Grand-parental investment is a special arena for testing predictions from inclusive fitness theory. Paternity uncertainty comes into play. A paternal grandfather has double the risk of genetic relatedness being severed. First, he might not be the father of his children. Second, his son might not be the father of his own children. Grandmothers, in contrast, are 100 percent certain that they are the genetic relatives of the children of their daughters. On the basis of this logic, we should expect mothers’ mothers to show the heaviest grand-parental investment, on average, and fathers’ fathers to show the least. The other two types of grandparents—fathers’ mothers and mothers’ fathers—should show investment patterns between these extremes because in each of these cases, there is one opportunity for genetic relatedness to be severed.
Post a brief (one or two paragraph) discussion of problems of kinship such as the one described above (other examples are also appropriate).