Is taking a nap then "going to bed" later basically the same thing as a 2 sleep night?
I think naps are a good modern example of a 2 sleep night. I wonder when people began napping? The Google Ngram Viewer makes me think we've been napping for years [1], except perhaps right after WW2, but then 1970 happened and we started getting tired. :)
[1] http://books.google.com/ngrams/graph?content=nap&year_st...