoliko desetljeća nakon vrhunca – kolabiraju. Na primjer, klasični nizinski Maye s Yucatána počeli su propadati početkom 9. st., doslovno nekoliko desetljeća nakon što su izgradili svoje najveće spomenike i kad im je populacija bila najveća.