* Having the option to ditch offspring when conditions are too harsh to sustain them is one of the survival advantages of being a marsupial, rather than a placental, mammal. A starving mother kangaroo can leave a joey behind, save herself, and live to breed again when conditions improve.
* Even today, some parents may willingly give up custody of their children if they cannot afford to raise them. Many countries have "safe haven laws" where a parent can leave a child (up to a certain age) at a hospital, clinic, police station, or firehouse and not be charged with child endangerment.
* In Nebraska the original safe haven law allowed any child under 18 to be left at a hospital. Resulting in 35 non-infant children being left at hospitals.
* In some cases the only way a parent can get a dangerously mentally disturbed child the help they need is to surrender their parental rights to the state.
* [[http://en.wikipedia.org/wiki/Harry_Harlow Numerous studies with monkeys]] has put forth the theory that not only is there a problem with outright neglect, but even emotional coldness or social isolation can create socially disordered (or autistic) children later on. The same studies found that a surrogate would produce strange but okay children. So, basically, it's better to be RaisedByWolves than have ParentalAbandonment.