Interesting last line, not sure if I agree with it. Here is why.
There were a lot of family bonds on plantations, there were also a lot of suicides and matricides as well; because of this, I would agree that a counter point that love (be in self or maternal/paternal) can sometimes override one's own survival instinct which is why you have so many parents killing and dying for their offspring.
In the historical context of slavery, mothers would rather kill their children than have them subjected to a life of slavery. I do believe that there may be elements of survival of self in there as well, but I do not believe that survival is the first law of humankind.
As I said before, very interesting point and for sure it has given me food for thought.