Looking at life today, it is difficult to imagine how complex biological processes and structures could have developed from simple building blocks. All cellular processes and reactions appear to be closely interdependent and necessarily occur within a cell membrane. There is no known organism that deviates from this pattern. But how did it come about?

In their article, the researchers show that simple heat flow across thin, water‐filled pores can accumulate a wide variety of molecules with different chemical and physical properties, and allow these molecules to interact and form reactions in a confined space, even in the absence of a cell membrane.

In this very simple protocell, there is a thermal gradient that takes over the functions of a cell membrane, but not yet any physical boundary between the reaction and the diluted water.

“Our investigations show that this simple physical mechanism, which would have been very common on early Earth, can perform many functions that would normally require a cell membrane,” says principal investigator of the study, Dieter Braun. The results suggest that heated rock pores could have been the natural setting in which biological cells emerged.