by Yohan J. John
No one knows exactly how life began, but a pivotal chapter in the story was the formation of the first single-celled organism — the common ancestor to every living thing on the planet. I like to think of the birth of life as the creation of the first boundary — the cell membrane. That first cell membrane enclosed a drop of the primordial soup, creating a separation between inside and outside, and between life and non-life. Through this act of individuation the cell could become a controlled environment: a chemical safe zone for the sensitive molecular machinery needed to maintain integrity and facilitate replication. The game of life consists in large part of perpetuating the difference between inside and outside for as long as possible. Death, then, is the dissolution of difference. But the paradox at the heart of life is that the inside cannot survive without the outside. The cell requires raw materials — nutrients and energy — to sustain itself and to reproduce, and these must be sought outside the safe zone, in the wild and unpredictable outside world.
The cell membrane has a dichotomous role. It must preserve the cell’s identity as an entity that is distinct from everything outside it, but it must not be an impenetrable wall. It must be a gateway through which the cell can absorb raw material and eject waste, but it cannot allow the inside to become inundated by the outside. It fulfills this challenge by being selectively permeable, carefully overseeing the traffic between the inside and the outside. The cell membrane must also be flexible, because it serves the roles of locomotion and consumption. In a single-celled organism, the cell membrane is therefore a primitive sense organ, a transportation system and a digestive system, all rolled into one.
The birth of life was a moment of cleaving: when the first cell membrane enveloped its drop of primordial ooze, it cleaved the inside from the outside, but it also became the conduit through which the inside could cleave to the outside. Like Janus, the two-faced Roman god of beginnings and endings, of doors and passageways, the cell membrane is a sentry looking in two directions simultaneously. Given its role in cellular transaction, transition and transformation, the cell membrane’s function might even be described as a precursor to intelligence.
