Given how evolution works, it would be highly unlikely for women not to have a maternal instinct. Genetically if not personally, it’s almost always better for a woman to care for her children; not only does she go to more risk and physical effort to produce them, unlike a male she can be sure they are hers. And when something is consistantly true, an instinct tends to evolve to push a species in that direction; I don’t recall the scientific name for the phenomenon. The ( name that starts with B ) effect ? Something like that. And given that humans are a species that tends to produce a few offspring that it invests a great deal of effort on, I’d expect humans to have an extra strong version of it.
On the other hand, such instincts seem to need to be “switched on” in some fashion; if the mother ( or father ) doesn’t bond to the child emotionally, the instinct in question likely won’t kick in. And humans being humans, I would also expect such instincts to be vague; evolved that way because human intelligence can fill in the details ( like language; we appear to have an instinct for the basic structure of language, but the details are learned ).
As for the children, I’d speculate that they’d start out much more instinctively drawn to the mother, if for no other reason than the mother is the one with the milk. Although I recall an interesting study that analyzed baby’s faces and discovered that the people who say things like “he/she has his/her father’s eyes” are quite right; babies resemble the father more than the mother - but not too much. The theory I heard to explain that is that it’s to reassure males that the baby is theirs ( thus the subtle resemblance ), but to also leave some uncertainty just in case the baby actually isn’t his ( which is why the resemblence isn’t too close ).
As the kid gets older, I’d expect his or her instincts to produce more divided loyalties. After all, both mother and father have genes in common with the kid. Also, to keep things complicated, as I understand it it appears that maternal and paternal genes are responsible for building different parts of the brain *, so that would logically produce conflicting instincts due to the different genetic interests involved.
- As I understand it, while the great majority of genes are inherited from both parents, many are only active depending on the gender of the parent they come from. Thus, for example, a woman born with a single X chromosome will have the edge in social skills etc typically seen in women if she inherits her mothers X chromosome, but will be no better than a male if she gets her father’s X. The genes are there in the secend case, but sealed off; one of the reasons why cloning mammals suddenly became possible was the discover of methods to reactivate those genes, since an embryo with only the genes of one gender active won’t develop properly, such as not forming a placenta ( which the ‘male’ genes are in charge of ).