In small scale societies, lethal attacks on another individual usually invite revenge by the victim's family. We might expect those who perpetrate such attacks to do so only when their own support network (mainly family) is larger than that of the potential victim so as to minimise the risk of retaliation. Using data from Icelandic family sagas, we show that this prediction holds whether we consider biological kin or affinal kin (in-laws): on average, killers had twice as many relatives as their victims. These findings reinforce the importance of kin as a source of implicit protection even when they are not physically present. The results also support Hughes' (1988) claim that affines are biological kin because of the shared genetic interests they have in the offspring generation.

中文翻译：

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家庭计数：决定何时在冰岛维京人中谋杀。

在小规模社会中，对另一个人的致命攻击通常会引起受害者家属的报复。我们可能希望那些实施此类攻击的人只有在其支持网络（主要是家庭）大于潜在受害者的支持网络时才这样做，以最大程度地减少报复的风险。使用来自冰岛家庭萨加斯人的数据，我们可以证明这一预测成立，无论我们考虑的是生物亲属还是亲戚亲戚：平均而言，杀手的亲属数量是受害者的两倍。这些发现加强了亲属作为隐性保护来源的重要性，即使亲属不存在。这一结果也支持休斯（Hughes，1988）的观点，即仿射是生物学上的亲缘关系，因为它们在后代中具有共同的遗传兴趣。