The two-sleep pattern electric light destroyed: we haven't always slept 8 hours straight

Before electric light, sleeping 8 hours straight was the abnormal thing to do

Waking up at 2 or 3 in the morning and being unable to fall back asleep is a common complaint among people over 45. Most see it as a problem. Yet for thousands of years, it was not a problem at all. It was exactly what the human body did naturally.

Historian Roger Ekirch has documented more than 500 references to "first sleep" and "second sleep" in medieval texts, personal diaries and medical records from Europe to the Arab world. First sleep began at nightfall and lasted 3 to 4 hours. It was trinc by a quiet waking period of 1 to 2 hours, during which people prayed, chatted or –contrary to the myth– rarely read, since most were illiterate and candle or oil lamp light was expensive and dangerous.

Then came the second sleep until dawn. This biphasic pattern was the rule, not the exception. With the arrival of electric light, the day grew longer and sleep was compressed into a single block of 7-9 hours, now considered the health standard.

Not everyone agrees that this pattern was universal. Some argue that segmented sleep was a luxury of clergy and nobles, while the peasant, exhausted by physical labour from dawn to dusk, slept straight through. Others point out that the interruptions were hardly pleasant when the cause was fleas, mosquitoes or the cold.

What is certain is that the debate about how our ancestors slept remains open. What does seem clear is that our current insistence on sleeping eight hours straight without waking may be a recent cultural pressure, not an immutable biological necessity. And that waking at 3 in the morning, far from being a disorder, could be an echo of our evolutionary past.