Sibling rivalry and intergenerational conflict are not limited to human beings. Among seals and piglets, storks and burying beetles, in bird nests and beehives, from apples to humans, family conflicts can be deadly serious, determining who will survive and who will perish. When offspring compete for scarce resources, sibling rivalry kicks in automatically. Parents sometime play favorites or even kill their young. In More Than Kin and Less Than Kind, Douglas Mock tells us what scientists have discovered about this disturbing side of family dynamics in the natural world.

Natural...