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 selection operates primarily for the benefit of individuals (and their genes). Thus a family member may profit directly, by producing its own offspring, or indirectly, by helping close kin to reproduce. Much of the biology of family behavior rests on a simple mathematical relationship called Hamilton’s rule, which links the benefits and costs of seemingly altruistic or selfish behavior to the degree of relatedness between individuals.

Blending natural history and theoretical biology, Mock shows how Hamilton’s rule illuminates the study of family strife by throwing a spotlight on the two powerful forces—cooperation and competition—that shape all interaction in the family arena. In More than Kin and Less than Kind, he offers a rare perspective on the family as testing ground for the evolutionary limits of selfishness. When budgets are tight, close kin are often deadly rivals.

The birth of a younger sibling can be a traumatic event for the older child. Unquestionably it places increased demands on parents and causes important changes in the inner balance of the family. Childrearing manuals are full of advice about how to get through this difficult time. But until now such advice has been based more on clinical guesswork than on direct observation of what really happens to families when a sibling is born.

With the arrival of Siblings, this gap in our knowledge is admirably filled. Judy Dunn and Carol Kendrick studied forty families for a period of approximately one year starting shortly before the birth of a second child. Some families, they found, weather the storm much better than others, and their book examines the full catalog of factors that can make the difference. There are, for instance, parenting styles that ease the impact on the older child, improve relations between siblings, and generally make life easier for the entire family. But there are also differences among children in such characteristics as sex, age, and temperament, all of which have a major influence totally beyond parental control.

Despite the undeniable stress involved, Dunn and Kendrick demonstrate that the advent of a sibling can be a stimulus for real cognitive and emotional growth on the part of the older child. No longer "the baby," the child must try to deal with a newcomer whose attempts to communicate are necessarily rudimentary. Siblings shows how the elder child's efforts to understand the baby can form the basis for a loving bond of extraordinary durability.

A sensitive and informative book, Siblings takes psychology into an area of family life and child development that has long received too little attention.

The sibling relationship, as any parent with two or more children knows, is an extraordinarily intense one: young brothers and sisters love and hate, play and fight, tease and mock each other with a devastating lack of inhibition.

Why do some siblings get along harmoniously and affectionately, while others constantly squabble? To what extent are parents responsible for differences in siblings' personalities, and how can they ease the tensions?

In this timely and unusual glimpse into the world of the child, Judy Dunn argues that in fighting, bullying, or comforting, very young sisters and brothers possess a far deeper understanding of others than psychologists have supposed. She challenges the usual assumptions that birth order, age gap, and gender are the most crucial factors in explaining dramatic differences between siblings within a family, and suggests that siblings themselves have an important influence on each other's development. She shows that by studying children with their brothers and sisters, rather than in unfamiliar situations, we gain a new and illuminating picture of how growing up with siblings affects children's personalities, their intelligence, their ways of thinking and talking, and their perceptions of themselves, their families, and their friends.

Full of practical advice for coping with the daily trials of parenting two or more children, this warm and accessible book, based on new research, gives a fresh perception of a relationship which for many people lasts longer than any other in life.