The studies they're quoting support the thesis that fathers aren't strictly necessary for child survival, only the role they perform is. So from the child survival point of view, a culture or society that does not have doting fathers but enough community support to fill those roles is just as beneficial as one that has doting fathers. Either way works, from a child survival p.o.v.

There may be other factors that we as a society consider beneficial that we wish to promote, that need present and involved fathers, and that's fine. But that doesn't mean a non-involved father is bad for the survival of the child. We currently based societal mores on more than just survival, though, and that is a sign of progress.