The way I see it, an infant sleeping with his mother is as old as humanity itself. Children are wired to believe that danger awaits them if they are not constantly close to thier care-givers. It might be a dilusion that a very young child can be happy sleeping without the comfort of knowing that protection is one heartbeat away. It seems a private room for a youngster is a convenience for adults and a distorted reality that young children have no need for.
While we all know that there are burglar alarms, gated communities, good neighborhoods, peace treaties, and police forces there to keep us safe - these are complex realities. Infants do not comprehend these things, and shouldnt be expected to. They are born thinking that they are in an orphanage in the jungle of fright, and it is our job to help them know that it isnt so (if it is indeed, not).
If they can understand fully that there are systems in place to keep them safe, then it would be fair to isolate them. Its too bad we cant tell them in a way that they would understand. Perhaps the only way we can is if we stay with them. They understand that message. But it would take thousands of years before evolution makes babies quiet or able to feel safe while alone.
Love and hold your child through the night, flip him and flop him over and over like a pancake all night long, if that is what he needs.
I hope mamas everywhere never forget to listen to our beautiful and time-tested instincts. The ones that embrace the children for who they are, what they need. These messages will never lead us astray if we tune in, and truly hear them. We all know the sound of them when we hear them. All other notes fade away. Sleeping alone is hard, even for the most seasoned adults.
The day that we can honestly tell them they are safe, we believe it to be true, and they can comprehend it, is the day that they should be expected to sleep alone. I hope that mamas everywhere are lovingly realistic about when that day should come.