I have not done ANY of the assigned reading yet - but I just wanted to weigh in on this maternal instinct stuff before I do. Maybe I will change my mind - but this is where I am coming from.
Maternal instinct as a phenomenon exists. It not only exists in humans but in any other species where the young need to be cared for until they care for themselves. In some species this means only their own young (with instances of the killing of the young of others), in others any young (even of another species) - and in some, most notably other primates, both.
What I believe we are discussing here is how that "instinct" affects our concious thought. We have many instincts that come from an entirely different part of our brain then our concious thought. Sex, Hunger, Survival (Flight or Fight) - even, the latest neurological studies show, our connection perhaps with a "higher power". Our concious rational mind needs to make sense of these, sometimes, seemingly-irrational impulses or instincts and yet they often form the majority of our concious thought (I find I think about sex constantly

) So in discussing the Maternal instinct we are not just discussing the instinct itself but how we percieve it in relationship to our lives. A great book on the discussion of this (and I have posted this before - so I greatfully receive another trout) is
Phantoms in the Brain: Probing the Mysteries of the Human Mind by by V. S. Ramachandran & Sandra Blakeslee.
Harumph - now I will sit down and do the required reading.

..-. .-. . . / -... . . .-. Glug Glug