Without saying this is true, I'm not sure how much this would disagree with Human Neurological Uniformity. It seems to me that guilt would be present everywhere but if the culture is one where shaming is used a lot, it wouldn't get as much exercise, which could lead to this.
Not to mention that we don't know for sure that there even is a significant population difference here. It could just as easily be one of the things which humans seem to be generally consistent on as a species.
The point I was making, albeit ineptly, is that good research on the topic would be interesting and any potential ideological fallout shouldn't deter people from it.
Related: The Psychological Diversity of Mankind, An African Folktale, many of the more interesting infanticide & abortion debates on this site
A fascinating post that however might need some background reading, most relevant material is linked in the article itself. I encourage reading up on the material.
Link to article.
Stories about changelings replacing babies and the recommended course of action being basically to expose the child is not a human universal, they are found only in European cultures. These rely more heavily on guilt and less on shame to regulate behavior than most other human societies. This may not be a coincidence. The stories look like they work as a ready made rationalization to reduce guilt from infanticide. Common problems often acquire common solutions like this.