> Biphasic sleep is still quite popular but it tends to be framed as taking a nap rather than as a 24-hour sleep regimen.
That's right! here in the warmer and highly humid states of Mexico (mainly in the Yucatan peninsula) the Siesta is very popular. A lot of people sleep between 3pm and 5pm (when the heat and humidity are higher) and wake up early in the morning around 5pm . I never got used to sleep siesta, as always woke up groggy.
Another valuable lesson I got from that rabbit hole is that a "segmented" night's sleep is actually nothing to get upset over. If you wake up in the middle of the night, it doesn't indicate anything is wrong, and you can spend an hour reading by candlelight before returning to sleep, and it won't affect your restedness in the morning. Unscientific source: https://www.polyphasic.net/segmented-sleep/
Biphasic sleep is still quite popular but it tends to be framed as taking a nap rather than as a 24-hour sleep regimen.