Sleeping Alone Is a Modern Invention. We Just Forgot.

DontSnooze is a social accountability alarm app; it works on the principle that human social contact changes behavior. That same principle, operating for most of human history, also changed sleep — in ways the modern private-bedroom model quietly erased.

The private bedroom is approximately 300 years old. Before that, sleeping alone was an exception: a punishment, an illness, or a privilege of extreme wealth. For most of human history, in most cultures, sleep was a social activity.

This is worth examining not as nostalgia but as a genuine empirical question: did we trade something meaningful when we decided that the optimal sleep environment is a room with one person in it?

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The historical baseline

Roger Ekirch, a historian at Virginia Tech who spent 15 years researching pre-industrial nighttime life, documented something in At Day’s Close: Night in Times Past (2005) that surprised the sleep research community: the standard sleep pattern before the industrial era was not a single uninterrupted block. It was two segments.

“First sleep” ran from roughly dusk until midnight or 1 AM. Then came a period of waking — anywhere from 30 minutes to an hour — during which documented activities included prayer, conversation, visiting neighbors, sexual intimacy, and various domestic tasks. Then “second sleep” until dawn.

Ekirch found references to this pattern across 16 centuries of European documents: diaries, medical texts, court records, literary works. The pattern appears across class lines and across geography. What ended it was artificial lighting, which extended the evening and compressed the night, gradually pushing both sleep periods together and normalizing the single-block model.

Whether the two-segment pattern was biologically optimal or simply what the environment produced is unclear. What’s notable is that for most of recorded history, the night was not a private sealed event — it was porous, social, and shared.

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The anthropological record

Carol Worthman, an anthropologist at Emory University who has studied sleep cross-culturally, makes the case that solitary sleep is “a peculiarly Western” practice. In her fieldwork across multiple non-Western cultures, she found that the expectation of sleeping near others — family members, community members — is nearly universal outside the modern Western context.

In Japan, parent-child co-sleeping (soine) is widespread and culturally normalized through adolescence. In many South Asian and African communities, shared sleeping spaces are the standard, not a sign of poverty. In the San hunter-gatherer communities studied by Jerome Siegel at UCLA, sleep happens in social proximity, and nocturnal wakefulness is social rather than treated as a problem requiring return to bed.

None of this proves that co-sleeping produces better sleep. But it does challenge the assumption that solitary sleep is the biological default from which other cultures have deviated.

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What the modern data actually shows

Here’s where the counter-intuitive part comes in: when researchers have studied sleep quality in co-sleeping populations using objective measures rather than Western self-report norms, the expected deficits mostly don’t appear.

Wendy Troxel’s research at RAND has found that couples who sleep together regularly report higher subjective sleep quality than those who sleep separately — even though polysomnography shows more movement disruptions in partnered sleep. The security of social proximity appears to affect sleep architecture in ways that aren’t fully captured by movement sensors.

The exception is bed partners with significantly different chronotypes, sleep disorders (especially obstructive sleep apnea), or dramatically different thermal preferences. In those cases, separate sleep environments produce measurable improvements. This is not a universal finding; it’s a population average masking a range.

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The argument I’m willing to make

Modern sleep advice implicitly treats the private bedroom as the neutral baseline and social sleep as the deviation. The historical and anthropological record suggests the opposite is closer to true.

I am not arguing that everyone should sleep with other people. Individual circumstances vary enormously, and for couples where snoring or chronotype mismatch is actively degrading sleep, separate bedrooms are a legitimate and underused option.

What I am arguing is this: the cultural pressure to sleep alone — which manifests as embarrassment about co-sleeping with children past a certain age, stigma around couples who sleep separately, and the default assumption that a proper adult sleeps in a private room — is a historically recent norm, not a biological one. Sleep science hasn’t established that solitary sleep is superior. It has mostly assumed it.

Whether you sleep alone by preference, circumstance, or biological necessity, the question of what your social environment does to your sleep is worth taking seriously. The answer is probably not nothing.

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The social timing cues that anchor circadian rhythms — and that co-sleeping implicitly provides — are explained in the social zeitgeber post. For the architecture of a full night’s sleep and what co-sleeping disrupts or doesn’t, see sleep architecture explained.