Since this text is all over the place, I need help in answering this: "Explain the main question or problem that motivated this piece or research."
When you are speaking about “the main question or problem” about this work, you are speaking about the prominent theme. Also keep in mind the full title of the work: Mothers and Others: The Evolutionary Origins of Mutual Understanding. It assumes that the theory of evolution (specifically our origination from apes) is true and goes beyond that theory. In short, this is a book about evolution of emotion (as opposed to evolution of physical traits).
The book begins by explaining how our evolution of emotion actually began in Africa. At one point, millions of years ago, a group of apes began teaching their babies differently than the apes before. As a result, new understanding was reached. These new understandings were the beginnings of humanity and has kept us alive as the dominant species. Mothers and Others: The Evolutionary Origins of Mutual Understanding gives its evidence in the interesting amount of “childhood” humans are given. Babies in the human world are taken care of for a long period of time (and sometimes for life) by extended family. The author argues, then, that this is where we got our ability to understand others and teach us to intuitively ascertain who will care for us. There are interestingly accurate descriptions of all kinds of mothers: marmoset mothers, ape mothers, chimpanzee mothers, wolf mothers, lion mothers, human mother, etc. Ideas are given as to why human men who function as hunter-gatherers are always hunting together (and not alone or with women).
In conclusion, Mothers and Others: The Evolutionary Origins of Mutual Understanding is a research text that deals with emotional evolution, especially in regards to motherhood. It is an interesting additional idea that “it takes a village” to raise children. This book absolutely supports that argument in saying that “villages” of our primordial ancestors took care of the young. It is built into our emotional upbringing.