Because of the behavioral phenotypic and likely increased genetic intragroup similarity, the concept of inclusive fitness (Hamilton, 1964) is applicable to the gang situation. Inclusive fitness involves not only the reproductive success of the individual, but also that of relatives who share his genes. The concept of inclusive fitness (as well as group selection and evolutionary explanation of altruism) originates from Darwin (1871), who noted that [a] tribe including many members who, from possessing in a high degree the spirit of patriotism, fidelity, obedience, courage, and sympathy, were always ready to aid one another, and to sacrifice themselves for the common good, would be victorious over most other tribes; and this would be natural selection (Part 1, p. 166).
