Way back in the day, if you lived under the same roof, you also shared a bedIn the Middle Ages and for some time after, in order to stay warm, protect each other, or just be closer to each other, it was very common to share a bed with a family member, your wife, or even friends, in Europe. But over the centuries, that trend started to change.Separate beds for better sleepLittle by little, people began to associate sleeping in separate beds with improved hygiene and sleep quality. So in the 18th century, sleeping in separate beds was a small lifestyle change that allowed people to wake up feeling more rested. Think of it as their version of laying off the caffeine in the evening, lowering room temperature, or limiting screen time in the hours leading up to your bedtime. Sleeping in a single bed was also perceived as modern, and the opposite was seen as a form of neglect of oneself and those close to you.Bed arrangements were reformed to limit the transmission of diseasesIn the 19th century, cholera epidemics raged and hygiene measures were reinforced in hospitals and homes, spreading the use of single beds even more. A concept called "the theory of miasma" further encouraged this practice.It was once thought that certain diseases, such as cholera, typhus, and scarlet fever, were transmitted through "miasma," a mass of dead organic particles mixed with sweat from our bodies that could contaminate both the air and sheets. So the whole point of sleeping in separate beds was to reduce the risk of contamination.Twin beds appeared shortly before the start of 20th centuryIn the early 1920s, twin beds came into the picture, and the middle class was particularly fond of them. Not only was their design much simpler than that of Victorian-era beds, but they also represented a kind of "bed revolution" for couples. Twin beds were associated with progressiveness, in that they allowed couples to have their privacy while also being autonomous and having their space. In a way, these beds also symbolized parity: same sized-beds for two people who are equally important. Until the 1950s, sleeping in twin beds implied its users were a stable, serious couple that had plans of being together long-term.Twin beds caused the Baby BoomBefore the Second World War, having children often caused problems, due to many families' precarious living conditions for families -- often, several generations were all housed under the same roof. But after the war, an increase in purchasing power gave families the option of living in their own homes, which changed the game. With their newfound financial freedom, couples began to bear children earlier, and cultural developments at the time soon led them to replace twin beds with more intimate double beds. In the end, twin beds became a symbol of a crumbling marriage. What a journey!