It turns out that there is no such things as trees or crabs. Yet, a lot of things end up in crab-shapes or tree-shapes. What is happening here? This is a question that is related to the work on physics and evolution put forward by people like Geoffrey West, especially in his book Scale; evolution ultimately unfolds under certain basic conditions and these conditions then echo in the way evolution maneuvers in the fitness landscape. A slight preference for the energy dispersal efficiency in trees – well, then expect trees. Interestingly this suggests that there may be more global (not global) solutions and more local solutions in the phylogenetic tree, if one reads it that way.
If we really want to speculate we could then suggest that this means that there is a higher probability that we will find trees and crabs when we first encounter aliens, that evolution operates within a physical solution space that is more narrow than we may have realized.
Noting this here to ensure I find some more literature on phylogenetics as problem solving.