Lipids will spontaneously form liposomes --- (roughly) spherical cells with bilipid layers, and these will spontaneously divide and fuse. (When I say spontaneously, I mean that no biological mechanism is required, it's just down to the physics of the lipids.) Note that fission does not spill the contents of the liposomes
So you could perfectly well have cell fission, in this sense, before you actually had life! --- and then life co-opted this ready-made process. The challenge then would be how best to regulate it.
In this paper
, the author comments:
Because liposomes undergo spontaneous fission and fusion, and are subject to osmotic forces, size regulation in the earliest protocells would essentially have been liposome physics. For successful protocells, averting osmotic lysis would have been the first order of business. However, from the outset size mattered too, because of sex and reproduction (i.e., genome mixing and genome copying in entities with phenotypes). Protocell fission and fusion would have blended seamlessly into protocell sex and reproduction, making any gene product that furnished control over protocell size changes doubly adaptive.
So protocells didn't have to be programmed to divide
, as such --- but once life started using these membranes, it was adaptive to acquire control over the process of division. It seems reasonable that any control would have been better than none, and more better than less, making this adaptation a prime candidate for evolution.
Edited by Dr Adequate, : No reason given.