Apparently one of the things they are currently investigating are the possibly severe physical constraints on evolution (here). The hero of this little linked to piece in Quanta is Jeremy England. He is at MIT and is considering the possibility that a lot of what we think of as evolution follows as a matter of natural physical law (thermodynamics in particular). In particular, life happens when energy is applied to atoms in a thermal bath. Do this and they tend to clump and form complex molecules to dissipate the energy. Do this enough and out pops life. Of course, what's interesting is that he apparently has the equations to prove this. Moreover, as England notes, this does not invalidate Darwinian thinking, rather it treats it "as a special case of a more general phenomenon," a thermodynamic one.
From my point of view, an interesting feature of this short piece is that nobody is calling England names. Even those that are skeptical, think that it is a hypothesis worth considering and that it will generate lots of good work regardless of whether it is true or false. In other words, his speculations (and calculations) are treated as quite reasonable and maybe even true.
The minimalistically inclined looking for examples of third factor explanations, might enjoy the discussion. At the very least, it shows that there is lots of very interesting work concerning the causal factors behind evolution. So when someone tells you (e.g. Evans most recently) that FL could not have evolved because the scenarios are incompatible with some (mis)understanding of Darwinian processes, recall that what these processes are and how they operate is currently a topic of lots of contentious and interesting new work (i.e. the scolds don't have the foggiest idea what they are talking about).