A stepwise model for the emergence of chemiosmosis, a key element in the origin of life on earth, proposes that primordial organisms used thermal cycling as an energy source (thermosynthesis), functioning essentially as a heat engine:
:self-organized convection in natural waters causing thermal cycling →
:: added β-subunit of F ATP Synthase 
:: (generated ATP by thermal cycling of subunit during suspension in convection cell: thermosynthesis) →
::: added membrane and F ATP Synthase moiety 
::: (generated ATP by change in electrical polarization of membrane during thermal cycling: thermosynthesis) →
:::: added metastable, light-induced electric dipoles in membrane 
:::: (primitive photosynthesis) →
::::: added quinones and membrane-spanning light-induced electric dipoles 
::::: (today's bacterial photosynthesis, which makes use of chemiosmosis).